Geological Survey of Denmark and Greenland Bulletin 1, 301-347 301 Sedimentology and sequence stratigraphy of the Bryne and Lulu Formations, Middle Jurassic, northern Danish Central Graben Jan Andsbjerg The Middle Jurassic Bryne and Lulu Formations of the Søgne Basin (northern part of the Danish Central Graben) consist of fluvially-dominated coastal plain deposits, overlain by interfingering shoreface and back-barrier deposits. Laterally continuous, mainly fining-upwards fluvial channel sandstones that locally show evidence for tidal influence dominate the alluvial/coastal plain deposits of the lower Bryne Formation. The sandstones are separated by units of fine-grained floodplain sediments that show a fining-upwards – coarsening-upwards pattern and locally grade into lacustrine mudstones. A regional unconformity that separates the lower Bryne Formation from the mainly estuarine upper Bryne Formation is defined by the strongly erosional base of a succession of stacked channel sandstones, interpreted as the fill of a system of incised valleys. Most of the stacked channel sandstones show abundant mud laminae and flasers, and rare her- ringbone structures, suggesting that they were deposited in a tidal environment, probably an estu- ary. Several tens of metres of the lower Bryne Formation may have been removed by erosion at this unconformity. The estuarine channel sandstone succession is capped by coal beds that attain a thickness of several metres in the western part of the Søgne Basin, but are thin and poorly developed in the central part of the basin. Above the coal beds, the Lulu Formation is dominated by various types of tidally influenced paralic deposits in the western part of the basin and by coarsening-upwards shoreface and beach deposits in central parts. Westwards-thickening wedges of paralic deposits interfinger with eastwards-thickening wedges of shallow marine deposits. The Middle Jurassic succession is subdivided into nine sequences. In the lower Bryne Formation, sequence boundaries are situated at the base of laterally continuous fluvial channel sandstones whereas maximum flooding surfaces are placed in laterally extensive floodplain or lacustrine mud- stones. The unconformity that separates the alluvial plain deposits of the lower Bryne Formation from the estuary deposits of the upper Bryne Formation is interpreted as a sequence boundary that bounds a system of incised valleys in the western and southern parts of the basin. Sequence boundaries in the Lulu Formation are situated at the top of progradational shoreface units or at the base of estuarine channels. Maximum flooding surfaces are located within marine or lagoonal mudstone units. Marine highstand deposits are partitioned seawards, in the eastern part of the basin, whereas paralic transgressive deposits are partitioned landwards, in the west. This marked sediment partitioning in the uppermost part of the succession resulted from the alternation of episodes of fault-induced half-graben subsidence with periods of slow uniform subsidence. Keywords: Danish Central Graben, Middle Jurassic, Bryne Formation, Lulu Formation, sedimentology, sequence stratigraphy, alluvial/coastal plain – shallow marine, sediment partitioning Geological Survey of Denmark and Greenland, Geocenter Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen K, Denmark. E-mail: ja@geus.dk Geological Survey of Denmark and Greenland Bulletin 1, 301–347 (2003) © GEUS, 2003 During the Middle Jurassic, the North Sea area was dominated by extensive coastal plain, delta plain and shallow marine environments. The resultant deposits have been described from the Viking Graben (Graue et al. 1987), from the Moray Firth and the Yorkshire coast along the western margin of the North Sea Basin (Hancock & Fisher 1981; Rawson & Wright 1995; Stephen & Davies 1998), from the Norwegian–Danish Basin along the eastern margin (Nielsen 2003, this volume), and from the Central Graben in the central and south- ern North Sea (Gatliff et al. 1994; Herngreen et al. 2003, this volume; Fig. 1). In the past two decades, several minor gas, condensate and oil fields with Middle Jurassic reservoirs have been discovered in the Søgne Basin, a minor sub-basin straddling the Danish–Norwegian boundary line along the eastern main boundary fault of the Central Graben. Production from these fields has started recently. The aims of this paper are threefold: (1) to provide a detailed environmental interpretation of characteristic sedimentary facies of the Middle Jurassic rocks and estab- lish their palaeogeographic relationships; (2) to establish a high resolution sequence stratigraphic framework for the Middle Jurassic succession in the Søgne Basin of the Danish Central Graben; and (3) to describe and inter- pret the important reservoir rocks in the upper part of the Middle Jurassic succession, their complex inter-rela- tionships and their relationship to surrounding rocks, and the processes that caused such complexities. Regional setting and structural development The Danish Central Graben forms part of the Central Graben (Fig. 1), a complex N–S-trending Mesozoic intra- cratonic rift basin. Subsidence of the Danish Central Graben was initiated in the Triassic but was most active during the Middle and Late Jurassic (Møller 1986). The Central Graben separates the Mid North Sea High to the 302 ■ ■ ■■ ■ ■ ■■ ■■ ■ ■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■■ ■■ ■ ■ ■■ ■■ ■ ■ ■ ■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■■ 55°N 4°E 100 km Structural high Outer Moray Firth V ik in g G ra be n Central Graben Ringkøbing– Fyn High N G NL UK DK Mid North Sea High Normal fault National border Well ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■■■■■ ■■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 ■■ C offee Soil Fault 20 km A B 57°30' 4° Ringkøbing–Fyn High East North Sea Block Sørvestlandet High ■ ■ ■ ■ ■ ■ ■■ ■■ ■ ■ ■ ■ ■ ■ Søgne Basin Tail End G raben ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ Fig. 1. A: Outline map of the Jurassic North Sea rift system showing the Danish sector of the Central Graben (blue) and the position of the map in Fig. 1B (red outline). DK, Denmark; G, Germany; N, Norway; NL, the Netherlands; UK, United Kingdom. B: Map of the northern Danish Central Graben showing the structural outline of the Søgne Basin (grey), straddling the Danish–Norwegian bound- ary, and the location of wells used in this study. west from the East North Sea Block of the Ringkøbing– Fyn High to the east (Japsen et al. 2003, this volume). The development of the Danish Central Graben was determined by differential subsidence of grabens along N–S- and NW–SE-trending faults. The Søgne Basin and Tail End Graben began to subside as separate half-grabens during the Middle Jurassic (Gowers & Sæbøe 1985; Møller 1986). Initiation of rift-associated subsidence was prob- ably related to domal uplift and subsequent dome col- lapse in the North Sea area (Whiteman et al. 1975; Eynon 1981; Ziegler 1982, 1990; Underhill & Partington 1993). Rotation probably began in the Søgne Basin in connec- tion with boundary fault activity during the Middle Jurassic (Gowers & Sæbøe 1985; Møller 1986; Cartwright 1991; Michelsen et al. 1992; Korstgaard et al. 1993) although it has been suggested that no syndepositional rotation took place in the Søgne Basin until Volgian time (Sundsbø & Megson 1993). According to Mogensen et al. (1992), salt structures were generated in the Søgne Basin in the Triassic. Middle Jurassic subsidence and faulting initi- ated the development of boundary fault salt pillows and up-dip salt structures in the southern Søgne Basin. Stratigraphic framework, concepts and methodology Lithostratigraphy Middle Jurassic sandstones with interbedded mudstones and coals were encountered by the Lulu-1 well, the first exploration well in the Danish part of the Søgne Basin (Fig. 1). Similar deposits encountered in the Nor- wegian part of the Central Graben were included in the Bryne Formation, a formation erected by Vollset & Doré (1984). Jensen et al. (1986) extended the Bryne For- mation to the Middle Jurassic deposits of the northern part of the Danish Central Graben, although referring similar, coeval deposits of the southern part of the 303 Fig. 2. Jurassic lithostratigraphy of the Danish Central Graben, from Michelsen et al. (2003, this volume). System Series Stage Ju ra ss ic T ri as si c Åsgard Formation Leek Member Bo Member Heno Fm Lola Formation Bryne Formation Danish Central Graben Ryazanian Volgian Kimmeridgian Oxfordian Callovian Bathonian Bajocian Aalenian Toarcian Pliensbachian Sinemurian Hettangian Rhaetian Norian Winterton Formation C re ta ce ou s Valanginian Fjerritslev Formation Vyl Fm Poul FmFarsund Formation Lo w er U pp er M id dl e Lo w er U pp er U L U L L U U M L L M U M L U L U U L L U M L U U L U M L Paralic and non-marine sandstones, siltstones, mudstones and coals Marine mudstones and siltstones Unconformity Offshore organic-rich marine shales Submarine fan sandstones and siltstones Shallow marine sandstones and siltstones Hiatus Middle Graben Formation Lulu Formation Danish Central Graben to the Central Graben Group of NAM & RGD (1980). In a re-evaluation of the litho- stratigraphy of the Danish Jurassic, the upper part of the Middle Jurassic succession in the northern part of the Danish Central Graben is referred to a new forma- tion, the Lulu Formation (Fig. 2; Michelsen et al. 2003, this volume). Most of the Middle Jurassic succession in the southern part of the Danish Central Graben previ- ously referred to the Central Graben Group is now included in the Bryne Formation, although the Middle Graben Formation, defined from the Dutch sector (see Herngreen et al. 2003, this volume), is retained in this area (Fig. 2; Michelsen et al. 2003, this volume). The boundary between the Bryne Formation and the Lulu For- mation is placed at the base of the first major coal or its correlative interval of thin coals and coaly mudstones in the upper part of the middle Jurassic succession. In the Søgne Basin, the Middle Jurassic succession unconformably overlies Triassic and Permian deposits and is either succeeded conformably by marine mud- stones of the Upper Jurassic Lola Formation (Jensen et al. 1986) or is overlain unconformably by Cretaceous deposits on structural highs. In the wells of the Søgne Basin, the thickness of the Middle Jurassic succession varies from 130 to 300 m; the succession may be absent from the top of structural highs, and it may attain a somewhat larger thickness in deeper parts of the basin. Based on detailed sedimentological analysis of cores, the Middle Jurassic of the Lulu-1 well was interpreted as deltaic interdistributary bay deposits overlain by coastal sediments (Frandsen 1986). Koch (1983) interpreted Middle Jurassic deposits further south in the Danish Central Graben as alluvial plain and delta plain deposits. Damtoft et al. (1992) suggested a fluvial channel and floodplain environment for the Bryne Formation, and Johannesen & Andsbjerg (1993) interpreted the Middle Jurassic succession in the Søgne Basin as an alluvial plain succession overlain by tidal and shallow marine deposits. Biostratigraphy Stratigraphically useful microfossils are rare in the stud- ied succession. The sparse biostratigraphic information available for this study comes from unpublished reports from the Geological Survey of Denmark and Greenland, reports from service companies, and the results of new investigations prepared for the sequence stratigraphic study by Andsbjerg & Dybkjær (2003, this volume). Only palynomorphs were used for dating in that study and the events are presented mainly as last occurrence datum (LOD) of dinoflagellate cyst species. The events used and their relation to boreal standard zones are presented in Andsbjerg & Dybkjær (2003, this volume, fig. 3). Age-specific microfossils have not been found in the lower part of the Bryne Formation in the study area. How- ever, the occurrence of the dinoflagellate cyst Scriniocassis sp. at 3730 m in West Lulu-1 indicates an Aalenian or earliest Bajocian age. In the middle and upper parts of the Bryne Formation, the occurrence of the dinoflagel- late cysts Ctenidodinium combazii, Impletosphaeridium varispinosum and the LOD of the pollen Quadraeculina anelliformis suggest a broad Late Bajocian to Callovian age. More specifically, the occurrence of Ctenidodinium combazii at 3742 m in the middle part of the Bryne Formation in West Lulu-3 suggests an age not older than Late Bajocian for that interval. The occurrence of Impletosphaeridium varispinosum in the incised valley deposits of the upper part of the Bryne Formation at 3602 m in West Lulu-1 and at 3705 m in West Lulu-3 indicates a latest Bathonian to early Callovian age. The LOD of the pollen Quadraeculina anelliformis either immediately beneath or just above the base of the incised valley deposits in several wells (e.g. 3717 m in West Lulu-3, 4479 m in Lulita-1) supports a latest Bathonian age for valley incision and the initiation of valley infilling. The Lulu Formation, which constitutes the upper part of the Middle Jurassic succession, is poorly dated. However, the occurrence of Durotrigia filapicata in the uppermost Lulu Formation at 4430 m in Lulita-1 suggests an age not younger than the Late Callovian, and the LOD of the dinoflagellate cyst Liesbergia scarburghensis in the lower part of the Lola Formation in several wells (Andsbjerg & Dybkjær 2003, this volume), indicates a Late Callovian – mid-Oxfordian age for the final transgression of the Søgne Basin. With ages spanning at least a period from the Early Bajocian to the latest Callovian, the Bryne and Lulu Formations represent about 18 Ma of deposition, according to the time-scale of Gradstein et al. (1994). Sequence stratigraphic concepts and nomenclature Sequence stratigraphic principles and nomenclature in this study follow Posamentier et al. (1988, 1992), Posa- mentier & Vail (1988), Van Wagoner et al. (1988, 1990) and Hunt & Tucker (1992, 1995). Andsbjerg & Dybkjær (2003, this volume) present the subdivision and naming of sequences that can be 304 traced throughout the Danish Central Graben. The pre- sent study attempts a more detailed sequence strati- graphic subdivision based on key-surfaces and units that are traceable across the Søgne Basin. Andsbjerg & Dyb- kjær (2003, this volume) subdivided the Middle Jurassic section into four sequences – the Aalen-1 (Aalenian), Baj-1, Bath-1, and Cal-1 sequences. In this higher res- olution local study, this nomenclature is retained but further subdivided (Fig. 3). Thus, Cal-1 of Andsbjerg & Dybkjær (2003, this volume) is divided into Cal-1A, 305 Upper paralic wedge Lithological units Lithological units Lithostrati- graphy Sequence stratigraphy Upper paralic wedge Upper marine wedge Lola Fm Lulu Fm LST/TST LST/TST HST/FSST LST/TST LST/TST LST/TST LST/TST HST HST HST HST SB MFS MFS MFS SB SB SB SB SB SB Bryne Fm Lower marine wedge Incised valley fill Channel sand C Channel sand B2 Channel sand B1 Channel sand A Middle paralic wedge Lower paralic wedge Middle paralic wedge Lower paralic wedge Incised valley fill Channel sand C Channel sand B2 Channel sand B1 Channel sand A MFS MFS SB Cal-1B Cal-1C Cal-1A Bat-1B Bat-1A Baj-1B Baj-1A Aalen-1B Aalen-1A SB Fluvial channel sandstones Floodplain mudstones Estuary channel sandstones Lagoonal/tidal flat mudstones/ heteroliths Coal Shoreface/mouth bar sandstones Shelf mudstones Fig. 3. Architecture, lithostratigraphy and sequence stratigraphic interpretation of the Middle Jurassic in the northern part of the Danish Central Graben. The Middle Jurassic sequences defined in this study are referred to according to their gross age, i.e. Callovian sequences are termed Cal-1A, Cal-1B etc. System tracts: LST, lowstand systems tract; TST, transgressive systems tract; HST, highstand systems tract; FSST, falling stage systems tract. Key surfaces: SB, sequence boundary; MFS, maximum flooding surface. Cal-1B and Cal-1C. The sequences and their most impor- tant key surfaces are shown in Figures 3 and 4. The hier- archical nature of sequence stratigraphy, i.e. the potential subdivision of larger sequences into a number of smaller sequences, reflects the fact that sequences represent the varying time-spans over which different combina- tions of causal factors may operate. Influenced by a vari- ety of factors such as glacio-eustacy, tectono-eustacy, tectonics of various scales, and climate, sequences form over time scales ranging from tens of thousands of years to hundreds of millions of years (see discussion in Vail et al. 1977, Van Wagoner et al. 1990, Miall 1997). Whereas the Middle Jurassic sequences outlined by Andsbjerg & Dybkjær (2003, this volume) represent time-spans of 5–10 Ma. which is consistent with the influence of intraplate stress (Cloetingh 1988; Hallam 1988; Miall 1997), the present study identifies sequences with dura- tions in the range 1–5 Ma., which may indicate a stronger influence of local tectonics. Key surfaces and systems tracts A systems tract is defined as a linkage of contempora- neous depositional systems defined by stratal geome- try at bounding surfaces, position within the sequence, and internal stacking patterns (Posamentier et al. 1988). Sequences are subdivided into the lowstand systems tract (LST), the transgressive systems tract (TST), the high- stand systems tract (HST) and the falling stage systems tract (FSST; alternatively termed the forced regressive systems tract by Hunt & Tucker 1992, 1995). The low- stand systems tract (LST) consists of deposits formed at the lowest relative sea-level stand, bounded below by the mainly subaerial sequence-bounding unconformity (SB) and above by the first transgressive surface (TS). The TST consists of a succession of backstepping parase- quences; individual parasequences may exhibit a progra- dational pattern. The lower boundary of the TST is the first TS and the upper boundary is the maximum flood- ing surface (MFS). The HST is characterised by a progra- dational stacking pattern, which may be interrupted by subordinate transgressive events. The systems tract is bounded at the base by the MFS and at the top by the SB or by a regressive surface of marine erosion (RSME) if it is overlain by a falling stage systems tract (FSST). The FSST consists of the sediments deposited during falling sea level and is bounded by the RSME at the base and by the SB at the top. There is a direct link between sequence development and relative sea-level change in the marine and marginal marine realm. In upland settings, sea-level changes do not influence sequential development of deposition sig- nificantly. A more pronounced influence may be present in non-marine deposits of lowland settings, although it may be subordinate to other factors. The sporadic occur- rence of tidal indicators in the non-marine deposits of the Bryne Formation suggests that deposition took place on the lower part of a coastal plain where sea-level changes may have exerted a strong influence on sedi- mentation patterns and sequence development. Data and methodology Data from 9 released wells penetrating the Bryne Formation in the Søgne Basin were used in the present study (Fig. 1). A total of 875 m of core has been exam- ined and described. Graphic core logs were matched to gamma-ray (GR) and sonic logs, supplemented by density, neutron and resistivity logs, in order to gain an improved interpretation of the cored successions. The observed core-to-log relationships have been used in the interpretation of well logs from uncored intervals by extrapolating sedimentological interpretations of cores to the uncored sections. The well logs and sedi- mentological core logs formed the basis for the con- struction of cross-sections. Well-to-well correlations of key surfaces and characteristic units form a framework that guide correlations of other units and form the basis for the construction of palaeogeographic maps. Sedimentary facies and depositional environments Approximately 875 m of slabbed cores were available for the description of sedimentary facies. Facies descrip- tions include the registration of lithology, grain size, pri- mary sedimentary structures and deformation structures including degree and type of bioturbation. A total of 30 facies are recognised (Table 1) and are grouped into nine facies associations (1–9), each of which represents a specific sedimentary environment. Non-marine deposits Sediments interpreted as mainly non-marine dominate the lower and middle part of the Bryne Formation. They are grouped into four facies associations repre- 306 C al -1 C C al -1 B C al -1 A Lo la Fm Lu lu Fm U pp er Br yn e Fm Lo w er Br yn e Fm Ba t- 1B Ba t- 1A Ba j-1 B Ba j-1 A A al en -1 B A al en -1 A C al -1 C C al -1 B C al -1 A Ba t- 1A Ba j-1 B Ba j-1 A A al en -1 B A al en -1 A G R G R G R G R G R G R G R D T D T D T D T D T D T D T W es t Lu lu -4 W es t Lu lu -2 W es t Lu lu -3 W es t Lu lu -1 3/ 7- 4 A B1B2C Lu lit a- 1 A m al ie -1 D ep os iti on al e nv ir on m en ts Sh el f m ud st on es Pa ra lic /s ho re lin e se di m en ts C oa l In ci se d va lle y fil l Fl oo dp la in /la cu st ri ne s ed im en ts Fl uv ia l c ha nn el s an ds to ne s Pr e- Ju ra ss ic s tr at a K ey s ur fa ce s Se qu en ce b ou nd ar y M ax im um fl oo di ng s ur fa ce N or m al fa ul t C or ed s ec tio n 50 m ■ ■ ■ ■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■■■ ■■ A m al ie -1 3/ 7- 4 Lu lit a- 1 Lu lu -1 W es t Lu lu 1 3 2 4 ■■ ■■ ■■ Sø gn e Ba si n 10 k m 307 Fi g. 4 . W el l lo g p an el o f th e M id d le J u ra ss ic i n t h e Sø gn e B as in . T h e d at u m l in e is t h e b as e o f th e lo w er m o st l at er al ly p er si st en t co al s ea m d ef in in g th e b as e o f th e Lu lu F o rm at io n ( co al s ea m R 1 o f P et er se n & A n d sb je rg 1 99 6) . T h e fl u vi al c h an n el s an d st o n e u n its A , B 1 , B 2 an d C in t h e lo w er B ry n e Fo rm at io n a re i n d ic at ed ( se e Lu lit a- 1, A m al ie -1 w el ls ). N o te t h e p ro m in en t tr u n ca - tio n o f m ar ke rs i n t h e lo w er B ry n e Fo rm at io n b y th e m aj o r in ci se d v al le y d ef in ed b y th e C al -1 A se q u en ce b o u n d ar y. D T , so n ic v el o ci ty l o g; G R , ga m m a- ra y lo g. 308 Facies Structureless and laminated siltstone and claystone Interbedded siltstone and sandstone Bioturbated siltstone and sandstone HCS-dominated sandstone SCS-dominated sandstone Trough and planar cross- bedded sandstone Horizontally laminated and planar cross-bedded sandstone Conglomerate and pebbly sandstone Poorly sorted, bioturbated muddy sandstone and heterolith Horizontally laminated and current rippled sandstone Structureless rooted sandstone Fining-upwards cross-bedded sandstone with mud drapes Fining-upwards interbedded mudstone and sandstone Coarsening-upwards sandstone with abundant mud laminae Coarsening-upwards cross-bedded sandstone with mud laminae Fining-upwards heterolithic sandstone and mudstone 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Description Structureless or mm- to cm-scale interlaminated siltstone and claystone Cm-scale interbedded siltstone and sandstone. Sharp-based, normal graded sand laminae show parallel lamination and wave ripples Bioturbated siltstone, very fine-grained sandstone beds with sharp bases may show wave or combined flow ripples, parallel lamination and HCS Very fine- and fine-grained sandstone with siltstone laminae. Sharp-based sandstone beds with HCS and subordinate wave ripple lamination Fine-grained sandstone, SCS, low-angle planar cross-bedding and scour structures Fine- to coarse-grained sandstone, occasionally pebbly. Trough cross-bedding, planar cross-bedding and subordinate current and wave ripples Fine- to coarse-grained sandstone. Parallel lamination with low-angle erosion surfaces and low-angle planar cross-bedding Clast-supported pebble and granule conglomerate, less common matrix-supported conglomerate and pebbly sandstone. Clast-supported conglomerate may show cross- bedding; conglomerate veneers on erosion surfaces Poorly sorted sandstone with subordinate siltstone. Soft-sediment deformation structures and bioturbation dominate, some wave and current ripples may occur Erosionally based fining-upwards units of very fine- to medium-grained sandstone. Parallel or gently inclined lamination, current ripples, local soft-sediment deformation structures or high-angle cross-bedding Various sandstones and heteroliths fully or partly homogenised by roots Fining-upwards units of fine- to coarse-grained sandstone. Planar and trough cross- bedding with ripple cross-laminated flaser and wavy bedding in upper parts of units. Abundant clay laminae; clay clasts and coal debris, interbedded sandstone and mudstone may occur Fine- and very fine-grained sandstone and heteroliths with mud clasts. Ripple cross- lamination, parallel lamination, flaser, lenticular and wavy bedding, cross-bedding Very fine- to fine-grained sandstone. Bioturbated with mud laminae and flasers, ripple cross-lamination Very fine- to medium-grained sandstone and heteroliths. Cross-bedding, cross- lamination, flaser bedding, mud laminae Thinly interbedded sandstone, mudstone and heteroliths. Ripple cross-lamination, parallel lamination, flaser bedding Table 1. Facies classification of the Bryne and Lulu Formations 309 Thickness Beds < 50 cm Beds max. 10 cm Silt beds less than 3 m, sand beds up to 10 cm, rarely to 50 cm 10–50 cm beds 20–50 cm beds 20–50 cm beds in units up to 3 m 5–15 cm beds in units up to 50 cm Conglomerate beds max. 10 cm, pebbly sandstone beds up to 30 cm 5–10 cm beds in units up to 1 m 5–20 cm beds 50 cm – 3 m 4–10 m fining-upwards units Fining-upwards units typically 50 cm – 2.5 m Coarsening-upwards units up to 2 m Coarsening-upwards units up to 4 m Units less than 1 m Biogenic structures Weak to moderate bioturbation: Anconichnus isp., Planolites isp. and Teichichnus isp. Moderate to intense bioturbation: Teichichnus isp., Thalassinoides isp., Skolithos isp., Planolites isp. Weak bioturbation Trace fossils are rare Bioturbation in the most fine-grained intervals: Diplocraterion isp. and Skolithos isp. Trace fossils are rare: roots and (?)Skolithos isp. Often thoroughly bioturbated: Teichichnus isp., Diplocraterion isp. Moderate bioturbation, roots may occur Thoroughly homogenised by roots Moderate, rarely intense bioturbation: Teichichnus isp. Moderate to intense bioturbation Moderate to intense bioturbation: Teichichnus isp. Generally moderate bioturbation: Teichichnus isp., Diplocraterion isp. Moderate to intense bioturbation: common Diplocraterion isp., Planolites isp. Interpretation Offshore, fair-weather deposition and suspension fall-out after storms Offshore, near storm wave base Offshore – offshore transition, storm activity alternating with long periods dominated by fair-weather conditions Offshore transition, storm and waning storm deposition Lower and middle shoreface, above fair-weather wave base Upper shoreface. Rip channels, nearshore bars and troughs Foreshore Beach and breaker zone deposits. May represent a transgressive lag Transgressive marine sandstone deposited below fair-weather wave base during rising sea level Washover sediments Beach ridge plain Major tidal channel or active tidal inlet Tidal creek or inactive major tidal channel Tidal sand bar/flat Proximal flood tidal delta or estuary sand bar Tidal flat and distal flood tidal delta 310 Facies Coarsening-upwards/fining-upwards sandstone and heterolith Structureless or laminated mudstone and bioturbated sandstone Organic-rich rooted mudstone Coal Fining-upwards interbedded sandstone and mudstone Sandstone, fining-upwards or no grain-size trend Intraformational conglomerate Fining-upwards thin-bedded or cross-bedded sandstone Chaotically bedded sandstone Sideritic siltstone and mudstone Coarsening-upwards units of deformed siltstone and sandstone Coarsening-upwards units of sharp-based sandstone and siltstone Disturbed silty mudstone Organic-rich laminated mudstone 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Description Coarsening-upwards very fine- to medium-grained sandstone units. Planar cross- bedding, parallel lamination, current and wave ripple cross-lamination and small-scale HCS/SCS. Commonly associated with fining-upwards channel units Parallel-laminated or structureless mudstone with interbeds and laminae of sandstone. Parallel lamination, wave ripples, flaser and lenticular bedding Organic-rich mudstones with plant fragments, thin coals and with abundant rootlets Sharp-based units, often fining-upwards, of cross-bedded and cross-laminated sandstone with abundant heterolithic beds and mud laminae. Abundant coal or mud clasts locally Sharp-based fining-upwards cross-bedded and cross-laminated sandstone. Heterolithic sandstones may dominate upper part of units; some beds may have abundant coal and mud clasts. Thick amalgamated units may show no overall grain-size trend Matrix- or clast-supported, pebble–cobble conglomerate, with sand matrix. Angular mud- or siltstone clasts. Conglomerate beds at base of fining-upwards sandstone units are parallel-stratified or cross-bedded Sharp-based fining-upwards sandstones. Thin-bedded with current ripple cross- lamination, parallel lamination or cross-bedding. Intraformational clasts and coal fragments, soft-sediment deformation Poorly sorted sandstone with deformed and overturned mud laminae. Coal and mud clasts scattered throughout Siltstone and mudstone with siderite bands and nodules, abundant plant remains and roots. Indistinct patches of sandstone may occur Stacked coarsening-upwards units of siltstone and sandstone. Dominated by soft- sediment deformation structures with current, wave, and climbing ripple lamination in sandstone units, parallel and climbing ripple lamination and wavy and lenticular bedding in siltstone units. Mudstone clasts and coal fragments locally abundant. Thinner, sharp based fining-upwards sandstones with deformed cross-bedding may occur at top of coarsening-upwards intervals Coarsening-upwards units of very fine- to medium-grained sandstone with silt- and mudstone. Common parallel lamination, current ripple cross-lamination, root traces, soft-sediment deformation. Base gradational to floodplain mudstones Mud- and siltstone, subordinate sandstone, coal debris. Parallel lamination, sediments disturbed by roots, soft-sediment deformation and pedogenesis Organic-rich mudstones with sand and silt laminae Table 1 (continued). Facies classification of the Bryne and Lulu Formations 311 Thickness Units up to 5 m Units less than 2 m Less than 50 cm Max. 5 m Units max. 12 m Units max. 8 m Beds up to 75 cm Units < 2 m Beds typically 20–50 cm Typically 0.5–2 m 2–5 m units. May be stacked in 10 m coarsening-upwards successions Beds 10–50 cm, units up to 2 m Typically < 1 m Max. 8 m Biogenic structures Moderately bioturbated: Teichichnus isp., Diplocraterion isp. Moderate to intense bioturbation by roots Moderate to intense bioturbation by roots Upper part of channel units may be bioturbated: Diplocraterion isp., Teichichnus isp. Thoroughly bioturbated, mainly by roots Interpretation Bay-head delta/bay shoreface Low energy outer estuary, estuary central basin or lagoon Marsh or vegetated coastal swamp Mire Tidally influenced fluvial channel Major fluvial channel Channel lag deposits Crevasse channel or minor fluvial channel Channel margin deposits of fluvial channels Abandoned channel fill Lacustrine delta. Stacked minor coarsening- upwards units capped by channel sandstones may represent delta lobes of a larger lacustrine delta Levee and crevasse spray Floodplain fines Lake and pond 312 cm 0 10 20 30 40 50 60 70 80 90 A West Lulu-3 3749.4 m B West Lulu-3 3751 m C West Lulu-3 3751.8 m D West Lulu-3 3753.3 m E West Lulu-3 3754.1 m F West Lulu-3 3756.4 m SB This page and facing page: Fig. 5. Core photographs of fluvial channel and floodplain facies (facies associations 1–4) and facies successions of the lower Bryne Formation (Baj-1B, Bat-1A, Bat-1B sequences). Consecutive core sections in this and subsequent core photographs are bracketed. A–F: Selected intervals of the fluvial channel unit B2 (sequence Baj-1B, LST/TST) in West Lulu-3 (base lower right, top upper left; for location of core sections, see Fig. 13). The basal sequence boundary (SB) overlying sequence Baj-1A lies immediately beneath the lowermost core section (F). Sections B–F illustrate the active channel fill (facies association 1), showing trough cross-bedded, ripple cross-laminated and structureless sandstones, with abundant coal and mudstone clasts. These are succeeded (A) by passive channel fill or floodplain deposits (facies associations 2, 4) comprising mudstones, interbedded mudstones and sandstones and thin coals associated with rootlets 313 (arrowed) and palaeosol mottling. G–K: Selected intervals from the fluvial channel sandstone unit C (sequence Bat-1A) in West Lulu-2 (base lower right, top upper left; for location of core sections, see Fig. 14). The channel base defining the sequence boundary (SB, see core section K) is overlain by the active channel fill (facies association 1) comprising structureless and cross-bedded sandstones with abundant mudstone clasts and coal fragments (I–K, lower point bar) succeeded by sandstone and mudstone heteroliths, disturbed in places by bioturbation (rootlets arrowed) and soil-forming processes (G, H; upper point bar). The channel fill is capped by coal (G; facies association 4). L: Sandstone and heterolithic sandstones showing climbing ripple cross-lamination, representing a lacustrine or crevasse delta (facies association 2). West Lulu-1, sequence Bat-1B; for location of core section, see Fig. 15. cm 0 10 20 30 40 50 60 70 80 90 G West Lulu-2 3851.1 m L West Lulu-1 3626 m H West Lulu-2 3859.3 m I West Lulu-2 3860 m J West Lulu-2 3861.6 m K West Lulu-2 3862.2 m SB senting fluvial channel fill, proximal floodplain, lake and distal floodplain, and vegetated floodplain. Facies association 1: fluvial channel fill (facies 21–26) Description. The fluvial channel fill association comprises erosionally based, up to 8 m thick, fining-upwards, chan- nel units. The channel units are dominated by sandstone in the lower part and become heterolithic in the upper part (Fig. 5B–F). A conglomerate of mudstone clasts may occur immediately above the erosional base. The most common facies of the channel fill association are trough and planar cross-bedded sandstone and ripple cross- laminated sandstone (Fig. 5B, D). The common chaoti- cally bedded sandstone facies is characterised by contorted bedding, soft sediment deformation and a chaotic tex- ture with abundant plant debris and intraformational mudstone clasts in places (Fig. 5E). In the upper part of the channel units, sandstone beds are interbedded with 10–30 cm thick heterolithic beds that may represent inclined heterolithic strata (Thomas et al. 1987), a vari- ant of epsilon cross-stratification characteristic of tidally influenced fluvial channels (Smith 1987). Mudstone lam- inae, double mud drapes and flaser bedding, abundant in the sandstone facies of some units, particularly in the upper part of the Bryne Formation, suggest occasional tidal influence in the river system. Interpretation. Fining-upwards channel units that can be correlated between most wells in the study area (Figs 3, 4), represent laterally extensive channel sand- stones deposited by laterally migrating, sinuous rivers. Chaotic bedding may be the result of bank collapse and/or post-depositional collapse of stems and other plant material deposited behind obstacles in the chan- nel. Similar deposits have been described by Alexander & Gawthorpe (1993; their facies S4) and by Guion et al. (1995) as part of their minor channel facies. The evi- dence of occasional tidal influence suggests deposition in a coastal plain environment. Facies association 2: proximal floodplain (facies 27–29) Description. The proximal floodplain association con- sists of interbedded sandstone, siltstone and mudstone (Fig. 5L). The sandstones are generally less than 2 m thick, but may be amalgamated into units 4–5 m thick. The sandstone units may fine upwards, coarsen upwards or show no overall grain-size trends. Primary structures include cross-bedding, current ripple lamination, climb- ing ripple lamination, wave ripple cross-lamination, parallel lamination and chaotic bedding with abundant mudstone and coal clasts. Soft sediment deformation structures are common. Siltstones and mudstones of this association are commonly structureless but may show deformation structures, parallel lamination and lenticular bedding. Interpretation. The sandstones were deposited in small channels, as crevasse splays, on levees and as small lacustrine deltas. Sandstone units that show bi-directional current ripples, mud flasers and abundant mud lami- nae were probably influenced by tidal processes dur- ing deposition in fluvial channels or distributaries. Siltstones and mudstones are interpreted as waning flow deposits on levees and in small fluvial and crevasse channels or as the passive infill of abandoned channels. Facies association 3: lake and distal floodplain (facies 28–30) Description. Mudstones and siltstones dominate the lake and distal floodplain association (Fig. 5K). Interbedded sandstones are not thicker than a few decimetres. Mudstones and siltstones form units up to 5 m thick; these are most commonly structureless or show paral- lel lamination. The parallel lamination is faint and may appear irregular and slightly deformed. Heterolithic units may show lenticular and wavy bedding and cur- rent and wave ripples in thin sand beds. Interpretation. The sediments are interpreted as hav- ing been deposited in ponds, shallow lakes and on the distal levee, or represent the passive infill of abandoned channels. Facies association 4: vegetated floodplain (facies 20, 29, 30) Description. Sediments with abundant root traces, mot- tled siltstones and mudstones and coal beds are com- bined in this facies association. Mottled siltstones and mudstones frequently have a light-coloured ‘leached’ appearance (Fig. 5G). Interpretation. The depositional environment was a floodplain where primary deposits were modified by 314 vegetation and soil-forming processes. Most soils formed under reducing conditions. Marginal marine deposits Back-barrier and estuarine deposits dominate the upper part of the Bryne Formation and, in the western part of the basin, the Lulu Formation. The marginal marine deposits are separated into five facies associations (5–9), representing estuary channels and bars, flood tidal deltas and washover fans, bay-head deltas and bay-fill, low- energy estuary and lagoon, and marsh and swamp. Facies association 5: estuary channel and bar (facies 12–15) Description. The estuary channel and bar association is represented by 4–10 m thick sandstone-dominated units that may fine upwards, coarsen upwards or show no clear grain-size trend, and as 0.5–4 m thick, fining- upwards, fine- to very fine-grained sandstones and het- eroliths. The sandstones show planar and trough cross-bedding with common mudstone laminae (Fig. 6D), and ripple cross-lamination with abundant mud- stone flasers (Figs 6C, E, 7). Coal fragments and mud- stone clasts occur in some beds, most commonly above erosional surfaces (Fig. 6K, L). Heterolithic strata, 5–20 cm thick, occur interbedded with the sandstones and may represent beds of inclined heterolithic stratification (Thomas et al. 1987). Interbedded sandstones, mud- stones and heteroliths in the fine-grained units show flaser, wavy and lenticular bedding and parallel lami- nation (Figs 6A, 8B, E). Up to 5 m thick coarsening- upwards units are formed by progressively thicker and coarser grained sandstone beds separated by thin mud- stone and siltstone beds (Fig. 9). These sandstone beds may show cross-bedding, ripple cross-lamination, and mudstone flasers and laminae, but may also be struc- tureless with the exception of a few inclined mudstone laminae and mudstone flasers. Intense bioturbation with abundant Teichichnus isp. is common (Fig. 9A, B). Interpretation. The fining-upwards sandstone units, dominated by cross-bedding and ripple cross-lamina- tion with abundant mudstone laminae, double mud drapes and flaser bedding, are interpreted as estuary point bar deposits (Reineck & Wunderlich 1968; Visser 1980). Sandstone units that show similar sedimentary structures but lack overall grain-size trends are inter- preted as amalgamated tidal channel sandstones. The finer-grained fining-upwards units represent the passive infill of major channels or the active fill of minor chan- nels. The coarsening-upwards sandstone units represent estuarine channel bars (Fenies & Tastet 1998) or mouth bar deposits of bay-head deltas. Facies association 6: flood tidal delta and washover fan (facies 14–16) Description. The flood tidal delta and washover fan asso- ciation consists of up to 3 m thick, generally coarsen- ing-upwards units of sandstones and heteroliths, that may be overlain by fining-upwards units of well-sorted sandstone (Fig. 10F–H). In the coarsening-upwards units, fine-grained heterolithic beds show lenticular and wavy bedding. The most fine-grained sandstones are commonly strongly bioturbated, but some may show flaser bedding and parallel lamination. Coarser grained sandstone facies include trough cross-bedded, parallel- laminated and ripple cross-laminated sandstone. The coarser grained sandstones may have erosional sur- faces overlain by thin conglomerates. The fining-upwards units are dominated by well-sorted, fine- or very fine- grained sandstone showing parallel lamination, low- angle planar cross-bedding, ripple cross-lamination and soft-sediment deformation structures. Interpretation. The fine-grained heterolithic beds char- acterised by wavy and lenticular bedding and the coars- ening-upwards sandstones with abundant mudstone laminae and flaser bedding, frequently interbedded with lagoonal mudstones, are interpreted as the deposits of flood tidal deltas and tidal sand flats. The coarsen- ing-upwards trend and the association of physical struc- tures correspond well with descriptions of recent flood tidal deltas (e.g. Nichol & Boyd 1993). The interbed- ding with lagoonal sediments further supports this inter- pretation. The well-sorted, erosionally based, fining- upwards units that locally overlie flood tidal delta and tidal flat deposits show a close likeness to washover deposits described by Schwartz (1982). Facies association 7: bay-head delta and bay-fill (facies 4–7, 17, 18, 21) Description. This association is typified by sandstones and heteroliths arranged in overall coarsening-upwards successions up to 8 m thick (Fig. 9D–G). The sediments 315 316 cm 0 10 20 30 40 50 60 70 80 90 A West Lulu-3 3667.3 m B West Lulu-3 3669.9 m C West Lulu-3 3670.8 m D West Lulu-3 3671.7 m E West Lulu-3 3674.2 m F West Lulu-3 3680.2 m G West Lulu-3 3684.6 m H West Lulu-3 3685.4 m This page and facing page: Fig. 6. Core photographs of the incised valley-fill (facies associations 5, 8) of the upper Bryne Formation (Cal-1A sequence) in West Lulu-3 (base of succession lower right, top upper left; for location of core sections, see Fig. 16). The erosional base of the incised valley, defining the Cal-1A sequence boundary (SB), is observed in the lowermost core section (L) succeeded by the lower unit of active fluvial or estuary channel fills (J–L; facies association 5); this unit is dominated by well-sorted sandstone showing faint cross-bedding or chaotic bedding with abundant coal and mudstone clasts and a basal mudstone clast conglomerate immediately overlying the sequence boundary (L). Lagoonal deposits (I; facies association 8) cap the lower channel unit, rep- resented by burrowed mudstones showing signs of soil-forming processes, and are succeeded by inferred bay-head delta deposits (H). The upper unit of active (B–G) and passive (A) estuary channel fills (facies association 5) is characterised by sand- stones with abundant double mud drapes (examples arrowed), flaser lamination (C) and cross-bedding (F, H). are dominated by current-generated structures, but wave-generated structures also occur. Sandstones with current-generated structures may occur as channel deposits in the upper part of coarsening-upwards suc- cessions. Minor units of well-sorted sandstone and het- erolith may show low-angle planar cross-bedding, swaley and hummocky cross-stratification, and wave ripple cross-lamination. Levels showing moderate bioturbation with Teichichnus isp. are evident in places. Deposits of this association frequently overlie fine-grained lagoonal deposits. Interpretation. This association is interpreted to record the progradation of bay-head deltas into estuaries, lagoons, or bays. Depending on the amount of wave influence, the deposits were either slightly modified by small-scale wave activity, or reworked thoroughly by storm wave activity. Deposits may be difficult to dis- tinguish from coarsening-upwards estuary bar deposits of association 5. Facies association 8: low-energy estuary and lagoon (facies 14, 16, 18, 19) Description. This facies association is represented by organic-rich mudstones, siltstones and heteroliths, show- ing parallel lamination, wavy and lenticular bedding, and ripple cross-lamination with mud-flasers, partly obliterated by biogenic activity (Figs 8D, E, 9I). Sed- imentary units of this association vary in thickness from a few decimetres to several metres. Interpretation. The dominance of finer grain sizes sug- gests deposition in a low-energy environment. The assemblage of sedimentary structures is typical of a tidally influenced environment such as an estuary cen- tral basin or a lagoon with extensive tidal flats. Facies association 9: marsh and swamp (facies 19, 20) Description. Coals, mudstones and associated rooted het- eroliths are grouped in the marsh and swamp associa- tion. Mudstones and rooted heteroliths have a dark grey to black appearance, reflecting the high organic content (Fig. 9C, D). Both vitrinite-rich and inertinite- rich coals are present. Interpretation. The vitrinite-rich coals represent depo- sition in a waterlogged, anoxic mire environment. The 317 cm 0 10 20 30 40 50 60 70 80 90 I West Lulu-3 3689.5 m J West Lulu-3 3699.6 m K West Lulu-3 3702.2 m L West Lulu-3 3710.5 m SB inertinite-rich coals represent a somewhat drier envi- ronment, with periodically oxic conditions in a swamp or raised bog. Pyrite in some coal beds suggests the occa- sional influx of marine water. The evidence of marine influxes and the association of the coals and rooted sediments with lagoonal deposits suggest that deposi- tion took place in back-barrier swamps and marshes (Petersen & Andsbjerg 1996). Marine deposits Marine deposits dominate the Lulu Formation in the cen- tral parts of the Søgne Basin, but thin units can be traced into the mainly paralic deposits in the western part of the basin. The marine deposits are separated into three facies associations: offshore, prograding shoreface and beach, and transgressive shelf and shoreface. Facies association 10: offshore (facies 1, 2, 9) Description. The offshore association consists of up to 50 cm thick units of structureless and laminated mud- stone, and cm-scale interbedded, heterolithic mudstone and sandstone. The association frequently forms coarsen- ing-upwards units with structureless mudstone in the basal part overlain by heterolithic mudstone with silt- stone and sandstone laminae and beds that show an upwards increase in thickness, grading into the more sandy deposits of the shoreface association (Figs 11A, F, 12I). Laminae may be normally graded, and show par- allel lamination and wave and combined flow ripple lam- ination. The sandstone beds are commonly sharp-based. The sandstone-dominated upper part of coarsening- upwards units may grade into hummocky cross-strati- fied deposits of the prograding shoreface and beach association. Bioturbation in the offshore association varies from weak to intense, but mudstones are com- monly completely bioturbated with few remaining phys- ical structures. Anconichnus isp., Palaeophycus isp., Planolites isp. and Teichichnus isp. occur in the sand- stone beds. Interpretation. Mudstones with rare laminae of siltstone or sandstone indicate that deposition took place below storm wave base. The thorough bioturbation of the mudstones suggests they were deposited on a shelf with oxic bottom conditions. A higher content of silt- stone and sandstone laminae suggests the occasional 318 cm 0 10 20 30 40 50 60 70 80 90 A West Lulu-3 3643 m B West Lulu-3 3643.9 m C West Lulu-3 3645.6 m SB Fig. 7. Core photographs of selected intervals from the middle paralic wedge of the Lulu Formation (Cal-1B sequence) in West Lulu-3 (base lower right, top upper left; for location of core sections, see Fig. 18). This core series illustrates the nature of the Cal-1B sequence bound- ary (SB) at 3646 m (C) defined by the erosional base of an estuary channel (facies association 5) cutting into bay/lagoon mudstones (facies association 8). The chan- nel fill sandstones (A–C) show an overall fining-upwards trend and display cross-bedding, flaser lamination and abundant double mud drapes (example arrowed). 319 cm 0 10 20 30 40 50 60 70 80 90 A Lulita-1 4504.2 m B Amalie-1 5074 m C Amalie-1 5110 m D Amalie-1 5111 m E Amalie-1 5112 m F Amalie-1 5118 m SB Fig. 8. Core photographs of the incised valley-fill of the upper Bryne Formation (Cal-1A sequence). A: Erosional surface (SB) marking the base of the incised valley (Cal-1A SB) cuts into mottled floodplain mudstones (Bat-1B sequence; facies association 3) and is overlain by estuary channel sandstones (facies association 5) showing cross-bedding and mudstone clasts. Lulita-1; for location of core section, see Fig. 17. B–F: Estuary channel sandstones and heterolithic beds in Amalie-1 (base lower right, top upper left; for location of core sections, see Fig. 17). The large- scale cross-bedded sandstones (C, F) with abundant mud drapes and mud- stone clasts represent the lower fill of estuary channels (facies association 5). The intervening heterolithic beds (B–E) may represent tidal flats (facies associa- tion 8) or fluctuating energy levels in the upper fill of estuary channels (facies association 5). 320 cm 0 10 20 30 40 50 60 70 80 90 A West Lulu-3 3647.4 m B West Lulu-3 3648.2 m C West Lulu-3 3650.8 m D West Lulu-3 3651.7 m E West Lulu-3 3652.6 m F West Lulu-3 3653.5 m G West Lulu-3 3654.2 m Fig. 9. Core photographs of back-barrier deposits of the lower paralic wedge in the Lulu Formation (Cal-1A sequence) in West Lulu-3 (base lower right, top upper left; for location of core sections, see Fig. 18). The selected core sections illustrate lagoonal mudstones with sandstone interbeds (facies association 8) at the base (G–I), erosively overlain (wavy line, 3654.8 m) by a broadly coarsening-upwards sandstone unit (C–G) – climbing ripple cross-laminated sandstones being succeeded by cross-bedded sandstones with double mud drapes and rare burrows. This coarsening-upwards sandstone unit (facies asso- ciation 5) shows rootlets (arrowed) towards the top and is capped by a coal bed (C, D); it is succeeded by thoroughly bio- turbated sandstones (A, B; mainly Teichichnus isp.) representing the upper part of an estuary sand bar that immediately underlies bay/lagoonal deposits spanning the MFS of the Cal-1A sequence (not shown in core, see Fig. 18). 321 influence of oscillatory currents near storm wave base. Sharp-based sandstone laminae are interpreted as storm-sand deposits, and their finer-grained interbeds represent fair-weather sediments and sus- pension fall-out after storms. Deposition took place between storm wave base and fair-weather wave base. Facies association 11: prograding shoreface and beach (facies 3–8) Description. The prograding shoreface and beach association is rep- resented by up to 12 m thick coarsening-upwards successions of sandstone and subordinate siltstone. The coarsening-upwards suc- cessions consist of very fine-grained, hummocky cross-stratified (HCS) and swaley cross-stratified (SCS) sandstones with siltstone interbeds in the lower part, overlain by low angle cross-bedded fine- to medium-grained sandstones and trough and planar cross- bedded fine- to coarse-grained sandstones (Figs 11B–E, 12). Parallel- laminated, low-angle cross-bedded and massive fine- to coarse-grained sandstones and pebble conglomerates may occur at the top of the successions. The HCS- and SCS-dominated sandstones occur as sharp-based, laminated beds ranging between a few decimetres and a few metres in thickness, separated by centimetres to decimetres thick siltstone beds. Lamination may be gently undulating, and typ- ically intersect and truncate at low angles. Individual hummocky cross- stratified units may grade into wave-rippled heterolithic siltstone and sandstone. SCS sandstones typically occur as thicker amalga- mated units that lack the heterolithic sub-units and the silty interbeds. The cross-bedded sandstones occur in poorly defined sets, usually a few decimetres thick. Interpretation. The coarsening-upwards successions are interpreted as the deposits of prograding shelf, shoreface and shoreline systems. Minor, 2–4 m thick, coarsening-upwards units of typical shoreface deposits may represent wave-influenced mouth bars or ebb tidal deltas. The HCS-dominated units, commonly lowermost in the suc- cessions, were deposited by storm wave activity below fair-weather wave base in the offshore transition zone. The SCS deposits repre- sent more continuous wave activity on the lower shoreface, whereas the cross-bedded sandstones of the upper part of the succession rep- resent migrating dunes on the upper shoreface. The horizontally lam- inated and low-angle cross-bedded sandstones uppermost in the successions represent foreshore, beach and strandplain deposits. Facies association 12: transgressive shelf and shoreface (facies 9, 10) Description. Deposits of the transgressive shelf and shoreface asso- ciation consist of poorly sorted, bioturbated muddy sandstones, sandy siltstones and mudstones and heteroliths, poorly sorted pebbly cm 0 10 20 30 40 50 60 70 80 90 H West Lulu-3 3655.7 m I West Lulu-3 3656.6 m 322 cm 0 10 20 30 40 50 60 70 80 90 A West Lulu-2 3781.6 m B West Lulu-2 3782.5 m C West Lulu-2 3790 m D West Lulu-2 3798.4 m E West Lulu-2 3799.2 m SB 323 cm 0 10 20 30 40 50 60 70 80 90 F West Lulu-3 3617.4 m G West Lulu-3 3618.2 m H West Lulu-3 3619.1 m I West Lulu-3 3620 m Fig. 10. Core photographs of the upper paralic wedge in the uppermost Lulu Formation (Cal-1C sequence) illustrating the facies development during the final paralic pulse, prior to regional transgres- sion. A–E: Selected core sections from West Lulu-2 (base lower right, top upper left; for location of core sections, see Fig. 18). Lagoonal mudstones and heteroliths of the Cal-1B sequence (E) include the Cal-1B MFS which correlates distally with marine mudstones of the upper marine wedge (Figs 18, 19). The mudstones are abruptly overlain at 3799.5 m (SB, Cal-1C SB) by stacked estuary channel fills and bar deposits (B–D; facies association 5). These are capped by sandstones and conglomer- ates (A, B) deposited in a washover and ravinement complex (facies associations 6, 12) that represents the composite transgressive surface of marine erosion of the Cal-1C sequence. F–I: Selected core sections from West Lulu-3 (base lower right, top upper left; for location of core sections, see Fig. 18) illustrating a comparable evolution to that seen in West Lulu-2. Estuary channel and bar sandstones and heteroliths and lagoonal deposits (G–I) are succeeded by washover/ravinement sandstones and conglomerates (F, G). 324 cm 0 10 20 30 40 50 60 70 80 90 A Lulu-1 3594.5 m B Lulita-1 4443.5 m C Lulita-1 4444.4 m D Lulita-1 4445.5 m E Lulita-1 4446.3 m F Lulita-1 4447.2 m G Lulita-1 4448.4 m H Lulita-1 4449 m TS TS Fig. 11. Core photographs of marine shelf and shoreface deposits (facies associations 10, 11) from the lower marine wedge of the Lulu Formation (Cal-1A sequence) in the Lulu-1 and Lulita-1 wells, close to the basin axis. A: Core section from Lulu-1 (for location, see Fig. 19) illustrating the transgressive surface (TS) overlain by 10–20 cm of thoroughly bioturbated muddy sandstone; this is suc- ceeded by shelf mudstones (facies association 10), including the maximum flooding surface within the interval 3595.2–3594.9 m, grad- ing up into mud-rich heteroliths at the base of a coarsening-upwards prograding shoreface succession (not illustrated here, see Fig. 19). B–H: Selected core sections from Lulita-1 (base lower right, top upper left; for location of core sections, see Fig. 19) illustrating a coarsening-upwards prograding shoreface succession (facies association 11). The transgressive surface (TS) at the base (H), over- lying lagoonal mudstones, is draped by a thin (1 cm) sandstone, passing abruptly up into structureless shelf mudstones. Upwards, the mudstones are interbedded with discrete storm sandstone beds (G) and grade up via heterolithic facies showing HCS (E, F) to sandstones with HCS, SCS and cross-bedding (B–D). The maximum flooding surface occurs within the interval 4448–4447.7 m. sandstones, and conglomerates (Fig. 10A, F). The deposits are characterised by intense burrowing and a diverse ichnofauna (Fig. 11A). Interpretation. These sediments were deposited in a shoreface or shallow shelf environment during a trans- gression. Physical structures reflecting the high energy level on the upper shoreface were partly or completely obliterated by burrowing organisms under more tran- quil conditions. Architecture, depositional environments and sequence stratigraphy A regional unconformity subdivides the Bryne Formation into two separate parts described here as the lower and the upper Bryne Formation (Figs 3, 4); evidence sup- porting the recognition of this unconformity is pre- sented below. The architecture and depositional envir- onments of the lower and upper Bryne Formation and the Lulu Formation are described here, together with a sequence stratigraphic analysis of these units. Lower Bryne Formation Depositional architecture and environments The lower Bryne Formation consists of floodplain deposits separated by several storeys of channel sand- stones. The four most distinct channel units are referred to as units A, B1, B2 and C (Figs 3, 4). These channel sandstones can be identified in most wells and proba- bly form laterally continuous sandstone sheets. The lowermost strata of the Bryne Formation are either fine- grained floodplain deposits located below the lower- most channel sandstone (unit A; West Lulu-1, West Lulu-4) or channel sandstone unit A resting directly and unconformably on Triassic or Permian deposits (West Lulu-2, West Lulu-3; Fig. 4). In some wells, channel sandstone unit A is a 10–30 m thick multi-storey sandstone section of stacked, fining- upwards, 5–15 m thick sandstone units separated by mudstone beds, 1–2 m thick. In other wells, it is a sin- gle storey sandstone, 1–2 m thick (Fig. 4). The thick- ness variations may be related to pre-Middle Jurassic topographic relief. Cores are not available from this unit. The two channel sandstone units B1 and B2 are closely associated, usually with the base of B2 lying c. 10 m above the top of B1 (Fig. 4). In many wells, the gamma-ray logs of the combined unit B1–B2 show a characteristic fining-upwards – coarsening-upwards – fining-upwards pattern (e.g. Amalie-1, 5280–5260 m; West Lulu-4, 3768–3740 m; Fig. 4). Cores are available from unit B2 in the West Lulu-3 well (Figs 5, 13). Channel sandstone unit C is a fining-upwards 10 m thick channel unit recognised in most wells and cored in West Lulu-1, West Lulu-2 and West Lulu-4 (Figs 5, 14). Unit C consists of cross-bedded sandstone with abun- dant wood fragments and mud clasts (Fig. 5H–K) and an increasing number of clay drapes up-section, some of which are paired. The upper part of the channel unit is heterolithic with decimetre thick sand/mud couplets in West Lulu-2 and abundant clay drapes and mud flasers in West Lulu-1. The channel units show features that are character- istic of the deposits of sinuous channels. Most of the channel bodies have fining-upwards grain-size profiles above erosional bases, they appear to be laterally con- tinuous and regularly spaced mudstone laminae or beds may represent mud drapes on low-angle accretion sur- faces (Fig. 14). In addition to these features, the cores from sand sheets B2 and C show trough and planar cross- bedding, ripple cross-lamination and abundant defor- mation structures; the basal beds contain intraformational mudstone clasts and wood fragments. The presence of double mud drapes, abundant flaser bedding and decimetre thick sand/mud couplets in channel unit C may indicate that the channel system was influenced by tidal processes. The channel sands were deposited in laterally migrating, sinuous river channels on a coastal plain. The evidence of tidal influence in unit C suggests it may have been connected downstream to an estu- ary. The upwards increase in tidal influence in this suc- cession may indicate an overall rise in relative sea level. The laterally continuous channel sandstones are sep- arated by up to 50 m thick successions of interbedded mudstone and sandstone (Fig. 4). The fining-upwards segments of these successions may appear as an upwards continuation of underlying fining-upwards channel deposits. A mudstone that varies in thickness from a few decimetres to three metres is present at the turnaround point between the fining-upwards and the coarsening- upwards segments of the succession (Fig. 4). The sand- stones form 1–4 m thick units that may fine upwards or show no clear grain-size trends (Figs 13–15; Fig. 15 faces page 332). The sandstones of both the fining- upwards and coarsening- upwards segments of the suc- cession show a diverse assemblage of sedimentary structures including climbing ripple lamination, plane 325 326 cm 0 10 20 30 40 50 60 70 80 90 A West Lulu-1 3566.9 m B West Lulu-1 3567.7 m C West Lulu-1 3568.5 m D Lulu-1 3575.3 m E Lulu-1 3576.2 m F Lulita-1 4428.6 m TSME MFS 327 G Lulita-1 4431.9 m H Lulita-1 4432.9 m I Lulita-1 4433.8 m J Lulita-1 4434.7 m TSME Fig. 12. Core photographs of marine shelf and shoreface deposits (facies associations 10–12) from the upper marine wedge of the Lulu Formation (Cal-1B sequence). A–C: Sandstones and heteroliths from wave-influenced mouth bar or protected shoreface deposits in West Lulu-1 (base lower right, top upper left; for location of core sections, see Fig. 18). Note the pebble lag (facies association 12) at the transgressive surface of marine erosion (TSME), and the maximum flooding surface (MFS), c. 10 cm higher in the section. D, E: Wave-dominated shoreface deposits (facies association 11) in the Lulu-1 well showing coarsening-upwards sandstones dominated by SCS (base lower right, top upper left; for location of core sections, see Fig. 19). F–J: Selected cores from a succession of stacked shoreface para- sequences (facies associations 10, 11) in Lulita-1 (base lower right, top upper left; for location of core sections, see Fig. 19). The lower parasequence of heterolithic sandstones (I, J) showing HCS and wave ripple cross-lamination is truncated by a transgressive surface of marine erosion (TSME) and overlain by shelf mudstones (I) that include the maximum flooding surface within the interval 4434.4–4434.1 m. The mudstones grade up into the next prograding shoreface parasequence, comprising heteroliths and sandstones showing HCS and SCS (G, H). Core section F illustrates the well-sorted swaley cross-stratified sandstones that typically cap the shoreface parasequences. 328 Sedimentary/biogenic structures Erosional surface Parallel bedding/lamination Planar cross-bedding Trough cross-bedding Low-angle cross-bedding Hummocky cross-stratification Cross-lamination and climbing ripples Bimodal current-ripple lamination Wave ripples Flaser bedding Wavy bedding Lenticular and silt-streaked bedding Mudstone/coal chips Disturbed bedding Load structures Water escape structures Synaeresis cracks Bioturbation Rootlets 5 m ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 West Lulu-3 GR fluvial channel floodplain distal floodplain and lake Channel sand B2 Baj-1B SB Baj-1B MFS Cal-1A SB 3711 m 3730 3758 5A 5B 5C 5D 5E 5F ■ ■ ■ ■ ■ ■ SiClay Sand Gr Lithology Coal Claystone Siltstone Sandstone Depositional environments Floodplain Fluvial channels Key surfaces Sequence boundary (SB) Maximum flooding surface (MFS) Søgne Basin 10 km Fig. 13. Sedimentological core log and gamma-ray (GR) log of sequence Baj-1B in West Lulu-3. The channel sand B2 is located above the Baj-1B SB in the basal part of the illustrated section. The Baj-1B MFS is placed in the middle of the thick floodplain/lake succession above the channel sand B2. The positions of cores illustrated with photographs here are indicated on the sedimentological logs (e.g. 5A indicates core photograph in Fig. 5A). Depths of important surfaces, facies changes or core breaks are indicated (in metres below reference level). The accompanying sedimentological legend is also applicable to Figs 14–19. lamination and slump structures, as well as dispersed rip-up mud clasts, root traces and pedogenic mottling (Fig. 5). The deposits are interpreted as levees, consisting of proximal crevasse splays, small channel fills and small deltas, and more distally as lake, swamp and dis- tal crevasse splay deposits; these sediments are referred to the proximal floodplain association, the lake and distal floodplain association and the vegetated flood- plain association. Palynological evidence for marine conditions is scarce in these deposits in the Søgne Basin, although rare marine palynomorphs have been found in the succession separating units B2 and C in West Lulu- 3 indicating that short-lived marine incursions may have occurred. The succession between channel unit C and the Cal-1A SB includes both channel sandstones and flood- plain deposits (Fig. 4). The succession attains a thick- ness of 30 m in Lulita-1, 50 m in West Lulu-1, 60 m in Amalie-1 and 65 m in 3/7-4. Channel sandstones dom- inate the succession in the West Lulu-1 and 3/7-4 wells. Cross-bedding is less prominent in the channel sand- stones of this succession than in units B2 and C. Mudstone clasts and soft-sediment deformation are com- mon, and current ripple and climbing ripple lamination occur in the upper part of channel units (Fig. 5). Root horizons and pedogenic mottling are abundant in the more fine-grained deposits. Fine-grained sediments dominate the succession in the wells closest to the basin axis. In Lulita-1, a 14 m thick section of coals and organic-rich mudstones overlie the channel sandstones at the base of the succession (Fig. 15). Most distinctive among the fine-grained deposits is a 50 m succession of mudstones with thin sandstone and siltstone interbeds in Amalie-1. Due to the lack of dinoflagellate cysts from this unit, it is interpreted to represent a lacustrine envi- ronment. Sandy and silty interbeds represent lacustrine delta and lacustrine delta plain/distal floodplain deposits. The 14 m thick coal-bearing section in Lulita-1 repre- sents a swamp environment. A relatively deep lake existed in the southern and central part of the basin simultaneously with an active floodplain along the western margin. At least some of the channel sandstones in West Lulu-1 and 3/7-4 may represent distributaries of lacustrine deltas (Fig. 15). Although there is no palynological evidence for marine conditions, short-lived marine incursions of the coastal plain may occasionally have turned the lake into a brackish water lagoon or bay. Sequence stratigraphy Key surfaces The basinwide extent of both the erosional bases of major channel sandstones and the mudstones that are located at the turnaround points of the fining-upwards – coarsening-upwards successions between the sand- stones, suggests that they are not simply the result of autocyclic facies shifts but more likely resulted from regional base-level changes. Both channel base diastems and turnaround points can thus be seen as sequence stratigraphic key surfaces. Sequence boundaries in the lower Bryne Formation are defined by channel base diastems of the major, lat- erally extensive channel sandstones (Fig. 4). Although key surfaces such as the maximum flooding surface (MFS) and the transgressive surface (TS) do not extend landwards beyond the bay-line (Posamentier & Vail 1988), non-marine equivalents to the MFS are assumed to occur within widespread lacustrine and floodplain deposits. The presence of an equivalent to the MFS in this setting results from the influence of relative sea-level fluctuations on the groundwater level in the lower coastal plain. Surfaces that separate units of amalgamated, laterally extensive channel sandstones from significantly more fine-grained floodplain successions may represent a land- wards expression of marine flooding events. In addi- tion, growth of coal-forming peat due to a rise in the groundwater table and associated generation of new accommodation, may be the landwards expression of a marine flooding surface (Petersen & Andsbjerg 1996). Systems tracts In the lower Bryne Formation, the fluvial sand sheets fine upwards or occur as amalgamated sandstones with- out a visible grain-size trend (e.g. Baj-1A in 3/7-4). The laterally continuous fluvial sand sheets typically found above the sequence boundaries in the alluvial plain deposits represent the LST and the lower part of the TST (Figs 3, 4). They are comparable to the low accom- modation systems tract of Dreyer et al. (1995), and the amalgamated fluvial sand sheet of Shanley & McCabe (1991, 1993, 1994) and Olsen et al. (1995). Channel development was probably initiated during falling or static base level, but the lateral migration of channels during early base-level rise may have caused erosion of a significant proportion of the lowstand deposits. Thus, the channel sandstones may largely rep- resent the lower part of the TST. Extensive reworking of the floodplain by lateral channel migration during 329 5 m W es t Lu lu -1 G R W es t Lu lu -2 G R W es t Lu lu -4 2. 5 km 1. 8 km G R 36 68m 36 81 38 48 5G 5H 5I 5J 5K m 38 62 38 74 36 92 36 99 36 98 36 85 36 67 36 49m flu vi al c ha nn el s he et ve ge ta te d flo od pl ai n ve ge ta te d flo od pl ai n Ba t- 1B S B Ba t- 1A S B Ba t- 1A M FS C ha nn el s an d C C al -1 A S B C oa l C la ys to ne Si lts to ne Sa nd st on e Fl oo dp la in Fl uv ia l c ha nn el s Se qu en ce b ou nd ar y (S B) M ax im um fl oo di ng s ur fa ce ( M FS ) Li th ol og y D ep os iti on al e nv ir on m en ts K ey s ur fa ce s Si C la y Sa nd G r Si C la y Sa nd G r Si C la y Sa nd G r ■ ■ ■ ■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■■■ ■■ A m al ie -1 3/ 7- 4 Lu lit a- 1 Lu lu -1 W es t Lu lu 13 2 4 ■■ ■■ ■■ Sø gn e Ba si n 10 k m Fi g. 1 4. L o g p an el ( G R a n d c o re l o gs ) o f se q u en ce s B at -1 A a n d B at -1 B i n W es t Lu lu -4 , W es t Lu lu -2 a n d W es t Lu lu -1 . T h e ch an n el s an d st o n e u n it C w h ic h r ep re se n ts a la te ra lly e xt en si ve f lu vi al c h an n el s an d i s lo ca te d a b o ve B at -1 A S B a t th e b as e o f th e se ct io n ; th e B at -1 A M FS r ep re se n ts a b an d o n m en t o f th e ch an n el s ys te m . T h e se c- tio n i s d ee p ly i n ci se d b y th e C al -1 A S B , in te rp re te d a s th e b as e o f an i n ci se d v al le y. T h e p o si tio n s o f co re s ill u st ra te d w ith p h o to gr ap h s h er e ar e in d ic at ed o n t h e se d - im en to lo gi ca l lo gs ( e. g. 5 K in d ic at es c o re p h o to gr ap h i n F ig . 5K ). D ep th s o f im p o rt an t su rf ac es , fa ci es c h an ge s o r co re b re ak s ar e in d ic at ed ( in m et re s b el o w r ef er en ce le ve l) . Fo r fu ll le ge n d , se e Fi g. 1 3; i n se t m ap s h o w s th e lo ca tio n o f th e tr an se ct r u n n in g SW –N E . 330 periods of lowstand and early base-level rise may have effectively prevented floodplain aggradation (Wright & Marriott 1993). The overbank-dominated deposits between the top of the channel sandstone sheets and the MFS, consti- tuting the upper part of the TST, are organised into a fining-upwards succession with a gradually decreasing sand/shale ratio. Mudstones of mainly lacustrine origin become increasingly common upwards. Soil profiles and root horizons are common (Fig. 5G, H, L). The overall fining-upwards trend and accompanying decreasing sandstone/mudstone ratio are interpreted to reflect a sea-level rise that caused a rising watertable and wetter conditions on the coastal plain. The increas- ing rate of creation of accommodation during rising base level favoured high levels of storage of floodplain sediments and more isolated channel bodies (Shanley & McCabe 1993; Wright & Marriott 1993). The transgres- sive floodplain deposits are equivalent to the heterolithic unit with isolated fluvial sandbodies of Olsen et al. (1995) and the lower part of the high accommodation systems tract of Dreyer et al. (1995). The floodplain highstand deposits are separated from the floodplain transgressive deposits by a MFS. The MFS is picked in a mudstone bed that is typically organic- rich and can be correlated through most or all the wells in the study area. The highstand floodplain deposits are a coarsening-upwards succession that shows an increase upwards in sandstone/mudstone ratio and sand bed thickness. The lacustrine and distal floodplain mud- stones are interbedded with siltstones and sandstones that were deposited as levee deposits, crevasse splays and crevasse deltas. Channel sandstones are less com- mon than in the transgressive floodplain deposits. The coarsening-upwards succession of proximal floodplain deposits developed as a result of decreasing rates of base-level rise and accommodation space generation. Similar successions in non-marine settings have been referred to the highstand systems tract by Shanley & McCabe (1991, 1993), as highstand depositional sys- tems by Wright & Marriott (1993) and as the uppermost heterolithic interval by Olsen et al. (1995). Sequences of the lower Bryne Formation The Bryne Formation consists of seven sequences of alluvial plain or fluvially-dominated coastal plain deposits. The Aalen-1, Baj-1 and Bat-1 regional se- quences of Andsbjerg & Dybkjær (2003, this volume) are subdivided here into the Aalen-1A, Aalen-1B, Baj-1A, Baj-1B, Bat-1A and Bat-1B sequences. The uppermost part of the Bryne Formation is included in the Cal-1A sequence (see below) that also includes sediments referred to the Lulu Formation (Fig. 4). Aalen-1A sequence. The deposits located between the base Middle Jurassic unconformity and the first intra- Middle Jurassic sequence boundary (SB Aalen-1B) are referred to the Aalen-1A sequence. Due to onlap of the pre-Middle Jurassic subcrop the Aalen-1A sequence is only seen in wells that penetrate the deepest parts of the Middle Jurassic. Aalen-1B sequence. Channel sandstone unit A is referred to the LST/TST of sequence Aalen-1B. Most of the flood- plain deposits separating channel sandstone units A and B1 form the HST of Aalen-1B. Baj-1A sequence. Channel unit B1 and the coarsening- upwards unit of floodplain deposits between B1 and B2 form sequence Baj-1A. Baj-1B sequence. This sequence is made up of chan- nel sandstone unit B2 and the fining-upwards – coarsen- ing-upwards succession of floodplain deposits separating unit B2 from unit C. Bat-1A sequence. In most wells, channel sandstone unit C forms the LST/TST of sequence Bat-1A. The HST is a unit of coarsening-upwards floodplain deposits. Bat-1B sequence. The Bat-1B sequence is not present in the westernmost wells where it has been removed by erosion at the Cal-1A SB. Where present, it consists of channel sandstones above the SB and a fining- upwards – coarsening-upwards succession of flood- plain and lacustrine deposits (Fig. 15). Recognition of the intra-Bryne regional unconformity In the Middle Jurassic succession, a number of units and surfaces can be readily correlated across the Søgne Basin. In most of the Bryne Formation, sequence bound- aries and maximum flooding surfaces are important correlatable key surfaces that are recognisable on both well logs and core logs. The maximum flooding sur- faces occur within the mudstone-dominated floodplain deposits between the main channel storeys, being defined by the turnaround point between intervals with increasing-upwards and decreasing-upwards gamma-ray 331 readings (Fig. 4). In the Lulu Formation (see below), the best markers are coal beds, which are easily recog- nisable on sonic logs and possibly represent ‘initial flooding surfaces’. Other surfaces that prove useful for correlation are maximum flooding surfaces (MFS) in the more marine intervals and channel-base diastems in the paralic successions (Fig. 4). Well-to-well correlation of the coal beds in the Lulu Formation suggests a sub-parallel arrangement, i.e. that thickness variations are insignificant. These markers are, however, discordant with the marker surfaces in the lower Bryne Formation (Fig. 4). The thickness of the succession between the Bat-1A MFS, which is the uppermost key surface of the Bryne Formation that is easily recognisable in almost all wells of the Søgne Basin, and the lowermost coal of the Lulu Formation varies from 12 m in West Lulu-4 to 110 m in 3/7-4 and 100 m in Amalie-1. This asymmetry may have resulted both from a higher rate of accommodation space gen- eration in the eastern part of the basin due to faulting at the eastern boundary fault and from erosion in the western part of the basin. The boundary between the succession with markers that parallel the Lulu Formation coal beds and the succession with the non-parallel markers seems to be the Cal-1A SB which is a distinct erosion surface at the base of the stacked channel sand- stones that dominate much of the upper Bryne Formation. Below this sequence boundary (Cal-1A SB), a succes- sion that includes two key surfaces (Bat-1B SB and Bat-1B MFS) can be recognised in the West Lulu-1, 3/7-4, Lulita-1, Lulu-1 and Amalie-1 wells. This suc- cession is missing from the wells in which the stacked channel sandstones above Cal-1A SB show their largest thickness (West Lulu-2, West Lulu-3), suggesting that the missing section is due to erosion at the Cal-1A SB and not to up-dip condensation (Figs 4, 15). However, in West Lulu-4, which is located furthest up-dip of the studied wells, the section between the Cal-1A SB and the Bat-1A MFS is thin although no significant erosion surface is recognised below the lowermost coal of the Lulu Formation. This may suggest that the section in this well is condensed rather than missing (Figs 4, 16; Fig. 16 follows page 332). The basinwide extent of the Cal-1A SB erosion surface and the variable but often significant amount of section that seems to have been erosionally removed suggests that the surface is an unconformity with significant relief. The stepwise increase over a relatively short distance of the thickness of the stacked channel sandstones between Cal-A SB and the lowermost coal in the Lulu Formation and the commonly associated increase in the amount of miss- ing section below Cal-1A SB suggest that the uncon- formity represents the basal surface of an incised valley. The base of the lowermost coal in the Lulu Formation is the first surface above the unconformity that can be correlated to all wells. In West Lulu-4, an interfluve sur- face is inferred within the 10 m thick succession of floodplain deposits that separate the lowermost coal of the Lulu Formation from the Bat-1A MFS. The occurrence of the dinoflagellate cyst Impleto- sphaeridium varispinosum in the basal part of the val- ley-fill in West Lulu-1 and West Lulu-3 suggests a Late Bathonian – Early Callovian age for the unconformity. This is supported by the presence of the LOD of Quadraeculina anelliformis in the same interval. Upper Bryne and Lulu Formations Depositional architecture and environments of the upper Bryne Formation The upper Bryne Formation consists of the sediments between the regional unconformity (Cal-1A SB) and the first thick coal seam at the base of the Lulu Formation (Figs 4, 16). The regional unconformity is interpreted to form the base of a system of incised valleys in the Søgne Basin. The southern margin of an E–W-trending valley is inferred to be situated between West Lulu-4 and West Lulu-2 (Fig. 1). The valley axis is interpreted to be close to the wells showing the thickest valley-fills, i.e. West Lulu-3 and Lulita-1. The position of the north- ern valley margin is not known due to lack of well data. Work on incised valleys from the Carboniferous of the North Sea area shows that valley-fills with a max- imum thickness of 30–40 m as seen in the upper Bryne Formation, usually correspond to a valley width of at least 5–6 km (Hampson et al. 1999). In the wells penetrating the more proximal parts of the valley (West Lulu-1, West Lulu-2, West Lulu-3), mas- sive channel sandstones are present throughout the succession from the basal unconformity to the overly- ing coal seam (Fig. 16). In wells further to the east and to the south, heterolithic and muddy deposits dominate the upper part of the succession. This is most pro- nounced in Amalie-1, which is inferred to penetrate a different valley branch, where 12 m of mudstones and heteroliths are located between the uppermost sand- stone body and the coal (Fig. 17, following page 332). The channel sands in the proximal wells occur as two to three storeys of amalgamated and stacked channel 332 sandstones separated by fine-grained deposits. Each sandstone storey commonly consists of an amalgamated sandstone unit without a distinct grain-size trend although poorly defined fining-upwards trends may occur (e.g. top upper channel storey of West Lulu-3; Fig. 16). The storeys vary in thickness from approxi- mately 5 m to 18 m (e.g. West Lulu-3). The valley-fill is a compound fill (Zaitlin et al. 1994), deposited during several minor base-level cycles. It contains significant erosion surfaces in addition to the principal sequence boundary at the base of the incised valley and one or two flooding surfaces on top of the channel storeys. A conglomerate of intraformational mudstone clasts, up to 60 cm thick, may be present at the base of the lowermost channel sandstone (the basal unconformity, Cal-1A SB; Figs 6L, 16). Most sandstones of this suc- cession belong to facies association 5, being characterised by trough and possibly planar cross-bedding, abundant coal and mudstone clasts on foresets and bed bound- aries, double mud laminae, flaser bedding and rare bimodal cross-lamination (Figs 6C–H, 16). They are interpreted as estuary channel and bar deposits. Bio- turbated organic-rich sandy mudstones that separate the upper and middle sandstone storeys in West Lulu-3 rep- resent lagoonal deposits that developed during a flood- ing event (Figs 6I, 16). Most sandstones show some degree of tidal influence, as exemplified by the lower- most and uppermost channel storeys of West Lulu-1 (Fig. 16). They are interpreted as the fill of tidal chan- nels, deposited mainly as point bars in major estuary channels (see comparable features in Fenies & Faugères 1998, fig. 8). The middle channel storey of West Lulu-3 is an example of a sandstone unit that lacks clear evi- dence of tidal conditions and may represent a fluvial deposit (Fig. 16). The lowermost sandstone bed (1 m thick) in West Lulu-2 also shows no evidence of tidal conditions, and may represent a preserved lowstand flu- vial deposit (Fig. 16). In the 3/7-4 and Lulu-1 wells, in the northern and cen- tral part of the study area, the sandstone units are thin- ner, typically 2–5 m thick (Fig. 17); they are separated by mudstone-dominated units 2–6 m thick (Fig. 17). Sandstone units and heteroliths may show a fining- upwards pattern, but coarsening-upwards units also occur. Sandstones show trough cross-bedding, wavy, flaser and lenticular bedding, bi-directional ripple cross- lamination and double mud drapes indicating a tidal environment (Fig. 8A). Some beds are highly altered by soft sediment deformation and locally by pedogenesis. A few thin coal beds with associated root horizons that occur within the succession suggest periods with veg- etation cover. The fining-upwards units represent minor tidal channels. Sand-dominated coarsening-upwards units may have been deposited as bay-head or tidal deltas, or as tidal channel bars. Heterolithic coarsening- upwards beds may represent tidal flat deposits. The combination of an overall tidal setting involving dom- inantly fine-grained or heterolithic sediments, with only minor channel sandstones as seen in 3/7-4, is indica- tive of deposition in the outer or marginal part of an estuary (Dalrymple et al. 1992). The Lulita-1 well dis- plays thicker sand units than in the 3/7-4 well, but thin- ner and slightly more fine-grained than in West Lulu-3; this suggests that Lulita-1 was situated close to the chan- nel-dominated axial part of the estuary but downstream from the West Lulu wells. In the southernmost part of the basin (Amalie-1), the lower 30 m of the succession is dominated by up to 12 m thick sandstone units that fine upwards or show no visible grain-size trend (Fig. 17). Although locally structureless with only faint trough cross-bedding, these sandstones commonly show trough cross-bedding, with foresets outlined by mud drapes, or ripple cross-lami- nation and grade up into heterolithic beds with flaser, wavy and lenticular bedding (Fig. 8C–F). Mudstone flakes are abundant in some sandstone beds; water- escape structures are also common in places. The upper- most 11 m of the succession mainly consist of fine- grained heteroliths and mudstone (Fig. 8B). Amalie-1 is located approximately 12 km south of the inferred valley axis trending from West Lulu-3 to Lulita-1 so that Amalie-1 is thought to penetrate the valley-fill deposits of a separate, N–S-trending valley. The occurrence of fine-grained heterolithic deposits in the upper part of the succession in the wells to the east and south-east may indicate an up-dip shift of facies due to a relative sea-level rise, with tidal flat and lagoonal facies becoming dominant in the lower reaches of the valley. However, this may also have resulted from an autocyclic shift of facies in an outer estuary envi- ronment, where widespread tidal flats bordered tidal channels. It is also possible that the shift to fine-grained sedimentation represents a change to deposition uncon- fined by valley walls when infill was complete in the lower reaches of the incised valleys. Depositional architecture and environments of the Lulu Formation Viewed in an east–west transect across the western and central parts of the Søgne Basin, the Lulu Formation 333 consists of three eastwards-thinning wedges of mainly paralic deposits and two westwards-thinning wedges of shallow marine and coastal deposits (Figs 3, 18, 19, 20B; Figs 18, 19 follow page 332). At the top of the Lulu Formation is a transgressive unit of shallow marine and coastal deposits, a few metres thick. Two regionally extensive coal seams/coal zones can be traced across the basin; one separates the Lulu Formation from the Bryne Formation and the other divides the Lulu Formation into a lower and an upper part of almost equal thickness (Fig. 20B). Coals The basal coal seam, locally split into several thinner seams, is up to 5 m thick in the Søgne Basin. Petersen & Andsbjerg (1996) have described this basal coal from West Lulu-2 as seams R1 and T2, which record a rela- tively dry peat-forming environment below (R1) suc- ceeded by a waterlogged peat-forming environment above (T2). The coal seam is a single, almost struc- tureless coal bed in West Lulu-1 and 3/7-4 but is rep- resented by two or three distinct coal beds in West Lulu-2, West Lulu-3 and West Lulu-4 and by a zone of interbedded thin coals and lagoon and marsh sediments in Lulu-1 and Amalie-1. The upper coal seam divides the Lulu Formation into a lower and an upper part of almost equal thickness (Figs 18, 19). This seam is located in the middle wedge of the three eastwards-thinning paralic wedges and can be correlated throughout the study area. It occurs as a single 0.2–0.4 m thick coal bed in the central and southern part of the Søgne Basin, and as two coal beds (max. 2 m thick) in the western- most wells. Paralic wedges The three paralic wedges thin from the west towards the east. Excluding the lower coal zone, the lower par- alic wedge is 11–13 m thick in the West Lulu-1, West Lulu-2 and West Lulu-3 wells (Fig. 18), 7 m thick in 3/7-4 and 1–3 m thick in the Lulita-1, Lulu-1 and Amalie-1 wells (Fig. 19). It is bounded below by the top of the lower coal seam/coal zone and above by a distinct flooding surface that separates it from deposits of the lower marine wedge. In the western part of the basin, the geometry of the middle paralic wedge is poorly constrained. The marine flooding surface that separates the middle paralic wedge from the upper marine wedge can be placed at two alter- native positions in the West Lulu-3 well – at a gamma- ray pick in an uncored section at 3639 m and at a wave- influenced heterolithic sandstone bed at 3626 m (Fig. 18). The latter interpretation implies an even more dramatic westwards-thickening of the middle paralic wedge than that seen for the lower paralic wedge. The former is preferred here, i.e. the flooding surface is placed at approximately the same level, above the upper regional coal marker, as in West Lulu-1 (Fig. 18). In West Lulu-2 and West Lulu-3, the lower boundary of the wedge is a channel-base diastem (Cal-1B SB). In all other wells, the boundary is picked at the top of the beach deposits that terminate the coarsening-upwards marine succes- sion of the lower marine wedge. The thickness of the wedge in the westernmost wells is 3 m in West Lulu-1, 6 m in West Lulu-2 and 10 m in West Lulu-3. In 3/7-4, Lulita-1, Lulu-1 and Amalie-1, the wedge has a con- stant thickness of approximately 2 m. The upper paralic wedge attains a thickness of 20 m in West Lulu-3, 21 m in West Lulu-2, 8 m in 3/7-4, and 3–6 m in Lulita-1, Lulu-1 and Amalie-1. Much of the wedge is assumed to have been removed by faulting in West Lulu-1. The lower boundary is a distinct chan- nel-base diastem (Cal-1C SB) in the West Lulu-2 well but is located at the shift from the shoreface and fore- shore deposits of the upper marine wedge to the over- lying strandplain and back-barrier deposits in the wells further to the east. In West Lulu-3 and West Lulu-1, the boundary has been placed at the erosional base of a coarsening-upwards sandstone unit interpreted as tidal bar or mouth bar deposits of a prograding bay-head delta, sitting below the Cal-1C SB. The upper bound- ary is the final marine flooding surface below the tran- sition to the offshore mudstones of the Lola Formation. This surface is placed at the base of a 1.5 m thick trans- gressive sandstone bed in 3/7-4, and in West Lulu-2 and West Lulu-3 at the base of a transgressive con- glomerate/pebbly sandstone unit. In the West Lulu-2 well, the paralic wedges are dom- inated by up to 10 m thick storeys of stacked sandstone units that fine upwards or show no grain-size trends. In the West Lulu-1 and West Lulu-3 wells, the paralic wedges are characterised either by coarsening-upwards mudstone–sandstone successions or by sandstones showing no clear overall grain-size trends. Both coarsen- ing-upwards and fining-upwards sandstones occur in 3/7-4. The sandstones show trough cross-bedding, cur- rent ripple cross-lamination and double mud drapes. Climbing ripple cross-lamination and bioturbation (abun- dant Teichichnus isp. burrows, less common Planolites isp. and Skolithos isp.; Fig. 9A, B) occur frequently in the coarsening-upwards units and the units showing no 334 grain-size trends. Flaser bedding, soft-sediment defor- mation structures and beds with abundant coal and mudstone clasts are characteristic of the fining-upwards sandstone units. Heterolithic intervals show wavy and lenticular bedding. The coarsening-upwards succes- sions are interpreted as tidal bar deposits or mouth bar deposits of prograding bay-head deltas. The sandstone units that fine upwards or show no grain-size trends rep- resent the fill of major estuary channels. Minor fining- upwards sandstone beds within, and typically near the top of, coarsening-upwards successions, may represent bay-head delta distributary channels. In both 3/7-4 and Lulita-1, the c. 1 m thick sandstone- dominated lower part of the upper paralic wedge con- sists of a succession of parallel-laminated and low-angle cross-bedded sandstones interpreted as strandplain deposits. This is overlain by a heterolithic unit, up to 2.5 m thick, showing flaser, wavy, and lenticular bed- ding deposited in a low-energy estuary or lagoon envi- ronment. In 3/7-4, the heterolithic succession is abruptly overlain by a 3 m thick unit of stacked sandstones with coal and mud clasts, which fines upwards into an organic-rich, heterolithic mudstone with abundant roots, and finally a coal bed. These sandstones are interpreted as the fill of a minor distributary channel. In the Lulu-1 and Amalie-1 wells, located in the cen- tral and southern part of the basin, the lower paralic wedge is represented solely by coals with interbedded clastic sediments of the lower coal zone. Paralic deposits above the coals have been reworked and incorporated in the lower marine wedge during transgression. The middle and upper paralic wedges consist of 1–1.5 m of poorly sorted, structureless sandstone with abundant coal debris and root traces; the sandstone may show irreg- ular ripple cross-lamination. These deposits are inter- preted as mainly strandplain deposits. The upper coal seam/coal zone is situated within the middle paralic wedge. The occurrence of minor coal beds and root hori- zons indicates periods with vegetation cover and peat accumulation. Marine depositional wedges The two marine wedges both thin towards the west. The lower marine wedge attains a thickness of 7.5–11.5 m in the Lulita-1, Lulu-1 and Amalie-1 wells, c. 3 m in 3/7-4 and West Lulu-1, and only about 1 m (preserved thick- ness) in West Lulu-2 and West Lulu-3 (Figs 18, 19). The upper marine wedge is approximately 10 m thick in the Lulita-1, Lulu-1 and Amalie-1 wells and attains a thick- ness of 6 m in 3/7-4 and 5 m in West Lulu-1. In West Lulu-3 and West Lulu-2, it is represented by an approx- imately 1 m thick mudstone bed. In both Lulu-1 and Amalie-1, the basal part of the lower marine wedge consists of an erosionally based, fining-upwards silty sandstone unit, 40–60 cm thick. The sandstone becomes increasingly heterolithic or muddy upwards, but primary structures have been oblit- erated by pervasive bioturbation (Fig. 11A). The sand- stone is interpreted as a transgressive shelf deposit. It is overlain by a unit of shelf mudstones that varies in thickness from about 0.5 m in Lulu-1 to approximately 11 m in Amalie-1, where it shows a coarsening-upwards trend. Above the mudstone unit in Lulu-1, Lulita-1 and Amalie-1 is an 8–12 m thick, coarsening-upwards suc- cession. The basal part of the coarsening-upwards suc- cession consists of mudstone–sandstone heteroliths, showing lenticular and parallel bedding/lamination and wave ripple cross-lamination in sand laminae. It is over- lain by sand-dominated heteroliths with abundant hum- mocky cross-stratification, sandstones with low-angle and swaley cross-stratification and trough cross-bedding, and uppermost by parallel bedded and low-angle cross- bedded sandstone (Figs 11A–F, 19). This represents a progradational succession from offshore transition to lower shoreface sediments overlain by upper shoreface and beach deposits. The wave-dominated sediments of the lower marine wedge can be traced to the west in West Lulu-1 and 3/7-4 as a unit up to 4.5 m thick. In West Lulu-1, a peb- ble veneer interpreted as a wave ravinement lag defines the base of the wedge. This is succeeded by a 0.5 m thick unit of hummocky cross-stratified and wave-rip- pled sandstone overlain by a thin mudstone and a 3 m thick coarsening-upwards sandstone unit dominated by swaley cross-stratification and low-angle cross-bed- ding with abundant Teichichnus isp. burrows. In the 3/7-4 well, the base of the wedge is picked at a flood- ing surface below which the uppermost paralic deposits are strongly bioturbated. The deposits of the marine wedge form several 0.5–2.5 m thick, coarsening-upwards sandstone units showing wave ripple lamination, low- angle cross-bedding and hummocky and swaley cross- stratification. Teichichnus isp. burrows are common. In both West Lulu-1 and 3/7-4, this succession is inter- preted as a condensed shoreface or a wave-influenced mouth bar. In West Lulu-2 and West Lulu-3, the west- ernmost correlative of the lower marine wedge consists of a few metres of mudstone. Thorough bioturbation with abundant Teichichnus isp. burrows in the top of the underlying paralic deposits indicates that a marine or brackish flooding event preceded deposition of the 335 mudstone. Erosion at the Cal-1B SB has removed all shal- low marine or coastal deposits of the lower marine wedge that may have overlain the mudstone. In the upper marine wedge, the shoreface succession in Lulita-1 and Lulu-1 is represented by three stacked, 1.2–4 m thick, coarsening-upwards parasequences sep- arated from each other by minor flooding surfaces. Further to the north in 3/7-4, the 10 m thick upper marine wedge has a similar architecture with three para- sequences (2 m, 2 m, 6 m) separated by distinct flood- ing surfaces. Each parasequence consists of a basal unit of heterolithic sandstones and mudstones that coarsens upwards to sandstones dominated by wave-generated structures, suggesting a shoreface origin (Fig. 12D–J). In 3/7-4, the facies assemblage indicates deposition in a mixed wave- and tide-dominated environment, pos- sibly a tidally influenced mouth-bar or an ebb tidal delta. In West Lulu-1, the upper marine wedge consists of a 3.5 m thick coarsening-upwards unit (Fig. 12A–C). It comprises heterolithic siltstone and sandstone show- ing parallel lamination, wave ripple lamination, lentic- ular bedding, and hummocky cross-stratification, and sandstone showing low-angle cross-bedding and pos- sibly swaley cross-stratification. Both in West Lulu-1 and 3/7-4, Teichichnus isp. and Diplocraterion isp. bur- rows are common. The abrupt upwards termination of the wedge in West Lulu-1 may be caused by a normal fault. The succession in West Lulu-1 represents a wave- dominated environment, interpreted as a progradational shoreface deposited in an area with limited accommo- dation, or a wave-influenced mouth bar. Final transgressive deposits The channel and estuarine bar sandstones of the upper paralic wedge are erosionally overlain by an up to 4 m thick unit consisting of sandstones and pebble con- glomerates. The base of this unit is commonly outlined by a pebble veneer draping an erosion surface. In West Lulu-3, this unit includes several erosionally-based beds, up to 10 cm thick, of graded clast-supported pebble con- glomerate (Fig. 10F). Interbedded with the conglomerates are beds of well-sorted sandstone and pebbly and gran- ule-rich sandstone. In 3/7-4, this part of the succession is represented by a 1.5 m thick heterolithic sandstone dominated by wave ripple lamination and wavy- and lenticular bedding. The erosional surface that lies at the base of the con- glomerates in West Lulu-2 and West Lulu-3 and sepa- rates the tidally influenced sandstones from the overlying fine-grained marine sediments in Lulu-1 and 3/7-4, is interpreted as a transgressive surface of marine erosion (TSME) or ravinement surface. The coarse-grained sed- iments above the ravinement surface in West Lulu-2 and -3 were deposited as beach and shoreface deposits during transgression (Bourgeois & Leithold 1984). Sediments of that grain size are rare in the underlying succession, and they are therefore interpreted as the result of storm-wave reworking of coarse fluvial sedi- ments supplied to the near-shore zone. The graded pebbly sandstones sandwiched between the conglom- erates and the overlying marine mudstones in West Lulu-2 (Fig. 10A, B) represent rapid deposition of sed- iment eroded by waves breaking on the shoreface (Bourgeois & Leithold 1984). Sequence stratigraphy of the upper Bryne Formation and the Lulu Formation Key surfaces Within the mainly estuarine deposits of the upper Bryne Formation, flooding surfaces (FS) separate stacked chan- nel sandstones from overlying lagoonal or marine mud- stones. Channel-base diastems that can be correlated throughout the incised valleys possibly represent sequence boundaries of higher order sequences although no attempt has been made to subdivide that part of the succession further. In tidally dominated paralic units in the Lulu Formation, sequence boundaries are defined by channel-base dia- stems (Fig. 18). In marine intervals, the sequence bound- aries occur as indistinct surfaces that separate beach deposits from overlying strandplain deposits (Fig. 19). In the wells located in the central and southern parts of the study area, the basal sequence boundaries of the Cal-1B and the Cal-1C sequences are placed immedi- ately above the beach deposits that form the top of the prograding shoreface successions (Fig. 19). The shift from beach deposits to the overlying laterally extensive coal- bearing or rooted beds indicates a basinwards shift of facies. In 3/7-4, the Cal-1B SB (3460 m) is identified at the base of a rooted sandstone bed sitting on top of the condensed shoreface or mouth bar succession that comprises the HST of Cal-1A; in this well, the Cal-1C SB is placed at the base of a rooted channel sandstone (3449 m). In West Lulu-1, the Cal-1B SB is represented by a bed of pebbly sandstone (core rubble) at 3572 m. In the West Lulu-2 and West Lulu-3 wells, the Lulu Formation is dominated by stacked channel sandstones; the sequence boundaries of the Cal-1B and Cal-1C sequences are placed at the base of coarse-grained 336 channel sandstones in these wells. The Cal-1B SB cuts into lagoonal mudstones in West Lulu-3 (Fig. 7C) and the Cal-1C SB cuts into lagoonal mudstones in West Lulu-2 (Fig. 10E; 3799 m). These lagoonal mudstones may include the Cal-1A and Cal-1B maximum flooding surfaces although these surfaces may have been trun- cated by the channel base diastem. The Cal-1B SB is located at the base of a thin sandstone at 3808 m in West Lulu-2; the Cal-1C SB is picked at the erosional base of a channel sandstone unit in West Lulu-3 at 3625 m. A marine flooding surface subdivides this sequence (Cal-1C) into a lower unit dominated by paralic sand- stones (uppermost Lulu Formation) and a mudstone- dominated upper unit (lowermost Lola Formation). In some wells, a transgressive surface of marine erosion (ravinement surface) can be seen immediately below the flooding surface. An erosion surface that separates shelf mudstones and shoreface transition heteroliths from overlying shoreface sandstones is interpreted as a regressive surface of marine erosion (RSME); it is located at 3582 metres in Lulu-1, 4433 metres in Lulita-1, 3457 metres in 3/7-4 metres and at 3565 metres in West Lulu-1 (Figs 18, 19). The shoreface sandstones above the RSME are referred to the falling stage systems tract (FSST). Systems tracts In the valley-fill deposits that constitute the upper Bryne Formation, LST-deposits of the Cal-1A sequence, if pre- sent, are to be found among the massive channel sand- stones that dominate the valley-fill. However, most of these channel sandstones show clear evidence for tidal processes, and are referred to the TST, recording an increase in the rate of relative sea-level rise. During the lowest sea-level stand, incised valleys acted as conduits for sediment by-pass, and much of the fluvial sediment deposited within the valley may have been eroded and shed further basinwards. A preserved fluvial sandstone bed, 1 m thick, at the base of the valley-fill succession in West Lulu-2 may represent the LST of the Cal-1A sequence (Fig. 16). In the Cal-1B and Cal-1C sequences, channel deposits directly overlying the sequence bound- aries in the West Lulu-2 and West Lulu-3 wells show evi- dence of strong tidal influence (Figs 7A, B, C, 10D). The thin sedimentary section between the Cal-1B SB and the overlying coal in the wells further east does not show any diagnostic sedimentary structures. A typical TST in the upper Bryne and Lulu Formations in the West Lulu area consists of a lower succession dom- inated by tidally influenced fluvial channel and estuary channel sandstones, some of which may have been deposited in an incised valley, and an upper succes- sion of outer estuary and lagoonal deposits. In the wells closer to the basin axis, estuary channel deposits are only important constituents of the TST when located in an incised valley. Otherwise, the TST in this area is dominated by outer estuary, marine bay, and trans- gressive shoreface and shelf deposits; a ravinement sur- face or transgressive surface of marine erosion (TSME) normally separates the lower estuarine part of the TST from transgressive shoreface deposits. The uppermost succession of the TST normally wedges out in a basin- wards direction. The TST is bounded above by the maximum flooding surface (MFS) represented by shelf or lagoonal mudstones. In the marine successions, the HST is a coarsening- upwards succession of shelf, shoreface and beach deposits. The HST wedges out in a landwards direc- tion where the succession consists of bay-head and tidal delta deposits overlying lagoonal or bay mud- stones reflecting a rapid, progradational infilling of estu- aries or bays. The HST is truncated above by a sequence boundary or in some cases by a regressive surface of marine erosion (RSME). Truncation at the Cal-1B SB causes the Cal-1A HST to be absent from West Lulu-2 and West Lulu-3. Similarly, the Cal-1B HST is missing in West Lulu-2 due to erosion at the Cal-1C SB (Fig. 18). A significant erosional break within the coarsening- upwards succession of regressive shoreface deposits in the Cal-1B sequence in Lulu-1 and Lulita-1 suggests that the upper shoreface and foreshore deposits above the break were deposited during a fall in relative sea level, which caused wave erosion of the already deposited lower shoreface and shelf sediments (Plint 1988). The deposits between the erosional break (RSME) and the next sequence boundary are referred to the falling stage systems tract (FSST). The FSST consists of coarsening-upwards shoreface, estuary mouth, fore- shore and beach deposits; their formation and preser- vation was dependent on the balance between sea-level change and subsidence. In addition to their occurrence in Lulu-1 and Lulita-1, regressive shoreface deposits may possibly be referred to a Cal-1B FSST in the West Lulu-1 and 3/7-4 wells (Figs 3, 19). Sequences of the upper Bryne and Lulu Formations The three sequences Cal-1A, Cal-1B and Cal-1C cover the uppermost part of the Bryne Formation, the Lulu Formation and the lowermost part of the Upper Jurassic Lola Formation (Fig. 20). 337 338 Cal-1C SB Cal-1B SB Cal-1A SB Cal-1C Cal-1B Cal-1A estuary channels estuary channels transgressive shoreface mouth bar deposits incised valley fill prograding shoreface A B Cal-1A SB Bat-1B SB Bat-1A SB Baj-1B MFS Baj-1B SB Aalen-1B SB Aalen-1A SB floodplain floodplain floodplain Channel sand C Channel sand B2 lacustrine deposits Channel sand B1 Channel sand A West East Depositional environments Floodplain Fluvial channels Lacustrine Mires, swamps Lagoon and tidal flats Estuary and tidal channels, bay-head deltas Shoreface, mouth bars and washovers Marine shelf Key surfaces Sequence boundary (SB) Maximum flooding surface (MFS) Fig. 20. Schematic representation of the sequence stratigraphy and stacking patterns of the lower Bryne Formation (A) and the upper Bryne Formation and Lulu Formation (B). Possible LST deposits and the lower TST of Cal-1A are represented by incised valley-fill deposits, referred to the upper Bryne Formation (Figs 16, 17). The remain- der of the Cal-1A sequence is made up of the lower paralic wedge and the main part of the lower marine wedge; these are assigned to the upper part of the TST and the HST (Figs 18, 19). In the Cal-1B sequence, possible LST deposits and most of the TST are represented by the middle paralic wedge; the upper marine wedge is assigned to the uppermost part of the TST, the HST and the FSST. The upper paralic wedge is referred to the LST(?) and the lower part of the TST of Cal-1C. The remainder of the Cal-1C sequence occurs within the lowermost Lola Formation, where the HST is represented by a progra- dational unit of shallow marine, strongly bioturbated mudstone and silty sandstone. Depositional history and palaeogeography Aalenian(?) – Late Bathonian Between the Aalenian/Early Bajocian and the Middle/ Late Bathonian, when base level was low, the study area was dominated by an alluvial plain with laterally migrat- ing, sinuous rivers that swept most of the floodplain (Fig. 21A). The presence of stacked, amalgamated channel sandstones in the West Lulu-1 and 3/7-4 wells in the vicinity of the Lulu salt structure and its northwards extension suggest that this area, in particular, was favoured by channels. Deposition took place on a coastal plain, where the upstream effects of tidal processes were occasionally felt in the river channels. Recurrent periods of rising base level resulted in the abandonment of the large river channels. The area changed into a wet floodplain environment dominated by ponds and minor channels. At the time of maximum flooding, extensive lakes occupied the axial part of the basin and other topographic lows (Fig. 21B). Brackish or fully marine waters may have entered the basin on occasion to form shallow bays or lagoons, particularly in the southern part of the Danish Central Graben. Regional drainage was from the north to the south where marine conditions existed in the Dutch part of the Central Graben until the Early Bathonian (van Adrichem Boogaert & Kouwe 1993; Hengreen et al. 2003, this volume). During periods with a decreasing rate of base-level rise, lacustrine deltas and crevasse splays filled in the lakes and lagoons, and a depositional environment dominated by laterally migrating rivers was re-established. During the Bathonian, more peren- nial lakes may have existed in the southern part of the Søgne Basin, while swamps developed in the northern and the central part of the basin. Late Bathonian – Callovian During formation of the base Cal-1A SB, major incised valleys were cut both at the western fringe of the Søgne Basin and in the south-eastern part of the basin close to the basin axis (Amalie-1; Fig. 21C). Late Bathonian – earliest Callovian datings have been obtained from the lower part of the incised valley-fill. Broad estuaries developed in the lower reaches of the incised valleys during relative sea-level rise. Deposition took place mainly in major channels in the more proximal parts of the valleys, and in outer estuary environments char- acterised by tidal flats, minor tidal channels and flood tidal deltas closer to the basin centre (Fig. 21C). Locally, a final phase of valley-fill is evident, characterised by fine-grained sediments deposited in tidal flat and lagoonal environments (e.g. Amalie-1; Figs 17, 22B). The general increase upwards in tidal influence and pre- served thickness of channel storeys seen in many val- ley-fill deposits suggests that deposition took place during rising sea level. Once the incised valleys were completely filled, sed- imentation was no longer laterally confined (Fig. 22). The estuary environment was replaced by a low-energy lower coastal plain, which was dominated by extensive coal-forming mires and swamps that extended over both the infilled valleys and the former interfluve areas. Mire aggradation resulted in thick coal-generating peat deposits in the western part of the Søgne Basin, whereas coastal swamps caused the formation of thin coals and coaly mudstones in the central and southern parts of the basin. The resulting coal seam records a stepwise increase in marine influence with time, as a continu- ously waterlogged environment with occasional sea- water incursions succeeded a relatively dry peat-forming environment (Petersen & Andsbjerg 1996). The growth of extensive peat-forming mires and swamps ended as a result of the combined effects of continued sea-level rise, causing transgression in the north-east, and clastic influx from up-dip sources in the west. Deposition of shelf mud began in the central part of the Søgne Basin following transgression, while a lagoonal/estuarine environment was established in the western part of the basin (Fig. 23A). Continued 339 340 Amalie-1 W. Lulu-3 W. Lulu-1 Lulu-1 Lulita-1 Lulita-1 W. Lulu-4 3/7-4 W. Lulu-2 Amalie-1 W. Lulu-3 W. Lulu-1 Lulu-1 W. Lulu-4 3/7-4 W. Lulu-2 Major lake Lacustrine deltas10 km 10 km 10 km Alluvial plain with river and ox-bow lake Floodplain and lacustrine delta Lake N N N 3/7-4 W. Lulu-3 W. Lulu-1 W. Lulu-2 Lulu-1 Amalie-1 W. Lulu-4 Estuary Interfluvial coastal plain Terrace Estuary with marsh and sandbar Coastal plain with river Lulita-1 A C B Incised valley Tidally influenced river Incised valley Fig. 21. A: Palaeogeographic map for the lower Bryne Formation (Aalenian – Late Bathonian). When regional base level was low, laterally migrating sinuous rivers dominated the floodplain. The absence of the lowermost Bryne Formation in the Lulu-1 well is attributed to uplift related to the underlying salt dome, forming a weak positive feature in the Aalenian – Early Bathonian. B: Palaeogeographic map for the upper levels of the lower Bryne Formation (Bathonian), depicting the high base-level scenario involving distal floodplain, lake and lacustrine delta depositional systems. The lake may have been influenced by marine incursions with the development of brackish bay/lagoonal conditions. Note that this palaeogeographic scenario is also applicable, in general, to times of high base level in the Aalenian – Early Bathonian although the detailed distribution of environments will have been modified by the Lulu-1 positive feature. C: Palaeogeographic map for the upper Bryne Formation (Late Bathonian – earliest Callovian). Major incised valleys with estuary channels and tidally influenced river channels repre- senting the LST and lowermost TST of the Cal-1A sequence. 341 interfluve estuary in incised valley estuary channel bars Early valley fill – LST/lower TST interfluve estuary in incised valley lagoon marsh A drowned estuary Late valley fill – lower TSTB Lower Bryne Fm Lower Bryne Fm Fig. 22. Block diagram showing the inferred palaeogeography during deposition of the uppermost Bryne Formation. Deep incision, creating the Cal-1A sequence boundary, resulted in two incised valley systems, the confluence of which is depicted here. The W–E transverse system, draining the hangingwall slope, is encountered particularly in the West Lulu wells whereas the rift-axial system, trending S–N parallel with the main boundary fault, is represented by the Amalie-1 section (Fig. 21C). In their lower reaches, as depicted here, the valleys were estuarine in nature and were progressively drowned; this evolutionary phase is recorded in the lower TST of the Cal-1A sequence. transgression towards the west and south caused rework- ing of coastal and back-barrier deposits, while a pro- gressively thicker succession of back-barrier deposits was preserved below the transgressive surface of marine erosion. The overall transgression of the Søgne Basin was interrupted on at least two occasions by regressive phases caused by periods of relative sea-level fall or still- stand. Each regressive phase began with prograding bay-head deltas infilling lagoons and estuaries in the western parts of the area. When infilling of lagoons and estuaries was complete, sediment began to bypass the coastal zone and was supplied to the shoreface. Shoreface sediments prograded into the deeper parts of the basin forming a wedge of shallow marine and coastal deposits (Fig. 23B). If the regressive phase was associated with a sea-level fall, the decreasing accom- modation caused increased wave scour on the inner shelf, and rapid progradation of the shoreface. A thin sheet of strandplain sediments deposited behind the pro- grading coastline is indicative of the completion of infill- ing. Thin extensive coal deposits that overlie the strand- plain deposits indicate a shift from regression to renewed transgression. During the final transgression of the area, probably in the Late Callovian, the top of the coastal plain deposits was eroded by wave action resulting in the formation of a ravinement surface. The rapid transition from par- alic sediments to offshore mudstones and siltstones indicates a rapid transgression across a low-gradient 342 Shelf and shoreface Barrier bar and tidal inlet Amalie-1 W. Lulu-3 W. Lulu-1 Lulu-1 Lulita-1 Lulita-1 W. Lulu-4 3/7-4 W. Lulu-2 Coastal plain 3/7-4 W. Lulu-4 Amalie-1 Lulu-1 Tidal inlet 10 km 10 km Beach and shoreface Strand plain and delta Shoreface transition and shelf RiverMarsh and lagoon Coastal plain with river and bay-head delta N N W. Lulu-3 W. Lulu-1 W. Lulu-2 A B Fig. 23. A: Palaeogeographic map for the Lulu Formation (Callovian) depicting transgressive shoreface, barrier coast and coastal plain settings, a scenario recorded by the upper TST of sequences Cal-1A and Cal-1B. B: Palaeogeographic map for the Lulu Formation (Callovian). This scenario, involving progradational shoreface, beach ridge plain and alluvial plain settings, is inferred from the HST/FRST of sequences Cal-1A and Cal-1B. coastal plain. Sediment sources were effectively removed from the vicinity of the study area. Deposition of par- alic and shallow marine sandstones of the Bryne Formation was terminated when the basin entered the rift climax phase. Sediment supply was no longer suf- ficient to keep pace with the increased rate of subsi- dence, and deposition of the Lola Formation shelf mudstones took over. Discussion The Middle Jurassic deposits of the Danish Central Graben form part of a major system of alluvial plain, coastal plain, delta plain and shallow marine deposits that extends over large tracts of the North Sea area. During the earliest Middle Jurassic, large-scale regional uplift, the ‘North Sea doming event’ and the subsequent dome collapse affected a large part of this area (Whiteman et al. 1975; Eynon 1981; Ziegler 1990; Underhill & Partington 1993). The pre-Middle Jurassic deposits in the Danish Central Graben are cut by a major unconformity that separates the Middle Jurassic succession from the Lower Jurassic Fjerritslev Formation in the southern and central part of the Danish Central Graben and from Triassic and Permian rocks in the Søgne Basin (Andsbjerg et al. 2001). In contrast to the Middle Jurassic in much of the North Sea area, fully marine deposits have not been found in the pre-Callovian of the Søgne Basin. In the northern Viking Graben, the lower part of the Brent Group is dominantly marine. In both the Cleveland Basin of eastern England and in the Norwegian–Danish Basin, marine deposits are well-represented in the lower part of the Middle Jurassic succession. In the Danish Central Graben, thin mudstones that yield dinoflagel- late cysts occur in the lower part of the Middle Jurassic succession more than 50 km south of the Søgne Basin (Andsbjerg 1997). Further south in the Dutch part of the Central Graben, the Aalenian – Lower Bathonian suc- cession comprises marine mudstones of the Werkendam Formation (van Adrichem Boogaert & Kouwe 1993; Herngreen et al. 2003, this volume). In the northern part of the Central Graben (Gatliff et al. 1994) and in the Moray Firth (MacLennan & Trewin 1989), Middle Jurassic deposits older than the Bathonian or latest Bajocian seem to be absent, probably due to their location near an early Middle Jurassic uplift centre. The occurrence of marine lower Middle Jurassic deposits in the southern part of the Central Graben simultaneously with non-marine deposits in the Søgne Basin and the possible absence of lowermost Middle Jurassic rocks in the northern Central Graben suggest that regional drainage patterns within the Central Graben was from the north towards the south, being strongly influenced by uplift patterns. In the late Middle Jurassic, the appearance of marine deposits in the Søgne Basin simultaneously with non- marine deposition to the south and south-west sug- gests a significant change in regional slope and drainage patterns. During the Callovian, drainage in the Danish Central Graben was from the west and south-west, down newly developed hangingwall slopes, and possibly from uplifted areas in the southernmost part of the North Sea. Most of the Middle Jurassic succession was deposited during the early stages of rift-related subsidence in the Søgne Basin. At some stratigraphic levels, sediments and facies patterns show an asymmetric distribution across the basin. Between the fluvial sand sheets, lacus- trine and distal floodplain deposits tend to dominate in the wells of the central and southern part of the basin closest to the main boundary fault whereas proximal floodplain deposits are dominant in the western part of the basin (Fig. 20B). The available well data do not suggest a preferred positioning of fluvial channels close to the main boundary fault, but a tendency to amalga- mation and thickening of channel sands is seen in the wells near the Lulu salt structure and its northwards extension. In a relatively arid environment, fluvial chan- nel sands parallel to the basin axis would show a ten- dency to cluster near the main boundary fault (Alexander & Leeder 1987; Leeder & Gawthorpe 1987). That this is not the case in the Søgne Basin may be explained by a setting on a coastal plain with a high groundwater level resulting in the development of lakes and wet floodplain environments in the deep parts of the basin as a response to subsidence at the main boundary fault. Under such conditions, during periods of active subsi- dence, transverse fluvial systems would be located on the hangingwall slope draining into the axial lakes (Alexander & Leeder 1987; Leeder & Gawthorpe 1987). Only during periods of tectonic quiescence could large, longitudinal fluvial systems develop after lake-infilling was complete. In the paralic to shallow marine succession in the upper part of the Middle Jurassic section, depositional units show a spatial partitioning such that paralic sed- iments dominate towards the west, deposited mainly during rising sea level, and offshore–shoreface sedi- ments dominate towards the east, deposited during highstand and possibly early fall in sea level. Such land- wards partitioning of paralic deposits during trans- 343 gression and seawards partitioning during highstands has been described previously by Ravnås & Steel (1998) and is analogous to the ‘reciprocal’ style of sedimenta- tion described from the Gallup Sandstone of New Mexico by Nummedal & Molenaar (1995). Coal beds that were deposited on a low-gradient coastal plain, are overlain by paralic deposits of the TST that show a progressive increase in thickness towards the west or up-dip on the hangingwall slope (Fig. 20B). In contrast, coastal and shallow marine deposits of the HST and FSST overly- ing the paralic paralic wedge thicken towards the east or down-dip on the hangingwall slope. The TSME, or in some places the MFS, that separates the two wedges, thus shows a significantly higher gradient than the coal below the paralic wedge. The widespread thick coals at the base of the succession indicate initial conditions characterised by a low gradient and negligible sedi- ment input. A transgression in that setting would be expected to be a rapid, low-angle non-accretionary transgression (Helland-Hansen & Martinsen 1996). However, the angular difference between the coals (the original depositional surface) and the transgressive shoreline trajectory represented by the TSME and the MFS above the preserved wedge of paralic transgres- sive deposits is suggestive of a change in slope before or during the early phases of transgression. Thus an accretionary transgression took place, possibly after an initial phase of low-angle non-accretionary transgres- sion (Helland-Hansen & Martinsen 1996; Fig. 20B). The westwards-thickening wedge of paralic sediments that formed during transgression left eastwards-increasing accommodation space unfilled at the time of maximum flooding. This accommodation space was filled by pro- grading mainly shallow marine deposits during the sub- sequent highstand or possibly the falling stage, resulting in the reciprocal distribution pattern of westwards-thick- ening TST deposits and eastwards-thickening HST/FSST deposits (Fig. 20B). The nature of the sediment partitioning and the occur- rence of an aggradational transgression rather than a low-angle non-aggradational transgression on the hang- ingwall slope, as may be expected from the initial con- ditions, can be explained by tectonic influence. Fault- induced tilting of the original depositional surface would have caused a slower transgression of a steeper slope and a concentration of the available volume of sediment within a narrower, but thicker on-lapping sediment prism. Thick back-barrier deposits accumulated below the ravinement surface or TSME, while a sheet of trans- gressive shelf sands was shed seawards. After infill of the remaining accommodation space with HST/FSST deposits, re-establishment of coal-forming mires and swamps indicates a new tectonically quiescent phase. Thus periods characterised by tectonic quiescence and slow uniform subsidence alternated with episodes of faulting at the main boundary fault, when the hang- ingwall slope was re-established and the newly cre- ated accommodation space was filled. However, com- paction of thick peat may also have favoured the preferential preservation of transgressive deposits in the western part of the Søgne Basin where the thick- est coals are found. Similar relationships have been described by Ravnås & Steel (1998) from the Middle Jurassic Tarbert Formation in the northern North Sea. These workers described how the destruction of shore- line barriers by steep-trajectory transgression resulted in sediment being partitioned landwards and seawards. Both the overall, gradual change from alluvial plain or fluvially dominated coastal plain deposits in the lower part to dominantly tidal and shallow marine deposits in the upper part of the Middle Jurassic suc- cession and the backstepping stacking pattern of the uppermost three sequences indicate that not only punc- tuated rift-related subsidence but also a large-scale eustatic sea-level rise or regional subsidence partici- pated in the creation of accommodation space. The important sequence boundary at the base of the Cal-1A sequence, which formed in late Bathonian or earliest Callovian times, cuts deeply into deposits both on the upper hangingwall slope and in basinal locations close to the main boundary fault. This sequence boundary can be traced into the southern part of the Danish Central Graben (Michelsen et al. 2003, this volume, fig. 36). This supports the suggestion that a regional fall in relative sea level rather than local rift-related tectonics is respon- sible for the formation of that sequence boundary. As a result of the tectonic influence on sedimenta- tion in the latter part of the Middle Jurassic, both estu- arine and shoreface depositional systems, which may both contain important reservoir rocks, show a sys- tematic distribution pattern that is related to the half- graben geometry of the basin and therefore potentially predictable. Shore and shoreface sandstones of the HST and FSST in the uppermost sequences occur as strike- parallel laterally extensive sheet sandstones. They can be correlated with negligible changes in thickness, grain size and facies for at least 15 km in the Danish Søgne Basin. In contrast, thick estuarine channel deposits of the TST in the uppermost sequences mainly occur in dip-parallel incised valleys. 344 Acknowledgements This study formed part of a Ph.D. undertaken at Copenhagen University. I am grateful to my supervisor Finn Surlyk for his thorough constructive critisism, which contributed significantly to the improvement of this paper, to reviewers Jan Alexander and Guy Plint for their helpful comments and to Jon Ineson for thorough editing. The work was supported by EFP-92 grant no. 1313/92-0002 from the Danish Energy Agency and by Mærsk Oil and Gas A/S and Norsk Hydro Udforskning A/S. I had fruitful discussions with colleagues Karen Dybkjær, Jon R. Ineson, Peter Johannessen and Lars H. Nielsen. Karen Dybkjær and Niels Poulsen kindly sup- plied me with palynological datings. References Alexander, J. & Gawthorpe, R.L. 1993: The complex nature of a Jurassic multi-storey alluvial sandstone body, Whitby, North Yorkshire. In: North, C.P. & Prosser, D.J. (eds): Characterization of fluvial and aeolian reservoirs. Geological Society Special Publication (London) 73, 123–142. Alexander, J. & Leeder, M.R. 1987: Active tectonic control on allu- vial architecture. In: Ethridge, F.G., Flores, R.M. & Harvey, M.D. (eds): Recent developments in fluvial sedimentology. Society of Economic Paleontologists and Mineralogists Special Publication 39, 243–252. Andsbjerg, J. 1997: Sedimentology and sequence stratigraphy of Middle Jurassic deposits, Danish and Norwegian Central Graben, 165 pp. Unpublished Ph.D. thesis, University of Copenhagen, Denmark. Andsbjerg, J. & Dybkjær, K. 2003: Sequence stratigraphy of the Jurassic of the Danish Central Graben. In: Ineson, J.R. & Surlyk, F. (eds): The Jurassic of Denmark and Greenland. Geological Survey of Denmark and Greenland Bulletin 1, 265–300 (this volume). Andsbjerg, J., Nielsen, L.H., Johannessen, P.N. & Dybkjær, K. 2001: Divergent development of two neighbouring basins fol- lowing the Jurassic North Sea doming event: the Danish Central Graben and the Norwegian–Danish Basin. In: Martinsen, O.J. & Dreyer, T. (eds): Sedimentary environments offshore Norway – Palaeozoic to Recent. Norwegian Petroleum Society (NPF) Special Publication 10, 175–197. Bourgeois, J. & Leithold, E.L. 1984: Wave-worked conglomerates – depositional processes and criteria for recognition. In: Koster, E.H. & Steel, R.J. (eds): Sedimentology of gravel and con- glomerates. Canadian Society of Petroleum Geologists Memoir 10, 331–343. Cartwright, J. 1991: The kinematic evolution of the Coffee Soil Fault. In: Roberts, A.M., Yielding, G. & Freeman, B. (eds): The geometry of normal faults. Geological Society Special Publication (London) 56, 29–40. Cloetingh, S. 1988: Intraplate stresses: a new element in basin analysis. In: Kleinspehn, K.L. & Paola, C. (eds): New per- spectives in basin analysis, 205–230. New York: Springer Verlag. Dalrymple, R.W., Zaitlin B.A. & Boyd, R.A. 1992: Estuarine facies models: conceptual basis and stratigraphic implications. Journal of Sedimentary Petrology 62, 1130–1146. Damtoft, K., Nielsen, L.H., Johannessen, P.N., Thomsen, E. & Andersen, P.R. 1992: Hydrocarbon plays of the Danish Central Trough. In: Spencer, A.M. (ed.): Generation, accumulation and production of Europe’s hydrocarbons II. European Association of Petroleum Geoscientists Special Publication 2, 35–58. Dreyer, T., Martinsen, O.J. & Ryseth, A.E. 1995: Sequence strati- graphic analysis of alluvial successions: outcrop examples and subsurface applications. In: Predictive high-resolution strati- graphy, Norwegian Petroleum Society (NPF), Stavanger, Norway, 6–8 November, 1995. Abstracts, 11 only. Eynon, G. 1981: Basin development and sedimentation in the Middle Jurassic of the northern North Sea. In: Illing, L.V. & Hobson, G.D. (eds): Petroleum geology of the continental shelf of North-West Europe: proceedings of the 2nd confer- ence, 196–204. London: Heyden & Son Ltd. Fenies, H. & Faugères, J.-C. 1998: Facies and geometry of tidal channel-fill deposits (Arcachon Lagoon, SW France). Marine Geology 150, 131–148. Fenies, H. & Tastet, J.-P. 1998: Facies and architecture of an estu- arine tidal bar (the Trompeloup bar, Gironde estuary, SW France). Marine Geology 150, 149–169. Frandsen, N. 1986: Middle Jurassic deltaic and coastal deposits in the Lulu-1 well of the Danish Central Trough. Danmarks Geologiske Undersøgelse Serie A 9, 23 pp. Gatliff, R.W. et al. 1994: United Kingdom offshore regional report: the geology of the central North Sea, 110 pp. London: Her Majesty’s Stationery Office for the British Geological Survey. Gowers, M.B. & Sæbøe, A. 1985: On the structural evolution of the Central Trough in the Norwegian and Danish sectors of the North Sea. Marine and Petroleum Geology 2, 298–318. Gradstein, F.M., Agterberg, F.P., Ogg, J.G., Hardenbol, J., van Veen, P., Thierry, J. & Huang, Z. 1994: A Mesozoic time scale. Journal of Geophysical Research 99, 24051–24074. Graue, E., Helland-Hansen, W., Johnsen, J., Lømo, L., Nøttvedt, A., Rønning, K., Ryseth, A. & Steel, R. 1987: Advance and retreat of Brent delta system, Norwegian North Sea. In: Brooks, J. & Glennie, K.W. (eds): Petroleum geology of North West Europe, 915–937. London: Graham & Trotman. Guion, P.D., Fulton, I.M. & Jones, N.S. 1995: Sedimentary facies of the coal-bearing Westphalian A and B of the Wales – Brabant High. In: Whateley, M.K.G. & Spears, D.A. (eds): European coal geology. Geological Society Special Publication (London) 82, 45–78. Hallam, A. 1988: A reevaluation of Jurassic eustacy in the light of new data and the revised Exxon curve. In: Wilgus, C.K. et al. (eds): Sea-level changes – an integrated approach. Society of Economic Paleontologists and Mineralogists Special Publication 42, 261–273. Hampson, G.J., Davies, S.J., Elliott, T., Flint, S.S. & Stollhofen, H. 1999: Incised valley fill sandstone bodies in Upper Car- boniferous fluvio-deltaic strata: recognition and reservoir char- 345 acterization of southern North Sea analogues. In: Fleet, A.J. & Boldy, S.A.R. (eds): Petroleum geology of Northwest Europe: proceedings of the 5th conference, 771–788. London: Geological Society. Hancock, N.J. & Fisher, M.J. 1981: Middle Jurassic North Sea deltas with particular reference to Yorkshire. In: Illing, L.V. & Hobson, G.D. (eds): Petroleum geology of the continental shelf of North-West Europe: proceedings of the 2nd confer- ence, 186–195. London: Heyden & Son Ltd. Helland-Hansen, W. & Martinsen, O.J. 1996: Shoreline trajecto- ries and sequences: description of variable depositional-dip scenarios. Journal of Sedimentary Research 66, 670–688. Herngreen, G.F.W., Kouwe, W.F.P. & Wong, T.E. 2003: The Jurassic of the Netherlands. In: Ineson, J.R. & Surlyk, F. (eds): The Jurassic of Denmark and Greenland. Geological Survey of Denmark and Greenland Bulletin 1, 217–229 (this volume). Hunt, D. & Tucker, M.E. 1992: Stranded parasequences and the forced regressive wedge systems tract: deposition during base- level fall. Sedimentary Geology 81, 1–9. Hunt, D. & Tucker, M.E. 1995: Stranded parasequences and the forced regressive wedge systems tract: deposition during base- level fall – reply. Sedimentary Geology 95, 147–160. Japsen, P., Britze, P. & Andersen, C. 2003: Upper Jurassic – Lower Cretaceous of the Danish Central Graben: structural framework and nomenclature. In: Ineson, J.R. & Surlyk, F. (eds): The Jurassic of Denmark and Greenland. Geological Survey of Denmark and Greenland Bulletin 1, 233–246 (this volume). Jensen, T.F., Holm, L., Frandsen, N. & Michelsen, O. 1986: Jurassic – Lower Cretaceous lithostratigraphic nomenclature for the Danish Central Trough. Danmarks Geologiske Undersøgelse Serie A 12, 65 pp. Johannessen, P.N. & Andsbjerg, J. 1993: Middle to Late Jurassic basin evolution and sandstone reservoir distribution in the Danish Central Trough. In: Parker, J.R. (ed.): Petroleum geol- ogy of Northwest Europe: proceedings of the 4th conference, 271–283. London: Geological Society. Koch, J.-O. 1983: Sedimentology of Middle and Upper Jurassic sandstone reservoirs of Denmark. In: Kaasschieter, J.P.H. & Reijers, T.J.A. (eds): Petroleum geology of the southeastern North Sea and the adjacent onshore areas. Geologie en Mijnbouw 62, 115–129. Korstgaard, J.A., Lerche, I., Mogensen, T.E. & Thomsen, R.O. 1993: Salt and fault interactions in the northeastern Danish Central Graben: observations and inferences. Bulletin of the Geological Society of Denmark 40, 197–255. Leeder, M.R. & Gawthorpe, R.L. 1987: Sedimentary models for extensional tilt-block/half-graben basins. In: Coward, M.P., Dewey, J.F. & Hancock, P.L. (eds): Continental extensional tec- tonics. Geological Society Special Publication (London) 28, 139–152. MacLennan, A.M. & Trewin, N.H. 1989: Palaeoenvironments of the late Bathonian – mid-Callovian in the Inner Moray Firth. In: Batten, D.J. & Keen, M.C. (eds): Northwest European micropalaeontology and palynology, 92–117. British Micro- palaeontological Society Series. Chichester: Ellis Horwood. Miall, A.D. 1997: The geology of stratigraphic sequences, 433 pp. Berlin: Springer Verlag. Michelsen, O., Mogensen, T.E. & Korstgaard, J.A. 1992: Pre- Cretaceous structural development of the Danish Central Trough and its implications for the distribution of Jurassic sands. In: Larsen, R.M. et al. (eds): Structural and tectonic modelling and its application to petroleum geology. Norwegian Petroleum Society (NPF) Special Publication 1, 495–506. Michelsen, O., Nielsen, L.H., Johannessen, P.N., Andsbjerg, J. & Surlyk, F. 2003: Jurassic lithostratigraphy and stratigraphic development onshore and offshore Denmark. In: Ineson, J.R. & Surlyk, F. (eds): The Jurassic of Denmark and Greenland. Geological Survey of Denmark and Greenland Bulletin 1, 147–216 (this volume). Mogensen, T.E., Korstgaard, J.A. & Geil, K. 1992: Salt tectonics and faulting in the NE Danish Central Graben. In: Spencer, A.M. (ed.): Generation, accumulation and production of Europe’s hydrocarbons II. European Association of Petroleum Geoscientists Special Publication 2, 163–173. Møller, J.J. 1986: Seismic structural mapping of the Middle and Upper Jurassic in the Danish Central Trough. Danmarks Geologiske Undersøgelse Serie A 13, 37 pp. NAM & RGD 1980: Stratigraphic nomenclature of the Netherlands. Verhandelingen van het Koninklijk Nederlands Geologischen Mijnbouwkundig Genootschap 32, 77 pp. (Nederlandse Aardolie Maatschappij & Rijks Geologische Dienst). Nichol, S.L. & Boyd, R. 1993: Morphostratigraphy and facies archi- tecture of sandy barriers along the eastern shore of Nova Scotia. Marine Geology 114, 59–80. Nielsen, L.H. 2003: Late Triassic – Jurassic development of the Danish Basin and the Fennoscandian Border Zone, southern Scandinavia. In: Ineson, J.R. & Surlyk, F. (eds): The Jurassic of Denmark and Greenland. Geological Survey of Denmark and Greenland Bulletin 1, 459–526 (this volume). Nummedal, D. & Molenaar, C.M. 1995: Sequence stratigraphy of ramp-setting strand-plain successions: the Gallup Sandstone, New Mexico. In: Van Wagoner, J.C. & Bertram, G.T. (eds): Sequence stratigraphy of foreland basin deposits – outcrop and subsurface examples from the Cretaceous of North America. American Association of Petroleum Geologists Memoir 64, 277–310. Olsen, T., Steel, R.J., Høgseth, K., Skar, T. & Røe, S-L. 1995: Se- quence architecture in a fluvial succession: sequence strati- graphy in the Upper Cretaceous Mesaverde Group, Price Canyon, Utah. Journal of Sedimentary Research 65, 265–280. Petersen, H.I. & Andsbjerg, J. 1996: Organic facies development within Middle Jurassic coal seams, Danish Central Graben, and evidence for relative sea-level control on peat accumu- lation in a coastal plain environment. Sedimentary Geology 106, 259–277. Plint, A.G. 1988: Sharp-based shoreface sequences and ‘offshore bars’ in the Cardium Formation of Alberta: their relationship to relative changes in sea level. In: Wilgus, C.K. et al. (eds): Sea-level changes – an integrated approach. Society of Eco- nomic Paleontologists and Mineralogists Special Publication 42, 357–370. Posamentier, H.W. & Vail, P.R. 1988: Eustatic controls on clastic deposition II – sequence and systems tract models. In: Wilgus, C.K. et al. (eds): Sea-level changes – an integrated approach. Society of Economic Paleontologists and Mineralogists Special Publication 42, 125–154. 346 Posamentier, H.W., Jervey, M.T. & Vail, P.R. 1988: Eustatic con- trols on clastic deposition I – conceptual framework. In: Wilgus, C.K. et al. (eds): Sea-level changes – an integrated approach. Society of Economic Paleontologists and Mineralogists Special Publication 42, 109–124. Posamentier, H.W., Allen, G.P., James, D.P. & Tesson, M. 1992: Forced regressions in a sequence stratigraphic framework: concepts, examples, and exploration significance. American Association of Petroleum Geologists Bulletin 76, 1687–1709. Ravnås, R. & Steel, R.J. 1998: Architecture of marine rift-basin suc- cessions. American Association of Petroleum Geologists Bulletin 82, 110–146. Rawson, P.F. & Wright, J.K. 1995: Jurassic of the Cleveland Basin, North Yorkshire. In: Taylor, P.D. (ed.): Field geology of the British Jurassic, 173–208. London: Geological Society. Reineck, H.E. & Wunderlich, F. 1968: Classification and origin of flaser and lenticular bedding. Sedimentology 11, 99–104. Schwartz, R.K. 1982: Bedform and stratification characteristics of some modern small-scale washover sand bodies. Sedimentology 29, 835–849. Shanley, K.W. & McCabe, P.J. 1991: Predicting facies architecture through sequence stratigraphy – an example from the Kaiparowits Plateau, Utah. Geology 19, 742–745. Shanley, K.W. & McCabe, P.J. 1993: Alluvial architecture in a sequence stratigraphic framework: a case history from the Upper Cretaceous of southern Utah, USA. International Association of Sedimentologists Special Publication 15, 21–56. Shanley, K.W. & McCabe, P.J. 1994: Perspectives on the sequence stratigraphy of continental strata. American Association of Petroleum Geologists Bulletin 78, 544–568. Smith, D.G. 1987: Meandering river point bar lithofacies models: modern and ancient examples compared. In: Ethridge, F.G., Flores, R.M. & Harvey, M.D. (eds): Recent developments in fluvial sedimentology. Society of Economic Paleontologists and Mineralogists Special Publication 39, 83–91. Stephen, K.J. & Davies, R.J. 1998: Documentation of Jurassic sed- imentary cycles from the Moray Firth basin, United Kingdom North Sea. In: de Graciansky, P.-C. et al. (eds): Mesozoic and Cenozoic sequence stratigraphy of European basins. SEPM (Society for Sedimentary Geology) Special Publication 60, 481–506. Sundsbø, G.O. & Megson, J.B. 1993: Structural styles in the Danish Central Graben. In: Parker, J.R. (ed.): Petroleum geology of Northwest Europe: proceedings of the 4th conference, 1255–1267. London: Geological Society. Thomas, R.G., Smith, D.G., Wood, J.M., Visser, J., Calverley-Range, E.A. & Koster, E.H. 1987: Inclined heterolithic stratification – terminology, description, interpretation and significance. Sedimentary Geology 53, 123–179. Underhill, J.R. & Partington, M.A. 1993: Jurassic thermal doming and deflation in the North Sea: implications of the sequence stratigraphic evidence. In: Parker, J.R. (ed.): Petroleum geol- ogy of Northwest Europe: proceedings of the 4th conference, 337–345. London: Geological Society. Vail, P.R., Mitchum, R.M. & Thompson, S. 1977: Seismic stratig- raphy and global changes of sea level; Part 3: Relative changes in sea level from coastal onlap. In: Payton, C.E. (ed.): Seismic stratigraphy – applications to hydrocarbon exploration. American Association of Petroleum Geologists Memoir 26, 63–97. van Adrichem Boogaert, H.A. & Kouwe, W.F.P. (compilers) 1993: Lower and Middle Jurassic (Altena Group). In: van Adrichem Boogaert, H.A. & Kouwe, W.F.P. (compilers): Stratigraphic nomenclature of the Netherlands, revision and update by Rijks Geologische Dienst and Netherlands Oil and Gas Exploration and Production Association. Mededelingen Rijks Geologische Dienst 50(section F), 20 pp. Van Wagoner, J.C., Posamentier, H.W., Mitchum, R.M., Vail, P.R., Sarg, J.F., Loutit, T.S. & Hardenbol, J. 1988: An overview of the fundamentals of sequence stratigraphy and key defini- tions. In: Wilgus, C.K. et al. (eds): Sea-level changes – an inte- grated approach. Society of Economic Paleontologists and Mineralogists Special Publication 42, 39–45. Van Wagoner, J.C., Mitchum, R.M., Campion, K.M. & Rahmanian, V.D. 1990: Siliciclastic sequence stratigraphy in well logs, cores and outcrops: concepts for high-resolution correlation of time and facies. American Association of Petroleum Geologists Methods in Exploration Series 7, 55 pp. Visser, M.J. 1980: Neap–spring cycles reflected in Holocene sub- tidal large-scale bedform deposits: a preliminary note. Geology 8, 543–546. Vollset, J. & Doré, A.G. (eds) 1984: A revised Triassic and Jurassic lithostratigraphic nomenclature for the Norwegian North Sea. Norwegian Petroleum Directorate Bulletin 3, 53 pp. Whiteman, A.J., Rees, G., Naylor, D. & Pegrum, R.M. 1975: North Sea troughs and plate tectonics. Norges Geologiske Undersøkelse 316, 137–161. Wright, V.P. & Marriot, S.B. 1993: The sequence stratigraphy of fluvial depositional systems: the role of floodplain sediment storage. Sedimentary Geology 86, 203–210. Zaitlin, B.A., Dalrymple, R.W. & Boyd, R. 1994: The stratigraphic organization of incised-valley systems associated with relative sea-level change. In: Dalrymple, R.W., Boyd, R. & Zaitlin, B.A. (eds): Incised-valley systems: origin and sedimentary sequences. SEPM (Society for Sedimentary Geology) Special Publication 51, 45–60. Ziegler, P.A. 1982: Geological atlas of western and central Europe, 130 pp. The Hague: Elsevier for Shell Internationale Petroleum Maatschappij. Ziegler, P.A. 1990: Tectonic and palaeogeographic development of the North Sea rift system. In: Blundell, D.J. & Gibbs, A.D. (eds): Tectonic evolution of the North Sea rifts, 1–36. Oxford: Clarendon Press. 347 Manuscript received 30 May 1997; revision accepted 19 December 2001. Bat-1B SB Bat-1B MFS Cal-1A SB 5 m m m m 4504 4511 4530 3618 3639 3680 3509 3540 3574 3/7-4 6 km 4.5 km GR West Lulu-1 GR Lulita-1 GR crevasse delta crevasse splay fluvial channels fluvial channels lake and distal floodplain fluvial channels ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 5L Coal Claystone Siltstone Sandstone Lithology Depositional environment Floodplain Fluvial channels Key surfaces Sequence boundary (SB) Maximum flooding surface (MFS) SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr Søgne Basin 10 km Fig. 15. Log panel (GR and core logs) depicting floodplain deposits with channel and crevasse sandstones and lacustrine mudstones of sequence Bat-1B in the 3/7-4, West Lulu-1 and Lulita-1 wells. Thick lacustrine mudstones are located around the Bat-1B MFS in West Lulu-1. The succession is incised by the Cal-1A SB, marking the base of an incised valley. The positions of cores illustrated with photographs here are indicated on the sedimentological logs (e.g. 5L indicates core photograph in Fig. 5L). Depths of important surfaces, facies changes or core breaks are indicated (in metres below reference level). For full legend, see Fig. 13; inset map shows the location of the transect. Cal-1A Lulu Fm Bryne Fm Cal-1A SB West Lulu-2 GR 2.5 km 1.8 km 1.4 km West Lulu-4 GR West Lulu-3 GR West Lulu-1 GR 3668 m m m m 3666 3685 3705 3711 6L 6K 6J 6I 6H 6G 6F 6E 6D 6C 6B 6A 3592 3606 3618 3834 3842 3848 3681 coastal mire coastal mire passive channel fill stacked estuary channels fluvial stacked estuary channels stacked estuary channels transgressive reworked barrier bay/lagoon stacked estuary channels ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 Coal Claystone Siltstone Sandstone Conglomerate Floodplain Mires, swamps Lagoon and tidal flats Estuary and tidal channels, bay-head deltas Shoreface, mouth bars and washovers Sequence boundary (SB) Maximum flooding surface (MFS) Lithology Depositional environments Key surfaces SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr 5 m Søgne Basin 10 km Fig. 16. Log panel (GR and core logs) showing incised valley fill deposits from the uppermost Bryne Formation (LST/lower TST of sequence Cal-1A). Possible LST deposits are limited to the lowermost two metres of the succession in West Lulu-3. Most channel sandstones show abundant sedimentary structures indicating a tidally influenced environment and represent estuary channel deposits. Line of section is broadly SW–NE, perpendicular to the inferred valley axis (see inset map). The positions of cores illustrated with photographs here are indicated on the sedimentological logs (e.g. 6A indicates core photograph in Fig. 6A). Depths of important surfaces, facies changes or core breaks are indicated (in metres below reference level). For full legend, see Fig. 13. Amalie-1 GR estuary channel estuary channel tidal flat stacked estuary channels stacked estuary channels lagoon/tidal flats bay/lagoon estuary channels estuary channels swamps estuary channels tidal channels and swamps outer or marginal estuary with minor channels lagoon and tidal flats Bryne Fm Cal-1A SB Lulu Fm ■ ■ ■ ■ ■ ■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 3476 m 3488 3509 4504 4480 5071 m 5088 5110 5119 4453 m 8A 8F 8C 8D 8E 8B 3/7-4 2 km 14 km GR Lulita-1 GR Coal Claystone Siltstone Sandstone Conglomerate Floodplain Mires, swamps Lagoon and tidal flats Estuary and tidal channels, bay-head deltas Marine shelf Sequence boundary (SB) Maximum flooding surface (MFS) Lithology Depositional environments Key surfaces SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr 5 m Søgne Basin 10 km Fig. 17. Log panel (GR and core logs) showing incised valley fill and valley mouth deposits (TST of sequence Cal-1A). Wells 3/7-4 and Lulita-1 represent distal valley fill or valley mouth deposits of the incised valley also depicted in Fig. 17. Amalie-1 represents valley fill deposits from an incised valley in the southern part of the Søgne Basin. The positions of cores illustrated with photographs here are indicated on the sedimentological logs (e.g. 8B indicates core photograph in Fig. 8B). Depths of important surfaces, facies changes or core breaks are indicated (in metres below reference level). For full legend, see Fig. 13; inset map shows the roughly NNW–SSE trend of the transect, broadly axial in the Søgne Basin. ? ? ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 West Lulu-1 GR 3/7-4 GR West Lulu-2 2.1 km 1.4 km 6 km GR West Lulu-3 GR 10A 10B 3780 m 3617 m 3625 3636 3646 3666 3592 3575 3572 3567 3560 m 3440 m 3449 3459 3460 3464 3476 3799 3800 3808 10C 10D 10E 10F 10G 10I 7A 7B 7C 9A 9B 9C 9D 9E 9F 9G 9H 9I 10H 12A 12B 12C lagoon estuary channels and bars lagoon bay-head delta mouth bar offshore Lola Fm Lulu Fm shoreface shoreface or mouth bar bay-head delta mouth bar washover and ravinement complex mires bay/lagoon lagoon bay-head delta with distributary channels estuary channels and bars Cal-1C Cal-1C SB Cal-1B Cal-1B SB Cal-1A Lola Fm Upper paralic wedge Upper marine wedge Middle paralic wedge Lower paralic wedge Lower marine wedge Cal-1C SB Cal-1B SB Cal-1B MFS RSME Cal-1A MFS Lulu Fm Lulu Fm Bryne Fm ■ ■ ■ ■ ■ ■ Coal Claystone Siltstone Sandstone Conglomerate Floodplain Mires, swamps Lagoon and tidal flats Estuary and tidal channels, bay-head deltas Shoreface, mouth bars and washovers Marine shelf Sequence boundary (SB) Maximum flooding surface (MFS) Regressive surface of marine erosion (RSME) Normal fault Lithology Depositional environments Key surfaces SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr 5 m Søgne Basin 10 km Fig. 18. Log panel (GR and core logs) showing paralic and marine wedges of the Lulu Formation (upper TST and HST of Cal-1A, Cal-1B and LST and lower TST of Cal-1C). The transect (see inset map) is largely within the westernmost part of the basin, dominated by the paralic sediment wedges. The marine wedges are present only in the West Lulu-1 and 3/7-4 wells, wedging out between paralic wedges to the west. The positions of cores illustrated with photographs here are indicated on the sedimentological logs (e.g. 10A indicates core photograph in Fig. 10A). Depths of important surfaces, facies changes or core breaks are indicated (in metres below reference level). For full legend, see Fig. 13. shelf shelf transgressive shelf transgressive shelf prograding shoreface prograding shoreface prograding shoreface or mouth bar shoreface or mouth bar back barrier swamps swamps shoreface offshore offshore shoreface ■ ■ ■ ■ ■ ■ Amalie-1 GR Lulu-1 11 km GR Lulita-1 3.5 km GR 3/7-4 2 km GR 3440 m 3449 3459 3460 3464 4454 4448 4439 4434 4426 m 12F 12G 12H 12I 12J 11B 11C 11D 11E 11F 11G 11H 3574 m 3584 3587 3595 11A 12E 12D 3600 5071 5061 5048 m 3476 Lola Fm Lulu Fm Lulu Fm Bryne Fm Cal-1C Cal-1B Cal-1A Cal-1C SB Cal-1B SB Cal-1B MFS RSME Cal-1A MFS Lower marine wedge Upper marine wedge ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■■ ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ Amalie-1 3/7-4 Lulita-1 Lulu-1 West Lulu 1 3 2 4 Coal Claystone Siltstone Sandstone Floodplain Mires, swamps Lagoon and tidal flats Estuary and tidal channels, bay-head deltas Shoreface, mouth bars and washovers Marine shelf Sequence boundary (SB) Maximum flooding surface (MFS) Lithology Depositional environments Key surfaces SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr SiClay Sand Gr 5 m Søgne Basin 10 km Fig. 19. Log panel (GR and core logs) showing marine and paralic wedges of the Lulu Formation (upper TST and HST of Cal- 1A, Cal-1B and LST and lower TST of Cal-1C). Line of section is NNW–SSE (see inset map) roughly parallel to the palaeocoast- line in the central part of the basin and dominated by deposits of the marine sedimentary wedges. Note that the prograding shoreface packet in the upper levels of the Cal-1C sequence has an abrupt erosional base; this surface is interpreted as a regressive surface of marine erosion (RSME), defining the base of the falling stage systems tract. The positions of cores illus- trated with photographs here are indicated on the sedimentological logs (e.g. 12F indicates core photograph in Fig. 12F). Depths of important surfaces, facies changes or core breaks are indicated (in metres below reference level). For full legend, see Fig. 13.