Basin dynamics and stratigraphy in a half graben system during latest Jurassic – earliest Cretaceous rift climax – the Wollaston Forland Basin in North-east Greenland.

Publikation: KonferencebidragAbstract ved konference


The latest Jurassic – earliest Cretaceous half graben system recorded by Vischer (1943) and described in detail by Surlyk (1978) is mainly exposed in the westernmost part of the Wollaston Forland Basin (NE Greenland), where a several kilometre-thick coarse clastic dominated succession was deposited along the main fault against the Caledonian crystalline basement. Deposition was characterized by breccias nearest to the fault, grading into conglomerates and sandstone fans away from the fault towards the basin axis. Towards the east the rift climax interval is buried beneath progressively younger Cretaceous deposits.
Recent core drilling and outcrop studies have provided new data on the Upper Jurassic – Lower Cretaceous in eastern Wollaston Forland and revise the understanding of the depositional system and its stratigraphy.
Two shallow cores provide a combined section covering the upper Kimmeridgian (Upper Jurassic) – Barremian (Lower Cretaceous) (Alsen et al., in press). The black mudstone-dominated intervals are dated primarily by dinoflagellates and ammonites, whereas the calcareous mudstones – sandwiched between the black mudstones – are dated by calcareous nannofossils. The stratigraphy demonstrates an almost complete succession in a core that represents a deep position in the half graben. This contrasts to previous models which predicted a latest Jurassic rift climax hiatus for the eastern Wollaston Forland Basin. The other core represents a position closer to a block crest where unconformities developed. In combination the cores provide a key biostratigraphic reference section for the Jurassic–Cretaceous boundary interval in the Arctic.
A markedly different depositional type is a record of a basinally-isolated breccia–pebbly sandstone couplet that occurs in the axial part of the latest Jurassic rift-climax halfgraben (Alsen & Surlyk 2023). Synrift breccias are otherwise restricted to a narrow zone along the scarp of the basin-margin fault. Towards the north the fault sidesteps en echelon towards the east. The breccia part of the couplet was transported by a noncohesive debris flow and the pebbly sandstone by a high-density turbidity. The couplet is located about 15 km east of the fault scarp and flowed southwards along the halfgraben axis. It is interpreted to have been derived from the fault side-step and had a run-out distance of at least 25 km. The angularity of the clasts reflects derivation directly from the fault scarp during a single catastrophic event. The occurrence of breccias thus cannot be taken as evidence of short transport and deposition at the foot of a scarp or steep slope.
Acknowledgements: This paper is based on the collaboration with numerous colleagues, especially Finn Surlyk, Stefan Piasecki, Jussi Hovikoski, Jørgen Bojesen-Koefoed, Henrik Nøhr-Hansen.
Alsen, P., Piasecki, S., Nøhr-Hansen, H., Pauly, S., Sheldon, E. & Hovikoski, J. (submitted Feb. 10th 2023; pending minor to moderate revision after review 28/04-2023): Stratigraphy of the Upper Jurassic to lowermost Cretaceous in the Rødryggen-1 and Brorson Halvø-1 boreholes, Wollaston Forland, NE Greenland. In Ineson, J. & Bojesen-Koefoed, J.A. (eds): Petroleum geology of the Upper Jurassic – Lower Cretaceous of East and North-East Greenland: Rødryggen-1 and Brorson Halvø-1 boreholes, Wollaston Forland Basin. Geological Survey of Denmark and Greenland Bulletin
Alsen, P. & Surlyk, F. 2023 (published online first, 2022). Long run-out distance of block breccia gravity flow along a halfgraben axis: uppermost Jurassic of East Greenland. Journal of the Geological Society (London) 180, 11 pp. https//
Surlyk, F. 1978a. Submarine fan sedimentation along fault scarps on tilted fault blocks (Jurassic-Cretaceous boundary, East Greenland). Grønlands Geologiske Undersøgelse Bulletin, 128, 1–108,
Vischer, A. 1943: Die Postdevonische Tektonik von Ostgrönland zwischen 74° und 75° n. Br. Meddelelser om Grønland, 133 (1), 1–195.
Antal sider2
StatusUdgivet - 19 sep. 2023
BegivenhedJurassica XV - Ilza, Polen
Varighed: 19 sep. 202322 sep. 2023


KonferenceJurassica XV


  • Programområde 4: Mineralske råstoffer