Neogene Climate Dynamics and Hydrocarbon Migrations on the Yermak Plateau, NW Spitsbergen - New Evidence from Borehole and Seismic data

Jochen Knies¹, Soma Baranwal¹, Karl Fabian¹, Carmen Gaina¹, Kari Grøsfjeld¹, Karin Andreassen², Katrine Husum², Rune Mattingsdal², Morten Hald², Monica Winsborrow², Stijn de Schepper³, Christoph Vogt³, and Nils Andersen^4
1Geological Survey of Norway, Trondheim, Norway.
²University of Tromsø, Tromsø, Norway.
³University of Bremen, Bremen, Germany.
⁴University of Kiel, Kiel, Germany.

Notwithstanding the recent IODP drilling on the Lomonosov Ridge, the Late Cenozoic history of the Arctic Ocean still remains elusive. The tectonic processes leading to the development of the only deep-water connection to the Arctic Ocean via the Fram Strait are still poorly understood. Also, the influence of the gateway region on changes in Arctic-Atlantic ocean circulation, uplift/erosion on the adjacent hinterland, as well as glacial initiation and its consequences for the petroleum systems in the regions, remain unclear. By revisiting Ocean Drilling Program (ODP) Leg 151, holes 911A and 910C and interpreting new multi-channel seismic data, we have now established a new comprehensive chronological framework for the Yermak Plateau and revealed important paleoenvironmental changes for the Atlantic-Arctic gateway during the late Cenozoic. The improved chronostratigraphic framework is established through continuous paleomagnetic and biostratigraphic data as well as selected intervals with stable d¹⁸O and d¹³C data derived from benthic foraminifera Cassidulina teretis. Supported by acoustic profiling, the new data indicate an early late Miocene age (~11 Ma) for the base of both holes. The depositional regime on the Yermak Plateau during the early late Miocene was rather shallow and water mass exchange between the Arctic and Atlantic was restricted. However, warm Atlantic water reached this high latitude site during the early late Miocene (~11 Ma) as reflected by the presence of the dinoflagellate cyst Operculodinium centrocarpum sensu Wall and Dale (1966) in ODP Hole 911A confirming the existence of a shallow passage between the Arctic and Atlantic. Dinoflagellate cyst and foraminiferal assemblages indicate a near-coastal environment with relatively warm (ice-free) surface water conditions. First indications of sea ice formation exist at ~6 Ma and may corroborate the establishment of the deep water passage of the Atlantic-Arctic gateway. This is consistent with tectonic modeling which reveals a shallow barrier on the Yermak Plateau until the late Miocene/early Pliocene. High-amplitude reflections corroborate the occurrence of greigite mineralization and stable carbon isotope excursions in planktic/benthic foraminifera during the late Miocene suggesting migration of hydrocarbons from deeper sources. Rapid sea-level drops, tectonic uplift, and re-activitation of faults during the late Miocene may be responsible for the leakage of hydrocarbons during the late Miocene.

 

AAPG Search and Discovery Article #90130©2011 3P Arctic, The Polar Petroleum Potential Conference & Exhibition, Halifax, Nova Scotia, Canada, 30 August-2 September, 2011.

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