Norw. J. of Geology: Sedimentology and palynology of the Lower Cretaceous succession of central Spitsbergen: integration of subsurface and outcrop data

The final version of the article “Sedimentology and palynology of the Lower Cretaceous succession of central Spitsbergen: integration of subsurface and outcrop data ” has been published in the Norwegian Journal of Geology. The authors are Sten-Andreas Grundvåg1, Mads Engholm Jelby2, Kasia Kamila Śliwińska3, Henrik Nøhr-Hansen3, Tore Aadland4, Sara Elvelund Sandvik5, Ingrid Tennvassås1, Thea Engen1 & Snorre Olaussen6.

1Department of Geosciences, UiT The Arctic University of Norway.
2Natural History Museum of Denmark, University of Copenhagen.
3Geological Survey of Denmark and Greenland (GEUS).
4Department of Earth Science, University of Bergen.
5Lundin Norway AS.
6Department of Arctic Geology, The University Centre in Svalbard.

Abstract:

The Lower Cretaceous succession in Svalbard is commonly considered as an important analogue to age-equivalent strata on the Barents Shelf which are sporadically targeted by exploration wells. In this study, the stratigraphic and genetic relationship between the Rurikfjellet (open marine), Helvetiafjellet (paralic) and Carolinefjellet (open marine) formations of the Lower Cretaceous succession in Svalbard is evaluated by combining sedimentological outcrop studies with well log and core data across Nordenskiöld Land, central Spitsbergen. Sedimentological characteristics and stratigraphic units are mapped within a refined dinocyst biostratigraphic framework, enabling relatively well-constrained palaeogeographic reconstructions. The Valanginian–lowermost Barremian Rurikfjellet Formation consists of a lower shale-dominated unit of offshore origin which grades upwards into storm-reworked lower shoreface sandstones displaying hummocky cross-stratification. Local occurrences of prodeltaic successions and thick successions of gravity flow deposits containing coal-bearing slump blocks of delta plain origin in some wells, reveal a late Hauterivian progradational pulse which has previously not been recorded in Svalbard. The lower Barremian–lower Aptian Helvetiafjellet Formation consists of fluvial braidplain and paralic deposits which rest unconformably on the Rurikfjellet Formation across the entire study area, reflecting regional uplift and widespread subaerial exposure prior to the onset of paralic deposition. The Helvetiafjellet Formation exhibits increased marine influence upwards, and in the investigated cores the uppermost part of the unit consists of wave-reworked mouth-bar deposits which are truncated by a transgressive conglomerate lag dominated by extrabasinal lithic clasts and intraformational siderite clasts. An up to 10 m-thick, regionally extensive, organic-rich (TOC up to 2.1 wt.%) shale unit of early Aptian age marks the base of the overlying Carolinefjellet Formation. The shale accumulated during a regional flooding event which drowned and eventually transformed the Helvetiafjellet Formation coastal plain into a shallow shelf. The organic facies of the shale unit (Type II–III kerogen) and a high Pr/Ph ratio (>2), in combination with abundant long-chained n-alkanes, suggest that the unit was deposited in a suboxic paralic marine environment strongly influenced by input of terrestrial organic matter. The investigated succession exhibits stratigraphic and petrographic resemblance to age-equivalent strata in NE Greenland, suggesting that these successions may have formed part of the same drainage system located on the northwestern margin of the Barents Shelf. Thus, by highlighting the Early Cretaceous palaeogeographic evolution in Svalbard, this study contributes to the regional stratigraphic understanding of the Lower Cretaceous succession on the wider northern Barents Shelf.

Keywords: Svalbard, northern Barents Shelf, Mesozoic, Early Cretaceous palaeogeography, facies analysis, sequence stratigraphy

Reference:

Grundvåg, S.A.; Jelby, M.E.; Śliwińska, K.K.; Nøhr-Hansen, H.; Aadland, T.; Sandvik, S.E.; Tennvassås, I.; Engen, T.; Olaussen, S. (2019): Sedimentology and palynology of the Lower Cretaceous succession of central Spitsbergen: integration of subsurface and outcrop data. Norwegian Journal of Geology 99. DOI: 10.17850/njg006. [intranet]