Geological Survey of Denmark and Greenland Bulletin 1, 893-930 893 The Lower Bathonian – Middle Oxfordian Charcot Bugt Formation is a marginal marine clastic wedge, which has received relatively little attention in the past due to its remote position and its coarse-grained, mostly unfos- siliferous nature (Bay 1895; Aldinger 1935; Håkansson et al. 1971; Callomon & Birkelund 1980). The aims of this study were to combine biostratigraphic and sedi- mentological data into a coherent depositional and sequence stratigraphic model for the Charcot Bugt Formation in Milne Land. In previous studies, the bio- Stratigraphy and sedimentology of a basement-onlapping shallow marine sandstone succession, the Charcot Bugt Formation, Middle–Upper Jurassic, East Greenland Michael Larsen, Stefan Piasecki and Finn Surlyk A rocky shore developed in early Middle Jurassic times by transgression of the crystalline base- ment in Milne Land at the western margin of the East Greenland rift basin. The basement is onlapped by shallow marine sandstones of the Charcot Bugt Formation, locally with a thin flu- vial unit at the base. The topography of the onlap surface suggests that a relative sea-level rise of at least 300 m took place in Early Bathonian – Middle Oxfordian times. The sea-level rise was punctuated by relative stillstands and falls during which progradation of the shoreline took place. Palynological data tied to the Boreal ammonite stratigraphy have greatly improved time reso- lution within the Charcot Bugt Formation, and the Jurassic succession in Milne Land can now be understood in terms of genetically-related depositional systems with a proximal to distal decrease in grain size. The sequence stratigraphic interpretation suggests that translation of the depositional systems governed by relative sea-level changes resulted in stacking of sandstone-dominated falling stage deposits in the eastern, basinwards parts of Milne Land, whereas thick, remarkably coarse- grained transgressive systems tract deposits formed along the western basin margin. The bulk of the Charcot Bugt Formation consists of stacked sandstone-dominated shoreface units that pro- graded during highstands. The overall aggradational to backstepping stacking pattern recognised in the Charcot Bugt Formation is comparable to that in the contemporaneous Pelion Formation of the Jameson Land Basin and in correlative units of the mid-Norway shelf and the Northern North Sea. We suggest that the long-term evolution of the depositional systems may have been controlled by long-term eustatic rise acting in concert with relative sea-level changes reflecting regionally contemporane- ous phases of rift initiation, climax and gradual cessation of rifting. Keywords: East Greenland, Milne Land, Bathonian–Oxfordian, Charcot Bugt Formation, Kap Leslie Formation, sedimentology, biostratigraphy, dinoflagellates, sequence stratigraphy, shallow marine, basement onlap, clinoform unit M.L. & S.P., Geological Survey of Denmark and Greenland, Geocenter Copenhagen, Øster Voldgade 10, DK-1350 Copenhagen 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, 893–930 (2003) © GEUS, 2003 stratigraphy was based solely on macrofossils; herein we present new correlations combining the existing ammonite stratigraphy with dinoflagellate data. These new biostratigraphic data also allow a better subdivi- sion of the coarse-grained marginal marine sandstones. Rocky shorelines are spectacular but rarely described features in the rock record. The onlap contact between the former subaerially exposed rock surface and the marine strata allows quantification of the relative sea- level changes during the Middle Jurassic. Facies analy- 894 70°45'N 25°30'W 5 km Kap Leslie Kosmocerasdal Parat Kløft Hartz Fjeld Bays Fjelde Aldinger Elv Visdal 25°45'W26°00'W Charcot Bugt Mudderbugt Jameson Land Traill Ø Scoresby Sund 72°N 71°N 26°W 22°W 500 km 25 km G re en la nd Charcot Gletch er 12 3 4 5 12 13 11 10 9 8 7 6 16 15 19 14 18 17 Greenland Milne Land Charcot Bugt Formation (Bathonian – M. Oxfordian) Kap Leslie Formation (Callovian – M. Volgian) Hartz Fjeld Formation (M. Volgian – Hauterivian) Palaeogene basalts Quaternary Ice Crystalline basement Section localities Fault Fig. 1. Map showing the distribution of Mesozoic sediments in Milne Land, East Greenland. The sandstones of the Bathonian – Middle Oxfordian Charcot Bugt Formation onlap Caledonian crystalline basement and are overlain by silty mudstones of the Middle Callovian – Middle Volgian Kap Leslie Formation; the boundary between the two formations is diachronous, younging to the west. Middle Volgian – Hauterivian sandstones of the Hartz Fjeld Formation are exposed to the east. The succession is unconformably overlain by Palaeogene flood basalts. Inset maps indicate the location of Milne Land, Jameson Land and Traill Ø in East Greenland; the red line indicates the log panel in Fig. 18. sis provides the basis for interpretation of the deposi- tional environments during an overall middle Jurassic sea-level rise that resulted in erosion of the former sub- aerially exposed area and the formation of unusually thick transgressive deposits. The giant-scale cross-sets that form the top of the Charcot Bugt Formation in Visdal were first described by Callomon & Birkelund (1980). Three-dimensional mapping of these cross-bed- ded units has revealed a complex internal upbuilding, each unit being composed of clinoform sets. It is sug- gested that the clinoforms formed by strong prograda- tion of the clastic shoreline, probably in response to pulses of falling relative sea level. Geological setting The Late Palaeozoic – Mesozoic East Greenland rift basin is part of the larger rift complex between Greenland and the Baltic Shield that existed prior to the opening of the North Atlantic (Ziegler 1988; Doré 1991). Rift basin formation was initiated in Devonian times, and Late Permian through Mesozoic basin evolution was governed by cooling and thermal contraction punctu- ated by phases of extensional faulting, resulting in the development of basin margin half-grabens (Surlyk et al. 1984, 1986; Surlyk 1990, 1991, 2003, this volume). The East Greenland continental margin was uplifted in Neogene times and now presents excellent exposures of a Mesozoic sedimentary succession deposited in an epicratonic rifted seaway. During the Middle Jurassic, the Jameson Land Basin formed a north–south elongate embayment, c. 140 km wide and more than 400 km long. The Lower Bathonian – Middle Oxfordian Charcot Bugt Formation was de- posited during a long-term transgression recognised throughout the East Greenland basin (Surlyk 1990, 1991, 2003, this volume), and a high gradient rocky shore was 895 40 0 30 0 20 0 10 0 Outcrop of onlap surface Contour of onlap surface (m) 5 km 25°30′W25°45′W 70°45′N Kap Leslie P CB CB KL B B CB SW NE P P Fig. 2. Outcrop of the Charcot Bugt (CB; c. 100 m thick) and Kap Leslie (KL) Formations at Visdal, viewed towards the north-west. Note the sharp boundary between the formations interpreted to represent a coincident sequence boundary and marine trans- gressive surface of erosion. The base of the Charcot Bugt Formation is a marine onlap surface and reflects the pre-Jurassic topogra- phy of the crystalline basement (B). High peaks are formed of Palaeogene flood basalts (P). Fig. 3. Contour map of the crystalline basement – sediment bound- ary representing the topography of the onlap surface in Bathonian–Oxfordian times in Milne Land. The map is corrected for post-Jurassic regional tectonic dip of 3.5° towards the south- east. formed along the faulted western basin margin (Fig. 1). In Milne Land, shallow marine sediments of the Charcot Bugt Formation onlap the irregular, south-east dipping surface of the Caledonian crystalline basement (Fig. 2; Larsen 1995). The orientation of the onlap surface has been corrected for post-Jurassic tilting of 3.5° and can be shown to have risen c. 300 m over a distance of 8–15 km in an up-dip direction (Fig. 3). This corresponds to an average dip of the basement surface of 1–2°, but locally around basement highs the dip is up to 36°. The amount of relative sea-level rise is estimated by tracing the surface representing the contact between the for- mer subaerially exposed basement and the onlapping marine deposits. Stratigraphy The main emphasis of previous studies of the Mesozoic of Milne Land was on the general stratigraphy (Bay 1895; Rosenkrantz 1929; Aldinger 1935), Late Jurassic ammonite biostratigraphy and lithostratigraphy (Spath 1935, 1936; Callomon & Birkelund 1980; Birkelund et al. 1984; Birkelund & Callomon 1985) and palynology (Piasecki 1979, 1980). Lithostratigraphy The 1 km thick Jurassic – Lower Cretaceous succession of Milne Land is subdivided into three formations (Callomon & Birkelund 1980; Birkelund et al. 1984). The Lower Bathonian – Middle Oxfordian Charcot Bugt Formation forms the basal sedimentary unit, and con- sists of coarse-grained sandstones and conglomerates (Fig. 4). It is overlain by, and passes laterally into, mud- stones and fine-grained sandstones of the Callovian – Middle Volgian Kap Leslie Formation (Fig. 4). In the east- ern part of Milne Land, shallow marine and deltaic sandstones of the Middle Volgian – Hauterivian Hartz Fjeld Formation overlie the Kap Leslie mudstones (Piasecki 1979, 1980; Birkelund et al. 1984; Surlyk et al. 1993). Palaeogene flood basalts unconformably over- lie the Mesozoic succession. Charcot Bugt Formation In outcrop, the Charcot Bugt Formation reaches a max- imum thickness of 195 m in the eastern part of Milne Land and thins towards the west. At Visdal (Fig. 1), the formation varies in thickness from 162 m in the south to 97 m in the north. The topographic relief of the underlying crystalline basement (Fig. 3) controls the general wedge-shaped geometry and local variations in thickness. The occurrence of progressively younger ammonites in the sediments immediately above the unconformity surface towards the west also reflects the onlapping nature of the formation (Fig. 4). The upper formation boundary is a strongly diachronous surface which youngs towards the west from the Early Callovian to the Late Oxfordian, as indicated by the ammonite and dinoflagellate stratigraphy (Fig. 4). The formation is subdivided into the Visdal and Mudderbugt Members (Callomon & Birkelund 1980). The Visdal Member forms the main part of the formation and consists of sandy conglomerates with clasts of local crystalline basement rocks overlain by medium- to coarse-grained sandstones with minor siltstone beds. The overlying Mudderbugt Member forms a south-eastwards thickening wedge of coarse-grained sandstones, up to 6 m thick, exposed only in the southern part of Visdal (Fig. 1, locality 6). It overlies the Visdal Member with a sharp, and in places erosional, lower boundary. Kap Leslie Formation The Lower Callovian – Middle Volgian Kap Leslie Formation is subdivided into eight members (Callomon & Birkelund 1980; Birkelund et al. 1984). The Kosmo- cerasdal Member (Lower Callovian – Upper Oxfordian) is the lowest and consists of bioturbated sandy silt- stones and fine-grained sandstones; it forms the off- shore fine-grained correlative of the upper Charcot Bugt Formation (Fig. 4). The member has a maximum thick- ness of 170 m along the east coast of Milne Land and thins westwards (Callomon & Birkelund 1980). In the southern part of Visdal, it is only about 10 m thick, although the exact position of the upper boundary in this area is difficult to establish (Callomon & Birkelund 1980; Piasecki 1980). It is overlain by the Upper Ox- fordian Aldinger Elv Member, which forms a wedge- shaped sandstone body thinning westwards from about 90 m on the east coast of Milne Land to a few metres at Bays Fjelde (Fig. 4; Fürsich & Heinberg 1983). The Aldinger Elv Member is overlain by dark silty mud- stones with abundant glauconitic levels, referred to the Bays Elv Member (Upper Oxfordian – Lower Kim- meridgian). The remainder of the Kap Leslie Formation was discussed thoroughly by Birkelund et al. (1984) and is not considered further here. 896 Ammonite stratigraphy Correlation of the Boreal lower Middle Jurassic ammonite zonation of East Greenland with the Tethyan European ammonite zonation is hindered by faunal provincialism; the faunal horizons in the basal Charcot Bugt Formation are referred to the Boreal zonation (Callomon 1959, 1972, 1993, 2003, this volume). In this study, two ammonite zones not previously recognised in Milne Land are reported. The oldest of these is the Lower Bathonian A. arcticus Chronozone, which is repre- sented by a single specimen of Arctocephalites cf. arcti- cus (Whitfield) found in the basal beds of the Charcot Bugt Formation at Visdal (Figs 1, 4, locality 8). This 897 Kosmocerasdal Member C ha rc ot B ug t Fo rm at io n K ap L es lie F or m at io n Boreal Chronozones Chrono- stratigraphy Ba jo ci an Ba th on ia n C al lo vi an O xf or di an M M M U U U U L L L L M id dl e Ju ra ss ic U pp er Ju ra ss ic A. rosenkrantzi A. regulare A. serratum A. glosense C. tenuiserratum C. densiplicatum C. cordatum Q. mariae Q. lamberti P. athleta E. coronatum K. jason S. calloviense P. koenigi C. nordenskjoeldi C. apertum C. calyx C. variabile A. cranocephaloide A. ishmae A. greenlandicus A. arcticus C. pompeckji C. indistinctus C. borealis Caledonian crystalline basement Bays Elv Member West East 12 locality M13 M12 M7 M1 M1 M13 M12 M10 M9 M6 M8 M5 M4 M3 M2 M1 6 5 4 3 M11 9 36 2 18/5 TST Coarse-grained sandstone Dinoflagellate assemblage, this study TST TST TST HST HST Visdal Member HST HST HST ? ? FSSTCB4 CB3 FSST FSST FSST CB2 CB1 HST HST Aldinger Elv Member 8 7 B A 1 1 2 4 8 2 kmHighstand systems tractHST Transgressive systems tractTST Falling stage systems tractFSST Fine-grained sandstone A Ammonite, this study Ammonite faunal horizon (Callomon & Birkelund 1980) Mudstone 7 Mudderbugt Member Fig. 4. Lithostratigraphy and chronostratigraphy of the Charcot Bugt Formation and lower Kap Leslie Formation; the boundary between these two formations is emphasised by a red line. The formations are interpreted to form genetically-linked depositional systems with the Kosmocerasdal Member as the fine-grained offshore correlative of the coarse-grained Charcot Bugt Formation. Note the west- wards backstepping of the Charcot Bugt Formation reflecting the overall transgression during the Bathonian – Middle Oxfordian. CB1–CB4, clinoform units within the Charcot Bugt Formation. Ammonite zonation based on Callomon (1993). specimen dates the timing of inundation of the Milne Land area to the Early Bathonian. However, unfossilif- erous sediments exposed in the eastern part of Milne Land (Fig. 1, localities 1, 2) are probably even older, given the progressive westwards onlap onto the east- erly dipping crystalline basement surface. The second ammonite zone not previously recognised is the Middle Bathonian A. ishmae Chronozone which is represented by a specimen of Arcticoceras harlandi (Rawson) found between localities 8 and 9 (Figs 1, 4). The Upper Bathonian A. cranocephaloide Chrono- zone is represented by specimens of Arcticoceras/ Cadoceras sp.nov.? aff. variabile (Spath) and Kepplerites tychonis (Ravn) from a conglomerate immediately above the contact to the crystalline basement surface at local- ity 14 (Fig. 1; Håkansson et al. 1971; Callomon & Birke- lund 1980, fauna M1). The A. cranocephaloide Chrono- zone is probably also represented at locality 1 in the western part of the area, c. 130 m above the basement (Fig. 1; Callomon & Birkelund 1980, fig. 2). At Visdal, a succession of medium-grained unfossil- iferous sandstones, approximately 60 m thick, overlies the bed containing fauna M1 (A. cranocephaloide Chro- nozone); the C. variabile, C. calyx, C. apertum, C. nor- denskjoeldi and P. koenigi Chronozones have not been documented by ammonites in Milne Land. In the upper- most part of the Charcot Bugt Formation in Visdal (the Mudderbugt Member), specimens of Perisphinctes (Arisphinctes) cf. or aff. maximum (Young & Bird) indi- cate the Middle Oxfordian C. densiplicatum Chronozone, probably the C. maltonense Subzone (Callomon 1961; Callomon & Birkelund 1980, fauna M7). A complete Middle–Upper Jurassic ammonite suc- cession from the Upper Callovian P. athleta Chronozone to the Middle Volgian L. groenlandicus Chronozone is present in the Kap Leslie Formation at locality 1 and eastwards (Fig. 1), and forms a standard for the Boreal ammonite zonation (Spath 1935, 1936; Callomon & Birkelund 1980; Birkelund et al. 1984). The Kosmoceras- dal Member yields ammonites of the Upper Callovian P. athleta Chronozone (faunal horizon M2 of Callomon & Birkelund 1980) from concretionary levels 12 m and 30 m above the top of the Charcot Bugt Formation (Figs 1, 4, locality 1). Ammonites representing the Lower Oxfordian Q. mariae and C. cordatum Chronozones and the Middle Oxfordian C. densiplicatum Chronozone are found higher in the succession (faunal horizons M3–M6 of Callomon & Birkelund 1980). The Middle Oxfordian C. tenuiserratum and the Upper Oxfordian A. glosense Chronozones are represented in the upper part of the Kosmocerasdal Member (faunal horizons M8–M10 of Callomon & Birkelund 1980). The Aldinger Elv Member contains fauna M11 of the Upper Oxfordian A. glosense and A. serratum Chrono- zones (Birkelund & Callomon 1980). The base of the Bays Elv Member corresponds to the Upper Oxfordian A. regulare Chronozone and appears to be isochro- nous throughout Milne Land (Fig. 4; Callomon & Birkelund 1980; Piasecki 1980). Dinoflagellate cyst stratigraphy Ongoing studies of the Jurassic dinoflagellate cyst stra- tigraphy in East Greenland show that the stratigraphic distribution of most species deviates significantly from the distribution reported from the North Sea region. The Jurassic sediments of East Greenland are therefore dated within the framework of the local dinoflagellate stratigraphy (Piasecki 1980; S. Piasecki and P. Milner, unpublished data) that is correlated with the Boreal ammonite zonation (Fig. 5). The mostly unfossiliferous coarse-grained sediments of the Charcot Bugt Formation have always represented a stratigraphic problem and have hitherto only yielded four horizons with ammonites. However, dinoflagel- late cyst assemblages have been found to occur in thin muddy beds and have greatly improved the subdivision and correlation within the formation. In the partly con- temporaneous, offshore marine Kap Leslie Formation, ammonites and dinoflagellate cysts occur more abun- dantly. The dinoflagellate cyst microflora is of Bathonian age in the lower part of Charcot Bugt Formation and of Callovian and Oxfordian age in the upper part of the formation and in the Kap Leslie Formation. The micro- flora is subdivided into eight stratigraphic assemblages (Appendix 1). Assemblages 1–5 and 7 are present in fine-grained beds in the Charcot Bugt Formation whereas assemblages 6 and 8 are from silty mudstones of the Kap Leslie Formation (Fig. 4). The dinoflagellate cyst zonation shows that the basal unit of the Kap Leslie Formation, the Kosmocerasdal Member in Kosmocerasdal to the east, is of Early Callovian S. calloviense Chron age (assemblage 6). This is considerably older than hitherto believed on the basis of ammonites of Late Callovian age found 12 m above the formation boundary (Callomon & Birkelund 1980). Samples from fine-grained levels in the upper part of the Charcot Bugt Formation show the presence of sed- iments of the Lower Oxfordian C. cordatum, and the Middle Oxfordian C. densiplicatum Chronozones (assem- 898 899 Boreal Chronozones Abundant occurrence Continuous occurrence Acme Uncertain occurrence Al do rfi a al do rfe ns is Si rm io di ni um g ro ss ii Ka llo sp ha er id iu m h yp or na tu m Pa ra go ny au la cy st a sp . Ct en id od in iu m s p. Cr us so lia p er ire tic ul at a Va le ns ie lla d ict yd ia G on ya ul ac ys ta p ec tin ig er a Ka llo sp ha er id iu m s p. Pa ra go ny au la cy st a re tip ha gm at a Ch yt ro ei sp ha er id iu m c hy tro ei de s Ch yt ro ei sp ha er id iu m h ya lin a El lip so id ict yu m c in ct um Ch yt ro ei sp ha er id iu m c er as te s At op od in iu m p ol yg on al is Lit ho di ni a sp on gi os a Pa re od in ia p ro lo ng at a M en di co di ni um g ro en la nd icu m W an ae a di gi ta ta W an ae a th ys an ot a W an ae a fim br ia ta Ri ga ud el ta a em ul a Sc rin io di ni um c ry st al lin um Ka lyp te a st eg as ta Am bo no sp ha er a ca llo via na D in go di ni um ju ra ss icu m St ep ha ne lyt ro n sp p. Ep ip lo sp ha er a bi re tic ul at a Lie sb er gi a sc ar bu rg he ns is Ev an sia ja ne ae Ba jo ci an Ba th on ia n C al lo vi an O xf or di an M id dl e Ju ra ss ic U pp er Ju ra ss ic Stratigraphic occurrence of selected species in East Greenland A. rosenkrantzi A. regulare A. serratum A. glosense C. tenuiserratum C. densiplicatum C. cordatum Q. mariae Q. lamberti P. athleta E. coronatum K. jason S. calloviense P. koenigi C. nordenskjoeldi C. apertum C. calyx C. variabile A. cranocephaloide A. ishmae A. greenlandicus A. arcticus C. pompeckji C. indistinctus C. borealis Fig. 5. Stratigraphic occurrence of selected dinoflagellate cyst species in Jameson Land, used for dating the assem- blages in Milne Land. 900 F ac ie s Li th ol og y St ru ct ur es Lo w er bo un da ry Bo dy a nd tr ac e fo ss ils Pr oc es s in te rp re ta tio n D ep os iti on al en vi ro nm en t 7 ) Pe bb ly la g Pe bb ly s an ds to ne s M as si ve , l oc al ly t ro ug h cr os s- be dd in g, ra re ri pp le fo rm se ts o n to p su rf ac e Sh ar p er os io na l Be le m ni te s, am m on ite s, bi va lv es , D ip lo cr at er io n ha bi ch i, S ko lit ho s is p. , M on oc ra te rio n te nt ac ul at um U pp er p ar t of lo w er flo w r eg im e. W av e w in no w in g an d la g fo rm at io n U pp er s ho re fa ce , tr an sg re ss iv e la g de po si ts 6 ) Pa ra lle l-l am in at ed sa nd st on e Fi ne - to m ed iu m -g ra in ed sa nd st on es , l oc al ly m ic ac eo us Lo w a ng le in cl in ed pa ra lle l l am in at io n, in te rn al t ru nc at io ns Er os io na l U pp er fl ow r eg im e sw as h– ba ck w as h Fo re sh or e, b ea ch 5 ) W av e ri pp le cr os s- la m in at ed sa nd st on e Fi ne -g ra in ed s an ds to ne s lo ca lly e nr ic he d in h ea vy m in er al s C ro ss -la m in at io n, ra re r ip pl e fo rm se ts G ra da tio na l Cu rv ol ith os m ul tip le x, Pl an ol ite s is p. , Sk ol ith os is p. , M on oc ra te rio n te nt ac ul at um Fa ir- w ea th er w av es W av e- do m in at ed up pe r sh or ef ac e 4 ) Tr ou gh c ro ss - be dd ed s an ds to ne Fi ne - to c oa rs e- gr ai ne d lo ca lly p eb bl y sa nd st on es Tr ou gh c ro ss -b ed di ng , se t he ig ht s 5– 30 c m Er os io na l R ar e am m on ite s Sk ol ith os is p. , Ar en ic ol ite s is p. , es ca pe b ur ro w s W av e- ge ne ra te d cu rr en ts , m ig ra tio n of t hr ee - di m en si on al d un es W av e- do m in at ed up pe r sh or ef ac e 3 ) Bi oc la st ic co ng lo m er at e Pe bb le - to c ob bl e- si ze d cl as ts o f c or al s an d cr ys ta lli ne r oc ks in a m ed iu m - to c oa rs e- gr ai ne d sa nd st on e m at ri x M as si ve , n or m al ly or r ev er se -t o- no rm al ly gr ad ed Sh ar p, lo ca lly er os io na l A llo ch th on ou s co ra ls , oy st er s, bi va lv es , be le m ni te s, ra re a m m on ite s Su ba qu at ic g ra vi ty fl ow s St or m -in flu en ce d ro ck y sh or ef ac e 1 ) R eg ol ith K ao lin is ed m ig m at ite , pe bb ly r eg ol ith M as si ve G ra da tio na l t o un w ea th er ed cr ys ta lli ne r oc ks Su ba er ia l w ea th er in g Su ba er ia lly e xp os ed su rf ac e in a w ar m , hu m id c lim at e 2 ) Pe bb ly s an ds to ne Pe bb ly, m ed iu m - to co ar se -g ra in ed fi ni ng up w ar ds in to fi ne -g ra in ed sa nd st on es . C ar bo na ce ou s de br is an d m ic a M as si ve , t ro ug h cr os s- be dd in g gr ad in g in to pa ra lle l l am in at io n Sh ar p, e ro si on al R ar e ar th ro po d gr az in g tr ac ks M ig ra tio n of t hr ee - di m en si on al d un es . Sc ou r an d fil l A llu vi al p la in , ch an ne l f ill T ab le 1 . C ha rc ot B ug t Fo rm at io n fa ci es c la ss ifi ca tio n 901 13 ) O ffl ap pi ng cl in of or m s C oa rs e- t o ve ry -c oa rs e- gr ai ne d sa nd st on es Fa n- sh ap ed c lin of or m se t (1 2 m ) w ith m as si ve or t ro ug h cr os s- be dd ed in tr as et s Er os io na l i n up di p pa rt , st ee p do w nl ap in do w n- di p di re ct io n T hr ee -d im en si on al d un es . Tr un ca tio n an d st ro ng pr og ra da tio n D el ta o r sh el f pr og ra di ng w ed ge , er os io na l p ha se 12 ) A gg ra di ng cl in of or m s M ed iu m - to c oa rs e- gr ai ne d sa nd st on es , co m m on m ud d ra pe s an d ca rb on ac eo us de br is C om po un d gi an t- sc al e cr os s- se ts ( 20 m ) w ith lo w -a ng le m as te r be dd in g. Pl an ar c ro ss -b ed de d in tr as et s G ra da tio na l, ve ry lo w -a ng le t an ge nt ia l do w nl ap Sk ol ith os is p. , P la no lit es is p. Tw o- di m en si on al d un es m ig ra tin g on c lin of or m su rf ac es . S lo w p ro gr ad at io n an d ag gr ad at io n D el ta o r sh el f pr og ra di ng w ed ge 11 ) Pr og ra di ng cl in of or m s M ed iu m - to c oa rs e- gr ai ne d lo ca lly p eb bl y sa nd st on es C om po un d gi an t- sc al e cr os s- se ts ( 29 m ), w ith hi gh a ng le m as te r be dd in g. Tr ou gh c ro ss -b ed de d in tr as et s H ig h- an gl e do w nl ap R ar e Sk ol ith os is p. T hr ee -d im en si on al d un es m ig ra tin g do w n di p on cl in of or m s ur fa ce s. H ig h ra te o f p ro gr ad at io n D el ta o r sh el f pr og ra di ng w ed ge 10 ) T id al ly b un dl ed pl an ar c ro ss -b ed de d sa nd st on es M ed iu m - to c oa rs e- gr ai ne d sa nd st on es w ith a bu nd an t ca rb on ac eo us m ud de br is T id al ly b un dl ed p la na r cr os s be dd in g (u p to 1 .5 m ). Ty pe B a nd C r ea ct iv at io n su rf ac es Er os io na l St ro ng b io tu rb at io n, Sk ol ith os is p. U pp er p ar t of lo w er flo w r eg im e, t w o- di m en si on al d un es , eb b- do m in at ed t id al cu rr en ts Eb b- do m in at ed tid al c ha nn el 9 ) La rg e- sc al e cr os s- be dd ed sa nd st on e M ed iu m - to c oa rs e- gr ai ne d sa nd st on es La rg e- sc al e pl an ar a nd el on ga te t ro ug h cr os s- be dd in g, se t th ic kn es s 0. 5– 4 m Er os io na l s et bo un da ri es Sk ol ith os is p. , A re ni co lit es is p. U pp er p ar t of lo w er flo w r eg im e, s tr on g tr ac tio n cu rr en ts Sh or ef ac e, d un e fie ld s in flu en ce d by lo ng sh or e cu rr en ts 8 ) La m in at ed m ud st on e Si lty m ud st on es a nd m ic ac eo us v er y fin e- gr ai ne d sa nd st on es H or iz on ta l l am in at io n, ra re w av e ri pp le s, ra re h um m oc ky cr os s- st ra tif ic at io n Sh ar p, p la na r A m m on ite s, bi va lv es Ch on dr ite s is p. , P la no lit es is p. , Ta en id iu m s er pe nt in um , ra re S ko lit ho s is p. Su sp en si on fa ll ou t, ep is od ic r ew or ki ng by w av e an d co m bi ne d cu rr en ts O ffs ho re m ar in e, tr an si tio na l t o st or m -in flu en ce d lo w er s ho re fa ce 902 Lo ca lit y 14 N or th So ut h Lo ca lit y 15 Lo ca lit y 8 Lo ca lit y 17 0246 Rocky shore association 8 0246 Alluvial/shoreface? association 8 0246 Shoreface association 8 0 F M ud Sa ndM C G r 246 Alluvial association Shoreface association 8 F M ud Sa ndM C G r F M ud Sa ndM C G r F M ud Sa ndM C G r m m m m k 20 0 0 0 1 2 km m Lo c. 1 4 Lo c. 1 5 Lo c. 8 Lo c. 1 7 K ap L es lie F or m at io n C ha rc ot B ug t Fo rm at io n Fi g. 6 . N o rt h –s o u th g eo lo gi ca l p ro fi le s h o w in g th e C h ar co t B u gt a n d K ap L es lie F o rm at io n s in V is d al , a n d r ep re se n ta tiv e se d - im en ta ry s ec tio n s o f th e b as al C h ar co t B u gt F o rm at io n . N o te t h e th ic kn es s va ri at io n o f th e sa n d st o n es d u e to t h e to p o gr a- p h y o f th e u n d er ly in g cr ys ta lli n e b as em en t su rf ac e. T h re e su cc es si ve a m m o n ite -b ea ri n g h o ri zo n s ar e in d ic at ed , ill u st ra tin g th e p ro gr es si ve o n la p o f th e ir re gu la r su rf ac e. T h e ac co m p an yi n g le ge n d a ls o a p p lie s to F ig . 8. blage 7) and thus preclude the existence of a major hia- tus between the Visdal and Mudderbugt Members, con- trary to the interpretation of Callomon & Birkelund (1980). The dinoflagellate cyst samples from the Kap Leslie Formation in Visdal to the west indicate the pres- ence of the Upper Oxfordian A. glosense and A. serra- tum Chronozones (assemblage 8) in the mudstones directly above the Charcot Bugt Formation. The paly- nological data allow correlation of the upper sandstone units with the offshore marine mudstones, which were previously interpreted to overlie the sandstones with a major hiatus (Callomon & Birkelund 1980). The new data thus indicate a genetic relationship between the Charcot Bugt Formation and the Kosmocerasdal Member of the Kap Leslie Formation (Fig. 4). Sedimentology Thirteen facies are recognised in the Charcot Bugt Formation (Table 1). They are grouped into the allu- vial, rocky shoreline, shoreface, prograding wedge, and offshore facies associations, each characterised by their constituent facies, geometrical arrangement of facies types, nature of bounding surfaces, and overall geom- etry. The facies associations are interpreted in terms of depositional environments and correspond to deposi- tional systems. Alluvial facies association (facies 1, 2) The alluvial facies association is restricted to the basal part of the formation, mainly situated in local topo- graphical basement lows (Fig. 6). The association con- sists of facies 1 (kaolinised migmatite/regolith) overlain by facies 2 (cross-bedded sandstones) showing an over- all fining-upwards trend (Table 1). Description The crystalline basement consists of gneissic migmatite and banded coarse-grained granitic migmatite (Bucher- Nurminen 1979; Henriksen & Higgins 1988). The rocks are progressively weathered upwards towards the con- tact with the sediments forming an up to 2.5 m thick regolith (facies 1; Fig. 6, locality 17). The overlying mas- sive sandstones (facies 2) are coarse-grained, locally pebbly, arkoses with lenses of subrounded quartz peb- bles, lithic fragments and kaolinised and fresh feldspar. 903 M ud st on e (c ar bo na ce ou s) Sa nd st on e Li th ol og y Pe bb ly s an ds to ne C on gl om er at e m at ri x- su pp or te d Br ec ci a C ry st al lin e ba se m en t, ka ol in is ed C ry st al lin e ba se m en t Pe bb le la g W ea k M od er at e St ro ng Pl an ar c ro ss -b ed di ng C lin of or m b ed w ith in tr as et s D ir ec tio n of p al ae oc ur re nt fr om r ip pl es D ir ec tio n of m ig ra tio n fr om cl in of or m d ip Bo un di ng s ur fa ce s D eg re e of b io tu rb at io n Se qu en ce b ou nd ar y M ar in e flo od in g su rf ac e Tr an sg re ss iv e su rf ac e of e ro si on k SB T SE FS H el m in th op sis m ag na Pl an ol ite s is p. Tr ac e fo ss ils Cu rv ol ith os m ul tip le x Ta en id iu m s er pe nt in um M on oc ra te rio n te nt ac ul at um D ip lo cr at er io n ha bi ch i Ro ss el ia is p. Sk ol ith os is p. St ru ct ur el es s Pl an ar b ed di ng Se di m en ta ry s tr uc tu re s Pl an ar la m in at io n W av y be dd in g W av e ri pp le c ro ss -la m in at io n Tr ou gh c ro ss -b ed di ng Be le m ni te A m m on ite O ys te r Pl an t fr ag m en t C oa lif ie d w oo d C or al En al lo co en ia c al lo m on i Fo ss ils Clasts are rounded to well-rounded, spherical and sub- discoidal pebbles of vein quartz, up to 9 cm in diame- ter. The sandstones grade up into cosets of trough cross-bedded, medium- to coarse-grained sandstone, with pebbly lenses and scattered pebbles (Fig. 6, local- ities 15, 17). Foreset azimuth orientations indicate trans- port directions towards the south-east. Even, parallel laminated well-sorted, very fine- to fine-grained sand- stones form the top of the fining-upwards successions. The lamination is defined by abundant flakes of mica and carbonaceous detritus. Bioturbation is restricted to scattered meandering grazing traces (pascichnia) pre- served as shallow epireliefs on bedding planes in the thin-bedded upper part of fining-upwards successions. Interpretation Weathering of the crystalline basement surface and for- mation of the regolith took place during a period of sub- aerial exposure. The dominance of kaolinite in the weathering profile may suggest a warm, humid climate (Curtis 1990; Retallack 1990). The overlying poorly sorted pebbly sandstones, con- taining reworked subangular lithic fragments, kaolinitic feldspars and quartz, are interpreted to have been deposited in an alluvial environment where clasts were transported only relatively short distances before depo- sition. The dominance of trough cross-sets and the uni- modal palaeocurrent direction perpendicular to the reconstructed palaeo-gradient further support this inter- pretation (Fig. 3; Larsen 1995). The sandstones were deposited by three-dimensional dunes in the upper lower flow regime, or represent the fill of shallow scours, and probably formed in shallow channels dom- inated by bedload transport (Miall 1977, 1978; Rust 1978, Kleinspehn et al. 1984). Deposits of the alluvial facies association may have formed a more extensive and continuous cover of the basement surface prior to the Middle Jurassic trans- gression, during which the main part was reworked and redistributed by marine currents or waves. The variation in thickness of the regolith may reflect primary variation in depth of weathering or later erosion. Rocky shore association (facies 3–6) The rocky shore association consists of bioclastic con- glomerates (facies 3), trough cross-bedded sandstones (facies 4), wave ripple cross-laminated sandstones (facies 5) and parallel-laminated sandstones (facies 6; Table 1). The facies occur in random successions with abundant internal scour and erosion surfaces. The association is present in the immediate vicinity of crystalline basement highs (Fig. 6, locality 14). Description The association onlaps the steeply rising crystalline basement surface in the northern part of Visdal (Fig. 6). In contrast to the low relief basement surface in the southern part of Visdal (see above), the crystalline rocks at the onlap surface are generally fresh. Neptunian dykes occur where small fractures in the surface are filled with coarse-grained sandstones and well-rounded crys- talline pebbles or fragmented oyster shells (Fig. 7A). Despite a thorough search, no in situ epifauna was found on the basement surface. A well-rounded gneiss boulder more than 1 m in diameter, surrounded by coarse-grained sandstones, occurs in the basal part of the succession near the basement surface at locality 14 (Fig. 6). The conglomerates (facies 3) are matrix-supported with pebble- to cobble-sized clasts in a coarse-grained sandy matrix. Clasts may be polymict, comprising quartz pebbles, lithic fragments, belemnites, fragments of corals and oyster shells (Fig. 7B) or they may be composed exclusively of fragments of the coral Enallocoenia cal- lomoni (Beauvais) (Fig. 7C). The corals have been affected by bioerosion and Gastrochaenolites borings, representing resting nests of bivalves such as Litho- phaga or Gastrochaena, are common (Fig. 7D; Frey & Seilacher 1980). The conglomerates form tabular beds, up to 50 cm thick, with a sharp, locally erosional base and inverse-to-normal or normal grading. Well-sorted fine-grained sandstone caps, up to c. 30 cm thick, show parallel lamination. Bedding surfaces locally show hor- izontal traces of Taenidium serpentinum and Helmin- thopsis magna. The conglomerates are associated with fine- to coarse-grained sandstones that are pebbly in places (facies 4). The sandstones are trough cross-bed- ded with set thickness between 5 and 30 cm. High angle scours may be partly filled with pebbly sand- stones, and clast-supported conglomerate sheets occur interbedded with the cross-sets (Fig. 7E). Foreset ori- entations in the trough cross-beds indicate dominant transport towards the south. The coarse-grained facies are interbedded with well- sorted fine- to medium-grained wave ripple cross-lam- inated sandstones (facies 5), showing intense burrowing 904 905 Fig. 7. Examples of sedimentary facies and faunas of the rocky shoreline association. Scale in centimetres. A: Subvertical contact between a coquina and unweathered crystalline basement. The shelly debris was deposited in a fracture in the basement surface forming a neptunian dyke. B: Polymict siliciclastic and bioclastic conglomerate with lithic fragments, quartz pebbles, fragmented corals (c), oys- ters (o), and worn well-rounded belemnites (b). C: Marine matrix-supported conglomerates with coral clasts. Photograph shows ver- tical stacking of three graded beds. Bed boundaries indicated by dashed lines. D: Compact hemispherical colony of the hermatypic coral Enallocoenia callomoni Beauvais recovered from a conglomerate. The coral shows sand-filled Gastrochaenolites borings prob- ably representing nests of boring bivalves. E: Pebbly sandstones filling a shallow scour interpreted as a rip-channel fill (lower part, under scale). Note the gradual upwards decrease in the dip of the foresets and concomitant decrease in grain size. The rip-channel fill is overlain by parallel-laminated sandstone (above scale). F: Wave-rippled sandstones truncated by pebbly trough cross-bedded sandstones. Note the abrupt changes in grain size and the abundant erosional surfaces. A E F B b o c c DC 2 cm 906 by Curvolithos multiplex, and parallel-laminated well- sorted fine- to medium-grained sandstones, locally rich in mica (facies 6). Bed thicknesses reach 30 cm, but may be reduced due to truncation by pebble-filled scours (facies 4; Fig. 7F). The parallel lamination of facies 6 is defined by coarse sand grains or fine quartz pebbles and small coralline fragments. The lamination dips a few degrees and shows low-angle internal truncations. Interpretation The generally poor sorting of the pebbly sandstones and the composition of the conglomerates point towards mix- ing of marine and terrestial sediments, suggesting marine reworking of alluvial sediments. Textural sorting and marked grain-size segregation between individual sets are characteristic of sediments deposited in the ambi- ent energy regime on a wave-dominated upper shoreface (Dupré et al. 1980; Clifton 1981; Nemec & Steel 1984; Leithold & Bourgeois 1984). The trough cross-stratified pebbly sandstones were deposited by strong unidirec- tional currents that may have been generated by storm surges either along the coast or in rip channels. The matrix-supported graded conglomerates contain dis- persed floating clasts, a fabric that invites comparison with debris flow deposits. The out-sized clasts, how- ever, consist primarily of corals, which may have shown a different hydrodynamic behaviour from siliciclastic material of equal size. The floating clasts therefore are not unequivocal criteria with respect to the deposi- tional process. However, the overall inverse-to-normal grading present in some beds and the lack of traction current generated structures support the interpretation that they represent high density gravity flow deposits (Lowe 1979, 1982). The cross-laminated fine-grained sandstones (facies 5) that form a cap on some of the conglomerate beds are interpreted to represent rework- ing by fair-weather waves. The shallow water depth in front of the rocky shoreline is reflected by the parallel- laminated sandstones formed by high-energy swash– backwash on the foreshore or by shoaling waves on the upper shoreface (Clifton 1969). The well-rounded gneiss boulder embedded in marine sediments indicates exposure to wave processes prob- ably on a high-energy beach before final burial (Dott 1974; Surlyk & Christensen 1974). It may have originated from wave erosion of the rocky coastline removing a joint-controlled weathering crust leaving the rounded boulder in place or it may have rolled or slid into the site of deposition. The rocky shore association is bounded by the crys- talline basement in a landwards direction. The associ- ation may be characterised as amalgamated marine lag deposits formed by progressive wave erosion of the base- ment and alluvial deposits and by winnowing of shore- face and foreshore deposits in a high energy rocky shoreline environment. Shoreface association (facies 4, 5, 7–9) Stacked units of the shoreface association form the bulk of the Charcot Bugt Formation. Each unit shows a basal erosional surface overlain by a coarse-grained lag deposit (facies 7). The lag is sharply overlain by silty mudstones forming the base of an overall coarsening-upwards suc- cession (facies 8, 4, 5, 9), up to 22 m thick (Fig. 8). Description The basal lag deposits reach a maximum thickness of 1 m and are composed of coarse- to very coarse-grained quartzitic sandstone with concentrations of worn belem- nites and ammonites. The lags are intensely burrowed by Skolithos isp. and Diplocraterion habichi (facies 7; Fig. 8). The upper bedding surfaces are planar or locally reworked into large-scale wave ripples. The lag deposits are abruptly overlain by laminated mudstones (facies 8) that form the lower part of the coars- ening-upwards successions. The siltstones grade upwards into well-sorted mica-rich, very fine- to fine-grained sand- stones, showing wave ripple cross-lamination and sym- metrical ripples on bedding planes (facies 5). The sand- stones are strongly bioturbated and show well-preserved Curvolithos multiplex and Planolites isp. The fine-grained sandstones are overlain by cosets, 6–10 m thick, of trough cross-bedded, medium-grained sandstones (facies 4). Individual sets are medium-scale trough cross-beds with set thickness between 5 and 25 cm and low-angle foresets. The Mudderbugt Member consists solely of coarse-grained sandstones of facies 4. In Visdal, the uppermost of the shoreface units con- tains cosets of very large-scale, planar and trough cross-bedded, medium- to coarse-grained sandstones (facies 9; Figs 8, 9). The cosets have a sheet-like geom- etry and are bounded by erosional planar surfaces. They are up to 9 m thick; individual sets are up to 4 m thick, with 0.5–1.5 m being most common. The set boundaries form more than 10 m wide troughs, with erosional boundaries to underlying sets (Fig. 9). Foresets are dominantly tangential or more rarely sigmoidal. Individual cross-sets show inversely or, rarely, normally graded simple avalanche foresets up to 40 cm thick. Locally, the foresets are compound showing internal low- angle trough cross-bedding. The large-scale foresets dip up to 23° with a consistent dip direction towards the south (mean 196°; Fig. 10). Bioturbation is rare; isolated Arenicolites isp. and Skolithos isp. burrows occur locally. 907 Scree covered FS TSE FS FS SB/TSE FS TSE FS TSE FS TSE FS TSE 60 40 30 20 10 0 50 m 110 100 90 80 70 m 4 4 7 4 8 11 11 7 8 11 8 9 9 7 4 4 4 8 7 8 8 4 5 5 4 7 120 Cl Si F M CGr Sand Cl Si F M CGr Kap Leslie Formation Sh or ef ac e as so ci at io n C ha rc ot B ug t Fo rm at io n, V is da l M em be r C ha rc ot B ug t Fo rm at io n, V is da l M em be r Pr og ra di ng w ed ge a ss oc ia tio n CB4 Sand Fig. 8. Sedimentological section measured through the upper part of the Charcot Bugt Formation showing stacked coarsening-upwards shoreface successions overlain by clinoform unit CB4. The small numbers indicate facies, as described in the text. For legend, see Fig. 6. Interpretation The lateral continuity of the erosionally-based pebbly sandstones and the presence of marine macrofossils and wave-generated ripples suggest that the lag (facies 7) formed by shoreface ravinement followed by shal- low marine winnowing (Swift 1968; Demarest & Kraft 1987; Nummedal & Swift 1987). The trace fossils belong 908 20 m TSE CB4 SB/TSE West East Shoreface Strike and dip direction Coarsening- upwards Offshore Offshore Prograding wedge Fig. 9. Prograding clastic wedge (CB4) forming the top of the Charcot Bugt Formation at Visdal. The unit is more than 50 m thick and downlaps onto marine mudstones that themselves succeed a coarsening-upwards shoreface succession lowermost in the photograph. View towards the north-east. The line drawing is based on the photograph and measured vertical sections. Note the steeply dipping clinoforms in the central part of the photograph. Person encircled for scale. 909 to the habichi ichnocoenosis (Heinberg & Birkelund 1984) and are interpreted to indicate shallow marine to intertidal, high energy environments characterised by highly varying sedimentation and erosion rates (Hein- berg & Birkelund 1984; Dam 1990). The overlying fine- grained sediments are interpreted as having been deposited from suspension fall-out below storm wave base and the transition thus indicates an abrupt increase in water depth and is designated a marine flooding sur- face. Although this surface is easily recognised in out- crop, the definition of the facies associations as genetically-related facies implies that the lower bound- ary of cycles in the shoreface association is placed at the erosional base (marine surface of erosion) of the coarse-grained lag (see Arnott 1995). The coarsening-upwards part of the successions is interpreted to represent shoreface progradation. The fine-grained strongly bioturbated sandstones indicating slow sedimentation rates and deposition in a low energy environment were deposited on the lower shoreface. The upper shoreface is represented by medium- and coarse-grained trough cross-bedded sandstones (facies 4) deposited by three-dimensional dunes in a high- energy wave-regime. The near-shore shallow marine sand sheets and shoreface environments are charac- terised by a high degree of reworking (Dupré et al. 1980; Clifton 1981). The high energy, shallow marine environment is also reflected by the trace fossils which are dominated by vertical burrows probably inhabited by suspension feeders. The interpretation of the very large-scale cross-sets (facies 9) is less straightforward. No unequivocal evi- dence of wave or tidal action is present and the con- sistent palaeocurrent direction, indicated by the dip of the very large-scale foresets, suggests unimodal cur- rents. Based on the sedimentary structures alone the sandstones may have been deposited by large sandbars or mouthbars in either fluvial, tidal or shallow marine environments. The association with upper shoreface facies and the presence of marine trace fossils (albeit scarce), however, suggest a tidal to shallow marine depositional environment. Tidally-driven current systems are often separated into an ebb- and a flood-dominated thalweg, and the lack of tidal structures may therefore not be significant. Berné et al. (1991) described large-scale dunes from recent sub- tidal environments, that were 0.7–9.4 m high with com- mon heights between 2–4 m and formed in water depths between 8 and 23 m. They migrated under the influence of tidal currents. Large-scale dunes may also form on epi- continental platforms by strong geostrophic currents, occasional storm surges and/or tidal currents (McCave 1971; Flemming 1978; Field et al. 1981). The sandstones (facies 9) are therefore interpreted to have been deposited by fields of linear or slightly sinuous subtidal dunes on the shoreface. The dune fields migrated southwards under the influence of coast-parallel currents. Surlyk & Noe-Nygaard (1991) described cross-bedded sandstones of similar scale from the Volgian Raukelv Formation in central Jameson Land, interpreted as having been deposited in dune fields driven by coast-parallel tidal currents. Prograding wedge association (facies 10–13) Four clinoform units (CB1–CB4) characterised by high- angle foresets or clinoforms are identified in the Charcot Bugt Formation. The units are bounded by major marine flooding surfaces or erosional surfaces, and consist of facies 10–13 (Table 1). They are of ?Middle–Late Bath- onian (CB1), Late Bathonian (CB2), Callovian (CB3) and Early–Middle Oxfordian (CB4) age, and form a back- stepping succession of sandstone-dominated clinoform units (Fig. 4). 10 20 30 40 % N = 19 V = 196° 10 20 30 40% N = 103 V = 126° 10 20 30 40% N = 56 V = 157° Shoreface foreset dip Prograding wedge (clinoform dip) Prograding wedge (intraset) Fig. 10. Equal-area rose plots showing the palaeocurrent direc- tion in the shoreface association (facies 4, 9) and the clinoform dip direction and intraset palaeocurrent direction in the pro- grading wedge association (facies 10–13). 910 Description The four clinoform units were mapped out in the field and have a bank or wedge-shaped geometry (in the sense of Mitchum et al. 1977). The maximum thicknesses of CB1, CB2, CB3 and CB4 are 21 m, 19.5 m, 31 m and 50.5 m, respectively. The four units are characterised by steeply dipping clinoforms extending from the top to the base of the unit (facies 11–13; Fig. 9). The cli- noforms downlap onto the top of large-scale cross-bed- ded sandstones (facies 10) or the offshore association. In a basinwards direction, the sandstone-dominated clinoform units pass into, and are overlain by, mudstones of the offshore facies association (the Kosmocerasdal Member). The clinoforms are tangential or locally sigmoid with an inclination of 5–20° towards the south-east, although the steepest middle part of the clinoforms may locally reach 24° (Fig. 9). Clinoforms are asymptotic towards the lower boundary where they merge into a carbona- ceous fine-grained clinoform toe. The sigmoidal clino- forms gradually merge upwards into a horizontally bedded, wave-influenced top, whereas the tangential oblique clinoforms are erosionally truncated at the top. The clinoforms are grouped into progradational, aggra- dational and offlapping clinoform sets (Sydow & Roberts 1994), according to the geometry of the clinoform sur- faces (Fig. 11). The clinoforms show intrasets of planar cross-strata or cosets of trough cross-strata that are char- acteristic of the different types of clinoform sets (facies 11–13; Table 1). The clinoform sets are bounded by ero- sional surfaces of local extent and/or their correlative surfaces. Progradational clinoform sets (facies 11) consist of steeply dipping (15–24°) clinoforms showing low-angle trough cross-bedded intrasets with set thicknesses up to 8 cm. The facies consists mainly of well-sorted coarse- grained sandstone with a low content of carbonaceous debris. Bioturbation is weak. Aggradational clinoform sets (facies 12) are sigmoidal or tangential with planar cross-bedded intrasets up to 1.4 m thick. Clinoforms dip 5–14° and consist of well- sorted fine- to medium-grained, locally coarse-grained sandstones with abundant carbonaceous debris. Bio- turbation is moderate to strong. Offlapping clinoform sets (facies 13) are entirely com- posed of trough cross-bedded coarse-grained sand- stones, forming cosets up to 12 m thick (Fig. 11). Bioturbation is absent except for Diplocraterion habichi extending downwards from the upper clinoform set boundary. Offlapping clinoform sets are typically found in the upper part of clinoform units and represent the final progradation of the clastic wedge. They show a downstepping (offlapping) geometric arrangement in CSB CSB CSB C lin of or m s et C P B O T O A Cu C M M A SB/TSE DS c lin of or m u ni t DS Downlap surface SB/TSE Coalesced sequence boundary and transgressive surface of erosion CSB Clinoform set boundary C Clinoform surface P Prograding clinoform set A Aggrading clinoform set O Offlapping clinoform set M Offshore mudstones Cu Condensed unit B Bottomset T Topset Fig. 11. Generalised section (scale arbitrary) through a clinoform unit showing the bounding surfaces, structures and geometric char- acteristics of the clinoform sets. Three types of clinoform sets are described based on the geometry and internal structures. They com- prise: prograding (P) (facies 11), aggrading (A) (facies 12) and offlapping (O) (facies 13). The clinoform sets are bounded by erosional surfaces and/or fine-grained condensed units. 911 the direction of migration. Up-dip, the offlapping cli- noforms may be traced into a strongly erosional sur- face. Clinoform unit CB1 CB1 is exposed in steep cliff faces at Kosmocerasdal and Parat Kløft (Fig.1, localities 1, 2). Minimum areal extent of the clinoform unit is 3 km2 and it can be followed in continuous outcrop for c. 1 km along strike. CB1 is 21 m thick in Parat Kløft and 17 m thick in Kosmocerasdal and consists of medium- to very coarse-grained sand- stones showing weak bioturbation by Skolithos-type burrows. It consists of a single set of progradational cli- noforms. The clinoforms are tangential with truncated upper parts and show maximum dip angles of 16° and migration direction towards the south-east (132°; Fig. 12). The clinoform surfaces bound single sets of trough cross-bedded sandstones. The geometry of CB1 cannot be determined, but it forms a tabular sandstone body in outcrop. It down- laps onto medium- to coarse-grained shallow marine sandstones and has a sharp truncated top. CB1 is over- lain by coarse-grained sandstones at Parat Kløft (local- ity 2) and dark silty mudstones at Kosmocerasdal (locality 1). The mudstones at Kosmocerasdal contain marine dinocysts (assemblage 3; Appendix 1) and a tentative stratigraphic correlation with the established stratigraphic scheme of Jameson Land suggests a Late Bathonian, A. cranocephaloide Chron or older age (Fig. 4; Piasecki 1980). This is supported by an ammonite fragment found in the transgressive lag at the top of CB1 in Kosmocerasdal (Callomon & Birkelund 1980, fig. 2). Clinoform unit CB2 CB2 is dominated by an aggradational clinoform set. It is exposed in the area around Parat Kløft (locality 2) over a minimum area of 3 km2 (Fig. 12). The geome- try of CB2 cannot be determined, due to limited expo- sure. The clinoforms are sigmoidal and show dip angles up to 15° with a migration direction towards the east (84°) whereas the intrasets show a migration direction towards the south-east (132°; Fig. 12). The sigmoidal clinoforms show a very gradual downlap with a rather thick carbonaceous toeset. Clinoforms bound planar cross-sets, up to 1.8 m thick, of medium- to coarse-grained sandstones rich in carbonaceous detritus and with scat- tered silicified wood. Bioturbation is restricted to localised Skolithos isp. burrows. CB2 is capped by a wave-influenced unit and is overlain by trough cross- bedded, medium- to coarse-grained sandstones with belemnites. The maximum thickness of CB2 is 19.5 m; it is Late Bathonian in age corresponding to the C. calyx and C. apertum Chrons based on dinoflagellate cysts (assemblage 4) found in the fine-grained toeset deposits. Clinoform unit CB3 CB3 consists of a single set of progradational clino- forms. The clinoform unit is exposed over 8 km2 at Kosmocerasdal (Figs 1, 12, locality 1) and Parat Kløft (locality 2) where it forms the uppermost unit of the Charcot Bugt Formation. Clinoforms are tangential to sigmoidal and show dip angles up to 20° with a migra- tion direction towards the east (90°, locality 1) and south-east (136°; Figs 1, 12, locality 2). Clinoforms bound single sets of trough cross-beds up to 8 cm thick, and each set can be traced down-dip for several metres. The trough cross-bedded sandstones are medium- to coarse-grained with scattered carbonaceous detritus and kaolinitic mudstone clasts. CB3 shows localised bioturbation (Skolithos isp.) and belemnites occur in the uppermost part of CB3 in Kosmocerasdal (Figs 1, 12, locality 1). CB3 downlaps onto horizontally bedded or low-angle cross-bedded, medium- to coarse-grained, shallow marine sandstones (facies 4). At Kosmocerasdal, CB3 shows a strongly truncated top and is overlain by a fine-grained sandstone bed, 30 cm thick, containing 70°45′N Kap Leslie 5 km 25°30′W25°45′W CB4 CB3 CB1,2 50 m 0 m Direction of migration (clinoform dip) Clinoform units CB1, CB2 Clinoform unit CB3 Clinoform unit CB4 with sandstone isopach Fig. 12. Isopach map showing thickness variation and geographical distribution of the four clinoform units CB1–CB4. scattered fine pebbles and abundant coalified wood pieces, whereas it shows a wave-influenced top at Parat Kløft. The sandstones are overlain by sandy siltstones of the Kap Leslie Formation. The clinoform unit has a wedge-shaped geometry with a planar lower surface and an eastwards inclined upper surface. Contours of the upper formation boundary (i.e. the upper boundary of CB3 in this area) show that the surface is planar and dips a few degrees towards the south-east. Dinoflagellate cysts in the bottomset (assemblage 5) indicate an Early Callovian age corresponding to the C. nordenskjoeldi or earliest P. koenigi Chrons. Dinocysts from the basal beds of the overlying Kap Leslie For- mation (assemblage 6) indicate the Middle Callovian S. calloviense or possibly K. jason Chronozones (Fig. 4; Piasecki 1980). The oldest ammonites present in the over- lying mudstone succession are found c. 12 m above CB4 and belong to the Upper Callovian P. athleta Chrono- zone, K. proniae Subchronozone (Callomon & Birkelund 1980). Clinoform unit CB4 Clinoform unit CB4 forms the uppermost part of the Visdal Member in the western outcrop area and is exposed in laterally continuous outcrops between localities 6 and 15 and between localities 4 and 5; it covers at least 40 km2 (Figs 12, 13). The clinoforms downlap onto marine carbonaceous mudstones in most of the area, but it erosionally overlies medium-grained sandstones of the shoreface association in the northern part of Visdal (Fig. 13; localities 11–13). The top of CB4 forms the upper formation boundary and is overlain by silty mudstones of the Kap Leslie Formation (localities 8–13). The Mudderbugt Member erosionally overlies CB4 in the southern part of Visdal (localities 6, 7). The age of CB4 is Early–Middle Oxfordian based on dinoflagellate cysts (assemblage 7) found in the underlying marine mud- stones and the carbonaceous toesets that are indicative of the C. cordatum and C. densiplicatum Chronozones (Fig. 4). The age given by the dinoflagellate cyst assem- blage is in accordance with ammonites in the overly- ing Mudderbugt Member (C. densiplicatum Chronozone; Callomon 1961). CB4 shows a lobe-shaped geometry with the maximum thickness in the proximal (western) area (Figs 1, 12, localities 8–13). The gradual decrease in thick- ness towards the east and south-east can be observed at outcrop between localities 5 and 4. Around locality 4, thin beds of coarse-grained sandstones are found embed- ded in offshore mudstones, probably representing the most distal part of the clinoform unit. Cross-bedded tidal sandstones of facies 10 occur in the proximal (western) part of clinoform unit CB4 and consist of medium- to coarse-grained, generally well- sorted sandstones with abundant disseminated carbon- aceous material. Tidally-influenced planar and trough cross-beds up to 1.5 m thick, (typically 0.30–0.45 m) form cosets up to 15 m thick (Fig. 14). The cosets gen- erally fine upwards and are capped by fine-grained car- bonaceous mudstone layers. The planar cross-bedded sets show rhythmic variation in bundle thickness, doub- le mud drapes, and type B and C reactivation surfaces indicating tidal influence (de Mowbray & Visser 1984; Nio & Yang 1991a). Double mud drapes, less than a few millimetres thick, extend from the bottomsets to approx- imately two-thirds up the set. Reactivation surfaces dip approximately 23° as compared to the maximum fore- set dip of 26°. Foreset inclinations change systematically, decreasing with decreasing bundle thickness. Palaeo- current readings from the planar cross-sets indicate a dominant southerly transport direction (mean 176°). Small reversed current ripples showing foreset azimuths towards the north climb up the reactivation surfaces and form sets up to 1.5 cm thick, draped by a layer of car- bonaceous mudstone. The tidally-influenced planar cross-beds show bioturbation concentrated along set boundaries and on the foreset laminae (Fig. 14B). The clinoform sets can be followed between outcrops in the valley of Visdal, and are arranged in a shingled fashion, such that superposed sets are offset in a south- wards direction. The clinoform sets in CB4 show all three geometrical styles defined above. The prograda- tional clinoform sets are most common in the central part of Visdal (localities 8 and 9), where they form the lower part of CB4 (Fig. 13). The thick progradational clinoform sets are associated with the maximum thick- ness of the clinoform unit. The progradational clinoform sets reach a maximum thickness of 29 m at locality 8. The clinoforms are tangential, with angles typically varying between 5° and 20°, although locally up to 24°. The clinoforms bound sandstones showing low-angle trough cross-sets, 3–14 cm thick (Fig. 15). The aggradational clinoform sets are most common in the northern part of the Visdal valley (localities 11, 12), where the low-angle sigmoidal clinoforms bound sets of planar cross-sets (Fig. 16). Clinoform dip angles are in the range 3–12°. The internal cross-sets are up to 1.5 m thick. The offlapping clinoform sets occur in the upper half of CB4 and are characteristically massive in appearance. The maximum thickness is 12 m (local- ity 9) and the offlapping sets are composed of cosets of low-angle trough cross-beds. 912 913 The clinoforms of CB4 show a consistent dip towards the south-east (mean of 123°; Fig. 12), indicating progra- dation in this direction, slightly oblique to the recon- structed palaeoshoreline. The internal cross-bedding is slightly offset to the south of the progradation direc- tion and shows a mean palaeocurrent direction towards 157°. Clinoform dip angles decrease asymptotically towards the lower boundary and merge into a clino- form toeset unit, several metres thick, rich in carbona- ceous detritus. Sigmoidal clinoforms in the upper part merge into a horizontally bedded, wave-influenced cli- noform top. It varies in thickness dependent on the amount of truncation and reaches a maximum thick- ness of 6.6 m at locality 9. In the southern part of the Visdal valley (locality 7), the upper part of CB4 is trun- cated by large-scale concave-up erosional surface over- lain by steeply dipping avalanche beds. The scour can be followed along strike for more than 1 km and down- dip for approximately 100 m. The dip angle of succes- sive avalanche beds in the scour fill decreases gradually upwards and down-dip from 30° to 6°. The top surface of CB4 shows a characteristic prox- imal (landwards) to distal (basinwards) development. The surface has been walked out in the Visdal area 50 m 40 14 67 30 20 10 0 E Mudderbugt Mb E SSE W 13 5 N 12 11a 11b W 8 9 10 4 Fig. 13. Fence-diagram of clinoform unit CB4 based on vertical sections at Visdal and Bays Fjelde. The cross-sections are somewhat idealised in order to show the component clinoform sets and the nature of the bounding surfaces. CB4 prograded towards the east and south-east and passes laterally into offshore mudstones (green) of the Kap Leslie Formation. Localities are shown in Fig. 1. 914 where it forms a spectacular, and easily recognisable surface separating cliff-forming coarse-grained sand- stones from soft silty mudstones (Fig. 2). In northern Visdal, localities 9–15, the surface is planar and roughly horizontal. South of locality 9, however, the surface dips approximately 6° towards the south-east. Small remnants of tidally-influenced sandstones erosionally overlie the uppermost prograding wedge association. The preserved thickness of this tidal unit varies along the valley and reaches a maximum of 5.5 m around local- ity 7. The boundary between CB4 and the tidally-influ- enced cross-sets is locally draped with fine pebbles. At locality 4, CB4 wedges out and the flooding surface capping CB4 coalesces with a flooding surface forming the top surface of the underlying sandstone unit. In the proximal area (localities 9–13), the upper boundary of CB4 is a strongly erosional surface truncating medium- to coarse-grained sandstones. The sandstones immedi- ately beneath the surface are cemented by siderite and show a characteristic reddish weathering colour in the uppermost 5 cm. The surface shows a microrelief of a few centimetres and is covered by a pebble lag, one clast thick (Fig. 17). The pebbles are subrounded to well- rounded, subprismoidal or spherical and consist of quartz and lithic fragments. The long axes are up to 4 cm long at locality 12, 2.5 cm at locality 11, and 3 cm at locality 9. The clasts form a laterally extensive pave- ment in the proximal area but are more dispersed bas- inwards. The trace fossils Skolithos isp. and Mono- craterion tentaculatum are common, with long vertical tubes descending from the top surface. 1 m N 20 cm Fig. 14. Sedimentary facies of the prograding wedge association, locality 11, northern Visdal. A: Coset of tidally-influenced planar cross-bedded sandstones; set boundaires indicated by dashed lines, coset boundary by the solid line. Area outlined shown in detail in Fig. 14B. B: Close-up of tidal cross-beds. Note the variation in bundle thickness interpreted as a cyclic variation controlled by the tidal cycle. Neap-tide bundles (N) are draped by carbonaceous mudstones. Note burrows extending down from set boundaries and at right-angles to the foreset surfaces. Bundle thickness increases and mud-drapes and bioturba- tion decrease from neap to spring-tide bundles. A B 915 Interpretation The deposition of large-scale cross-bedded units in marine settings has been attributed to a number of dif- ferent depositional settings (see review by Pomar & Tropeano 2001); a characteristic feature of these deposits is that they comprise coarse-grained laterally extensive bodies encased in fine-grained shelf or offshore deposits. The clinoform units described in this study may be in- terpreted to have formed by progradation of Gilbert- type deltaic lobes or progradational wedges deposited at the shoreface edge (transition-slope deposits of Pomar & Tropeano 2001). As stressed by Pomar & Tropeano (2001), however, differentiation between large-scale cli- noform units formed as shore-parallel tabular bodies and deltaic (Gilbert-type) lobes is only possible if extensive 3-D data are available. In this study, 3-D outcrops of the individual clinoform units are present in Visdal (Fig. 1), but regionally their large-scale geometry is poorly con- strained. We therefore adopt the purely descriptive term clinoform unit for the large-scale cross-bedded sand- stone beds rather than using a generic term such as tran- sition-slope lithosome or delta lobe. The clinoforms represent the depositional surfaces of the prograding wedges at specific times. Progradation was largely controlled by the migration of ripples and dunes transporting sediment across the shelf/delta plat- form and down the front of the prograding wedge. The migration of these bedforms was at a slightly oblique angle to the main direction of progradation and was probably influenced by southwards-directed longshore currents. Wave influence was rather limited and seems Fig. 15. A: Prograding clinoform set in Visdal (CB4, locality 8) showing clino- forms dipping towards the south-east (to the right). The clinoforms bound sets of small-scale low-angle trough cross-sets. Scale (encircled) is 20 cm long. B: Close-up of A showing clinoforms (arrows) with internal trough cross-sets. The ripples forming the intrasets migrated at a slightly oblique angle to the progradation direction of the clino- forms. Scale divisions are centimetres. A B 916 1 m Fig. 16. A: Prograding clinoform set in Visdal (CB4, locality 9) showing clino- forms dipping towards the viewer in a south-easterly direction. The clinoforms bound small-scale low-angle trough cross-sets and planar cross-sets. Outlined area shown in Fig. 16B. B: Close-up of A showing planar cross-bedded intrasets. Scale is 20 cm long. Fig. 17. Pebbly sandstone lag (bedding plane view) deposited on the coalesced sequence boundary and transgressive surface of erosion forming the upper boundary of CB4. Locality 12, northern Visdal; scale in centimetres. A B only to have influenced deposition in the uppermost part of the clinoform unit, whereas tidal influence was locally strong. The tidal currents were probably restricted to channels and their deposits may be characteristic of certain phases of the progradation event. The base of the prograding wedge (the toe of the clinoforms) was situated below storm wave-base as indicated by the absence of wave-generated structures. The water depth in front of the prograding wedge can be estimated from the thickness of the clinoform unit and was at least 50 m during the progradation of CB4. The basin floor was dominated by deposition of silt and mud from sus- pension accompanied by strong bioturbation. Progradation was not a continuous process, and can be divided into phases based on the different types of clinoform sets (facies 11–13). Each of the clinoform types is thus interpreted to represent a particular progra- dational phase controlled by autocyclic processes (sedi- ment supply) and/or changes in relative sea level. The clinoform units CB1, CB2, and CB4 are dominated by the steep clinoforms of the prograding clinoform sets (facies 11). The rather high angle of the clinoforms is unusual, but such angles have been described as a char- acteristic feature of bed-load dominated systems pro- grading during a fall in relative sea level (Posamentier & Morris 2000). The change in sea level results in erosion of previously deposited sediments and hinders aggrada- tion. This creates a high relief front of the progradational wedge with steeply dipping foresets as the depositional system is forced to prograde into deeper water. The high inclination of the clinoforms is controlled firstly by an abrupt deepening in front of the prograding wedge, sec- ondly by the coarse grain size and thirdly by prograda- tion during falling sea level. Examples of such steeply dipping large-scale foresets have been described from the Recent Alta delta (Norway) in which the foresets dip at angles of 8–37° (Corner et al. 1990), from the Campanian Panther Tongue Member in Utah (Posamentier & Morris 2000), in which the clinoforms of the delta front are up to 15 m high and dip at angles up to 27°, and from the Calcarenite di Gravina Formation in southern Italy (Pomar & Tropeano 2001) which displays large-scale cross-bed- ding with foreset dips up to 35°. In CB4, the progradational clinoform sets locally show a gradational upwards change to planar cross-bedded low-angle clinoform sets (facies 12; aggradational). This may reflect the build-up of smaller depositional units on the shelf platform in response to short periods of rising sea level. The platform deposits are capped by a fine- grained and strongly bioturbated sandstone unit which represents the abandonment of the depositional system in response to rising sea level or a shift in the current sys- tem transporting sediment to the prograding wedge. The progradation of the coarse-grained unit probably took place during a short time interval relative to the accu- mulation of the fine-grained carbonaceous facies. The downstepping of successive clinoform sets (facies 13; offlapping) accompanied by erosion of the previ- ously deposited sediments suggests that deposition occurred in response to falling relative sea level. Certain clinoform sets can be followed in outcrop and show a southwards shingling. The southwards migration of the depositional system was probably controlled by southerly-directed currents, which also dominated de- position of the shoreface facies association. In the proximal western area, the very low-angle depositional surfaces and the well-developed planar cross-sets indicate deposition under the influence of tidal currents. The large-scale planar cross-sets, up to 1.5 m thick, reflect deposition by large-scale two-dimen- sional dunes. The dunes are ebb-dominated as shown by the southerly current direction. The reactivation sur- faces, systematic changes in bundle thickness and reversed current ripples associated with double mud drapes testify to active tidal currents during dune migra- sion and suggest a strongly asymmetric and rectilinear character of the tidal current ellipses (Nio & Yang 1991a, b). Deposition of mud drapes and formation of reacti- vation surfaces would be strongly favoured by chan- nelised tidal currents with pronounced slack water periods and a relatively weak wave influence charac- terising an in-channel depositional environment (Nio & Yang 1991a, b). The geometry of the channel can- not be recognised but a channel environment is sup- ported by the erosional lower boundary and the fining-upwards and thinning-upwards trends. Offshore association (facies 8) The offshore facies association consists of parallel-lam- inated silty mudstones with thin sandstone layers and concretionary horizons (facies 8). The association forms the bulk of the Kosmocerasdal Member, representing the distal equivalent to sandstones of the Charcot Bugt Formation (Fig. 4). Description At Kosmocerasdal (Fig. 1, locality 1), the association is characterised by silty and sandy mudstones forming 917 coarsening-upwards successions up to 20 m thick, capped by a sandy bed or a concretionary layer with abundant ammonites. The mudstone succession is other- wise unfossiliferous and bioturbation is rare. The total organic carbon (TOC) content is below 1% which is char- acteristic for the lower part (Callovian) of the Kosmo- cerasdal Member. At Visdal, the basal few metres of the offshore suc- cession (Middle Oxfordian) consist of black finely lam- inated mudstones with abundant small Chondrites isp. burrows. Several horizons are glauconitic. Above the basal unit, the succession consists of monotonous mud- stone units interbedded with thin layers and concre- tionary horizons of fine-grained sandstones. Geochemical analysis shows TOC values of 4–7%, decreasing upwards to less than 1%. Macrofossils are rare and restricted to ammonites and bivalves. Well-sorted, erosionally based, fine-grained sand- stones, up to c. 30 cm thick, are interbedded with the silty mudstones. The sandstones are highly micaceous and may contain abundant carbonaceous detritus. They are massive or show small-scale wave ripple cross-lam- ination which passes laterally into hummocky cross-strat- ification. The sandstones are bioturbated; Skolithos isp. and Taenidium serpentinum are common. Body fos- sils are common in the sandstones but not in the silty mudstones (Callomon & Birkelund 1980; Fürsich 1984). This may reflect the nature of the exposures, but may also reflect primary differences in abundance. Interpretation The muds were deposited from suspension fall-out in a marine offshore environment around and below storm wave base, as testified by the fine grain size and the parallel lamination. The sharp-based sandstone beds are interpreted as having been deposited during single storm events whereas the thicker units represent amal- gamated deposits formed during successive storms. The well-sorted fine-grained sediment and the small-scale wave ripple cross-lamination associated with hummocky cross-stratified levels suggest deposition on a shoreface between fair-weather and storm wave base (Duke 1985). Comparison with recent shallow marine environments suggests water depths of 15–30 m (Harms et al. 1975, 1982; Dott & Bourgeois 1982; Brenchley et al. 1986, 1993). The sands were probably transported in sus- pension by storm-induced currents into the otherwise mud-dominated offshore environment. The fine-grained development of the offshore association at Visdal in the upper C. tenuiserratum and A. glosense Chronozones is also associated with glauconitic horizons, which rep- resent periods of low sedimentation rates. On modern shelves, glauconite is characteristic of sediment-starved offshore environments seawards of the 30 m isobath (Blatt et al. 1980; Swift & Parsons 1995). Facies successions Two facies successions representing a basinal (eastern) and proximal (western) position, respectively, are de- scribed in order to illustrate changes in the depositional environments through time. Recognition of the facies successions is based on vertical sections; they are shown in the geological cross-section in Figure 18. The eastern basinal area The succession in the eastern, most basinwards position, probably comprises the oldest sediments outcropping in Milne Land (Fig. 4). From below, the succession con- sists of a poorly exposed unit of the alluvial associa- tion overlain by a thick succession of stacked shoreface sandstones. In the better-exposed upper part of the succession three stacked clinoform units CB1–CB3 occur (Fig. 18). Each of these units represents a seawards shift in facies suggesting that they formed in response to relative falls in sea level (see previous discussion under the prograding wedge association). The stack- ing of such sand bodies may be controlled by the fixed position of the basin margin or by a change in shoreface gradient due to underlying faults (Jerzykiewicz & Wojewoda 1986; Trincardi & Field 1991). The geome- tries of the clinoform units CB1–CB3 cannot be ascer- tained due to limited exposure, but it is possible that they represent laterally extensive sheet-like bodies as described from the Volgian Raukelv Formation of Jameson Land (Surlyk & Noe-Nygaard 1991) and from the Calcarenite di Gravina Formation of Italy (Pomar & Tropeano 2001). The sandstone bodies are truncated by transgressive surfaces of erosion overlain by a ravinement bed (facies 7) containing worn belemnites and vertical burrows of Diplocraterion habichi. In CB3, the pebbly sandstone lag is directly overlain by offshore marine mudstones indicating a marine flooding and a marked landwards shift in facies. Offshore mud deposition continued throughout the Late Callovian – Middle Oxfordian at this locality indicating that the sand-dominated depositional 918 919 10 m 1 km 3 5 12 W es t Ea st 2 1 M ud st on e Li th ol og y St ru ct ur e Tr ac e an d bo dy fo ss ils K ey s ur fa ce s Sa nd st on e C on gl om er at e C ry st al lin e ba se m en t Pe bb le la g Se qu en ce b ou nd ar y (S B) Fa ci es a ss oc ia tio ns A llu vi al R oc ky s ho re Sh or ef ac e M as si ve Lo w o rd er H ig h or de r H ig h or de r H ig h or de r Lo w o rd er H ig h or de r Lo w o rd er ? ?? A m m on ite Be le m ni te Sk ol ith os is p. D ip lo cr at er io n ha bi ch i Pl an ol ite s is p. Pa ra lle l- la m in at ed La rg e- sc al e cr os s- be dd ed Tr ou gh cr os s- be dd ed Pr og ra di ng w ed ge O ffs ho re C lin of or m s C ov er ed D ir ec tio n of cl in of or m pr og ra da tio n D at um C. c or da tu m C hr on oz on e C ry st al lin e ba se m en t M ar in e flo od in g su rf ac e (F S) C B 4 m ud sa nd m ud sa nd m ud sa nd m ud sa nd m ud sa nd C B 1 C B 2 C B 3 Fi g. 1 8. C ro ss -s ec tio n t h ro u gh t h e C h ar co t B u gt a n d l o w er K ap L es lie F o rm at io n s sh o w in g fa ci es a ss o ci at io n s an d s eq u en ce s tr at ig ra p h ic k ey s u rf ac es . T h e cr o ss -s ec tio n i s b as ed o n se le ct ed k ey s ec tio n s (f o r lo ca tio n s, s ee F ig . 1) . system remained in a more landwards position, proba- bly due to a major rise in relative sea level. It is also pos- sible that a barrier formed by a step in the crystalline basement surface was transgressed in the Late Callovian resulting in a more permanent landwards translation of the sandstone-dominated depositional system, even dur- ing a relatively small rise in relative sea level. The western basin margin At Visdal, coarse-grained deposits formed by rework- ing of alluvial and shoreface deposits during an over- all Middle Jurassic transgression dominate the basal part of the Charcot Bugt Formation (Fig. 18). The most characteristic deposit is the coarse-grained rocky shore association which rests either directly on the subaerial unconformity formed by the crystalline basement sur- face or on a submarine ravinement surface developed on top of alluvial sediments. The coarse-grained deposits represent stacked lags formed by wave ravinement dur- ing several sea-level cycles and are time transgressive (see Kidwell 1989). The marine conglomerates are trun- cated by numerous erosional surfaces, some of which may have formed in response to relative sea-level changes of regional significance. The coarse-grained amalgamated nature of the succession and evidence of local erosion by rip channels and shoaling waves, however, preclude distinction between local and regional surfaces. The nature of the exposures also precludes direct tracing of the erosional surfaces into the shoreface deposits. A few kilometres seawards of the rocky shore, the deposits are dominated by stacked coarsening-upwards progradational shoreface units forming parasequences or simple sequences (Fig. 18). Within the shoreface units, the transgressive part is subordinate (Arnott 1995) and is only represented by a thin lag conglomerate, which may be overlain by a mudstone unit less than one metre thick. The bulk of the units represent progra- dational shoreface deposits formed in response to increasing sediment supply or were controlled by changes in relative sea level. The upper part of the Charcot Bugt Formation at Visdal shows a marked change from the stacked high- stand shoreface units to clinoform unit CB4. It reaches a thickness of 50 m and downlaps onto transgressive mudstones overlying large-scale cross-bedded shoreface deposits (Fig. 18). In the most proximal western areas, the lower boundary cuts deeply into the underlying deposits. Two stacked fining-upwards units that con- sist exclusively of tidally-influenced cross-sets (facies 10) dominate the overlying deposits and the incision may mark the position of a tidal channel. These deposits are downlapped by high-angle, tangential clinoforms of a progradational clinoform set. CB4 has a lobate plan geometry and wedges out over a few kilometres towards the south-east and east. The top of clinoform unit CB4 is strongly truncated in the proximal western part where it is overlain by a coarse-grained pebble lag of fluvial affinity. Towards the east, the lag fines and grades into a lag deposit of flat, rounded quartzitic pebbles and worn belemnites that is interpreted to have formed by wave winnowing during marine transgression. CB4 is erosionally overlain by coarse-grained shoreface sandstones (Mudderbugt Member) in the southern part of the Visdal valley. Following progradation of CB4, the depositional sys- tem was drowned and succeeded by offshore marine muds indicating that the sand-dominated depositional system shifted further westwards during the Middle Oxfordian. The mudstones are characterised by small Chondrites isp. burrows and glauconitic horizons, sug- gesting a sediment-starved, oxygen-restricted environ- ment. Biostratigraphic data show that the offshore mudstones of the lower Kosmocerasdal Member in the eastern outcrop area are contemporaneous with the coarse-grained marine deposits of the Charcot Bugt Formation to the west. The variation in grain size and content of organic material reflect changes in energy regime, sedimentation rates and probably water depths. The coarsening-upwards offshore successions corre- late with progradational units in the Charcot Bugt Formation and shallow-water sandstones encountered in the easternmost outcrops correspond to the final progradation of the Charcot Bugt Formation during the C. tenuiserratum Chron (Fig. 4). In contrast, the most fine-grained levels were deposited during periods of increasing water depth. Condensation reflected by high diversity and density of dinocysts and high TOC val- ues are seen in mudstones of the Q. lamberti ?, upper Q. mariae – lower C. cordatum and upper C. tenuis- erratum – A. glosense Chronozones. Bioturbation dur- ing these periods was dominated by Chondrites isp. Sequence stratigraphic model A hierarchy of depositional sequences is recognised in the Middle–Upper Jurassic succession of Milne Land and is related to two, or possibly three, orders of rela- tive sea-level change. The low order cycle has a dura- tion of c. 30 Ma (Bathonian–Volgian) and corresponds 920 in duration to the second order cycles of Vail et al. (1977). The higher order cycles of the Charcot Bugt Formation may correspond to third order cycles, al- though a genetic background for cycle orders has never been demonstrated (see discussion by Miall 1997). The highest order cycles that can be differentiated are related to the internal upbuilding of the clinoform units, although it is difficult to separate sea-level from autocyclic con- trol at this level. Low order cycle The Jurassic – lowermost Cretaceous succession of East Greenland has been interpreted within a low-resolution sequence stratigraphic framework (Surlyk 1990, 1991). The cycle is bounded below by a regional sequence boundary, which in Milne Land coincides with the onlap unconformity between the crystalline basement and the Middle Jurassic sediments. No low order lowstand deposits are preserved along the western basin margin, which was probably bypassed by sediment during most of the Early Jurassic. A rise in relative sea level is reflected by the Bathonian – Middle Oxfordian westwards onlap onto the crystalline basement and by the marked back- stepping of the depositional systems. The Charcot Bugt Formation and the lower part of the Kap Leslie Formation are thus interpreted to represent the transgressive deposits of a low order sea-level cycle. The maximum flooding zone is represented by Lower Kimmeridgian laminated organic-rich shales of the Gråkløft Member, Kap Leslie Formation (Birkelund et al. 1984). The sequence is bounded at the top by a major unconformity that is recognised within the sandstone-dominated Hartz Fjeld Formation (Birkelund et al. 1984; Surlyk et al. 1993). The low order depositional cycle probably reflects increasing rates of subsidence from the onset of rifting in the Late Bajocian to rift climax in the Middle Volgian followed by decreasing subsidence rates accompany- ing waning of rifting in the latest Volgian – earliest Cretaceous. The regional sea-level cycle correlates with the onset, increase and climax of rifting as recognised throughout the Northern North Sea – North Atlantic region (Ziegler 1988). High order cycles The high order sequence stratigraphic interpretation is based on facies successions and the identification of stratigraphic surfaces across which occur major shifts in facies. The correlation and interpretation of high order cycles are supported by biostratigraphic data, but due to their low resolution we are not able to docu- ment hiati across the identified sequence boundaries. A subdivision of the entire succession into a definite number of high order cycles is hampered by exposure quality and lack of correlation between the eastern area (localities 1, 2) and the western area (localities 3–19). In the following, however, we discuss sedimentary suc- cessions that we believe formed as a result of high order relative sea-level changes. The clinoform units CB1–CB4 unconformably over- lie marine shoreface sandstones or offshore mudstones and represent periods of rapid progradation introduc- ing relatively coarse-grained sandstones into more basi- nal environments. The clinoform units are interpreted as having been formed during falling sea level and pos- sibly early lowstand and define high order sequences. The sandstones may thus be placed in the falling stage systems tract and are capped by the sequence bound- ary (Hunt & Tucker 1993, 1995; Plint & Nummedal 2000). The stacking of CB1–CB3 in a relatively basinal position and the relatively steep nature of the clinoforms suggests that the clinoform units were deposited in a shelf-edge position and thus mark the maximum progra- dation during a fall in relative sea level. The clinoform units are truncated by a transgressive surface of ero- sion concealing a sequence boundary, and are overlain either by a shoreface unit (CB1, CB2) or directly by off- shore mudstones (CB3, CB4). Following progradation of CB3, a marked backstep- ping of the entire depositional system translated the shoreline far to the west of the present-day outcrop area and deposition in Milne Land was characterised by silty mudstones of the Kosmocerasdal Member. During a subsequent sea-level fall, the clinoform unit CB4 prograded, but did not reach the former position of the shelf-edge. In the proximal areas, the presence of a distinct pebble lag suggests that a fluvial system was developed during the final phase of progradation. The upper part of CB4, however, was reworked during the following transgression and the top of CB4 represents a coalesced sequence boundary and transgressive surface of erosion. The transgressive shoreface deposits of the Mudderbugt Member were formed by reworking of the prograding wedge sands in the southern part of the Visdal valley. The transgressive surface of erosion form- ing the upper boundary of the Charcot Bugt Formation is overlain by offshore glauconitic marine mudstones of the Kap Leslie Formation which are interpreted to form the transgressive systems tract of the following sequence. 921 The boundary between the Charcot Bugt and Kap Leslie Formations appears, at first sight, to represent a single transgressive surface of erosion. Detailed sedi- mentological and biostratigraphical data show, how- ever, that it represents a system of shingled sub-hori- zontal transgressive surfaces of erosion (Figs 4, 18). The transgressive surfaces apparently merge basin- wards, as suggested by Surlyk (1991) for the boundary between the contemporaneous Pelion and Fossilbjerget Formations in Jameson Land. The understanding of the stratal geometry is crucial for the sequence stratigraphic interpretations and for the correct correlation of genet- ically linked depositional systems (Posamentier et al. 1992). Marine transgressive surfaces of erosion are the most regionally extensive and continuous surfaces in the Charcot Bugt Formation and some may be traced throughout the entire outcrop. This may be due to their high preservation potential and the fact that marine trans- gressive erosion commonly removes evidence of subaerial and marine surfaces formed during times of fall and low- stand of sea level leaving only a thin lag deposit (Plint 1988; Posamentier et al. 1992). Wave ravinement is able to remove a significant amount (up to 20 m) of the pre- viously deposited succession (Demarest & Kraft 1987). The sequence stratigraphic model for the Charcot Bugt – Kap Leslie Formations suggests a marked spa- tial shift in depocentres of the deposits of the different systems tracts, although each of the facies associations contain facies deposited during both falling and rising relative sea level (Fig. 18). The basinwards eastern area is dominated by stacked falling stage/lowstand sand- stone bodies erosionally overlain by thin transgressive lags. Highstand deposits occur, but are thin. In the prox- imal western areas near the structurally controlled basin margin, transgressive deposits onlap the crystalline base- ment. They are remarkably coarse-grained and thickly developed due to the steep gradient rocky shore. Alluvial sediments are preserved in topographic lows. These sediments overlie the sequence boundary and are trun- cated by the transgressive surface of erosion; they thus belong to the lowstand systems tract. Off the rocky shore, the succession is dominated by stacked parase- quences representing progradational shoreface units referred to the highstand systems tract (Fig. 18). Contemporaneous successions The Charcot Bugt Formation forms the basin margin cor- relative of the Pelion, Fossilbjerget and Olympen Formations of Jameson Land. The detailed Middle Jurassic Boreal ammonite zonation allows direct cor- relation of the successions and the stacking of deposi- tional units can be shown to be broadly similar (Fig. 19; Engkilde & Surlyk 2003, this volume; Larsen & Surlyk 2003, this volume). Progressive basin margin onlap to the west and north in the basin occurred during depo- sition of the Upper Bajocian – Lower Bathonian se- quences P2 and P3, accompanied by a northwards shift of the depocentre (P after Pelion Formation, see Engkilde & Surlyk 2003, this volume). Sequence P3 was deposited during the Early Bathonian A. arcticus Chron and can be correlated with shallow marine sandstones of the basal Charcot Bugt Formation (Fig. 19). Engkilde & Surlyk (2003, this volume) suggested that sequence P3 correlates with sandstones forming a thick transgressive systems tracts on the islands of Traill Ø and Geographical Society Ø (Fig. 1). The backstepping of high order sequences and the formation of thick transgressive deposits at the basin margin are thus characteristic fea- tures of the Boreal Upper Bajocian – Lower Bathonian Jameson Land Basin (Engkilde & Surlyk 2003, this vol- ume). In Milne Land, the Middle Bathonian A. ishmae Chrono- zone is represented by shoreface sandstones in the lower part of the Charcot Bugt Formation and can be correlated with sequence P4 in Jameson Land. Deposition of sequences P4 and P5 of the Vardekløft Group was characterised by backstepping in response to continued sea-level rise. The transgressive systems tract of sequence P5 is characterised by ammonites of Tethyan affinity suggesting that the transgression may be significant outside East Greenland, opening for oceanic circulation to the south (Callomon 1993; Engkilde & Surlyk 2003, this volume; Alsen & Surlyk in press). In Milne Land, the Middle Bathonian A. crano- cephaloide Chronozone is represented by a thick rocky shoreline succession, which can be correlated with highstand deposits of sequence P5. Backstepping con- tinued through sequences P6–P8, but was interrupted by a short progradational event reflected in the depo- sition of the sandy Parnas Member (highstand deposits of P6) in northern Jameson Land (Heinberg & Birkelund 1984; Engkilde & Surlyk 2003, this volume). The progra- dation took place near the boundary between the Lower Callovian C. nordenskjoeldi and P. koenigi Chronozones. This may correlate with the marked progradation of CB3 in Milne Land (Fig. 21). The maximum transgression recorded in the Varde- kløft Group is represented by highly condensed deposits of sequence P8 and the overlying condensed mudstone succession of the Fossilbjerget Formation, which formed 922 during the Callovian S. calloviense, K. jason and E. coro- natum Chrons (Surlyk et al. 1973; Callomon 1993; Engkilde & Surlyk 2003, this volume). This transgres- sive interval correlates with the backstepping of the Charcot Bugt Formation in Milne Land and deposition of the thick mudstone succession of the lower Kosmo- cerasdal Member (Fig. 19). A renewed progradational phase occurred in Jameson Land in the P. athleta Chron and is represented by deep-water turbidites of the Athene Member of the lower Olympen Formation (Larsen & Surlyk 2003, this volume). In Milne Land, the succession is poorly documented but may tentatively be correlated with a thick unfossiliferous sandstone succession exposed at Visdal and Aldinger Elv. The sandstones are overlain by carbonaceous mudstones rep- resenting a major drowning of the coarse-grained depo- sitional system. The mudstone succession in Milne Land is rich in dinoflagellates and is correlated with the C. cordatum Chronozone in Jameson Land. It is repre- sented by a thick mudstone succession in the Hades Member of the Olympen Formation (Fig. 19). The thick clinoform unit CB4 represents the final progradation of the Charcot Bugt Formation in Milne Land. It prograded during the late C. cordatum and C. densiplicatum Chrons and correlates with coarse-grained deltaic deposits of the upper Olympen Formation (Fig. 19, Zeus Member; Larsen & Surlyk 2003, this volume). The close correlation of the successions in Milne Land and Jameson Land suggests that they were de- posited in a major basin covering the entire area. The facies differences probably reflect the position relative to the basin margins and to the main sediment entry points. The marked change from the Bajocian–Callovian ramp setting into the Oxfordian–Kimmeridgian shelf- slope setting illustrated by the Pelion, Fossilbjerget and Olympen Formations (Engkilde & Surlyk 2003, this vol- ume; Larsen & Surlyk 2003, this volume), is thus not significant in the Milne Land succession where a shal- low shelf environment existed throughout the Middle and early Late Jurassic. Stratigraphic correlation on formation scale between lithostratigraphic units in East Greenland and the North 923 A. rosenkrantzi A. regulare A. serratum A. glosense C. tenuiserratum C. densiplicatum C. cordatum Q. mariae Q. lamberti P. athleta E. coronatum K. jason S. calloviense P. koenigi C. nordenskjoeldi C. apertum C. calyx C. variabile A. cranocephaloide A. ishmae A. greenlandicus A. arcticus C. pompeckji C. indistinctus C. borealis Boreal Chronozones Chrono- strati- graphy Dinoflagell. cyst assembl. Milne Land Ba jo ci an Ba th on ia n C al lo vi an O xf or di an M M M U U U U L L L L M id dl e Ju ra ss ic U pp er Ju ra ss ic Sequence stratigraphy 140 km 200 km Milne Land Jameson Land W E S N Ass. 8 Ass. 7 Ass. 6 Ass. 5 Ass. 4 Ass. 1 Ass. 3 Ass. 2 Hareelv Fm Hades MbOlympen Fm Fossilbjerget Fm No exposure Zeus Mb Athene Mb P8 P7 P6 P4 P3 P2 P1 P5 Pelion Fm Lower Jurassic Fine-grained sandstone Coarse-grained sandstone Mudstone Crystalline basement No exposure ? ? CB1 CB2 CB3 CB4 Aldinger Elv Mb Kosmocerasdal Mb Kap Leslie Fm Bays Elv Mb Charcot Bugt Fm Fig. 19. Sequence stratigraphic model for the Milne Land – Jameson Land successions based on Larsen (1995), Engkilde & Surlyk (2003, this volume), Larsen & Surlyk (2003, this volume), and this study. Atlantic and the Northern North Sea has been made by numerous authors (e.g. Birkelund 1975; Larsen 1987; Doré 1991; Partington et al. 1993; Dam & Surlyk 1995, 1998). Surlyk et al. (1993) and Engkilde & Surlyk (2003, this volume) demonstrated the close similarities between sequence stacking patterns of the Vardekløft Formation in East Greenland and correlative rocks in the North Atlantic region. The coarse-grained falling stage/low- stand sandstone bodies of the Charcot Bugt Formation thus represent an excellent reservoir analogue and may form the basis for developing a new Middle Jurassic strati- graphic play. Conclusions New biostratigraphic data are presented for the Middle and Upper Jurassic succession of Milne Land based on ammonite collections and palynology. Correlation of the coarse-grained sandstones of the Charcot Bugt with the fine-grained offshore Kap Leslie Formation suggests a genetic depositional relationship with a proximal to distal decrease in grain size. A widespread transgression in East Greenland took place following a major uplift period in late Early Jurassic – earliest Middle Jurassic times and the coarse-grained amalgamated deposits of the basal Charcot Bugt For- mation were deposited in front of a steep rocky shore. Estimates of the Middle Jurassic relative sea-level rise are based on contour maps of the onlap surface between crystalline basement and shallow marine sediments. An overall sea-level rise of more than 300 m is documented, which is independent of sediment supply except for the loading effects. The most characteristic facies is represented by cli- noform units up to 52 m thick with compound clino- forms dipping up to 24°. The clinoform units consist of coarse-grained, locally pebbly sandstones forming a progradational wedge deposited during falling relative sea level. The unusually steep clinoforms are probably a function of the coarse grain size and high prograda- tion rates into a relatively deep-water basinal setting. A sequence stratigraphic interpretation involving two orders of sea-level cycles is presented based on spatial changes in depositional systems (facies associations), the nature of bounding surfaces and biostratigrapic data. This model suggests that lateral shifts in depocen- tres are related to changes in the relative sea level. Thus, falling stage/lowstand prograding wedges occur to the east in a relatively distal position and are encased in distal shoreface and offshore deposits. Acknowledgements M.L. gratefully acknowledges the Carlsberg Foundation for funding of a Ph.D. stipendium and field work in East Greenland (91-0683/20, 92-0505/20, 93-0735/20). The stratigraphic analysis was supported by the Danish Energy Agency, EFP93/0010 and 0017. 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Samples 409552, 409553 and 409554 were collected from silty mudstones below the horizon containing ammonites of the A. arcticus Chronozone at locality 8 in Visdal (Fig. 6). Description. The assemblage comprises Crussolia perireticulata, Lithodinia cf. reticulata, Solisphaeridium ankyleton, Pareodinia ‘birkelundia’, Sentusidinium pelionense, Dichadogonyaulax sell- woodii, Durotrigia daveyi, Kallosphaeridium hypornatum, Pareodinia halosa and Sirmiodinium grossii. The assemblage is of low density and diversity. In Jameson Land, most of these morphologically characteristic species have their stratigraphic base in the C. pompeckji Chronozone or lower (Fig. 5). In con- trast, Sirmiodinium grossii first appears in the lowermost A. arcti- cus Chronozone in Jameson Land. The presence of Crussolia perireticulata, Atopodinium sp. and especially A. haromense in this assemblage indicates that these species appear at a lower stratigraphic level than in nearby Jameson Land. The palyno- logical evidence of the age of assemblage 1 is not very clear, but the presence of S. grossii is suggestive of the earliest A. arcticus Chron, in accordance with the ammonite data. Chronostratigraphy. A. arcticus Chronozone, Bathonian. Assemblage 2 Ammonite stratigraphy. The palynomorph assemblages were obtained from samples collected between horizons containing ammonite faunas referred to the A. arcticus (Jameson Land fauna 9–10) and A. cranocephaloide/C. variabile Chronozones (Fig. 5; Milne Land fauna M1 and younger, Jameson Land fauna 18–21). Samples. Sample 409455 (409457 barren) from locality 8 in Visdal. Description. The common occurrence of Gonyaulacysta pec- tinigera, Aldorfia aldorfensis and Chytroeisphaeridia chytroeides in the sample indicates an earliest C. variabile Chron age, on the basis of correlation with data from Jameson Land. Chronostratigraphy. C. variabile Chronozone, Bathonian. Assemblage 3 Ammonite stratigraphy. The palynomorph assemblage occurs above ammonite-bearing beds referred to the A. cranocephaloide? Chronozone (Milne Land fauna M1 and Jameson Land fauna 18–19). Samples. Sample 234049 is from a mudstone bed overlying sand- stones that yielded an ammonite referred to the A. crano- cephaloide? Chronozone at Kosmocerasdal (Fig. 1, locality 1; Callomon & Birkelund 1980). Description. This odd assemblage from just one sample is char- acterised by a flood of Ctenidodinium sp.; this event has not been identified in Jameson Land. The appearance of Evansia granu- lata supports the age indicated by the ammonite from the under- lying beds as it has its first occurrence in the A. cranocephaloide Chronozone in Jameson Land; the underlying A. ishmae Chronozone has not, however, been studied in detail. The mini- mum age of this assemblage is poorly constrained both on the basis of ammonites and dinoflagellate cysts, but Kallosphaeri- dium inornatum and Lithodinium cf. reticulata, both of which are present in the assemblage, occur in the uppermost part of the P. koenigi Chronozone in Jameson Land. Chronostratigraphy. A. cranocephaloide/C. variabile Chronozones, Bathonian. Assemblage 4 Ammonite stratigraphy. Sample 255155 was collected from above beds referred to the A. cranocephaloide/C. variable Chronozones on the basis of ammonites (Jameson Land fauna 19–21). Samples. Samples 255148, 255155 and 409556 are from locality 1 at the base of clinoform unit CB2 in Kosmocerasdal and locality 8 in Visdal (Fig. 1). Sample 409556 is from a mudstone horizon above, but close to an ammonite horizon indicating the A. crano- cephaloide/C. variabile Chronozones. Samples 255155 and 255148 are thought to be from the same horizon but are separated laterally and direct correlation is not possible. Description. The diversity of the assemblage varies but abundant Chyctroeisphaeridia hyalina, Evansia granulata, Sentusidinium pelionense and Lithodinia cf. reticulata characterise the microflora. The appearance of abundant new species suggests a clear sep- aration in time from the underlying assemblage. Chytriasphaeridia hyalina, Atopodinium polygonalis and Evansia granulata be- come abundant for the first time in the C. calyx Chronozone in 929 Jameson Land. Evansia janeae occurs only in the C. calyx Chronozone in Jameson Land in contrast to the occurrence in Milne land. Lithodinia spongiosa is restricted to the C. calyx and C. aper- tum Chronozones in Jameson Land. A number of characteristic species appearing in this assemblage, viz. Evansia cerebraloides, Paragonyaulacysta sp. (cf. calloviense, Baylei et al.), Kalyptea stegasta, Sentusidinium sp. D (Fensome 1979), Ctenidodinium thulium and Meiourogonyaulax cf. planoseptata, are considered stratigraphically significant but cannot yet be correlated precisely with the succession in Jameson Land. Chronostratigraphy. C. calyx/C. apertum Chronozones, Bathonian. Assemblage 5 Ammonite stratigraphy. None. Samples. Three samples in stratigraphic succession from the bot- tomset of clinoform unit CB3 at Kosmocerasdal (locality 1): 409697, 409698 and 409699. Description. Abundant new species appear in assemblage 5, again indicating a clear time difference to the underlying assemblage. The assemblage is of high density and diverse in contrast to the earlier assemblages. Sirmiodinium grossii, G. pectinigera, Litho- sphaeridium cf. reticulata, Atopodinium sp., Evansia cerebraloides, Ctenidodinium thulium and Sentusidinium sp. D (Fensome 1979) become abundant and Rhynchodiniopsis cladophora, Gonyaula- cysta cf. helicoidea, Gonyaulacysta jurassica, Fromea tornatilis, Chytroeisphaeridia chytroeides, Ellipsoidictyum cinctum and Lithodinium jurassica appear for the first time. Approximately 50% of the species in assemblage 5 occur in the earlier assem- blages but not with this high abundance. Only a few of the new species in the assemblage are abundant. Local correlation. Abundant G. pectinigera has an upper limit in the basal P. koenigi Chronozone in Jameson Land; this limit is recognised within this assemblage. Crussolia perireticulata has an apparent top in the C. nordenskjoeldi Chronozone in Jameson Land and this may also be recognised within this assemblage. Chytroeisphaeridia chytroeides is almost wholly restricted to this interval, and is similarly present or abundant in the C. norden- skjoeldi Chronozone in Jameson Land. Atopodinium polygonalis is only recorded in the C. calyx and C. apertum Chronozones in Jameson land, whereas Paraevansia brachythelis is recorded in the C. apertum and C. nordenskjoeldi Chronozones. A suite of species which are uncommon in the assemblage have their strati- graphic tops in the basal P. koenigi Chronozone in Jameson Land. Chronostratigraphy. C. nordenskjoeldi – earliest P. koenigi Chronozone, Lower Callovian. Assemblage 6 Ammonite stratigraphy. The assemblage occurs beneath ammo- nite-bearing beds referred to the P. athleta Chronozone. Samples. Two samples (255153, 255154) in the basal strata of the Kap Leslie Formation in Kosmocerasdal (locality 1). Description. The assemblage is characterised by medium diver- sity and low abundance. Chytroeisphaeridia hyalina is the only abundant species accompanied by Pareodinia prolongata in one sample. Only few stratigraphically new species appear in the assemblage suggesting stratigraphic proximity to the underlying Assemblage 5. Local correlation. The ammonite and dinoflagellate stratigraphy in the Jameson Land Basin is not well correlated in the interval between the S. calloviense and P. athleta Chronozones (fauna M2), but the distribution of dinoflagellate cysts in both chronozones is fairly well known. In Jameson Land, Chytroeisphaeridia hyalina occurs in abundance in the S. calloviense Chronozone, coinci- dent with the last continuous occurrence of Gonyaulacysta pec- tinigera. The only abundant dinoflagellate recorded by Fensome (1979) from the S. calloviense Chronozone of Jameson Land was Valensiella dictydia (15–30% of the assemblage), associated with Gonyaulacysta pectinigera and Valensiella ovula (5–15% of the assemblage). V. dictydia and V. ovula have been recorded pre- viously from these strata (Piasecki 1980; Smelror 1988) but were not observed in the present samples. Fensome (1979) also described Paragonyaulacysta sp. (possibly equivalent to Para- gonyaulacysta retiphragmata) from this chronozone and his species is recorded here. The assemblage is correlated with the S. calloviense Chronozone. Chronostratigraphy. S. calloviense Chronozone, Lower Callovian. Assemblage 7 Ammonite stratigraphy. None. Samples. Samples (255147, 255149–255151, 409543, 409544, 409550, 409558) from the bottomset of clinoform unit CB4, in the uppermost Charcot Bugt Formation in Visdal (localities 8, 9, 11). Description. The dinoflagellate assemblage is dominated by Gonyaulacysta jurassica, Rhynchodiniopsis cladophora, Liesbergia 930 scarburghensis, Rigaudella aemula and Pareodinia stegasta at successively higher stratigraphic levels. Local correlation. The presence of Wanaea thysanota in associ- ation with Rigaudella aemula, Liesbergia scarburghense and Scriniodinium crystallinum corresponds to the interval between ammonite faunas M4 and M5 of Milne Land (C. cordatum to low- ermost C. densiplicatum Chronozones) in the fine-grained Kap Leslie Formation. The samples in the same bed towards the east show the top of abundant Rigaudella aemula, followed by an acme of Pareodinia stegasta. These two events correspond to the level between Milne Land ammonite faunas 6 and 7, indicative of the upper C. densiplicatum Chronozone. Chronostratigraphy. C. cordatum to C. densiplicatum Chrono- zones, Lower–Middle Oxfordian. Assemblage 8 Ammonite stratigraphy. None. Samples. Samples (409546, 409551, 409559) from the basal part of the Kap Leslie Formation onlapping the Charcot Bugt Formation, from the east towards the west (Fig. 1, localities 5, 12). Description. Dinoflagellate cysts from two samples of the basal mudstones (409546 is effectively barren) reflect the stratigraphic onlap. The common presence of Ambonosphaera calloviana and Dingodinium sp. indicate a level corresponding to Milne Land ammonite fauna 10 (upper A. glosense Chronozone), and in the succeeding sample, Epiplosphaera bireticulata and Stephanelytron redcliffense appear and indicate the stratigraphic level above Milne Land ammonite fauna 10 (A. glosense to A. serratum Chronozones). Chronostratigraphy. A. glosense to A. serratum Chronozones, Upper Oxfordian.