A New, Formal Palynozonation for the Triassic Succession of the Barents Sea Aea - A solid, Crrelative Tool for the Norwegian Arctic

Gunn Mangerud

The Norwegian Barents Shelf with Svalbard forming its exposed north-western corner reveals an almost complete Triassic sedimentary record when combining outcrops with stratigraphic cores and explorations wells. Dating and reliable correlation tools are essential in exploration, and palynological studies from these sections have been carried out resulting in the definition of fifteen palynological Composite Assemblage zones (CAz). Calibrations with ammonoids recovered from Lower and Middle Triassic deposits cored on the Svalis Dome, the Bjarmeland Platform, in Finnmark East and in the Nordkapp Basin permit exact dating of the co-appearing palynological assemblages and confident correlation with the ammonoid-dated sections on Svalbard. Shallow cores from Sentralbanken and off Kong Karls Land add valuable knowledge of the Late Triassic and the variable depositional environments and breaks in deposition during the Carnian and Norian. Important data are added based on exploration wells. At the Triassic-Jurassic transition on Svalbard, where Lower Jurassic deposits directly overlie Norian beds, we demonstrate that reworked Late Triassic palynomorphs dominate. In exploration wells further to the southeast, Rhaetian strata represent the youngest Triassic deposits in the area. Seven composite assemblage zones have been defined for the lower Triassic. These include the Uvaesporites imperialis, Reduviasporonites chalastus, Proprisporites pocockii, Maculatisporites spp., Naumovaspora striata, Pechorosporites disertus and Jerseyiaspora punctispinosa CAz. These appear to have a variable west-east presence on Svalbard. Four composite assemblage zones have been defined for the Middle Triassic. These include the Anapiculatisporites spiniger, Triadispora obscura, Protodiploxypinus decus, and the Echinitosporites iliacoides CAz and are present in most measured sections on Spitsbergen. On Bjørnøya there is a major stratigraphic break above Smithian beds where the oldest Middle Triassic is represented by the Ladinian E. iliacoides CAz. Four Composite Assemblage zones have been defined for the Late Triassic. These include the Aulisporites astigmosus, Rhaetogonyaulax spp., Limbosporites lundbladii and Quadraeculina anellaformis CAz. However, in most localities on Svalbard only the Carnian A. astigmosus CAz is recognised. The present study represents a comprehensive compilation of palynology from the Triassic succession of the Norwegian Arctic. There is still a huge potential for further detailed work of the palynoassemblages and their application in palaeoenvironmental as well as stratigraphic interpretations and reconstructions. The results will be presented in the book: J. O. Vigran, G. Mangerud, A. Mørk, D. Worsley, P. A. Hochuli. 2013: Palynology and geology of the Triassic succession of Svalbard and the Barents Sea. Norwegian Geological Survey, Special Publication.

AAPG Search and Discovery Article #90177©3P Arctic, Polar Petroleum Potential Conference & Exhibition, Stavanger, Norway, October 15-18, 2013