Geological Survey of Denmark and Greenland Bulletin 1, 931-948 931 Shelf-edge delta and slope deposition in the Upper Callovian – Middle Oxfordian Olympen Formation, East Greenland Michael Larsen and Finn Surlyk The Upper Bajocian – Upper Volgian succession of the Jameson Land Basin in East Greenland forms an overall transgressive–regressive cycle. The Upper Callovian – Middle Oxfordian Olympen Formation represents the first regressive deposits after maximum flooding in the Middle to early Late Callovian. The formation was deposited during two southwards progradational phases sep- arated by a major drowning event in the Early Oxfordian. The first phase was marked by incom- ing of massive slope and base-of-slope sand (Athene Member), but the delta front and top did not reach the area of present-day exposure. The second phase was initiated by deposition of a thick mud succession (Hades Member) indicating that the delta had shifted far to the north dur- ing the drowning event. Southwards progradation of the delta was heralded by gully erosion and the deposition of lenticular bodies of massive slope sand; on this occasion, medium- and large- scale cross-bedded sand of the delta front and top (Zeus Member) reached the area. The boundary between Middle–Upper Callovian mudstones in the upper part of the underly- ing Fossilbjerget Formation and the Upper Callovian Athene Member sandstones formed at the turn-around point between sea-level rise and fall. The Athene Member sandstones are inter- preted as an undifferentiated falling stage – lowstand systems tract and span a sequence bound- ary. The top of the Athene Member is the basinal correlative of the transgressive surface. The basal few metres of the overlying Hades Member mudstones represent the transgressive systems tract and a level with organic-rich mudstones is interpreted to represent the maximum flooding zone. The remainder of the Hades Member and the slope sandstones are assigned to the high- stand systems tract. The succeeding cross-bedded delta front sandstones of the Zeus Member are placed in the falling stage systems tract and their sharp base is interpreted as a marine regres- sive surface of erosion. Comparison of this history with published sea-level curves suggests that the short term changes may be eustatic in origin including the Middle Callovian maximum flood- ing (K. jason – lower P. athleta Chronozones), Late Callovian regression (P. athleta – Q. lamberti Chronozones), latest Callovian – Early Oxfordian flooding (Q. mariae – C. cordatum Chronozones) and late Early – Middle Oxfordian regression (C. densiplicatum Chronozone). Keywords: East Greenland, Jameson Land Basin, Middle–Upper Jurassic, sedimentology, lithostratigraphy, sequence stratigraphy, shelf-edge delta, slope gullies, massive sandstones, sediment gravity flow, sea-level curve M.L., Geological Survey of Denmark and Greenland, Geocenter Copenhagen, Øster Voldgade 10, DK-1350 Copen- hagen K, Denmark. E-mail: mil@geus.dk F.S., Geological Institute, University of Copenhagen, Geocenter Copenhagen, Øster Voldgade 10, DK-1350 Copen- hagen K, Denmark. Geological Survey of Denmark and Greenland Bulletin 1, 931–948 (2003) © GEUS, 2003 Shelf-edge deltas and their associated slope/base-of-slope deposits are becoming increasingly well-known, especially from the passive margins of the Gulf of Mexico and the western Mediterranean (Suter & Berryhill 1985; Suter et al. 1987; Tesson et al. 1990, 1993; Sydow & Roberts 1994; Gensous & Tesson 1996; Henriksen & Weimer 1996). In this study we describe Upper Callovian – Middle Oxfordian sandy shelf-edge deltas and slope gravity flow deposits formed during the early stages of Jurassic rifting in the East Greenland basin. In the Jameson Land Basin, rifting was initiated in the Early Bajocian, reached a climax in the Volgian and waned in the earliest Cretaceous. The resulting marine Middle – lower Upper Jurassic rift suc- cession forms an overall transgressive–regressive cycle with a duration of c. 30 Ma. The basin axis was oriented north– south, deepening southwards. Middle Jurassic sed- iment influx was from the north and transport was mainly axial towards the south resulting in a marked north–south grain-size gradient with a thick succession of shallow marine sandstones in the northern part of the basin pass- ing into thinner offshore mudstones towards the south. The aim of the study is to describe the development of the forestepping Late Callovian – Middle Oxfordian shelf- edge delta and slope system constituting the Olympen Formation of the Jameson Land Basin (Surlyk et al. 1973; Surlyk 2003, this volume, fig. 5). It marks the initiation of the stepwise Late Jurassic regression after Middle to early Late Callovian maximum flooding of the basin. 932 3 km 71°27'N 23°40'W 23°20´ Ice Quaternary Olympen Formation Olympen Formation Fossilbjerget Formation Lower and Middle Jurassic undifferentiated Olympen 71°24'N Sections 1–9 25 km 22°W24°W 71°N Jameson Land Olympen Antarctic Havn Parnas Fossilbjerget Mikael Bjerg 23°30'W Parnas O ly m pe lv en Greenland Fig. 1. Map showing the distribution of the Upper Callovian – Middle Oxfordian Olympen Formation in Jameson Land and place names mentioned in the text. Geological setting The onshore part of the Late Paleozoic – Mesozoic rift basin of East Greenland is about 600 km long and about 200 km wide at the southern end where the Jameson Land Basin is located (Fig. 1). The basin was uplifted in Tertiary times and the Mesozoic succession is excel- lently exposed. In East Greenland, the Early Jurassic period was tec- tonically quiescent and deposition was restricted to the Jameson Land Basin, whilst the northern parts of the rift basin were emergent. Marine communication between the Boreal Sea and the Tethys Ocean was effectively obstructed at the end of the Early Jurassic by uplift of the North Sea dome (Surlyk et al. 1973; Underhill & Partington 1994). Distinct faunal provinces rapidly developed and a separate ammonite-based bio- stratigraphic scheme is used for the Bajocian – Lower Callovian interval in the Boreal Realm (Callomon 1993; 2003, this volume). A combination of Bathonian–Callovian eustatic sea- level rise, domal deflation and erosion, and onset of the important Middle–Late Jurassic rift phase led to grad- ual resumption of the north–south marine connection from mid-Callovian times. Although there was still a marked faunal provincialism in the Oxfordian–Kim- meridgian, the degree of faunal overlap allows good correlation between East Greenland and Europe. Maximum flooding of the Jameson Land Basin took place in the Middle to early Late Callovian when the Middle Jurassic sand-dominated system was completely drowned and offshore muds were deposited through- out the basin. Rifting increased in the Oxfordian– Kimmeridgian and reached a climax in the Volgian, con- temporaneous with the onset of a Late Jurassic eustatic sea-level fall. This led to a punctuated Late Jurassic regres- sion and by Late Volgian times, deltaic deposits had pro- graded to the southernmost end of Jameson Land. During the early part of the rift phase, in Bajocian– Bathonian times, the sea floor was essentially flat and differentiation into shelf, slope and basin was not devel- oped. However, continued southwards axial sediment transport resulted in higher sedimentation rates and preferential sand deposition in the northern part of the basin, whereas the southern part mainly received mud. This led to the gradual development of a northern shal- low marine shelf passing southwards into an east–west striking ramp with an incipient slope grading into a deeper-water basin towards the south. Two important regressive phases separated by a major drowning event took place in the Late Callovian and Middle Oxfordian, respectively, and southwards axial progradation of shallow marine and deltaic sands reached central Jameson Land. A marked slope was formed in front of the two forestepping successions, and well-developed slope and shelf-edge delta deposits are preserved on several mountain tops in central Jameson Land (Fig. 1). The slope facies are composed of dark grey mud- stones and massive, sediment gravity flow sandstones. Similar facies types are known from the slightly younger Upper Oxfordian – Volgian Hareelv Formation in south- ern Jameson Land (Surlyk 1987) but this latter unit has experienced major post-depositional modification char- acterised by syndepositional loading structures and evi- dence of post-burial liquefaction and intrusion of sands into the adjacent and overlying mud (Surlyk & Noe- Nygaard 2001). Post-Middle Oxfordian shelf-edge deltas are only preserved in the Middle–Upper Volgian part of the succession in southernmost Jameson land, due to present-day erosion levels. The shelf-edge delta and slope deposits of the Late Callovian and Middle Oxfordian progradational phases constitute the Olympen Formation of Surlyk et al. (1973; Fig. 2). The Olympen Formation Stratigraphy The Olympen Formation was defined by Surlyk et al. (1973) for an Upper Callovian – Middle Oxfordian tri- partite sandstone–mudstone–sandstone succession form- ing the youngest pre-Quaternary sedimentary unit in central Jameson Land (Fig. 1). The formation is divided into three members following the revised lithostrati- graphic scheme for the Jurassic of East Greenland, provisionally introduced by Surlyk (2003, this volume, fig. 5). It consists of: (1) a lower unit of massive, fine- to medium-grained sandstones intercalated with sub- ordinate, laminated, dark silty mudstones and fine- grained laminated sandstones termed the Athene Member, (2) a middle unit, termed the Hades Member, of dark silty mudstones which passes upwards into sandy mudstones intercalated with lenticular bodies of massive sandstones and (3) an upper unit of massive or large-scale cross-bedded, medium- to coarse-grained sandstones with subordinate intercalations of silty mud- stones termed the Zeus Member (Figs 2, 3; Surlyk 2003, this volume, fig. 5). The complete thickness is not known as the forma- tion forms the top of the succession in central Jameson 933 934 mud F M C Gr 80 70 60 50 40 30 20 10 0 poor exposure poor exposure Q. mariae Chronozone (Early Oxfordian) lower–middle P. athleta Chronozone (Late Callovian) P. athleta Chronozone (Late Callovian) K. jason Chronozone (Middle Callovian) C. densiplicatum Chronozone (Middle Oxfordian) ba si n flo o r O ly m pe n Fo rm at io n Fo ss ilb je rg et Fo rm at io n sl o pe a pr o n A th en e M em be r H ad es M em be r Z eu s M em be r ba si n flo o r/ sl o pe ba si n flo o r/ sl o pe sl o pe g ul ly de lt a to p de lt a to p de lt a fr o nt Lo w er c yc le U pp er c yc le c. 900 m Massive sandstone Planar cross-bedded sandstone Trough cross-bedded sandstone Laminated silty mudstone Parallel-laminated sandstone Carbonate concretion Pebbles Carbonaceous material Ripple formset Ripple cross-lamination Climbing ripple lamination Wave ripple lamination Antidunes Load structures Ripple lamination Planar cross-bedding Gully axis Ammonite Belemnite Bivalve Leaf imprints Helminthoida isp. Planolites isp. Diplocraterion habichi Skolithos isp. Piscichnus ?kulindrichnus mm 160 150 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0 Fossils Facies Directional features Trace fossils sand mud F M C Gr sand 3 7 Fig. 2. Vertical sections including the type section (left) of the Olympen Formation at the head of the river Olympelven. The Olympen Formation overlies mudstones of the Fossilbjerget Formation. Note the tripartite lithostratigraphic subdivision of the Olympen Formation into lower and upper sandstone-dominated units of the Athene and Zeus Members, respectively, separated by the middle mudstone-dominated Hades Member. The upper boundary is not exposed as the formation forms the summit of the mountains in central Jameson Land. 935 Land. The type section (Figs 2–4, section 3) at the top of the Olympen mountain measures 150 m, but the thick- ness in this area may reach 250 m, the upper part being poorly exposed below scree, till and ice. At the Parnas, Fossilbjerget and Mikael Bjerg mountains, the formation is 300 m, 250 m and 200 m thick, respectively; further south, in the Hurry Inlet region, it wedges out com- pletely or is only represented by a few metres of mud- stones (Surlyk 1991). The Olympen Formation conformably overlies fos- siliferous Middle and lower Upper Callovian mudstones of the Fossilbjerget Formation of Surlyk (2003, this vol- ume, fig. 5; equivalent to the Fossilbjerget Member of Surlyk et al. 1973). The base of the Olympen Formation is defined by the base of the first thick massive sand- stone in the succession (Fig. 2). The age of the lower boundary of the formation generally becomes younger from north to south. At the type section, ammonites of the Middle Callovian K. jason Chronozone occur 20 m below the base of the Olympen Formation and the lower Upper Callovian P. athleta Chronozone is rep- resented 13 m below the base (Fig. 2). Ammonites from the lower–middle P. athleta Chronozone (Kosmoceras (Zugokosmokeras) cf. proniae Teisseyre) occur 3 m below the base, close to the type section, and have also been found 15 m above the base north of Olympen (Figs 1, 2; Birkelund et al. 1971). At Mikael Bjerg, the upper part of the Fossilbjerget Formation yields ammonites of the lower P. athleta Chronozone (Longaeviceras key- serlingi Sokolov) in contrast to the northernmost out- crops at Antarctic Havn where the same ammonite fauna occurs in the lowermost member (Athene Member) of the Olympen Formation (Callomon 1993). The mid- dle mudstone-dominated Hades Member has yielded ammonites of the Lower Oxfordian Q. mariae Chrono- zone, C. scarburgense Subzone (Surlyk et al. 1973; Callomon 1993). Scattered finds of ammonites from the upper sandstone-dominated Zeus Member indicate the presence of the Middle Oxfordian C. densiplicatum Chronozone, C. vertebrale Subzone (Birkelund et al. 1971; Callomon 1993). The base of the Olympen Formation is located just above a regional drowning surface at the turn-around point between the backstepping Upper Bajocian – Upper Callovian Pelion–Fossilbjerget Formation coup- let and the forestepping Upper Callovian – Middle Oxfordian Olympen Formation (Surlyk 1991; 2003, this volume). The Olympen Formation records two marked progradational phases, one in the Late Callovian (P. athleta Chronozone) and one in the early Middle Oxfordian (C. densiplicatum Chronozone), separated by a drowning event in the Early Oxfordian (Q. mariae Chronozone). Sedimentary facies Recent field work has demonstrated that the Upper Bajocian – Upper Volgian package of the Jameson Land Basin forms an overall transgressive–regressive cycle and that massive base-of-slope sandstones are developed in front of stacked, forestepping shelf-edge deltas from the Late Callovian and through the rest of the Jurassic period (Surlyk 2003, this volume). The facies of the Olympen Formation clearly fall within this spectrum of shelf-edge delta and slope deposits and are described below. 1 2 Fossilbjerget Fm Olympen Fm Athene Member Olympen Fm Hades Member Olympen Fm Zeus Member 3 4 5 6 7 8 9 NESW 50 m Fig. 3. Photomosaic of the type locality at Olympelven on the south side of the glacier-covered mountain Olympen. The positions of the measured vertical sections (1–9) are shown (see also Fig. 4). 936 mud F M C Gr mud F M C Gr mud F M C Gr mud F M C Gr 1 2 3 4 10 20% n = 43 v = 191° 100 m 150 m300 m 500 m South Delta top, Zeus Member Planar cross-bedding T ST H ST HST FS ST FS ST –L ST poor exposures sand sand sand sand Fig. 4. North–south correlation panel of the Olympen Formation at the type locality. Sheet-like beds of massive sandstone deposited from sediment gravity flows dominate the Athene Member. The Hades Member consists of silty mudstones with lenticular bodies of gravity flow sandstones (sections 7–9) and is overlain by cross-bedded, coarse-grained sandstones of the Zeus Member. The succes- sion represents two cycles of slope and shelf-edge delta progradation. For legend, see Fig. 2; n = number of measurements, -v = vec- tor mean. 937 mud F M C Gr mud F M C Gr mud F M C Gr mud F M C Gr mud F M C Gr 5 6 7 8 9 1020% n = 26 v = 151° 50 m 400 m 500 m 50 m North Turbidites, Athene Member Cross-lamination 10 m RSE MFZ TLST MFZ sand sand sand sand sand HST Highstand systems tract FSST Falling stage systems tract LST Lowstand systems tract TST Transgressive systems tract MFZ Maximum flooding zone TLST Top of lowstand surface RSE Regressive surface of erosion 938 Facies 1. Laminated mudstones The facies consists of dark brown or dark grey to black, micaceous, silty and sandy mudstones. They are gen- erally well-laminated although the lamination is com- monly disrupted by bioturbation. At some levels, the facies is heterolithic with alternating very fine-grained sandstone and mudstone laminae giving the facies a striped appearance (Fig. 5A). Locally the sandstone laminae pinch and swell with incipient ripple formsets some of which show cross-lamination. Helminthoida isp. grazing or crawling traces occur in high densities on bedding planes. The mudstones have a total organic carbon (TOC) content of 1–9% and a total sulphur (TS) content of 0.1–1.3%. The highest TOC value is shown by a black finely laminated mudstone 2 m above the base of the Hades Member (Fig. 2, section 3, 78 m). Carbonate concretions are common and form isolated lenses or lensoid layers. They have nuclei of fossil wood and, in a few cases, ammonites. The mudstones con- tain rare belemnites, bivalves and ammonites. A marine, low diversity dinoflagellate cyst assemblage was de- scribed by Fensome (1979). Facies 1 is dominated by fine-grained sediment de- posited from suspension. Intervals of ripple cross-lam- inated siltstones and fine sandstones, however, indicate traction current action representing low-energy turbid- ity currents or weak bottom currents. Facies 2. Cross-laminated sandstones The facies consists of well-sorted, very fine- or fine- grained current ripple cross-laminated sandstone. Set Fig. 5. A: Heterolithic mudstones and fine-grained sandstones (facies 1) intercalated with thin-bedded, massive sandstones (facies 4). The upper massive sandstone is strongly erosional and probably represents a local cut-and-fill. Athene Member, section 4. Pencil is 14 cm long. B: Fine-grained sandstones showing climbing ripple cross-lamination (facies 2). The sandstones are closely associated with laminated mudstones and parallel-laminated sandstones and represent low-density turbidites. Scale is 10 cm long. A B 939 thickness normally varies from 0.5–2 cm, but may reach 4 cm. Asymmetric ripple-formsets and climbing-ripple cross-lamination occur locally (Fig. 5B). Ripple asym- metry and orientations of foresets indicate a south to south-easterly palaeocurrent direction (Fig. 4). The facies forms sandstone-dominated packages with gra- dational boundaries to facies 1. The rippled sandstones were deposited from low-den- sity turbidity currents (Bouma 1962) or weak bottom currents. The close association with mudstones of facies 1 suggests that the cross-laminated sandstones were deposited in a deep-water environment with only episodic sand deposition. Facies 3. Parallel-laminated sandstones The facies is composed of well-sorted, very fine-grained or fine-grained sandstones forming beds up to 60 cm thick. These beds show marked lateral changes in thick- ness from a few centimetres to 60 cm over a few tens of metres, and pinch-and-swell morphology is com- mon. The thicker beds show parallel and low angle hummocky-like stratification associated with soft-sedi- ment deformation structures including overturned folds. Antidune lamination showing aggradation on the up- slope side of low-angle bedforms and draping of pre- vious topography by parallel-laminated sandstones is also represented. The parallel-laminated sandstones mainly have flat bases, but scouring occurs locally. The erosional topography is filled by laminated sandstones with divergent laminae thickening over the deepest part of the scour depressions. Facies 3 is interpreted as having been deposited from low density turbidity currents (Tb division; Bouma 1962). Some of the structures show a superficial resemblance to hummocky cross-stratification, but are interpreted as having been formed in the upper flow regime with plane bed deposition transitional to antidune bedding (Skipper 1971; Hand et al. 1972; Prave & Duke 1990). Facies 4. Massive sandstones The facies consists of white to light grey, micaceous, fine- to medium-grained well sorted, massive sandstone beds commonly with a slightly graded, parallel-laminated top rich in disseminated plant material. Two subfacies are recognised. Subfacies 4a. Sheet-like massive sandstones The subfacies includes sheet-like units of massive sand- stones, up to 8 m thick, built up of amalgamated beds 0.5–2 m thick, or occasionally comprising single beds. The lower boundaries of the sandstone sheets are sharp, but typically flat and apparently non-erosional (Fig. 6). The sandstone beds in general show parallel bound- aries, but emplacement folds and local scouring some- times occur at amalgamation surfaces (Fig. 7A; Heller & Dickinson 1985). The individual sandstone beds are massive with grading in the uppermost few centime- tres. The graded tops are rich in disseminated, carbon- aceous plant material and commonly show deformation by water-escape and loading (Fig. 7B). Amalgamated beds may split into separate beds over a distance of a Fig. 6. Sheet-like units of amalgamated, massive, fine-grained sandstone beds (facies 4a) interbedded with mudstone- dominated intervals (facies 1–3) in the Athene Member. Note the sharp but apparently non-erosional lower boundary of the sandstones (arrows). The white sandstone bed in the centre of the photo is 8 m thick. Section 1, 15–40 m above base of Athene Member (Fig. 4). 940 2 cm Fig. 7. A: Amalgamated, massive, fine- grained sandstone beds separated by thin carbonaceous levels in the lower part of the Athene Member (facies 4a). Note the truncation of the lower beds in the centre of the photograph (arrows). Person for scale. B: Top of a massive sandstone bed (facies 4). Note the horizon of carbonaceous plant material showing flow structures (arrow) overlain by parallel-laminated fine-grained sandstones. The top part shows a concentration of low-density organic material and the upwards change in structures suggest deposition from the waning phase of a turbidity current. The sharp base of the overlying bed is indicated by a dashed line. Section 3. Fig. 8. Massive sandstone bed (facies 4), 12 m thick, forming the top of the Athene Member. The massive nature of the sandstone suggests deposition from either a sandy debris flow or a sustained high-density turbidity current. Section 5; person (encircled) for scale. A B 941 few hundred metres. Pyrite concretions, up to 3 cm in diameter, are common along the lower bed boundaries. In the upper part of the sandstone-dominated Athene Member, an up to 17 m thick massive sandstone bed is referred to facies 4a (Fig. 8). The base of the bed shows evidence of loading, but only minor erosion. The massive sandstones are interpreted as the deposits of sediment gravity flows, either turbidity currents or sandy debris flows (Lowe 1982; Surlyk 1987; Kneller & Branney 1995). The graded tops with abundant car- bonaceous plant material, however, suggest deposition from turbidity currents. This implies that the thick, ungraded part of each bed was probably formed by grad- ual aggradation of sand beneath a sustained steady or quasi-steady current (Kneller & Branney 1995). The largely planar and parallel lower and upper bed bound- aries indicate that the flows were in a largely non-ero- sive stage and deposition probably occurred in a base-of-slope and basin floor setting (Heller & Dickinson 1985). The thicker beds commonly consist of amalga- mated units, as indicated by horizons of carbonaceous plant material. Emplacement folds between amalga- mated sandstones suggest that the sands of the upper bed were emplaced upon the still largely unconsolidated substratum of the underlying bed (Heller & Dickinson 1985). The common occurrence of packets of amalga- mated sandstones separated by thick mudstone units suggests that sandstone deposition occurred in discrete pulses separated by longer periods of background sed- imentation of fines. Fig. 9. Gully fill (facies 4b) at the top of the middle unit (sections 7–9). A: Large slab of mudstone lifted by intrusive sand at the base of the gully. The left side of the slab is partly in situ, whereas the right side is lifted and truncated. B: Mudstone rip-up clast in the lower part of the gully fill sandstone. Note the sharp lower boundary of the sandstone (arrows); hammer for scale. A B 942 Subfacies 4b. Lenticular massive sandstones The subfacies consists of lenticular sandstone bodies, up to 16 m thick, that fill deep erosional scours or gul- lies several tens of metres wide in cross-section. The most spectacular example occurs in the upper part of the Hades Member (Fig. 4, section 7). At this locality, a large slab of mudstone is partially detached, and trun- cated by massive sands at the base of the gully fill (Fig. 9A). The sandstone fill is massive, fine- to medium-, or locally coarse-grained, and shows normal grading in the lower levels and at the top. Floating well-rounded, oblate quartzite pebbles occur in the lower levels of one thick gully fill (Fig. 2, section 7, 30 m). Mudstone clasts ranging from a few millimetres to several metres in largest dimension occur scattered or in distinct horizons (Fig. 9B). The larger clasts are found relatively close to the base of the sandstone beds. The mudstone clasts are commonly undeformed except for torn-up ends (Fig. 10A), but sheared clasts occur along the lower margins of some beds. The axis of the gully exposed in section 7 strikes NW–SE (137°). The massive sand- stones grade upwards into parallel-laminated sand- stones from a few centimetres to several metres thick, capped by cross-laminated sandstones (Fig. 10B). The massive sandstone bodies were emplaced by sed- iment gravity flows (Lowe 1982; Kneller & Branney 1995). The basal grading and the upwards change into paral- lel-laminated sandstones suggest deposition from sus- tained high-density turbidity currents (Kneller & Branney 1995) although a sandy debris flow origin is also possi- ble. Horizons of mudstone intraclasts may mark the for- Fig. 10. A: Zones with aligned mudstone clasts in the lower part of the gully fill indicate that deposition occurred in pulses or as separate flows that followed shortly after one another. B: Several metres thick unit of parallel-laminated fine-grained sandstones forming the top part of the gully fill, section 7. Hammer (centre right) for scale. A B 943 mer position of the rising depositional flow boundary or may, in some cases, show the presence of thinner depo- sitional units separated by subhorizontal amalgamation surfaces. The shape of the clasts shows that the adjacent mudstones were cohesive or partly consolidated at the time of gully erosion and sandstone deposition. Facies 5.Trough cross-bedded sandstones The facies consists of trough cross-bedded, medium- to coarse-grained sandstones with sets 10–15 cm thick, forming cosets up to 1.5 m thick. Trough axes indicate palaeocurrent directions towards the south-east. Bio- turbation is common and includes Diplocraterion habichi and Skolithos isp. The facies is confined to the Zeus Member (Fig. 2). The trough cross-sets are commonly located at the down-current termination of lenticular bod- ies of large-scale cross-bedded sandstones of facies 6. The facies was deposited by traction currents in the upper part of the lower flow regime. The trace fossil assemblage suggests a shallow marine environment. Facies 6. Large-scale cross-bedded sandstones The facies consists of coarse-grained sandstones show- ing large-scale cross-bedding with tangential, locally sigmoidal foresets (Fig. 11). The thickness of the cross- beds varies from 0.4–6 m, but is mainly 2–4 m. The cross- sets are composed of graded avalanche foresets that reach maximum dips of 26°. They pass downwards into carbonaceous, strongly bioturbated toesets. Double mud drapes are found locally in the sandstones, but no systematic changes were recorded in foreset thicknesses. The cross-sets are commonly truncated at the top and are overlain by trough cross-bedded sandstones. In the upper part of the Zeus Member, wave-rippled topsets occur. Dip azimuths of foresets indicate unimodal palaeocurrent directions towards the south with a vec- tor mean of 191° (Fig. 4). Bioturbation is concentrated along set boundaries and shows high density and diver- sity. The trace fossil assemblage includes horizontal burrows of Planolites isp., Taenidium serpentinum, Gyrochorte comosa, vertical burrows of Diplocraterion habichi, Skolithos isp. and the resting trace Piscichnus ?kulindrichnus. The facies is only present in the Zeus Member (Fig. 2). The large-scale cross-sets may pass downcurrent into trough cross-bedded sandstones of facies 5. The cross-beds were formed by southwards progra- dation of subtidal sand bodies, the top of which were periodically exposed to wave reworking indicating a water depth around wave base. Comparison with sim- ilar facies in the Volgian Raukelv Formation of south- ern Jameson Land (Surlyk & Noe-Nygaard 1991) suggests that the cross-beds may form intrasets in large-scale compound foreset beds. Facies successions The facies of the Olympen Formation form an overall progradational megacycle that is made up of two shal- lowing-upwards cycles: (1) the uppermost Fossilbjerget Formation together with the Athene Member and (2) Fig. 11. Cross-bedded, coarse-grained sandstones (facies 6) of the Zeus Member. Individual sets are up to 3 m thick (locally up to 6 m), and are separated by heterolithic mudstones and fine-grained sandstones. Foresets are commonly tangential with strongly bioturbated toesets and truncated topsets. Section 3. 2 m the Hades and Zeus Members of the Olympen Formation (Fig. 2). They are described in turn and interpreted within the framework of the delta-fed turbidite ramp model of Heller & Dickinson (1985) and Surlyk (1987). Lower cycle The lower shallowing-upwards cycle is formed by the silty mudstones of the uppermost part of the Fossilbjerget Formation and the sharp-based, mainly massive sand- stones (facies 4) intercalated with mudstones (facies 1) and fine-grained sandstones (facies 2 and 3) forming the Athene Member (Fig. 2). The first sandstone bed is 4 m thick and abruptly overlies a uniform succession of silty mudstones, several tens of metres thick. Above this level, massive sandstones of facies 4 dominate vol- umetrically. They are commonly amalgamated and may form units up to 17 m thick, whereas single beds may reach 8 m in thickness. The laterally persistent sheet- like beds of massive sandstone (facies 4a) dominate the lower part of the cycle, whereas the upper part of the cycle is characterised by thick, lenticular sandstones (facies 4b). A few beds of ripple cross-laminated sand- stones (facies 2) and parallel-laminated sandstones (facies 3) are intercalated with mudstone units in the middle part of the cycle. The mudstones change from non-bioturbated to bioturbated c. 20 m above the base of the first sandstone bed. A marked change in facies occurs at the transition to the overlying mudstone-dominated association of the Hades Member and the top of the uppermost mas- sive sandstone bed has been reworked into low-angle inclined sets. At locality 4 (Fig. 4), an isolated cross-bed- ded coarse-grained sandstone bed is intercalated in mudstones, c. 2 m above the base of the upper cycle. The sandstones at the top of the lower cycle are inten- sively bioturbated and show a diverse trace fossil assem- blage compared to the underlying sandstones. Upper cycle The base of the upper cycle is marked by a sharp boundary between sandstones at the top of the Athene Member and dark silty mudstones of the Hades Member (facies 1; Figs 2, 4). The mudstone-dominated lower portion is about 50 m thick and shows a slight coarsen- ing-upwards trend in the upper 15 m. The most fine- grained mudstones occur at 1.5 m and 6 m above the base of the cycle and are black, organic-rich (9% TOC) and finely laminated. With these exceptions, the mica- rich mudstones are typically silty, locally sandy and intensely bioturbated. At locality 7 (Fig. 4), the mudstones are succeeded by about 16 m of massive, fine- to medium- grained sandstones (facies 4b), which fill a deep ero- sional scour or gully cut into the mudstones (Figs 4, 9). Elsewhere, the mudstone succession is sharply over- lain by a coarse-grained sandstone succession composed of stacked sets of large-scale cross-bedded sandstones (facies 6), trough cross-bedded sandstones (facies 5) and intercalated mudstones (facies 1; Figs 2, 4). Channelling and scouring are common. The coarse-grained sand- stones are strongly bioturbated and show a diverse trace fossil assemblage. In the uppermost part of sec- tion 3 (Fig. 4), wave-ripple formsets are common on the upper bedding planes of large-scale cross-sets. The uppermost part of the upper cycle is poorly exposed. Isolated outcrops suggest, however, that the coarse- grained cross-bedded sandstone facies continues to the top of the formation. Depositional model for the Olympen Formation The lower cycle represents Late Callovian progradation of a proximal basin and base-of-slope setting. The dom- inance of laterally continuous, massive, non-erosional gravity flow sandstones (facies 4a), and the lack of obvious vertical organisation of the sandstones suggest that they represent a proximal ramp facies of a delta- fed turbidite system (Heller & Dickinson 1985; Surlyk 1987). The shallow marine part of the delta front did not reach the present outcrop area and the interpreta- tion is thus based on comparison with the upper cycle and with shelf-edge deltas and redeposited mass-flow sandstones of the Volgian Raukelv Formation (Surlyk & Noe-Nygaard 1995). The abrupt incoming of sand- stones in the basin plain facies contrasts with the model of Heller & Dickinson (1985), which predicts a gradual increase in bed thickness and grain size from the basin plain – distal ramp facies to the proximal ramp. The con- centration of pyrite concretions in the lower part of the cycle and the upwards change towards more bioturbated sediments suggests a change from a poorly oxygenated deeper-water setting into a more well-aerated, relatively shallow-water environment. A major drowning event occurred in latest Callovian – Early Oxfordian times before the inferred shelf-edge delta of the lower cycle had reached the area of pre- sent-day outcrop. This was followed by renewed progra- 944 945 dation in the Early–Middle Oxfordian. The relatively great thickness of the Lower Oxfordian basinal mud- stones, which form the lower 50 m of the upper progra- dational cycle, suggests that the drowning event had translated the shelf edge far northwards. At Olympen, shelf-edge delta progradation was heralded by the incoming of thick amalgamated slope sandstones with a strongly scoured base. They were probably deposited in a slope gully of the same type as described from the Upper Oxfordian part of the Hareelv Formation further south in Jameson Land (Surlyk 1987; Surlyk & Noe- Nygaard 2001). Finally the shelf-edge delta reached the outcrop area as marked by the incoming of coarse- grained high-angle cross-beds. Such beds are charac- teristic of lowstand deltas that prograded to the edge of the shelf in the Middle Jurassic (Pelion Formation; Engkilde & Surlyk 2003, this volume) and especially in the Volgian (Raukelv Formation; Surlyk & Noe-Nygaard 1991, 1995; Surlyk et al. 1993; Surlyk 2003, this volume). Sequence stratigraphy A sequence stratigraphic interpretation of the Olympen Formation is not straightforward due to the relatively deep-water nature of most of the succession. The mud- stones at the base of the lower cycle represent Late Callovian maximum flooding of the whole Jameson Land Basin. The delta top of the lower unit is not preserved in Jameson Land. The slope and base-of-slope mass-flow sandstones were most likely deposited during late fall, maximum lowstand or early rise. Thus, the base of the lower sandstone package may not necessarily represent the time of maximum sea-level lowstand and the cor- relative surface to the subaerial sequence boundary could be found within the sandstone package (Hunt & Tucker 1993, 1995). However, it has not been possible to define this deep-water correlative surface in the suc- cession and present-day exposures do not allow trac- ing of the surface from the basin margin into the slope system. In our view, the sandstone succession is thus best interpreted as an undifferentiated falling stage and lowstand systems tract (Fig. 4). The drowning surface at the top of the lower cycle is interpreted to represent the slope correlative of the transgressive surface defining the top of the lowstand systems tract. It probably passes up-dip into a ravine- ment surface, which extended across the inner shelf to the north. The thin organic-rich mudstone unit in the basal part of the second cycle represents the maximum flooding zone overlying a transgressive systems tract which is only a few metres thick (Fig. 4). It is overlain by a thick coarsening-upwards mudstone-dominated highstand systems tract. The incoming of massive sandstones indi- cates that the delta had prograded to the shelf edge, and massive sands were shed down the slope from the delta front. The sharp base of the overlying cross-bed- ded delta front sandstones was possibly formed by marine erosion in front of the prograding delta and may represent a marine regressive surface of erosion (Posamentier et al. 1992). The cross-bedded delta front sandstones (Fig. 4) are thus tentatively placed in the falling stage systems tract (Hunt & Tucker 1993, 1995; Nummedal et al. 1993). Comparison with eustatic sea-level curves Since the seminal work of Vail et al. (1977; see Miall 1997 for an overview), the validity of global sea-level curves has been extensively debated. However, as data from different regions are added and the dating of observed sea-level changes is refined, portions of the curve may prove to be eustatic. A regional sea-level curve for the Jurassic of East Greenland was presented by Surlyk (1990) and compared with the eustatic curves of Haq et al. (1988) and Hallam (1988). Sea-level changes based on the sequence stratigraphic interpretation of the Olympen Formation can be tied to ammonite chronozones and allow refinement of the regional sea-level curve for the late Middle and early Late Jurassic of the Jameson Land Basin of East Greenland (Fig. 12). The Late Jurassic part of the curve is supplemented with data from the Charcot Bugt Formation in Milne Land situated at the western mar- gin of the East Greenland basin (Larsen 1995; Larsen et al. 2003, this volume). The sea-level changes recorded in the Olympen Formation include a sea-level rise in the Middle Callovian (K. jason Chron), a Late Callovian fall (early–middle P. athleta and possibly Q. lamberti Chrons), an end Callovian – Early Oxfordian rise (Q. mariae Chron) and a late Early – Middle Oxfordian fall (C. densiplicatum Chron) (Fig. 12). These changes can be matched closely with a proposed eustatic sea-level curve for the central part of the Russian Platform (Sahagian et al. 1996). The Callovian part of the curve does not match the sea- level curve of Haq et al. (1988), whereas the Early Oxfordian rise followed by Middle Oxfordian fall is recorded in all three curves (Fig. 12). Conclusions The Upper Bajocian – Upper Volgian succession in the Jameson Land Basin, East Greenland forms a long-term transgressive–regressive cycle with maximum flooding in the Middle Callovian and Early Kimmeridgian and regressive pulses in the Late Callovian, and the Middle and Late Oxfordian. The Upper Callovian – Middle Oxfordian Olympen Formation represents the initial regression following Middle Callovian flooding. The for- mation consists of a tripartite sandstone–mudstone–sand- stone package overlying Upper Callovian mudstones of the Fossilbjerget Formation. The top of the Fossilbjerget Formation and the lower sandstone-dominated Athene Member of the Olympen Formation together record Late Callovian progradation of the shelf-edge delta and slope towards the south. The delta top did not reach the area of present-day exposure, however, and the sandstone unit consists solely of massive gravity flow sandstones deposited on the slope and base-of-slope. Progradation was terminated by a major Early Ox- fordian drowning event. Renewed progradation took place in the Early–Middle Oxfordian heralded by slight coarsening-upwards of the Hades Member mudstones and the formation of erosional slope gullies filled with mas- sive gravity flow sandstones, tens of metres thick. They are directly overlain by delta front and coarse-grained, cross-bedded delta top sandstones of the Zeus Member indicating that the delta finally reached the area. The Athene Member of the Olympen Formation rep- resents an undifferentiated falling stage – lowstand sys- tems tract. The drowning surface at the top of the Athene Member is interpreted as the top lowstand sur- face forming the distal correlative of the transgressive surface. A maximum flooding zone is recognised in the basal part of the mudstones of the Hades Member, fol- lowed by a thick, coarsening-upwards mudstone suc- cession with lenticular bodies of massive sandstones representing the highstand systems tract. The sharp base of the overlying cross-bedded delta front sandstones of the Zeus Member is interpreted to represent a marine regressive surface of erosion, and the sandstones are tentatively placed in a falling stage systems tract. Comparison of this history of Middle Callovian max- imum flooding (K. jason Chron), Late Callovian fall (early–middle P. athleta and possibly Q. lamberti Chrons), latest Callovian – Early Oxfordian flooding (Q. mariae Chron) and late Early – Middle Oxfordian (C. densiplicatum Chron) regression with published eustatic sea-level curves suggests that the short-term changes can be matched within the resolution of ammonite zones. 946 Geochronology Haq et al. 1988 Sahagian et al. 1996 This study Chronozones G. transversarium C. tenuiserratum C. densiplicatum C. cordatumC. cordatum P. plicatilis Q. mariaeQ. mariae Q. lambertiQ. lamberti P. athleta Short-term Long-term P. athleta E. coronatumE. coronatum K. jason S. calloviense K. jason S. calloviense Chronozones Low High Low High Low HighAgePeriod Submediterranean Province Boreal–Subboreal Province O xf o rd ia n La te Ju ra ss ic M id dl e M id dl e M id dl e La te Ea rl y Ea rl y C al lo vi an Ammonite dating Fig. 12. Comparison of sea-level curves for the Callovian–Oxfordian time interval based on the data in this study (East Greenland), Haq et al. (1988) (global) and Sahagian et al. (1996) (Russian platform). Note the close correlation between short-term changes in the East Greenland and Russian platform curves. Amplitudes of the curves have been rescaled for illustration purposes. Ammonite zona- tion based on Sykes & Callomon (1979) and Callomon (2003, this volume). 947 Acknowledgements M.L. gratefully acknowledges a three-year Ph.D. stipend from the Carlsberg Foundation (91-0683/20, 92-0505/20 and 93-0735/20). The Danish Natural Science Research Council supported subsequent work. We wish to thank Michael Engkilde and John H. Callomon for sedimento- logical and stratigraphic discussions and the referees, Stephen P. Hesselbo, Kevin T. Pickering and Duncan Pirrie, for their thorough reviews and suggestions to improve the manuscript. 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Danmarks og Grønlands Geologiske Undersøgelse (GEUS) Geological Survey of Denmark and Greenland Øster Voldgade 10, DK-1350 Copenhagen K Denmark Geological Survey of Denmark and Greenland Bulletin is a new series started in 2003 to replace the two former bulletin series of the Survey, viz. Geology of Greenland Survey Bulletin and Geology of Denmark Survey Bulletin. The twenty-one volumes published since 1997 in those two series are listed below, followed by titles in the new bulletin series. The new series, together with Geological Survey of Denmark and Greenland Map Series, now form the peer-review scientific series of the Survey. Geology of Greenland Survey Bulletin (discontinued) 173 Cambrian shelf stratigraphy of North Greenland, 120 pp., 1997. By J.R. Ineson & J.S. Peel. 250.00 174 The Proterozoic Thule Supergroup, Greenland and Canada: history, lithostratigraphy and development, 150 pp., 1997. By P.R. 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Stemmerik. 160.00 188 The structure of the Cretaceous–Palaeogene sedimentary-volcanic area of Svartenhuk Halvø, central West Greenland, 40 pp., 2000. By J. Gutzon Larsen & T.C.R. Pulvertaft. 130.00 189 Review of Greenland activities 2000, 131 pp. (17 articles), 2001. Edited by A.K. Higgins & K. Secher. 160.00 190 The Ilímaussaq alkaline complex, South Greenland: status of mineralogical research with new results, 167 pp. (19 articles), 2001. Edited by H. Sørensen. 160.00 191 Review of Greenland activities 2001, 161 pp. (20 articles), 2002. Edited by A.K. Higgins, K. Secher & M. Sønderholm. 200.00 Geology of Denmark Survey Bulletin (discontinued) 36 Petroleum potential and depositional environments of Middle Jurassic coals and non-marine deposits, Danish Central Graben, with special reference to the Søgne Basin, 78 pp., 1998. By H.I. Petersen, J. Andsbjerg, J.A. Bojesen-Koefoed, H.P. Nytoft & P. Rosenberg. 250.00 37 The Selandian (Paleocene) mollusc fauna from Copenhagen, Denmark: the Poul Harder 1920 collection, 85 pp., 2001. By K.I. Schnetler. 150.00 Geological Survey of Denmark and Greenland Bulletin (new series) 1 The Jurassic of Denmark and Greenland, 948 pp., 2003. 500.00 Edited by J.R. Ineson & F. Surlyk. 2 Fish otoliths from the Paleocene of Denmark, 94 pp., 2003. By W. Schwarzhans. Forthcoming volumes Late Quaternary environmental changes recorded in the Danish marine molluscan faunas. By K.S. Pedersen. The Jurassic of North-East Greenland. Edited by L. Stemmerik & S. Stouge. Review of Survey activities, 2003. Edited by M. Sønderholm & A.K. Higgins. Prices are in Danish kroner exclusive of local taxes, postage and handling