The CentralGrabenarea wasfilled withathick pileofsediments duringthe MiddleM ioceneQuaternary,correspondingto aperiodof15Ma.Ashydrocarbon expulsion from the most prolific source rock, the UpperJurassic BoMember,wasinitiated only 20 Ma BP andstill occurs today,the MiddleM ioceneQuaternary evolution isimportant.Int he MiddleMiocene, the CentralGrabenarea wascovered byasea with waterdepthof500 -700 m. Duringthe LateMiocene(Tortonian),the basinwassuccessively filled byprograding slopeanddeltaic sedimentsfrom the northeast. The progradationalinfill resulted inlocaltiltingofthe substratum dueto the loadinge ffecto fthe deposits. Int he latest LateM iocene(Messinian),the maininput ofsediments occurred from the south, asillustrated byathick onlappingsuccession ofupperMessiniansediments. Pliocene sedimentation wascharacterized byr egularinfill from the east withinashelfto shallow marined epositional environment.Followingthe Miocenea ndP liocene, the NorthS ea Basint ilted dueto stronguplifto fthe Fennoscandians hielda ndi ncreased subsidence andsedimentation ratesw ithint he CentralGrabenarea.This furthercomplicated the maturation ofthe source rock, migration pathways anda ccumulation ofh ydrocarbons. The consequence ofthiscomplexburialhistory isexemplified bythe Kraka andHalfdanfields. The Kraka Field hasalarge down-flankoilaccumulation,which ist he result ofaporosity anomaly resultingf rom anearly invasion ofoilint hisp osition beforethe latetiltingofthe NorthS ea Basin. The history ofthe non-structural accumulation ofthe HalfdanFieldcanbe readily modelled;itconstituted asimplefour-waydipclosureduring the LateMiocenewhenpeak oilmigration occurred.The Quaternary tiltingofthe NorthSea Basindueto upliftof the FennoscandianShielda ndstrongsubsidence ofthe CentralGrabenarea resulted inad istinctgradient favouringlong-distance migration ofhydrocarbons. The occurrence ofviablemigration routes,especially within Paleocenesandlayers,hasresulted inlong-distance migration ofoilinto the Sirisubmarinevalleysystem. The most northern indication ofh ydrocarbons hasbeenr ecognized asfaras7 5kmfrom the source area.Longdistance migration ofh ydrocarbons isalso indicated bydirecthydrocarbon indications( DHIs) throughoutt he Cenozoic succession int he DanishN orthS ea.DHIsareparticularly prominent abovek nown hydrocarbon accumulationsint he CentralGraben. Thisindicatesp ronounced verticalm igration,f or instance alonga ctive faults,abovethesestructures.
An updated and revised lithostratigraphic scheme is presented for the Cretaceous of North-East Greenland from Traill Ø in the south to Store Koldewey in the north. The Ryazanian to lower Maastrichtian succession is up to several kilometres thick and comprises four groups, 12 formations and 18 members. The groups record the tectonic evolution of the East Greenland depocentre on the western flank of the evolving proto-Atlantic seaway. The Wollaston Forland Group encompasses the uppermost Jurassic – lowermost Cretaceous rift-climax succession and contains the Lindemans Bugt and Palnatokes Bjerg Formations; two new members of the latter formation are erected from Store Koldewey. Post-rift Cretaceous strata are referred to the new Brorson Halvø Group and the Home Forland Group. The Brorson Halvø Group (uppermost Hauterivian – middle Albian) is dominated by slope and basinal mudstones of the new Stratumbjerg Formation but also includes fluvio-deltaic and shallow marine sandstones of the revised Steensby Bjerg Formation on northern Hold with Hope and submarine slope apron breccias and conglomerates of the revised Rold Bjerge Formation on Traill Ø. The Home Forland Group covers the middle Albian – Coniacian succession. The basal unconformity records an important mid-Albian tectonic event involving intrabasinal uplift, tilting and erosion, as exemplified by the middle Albian conglomerates of the new Kontaktravine Formation on Clavering Ø. The Home Forland Group is dominated regionally by mud-dominated slope to basinal deposits of the elevated and revised Fosdalen Formation; it also includes lowstand basin-floor fan sandstones of the new upper Albian Langsiden Member. The new Jackson Ø Group (upper Turonian – lower Maastrichtian), records a phase of basin reorganisation marked by a significant fall in sedimentation rate in North-East Greenland, probably linked to rift events in, and bypass to, the central proto-Atlantic rift system. The base of the group is an erosional unconformity on Traill Ø and Geographical Society Ø overlain by submarine slope-apron conglomerates of the Turonian Månedal Formation. The base is conformable on Hold with Hope but is defined by a condensed interval (the Coniacian Nanok Member) that is succeeded conformably by slope and basin-floor turbidite sandstones of the Coniacian–Santonian Østersletten Formation and slope to basinal mudstones of the Campanian – lower Maastrichtian Knudshoved Formation. The new Leitch Bjerg Formation of Campanian slope-apron conglomerates and sandstones in eastern Geographical Society Ø erosionally overlies the Knudshoved Formation.
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