AAPG Europe Regional Conference, Global Analogues of the Atlantic Margin

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Controls in the deposition of Lower Cretaceous clastic wedges in the southwestern Barents Sea

Abstract

The southwestern Barents Sea is a frontier area that has been affected by two main Late Jurassic–Early Cretaceous tectonic events: an extensional event related to the initial rifting between Greenland and the western Barents Sea, that did not evolve to break up, and uplift of the Loppa High (Fig. 1) (Sund et al., 1986; Berglund et al., 1986; Faleide et al., 1993). The interest in the Lower Cretaceous has increased in the area, after some technical discoveries in recent years (e.g. Skalle, Kayak and Salina prospects). Traditionally, the Lower Cretaceous reservoir rocks have been assigned to the Valanginian–lower Barremian Knurr Formation and interpreted to represent turbidite sandstones (Seldal, 2005). However, recent results by the LoCrA consortium (http://locra.ux.uis.no/; Grundvåg et al., 2017; Marin et al., 2017a, b; Serck et al., 2017) show clear evidence that the age and depositional environments of the Lower Cretaceous succession is more complex than previously interpreted. This study integrates two and three dimensional seismic and well data, palynological information and sedimentological log descriptions to improve the knowledge of the Lower Cretaceous in the SW Barents Sea. We establish a sequence stratigraphic framework of seven sequences and classify the seismic facies within the sequences in order to better understand the depositional environments and paleogeography of the area. We suggest that: 1) during the Boreal Berriasian to early Barremian the Troms-Finnmark, Asterias and Bjørnøyrenna fault complexes were active and syn-rift clastic wedges were deposited in the area (Fig. 1). The depositional environment is interpreted as shallow marine for wedges deposited in the flanks of the Loppa High and deep shelf to deep marine for wedges deposited along the hanging wall of the Troms-Finnmark fault complex; 2) During the late Barremian to Aptian, the activity along the Ringvassøy Loppa fault complex renewed the western topography of the Loppa High. Shallow to deep marine wedges were deposited preferentially along this fault complex and in the western part of the Hammerfest Basin (Fig. 1); and 3) Albian–Cenomanian post-rift clastic wedges were more restricted to the SE and NE part of the Hammerfest Basin and to some areas along the Ringvassøy Loppa fault complex (Fig. 1). The deposition of the Lower Cretaceous wedges in the southwestern Barents Sea is highly dependent of: along the strike variability in the throw and steps of the main faults, diachronous movement and reactivation of the faults, nature of the feeder system, the influence of rifting in adjacent basins and by the inherited remnant topography.