Stratigraphic framework and sedimentary environments of the East Shetland Platform in the Paleocene – Preliminary Results

In the East Shetland Platform (ESP) during the Paleocene, thick third order sequences (0.5 – 3 Myrs) were deposited during overall shelf progradation into the central North Sea, resulting in shelf - basin floor depositional profiles being preserved from Danian to Ypresian times. We interpreted the depositional record east of Shetland using over 40 000 km² of 3D seismic data and circa 100 wells with biostratigraphic and lithostratigraphic picks, drawing key comparisons between the geometries of individual sequences along strike. We constructed multiple chronostratigraphic charts and relative sea-level curves for the area, which will later be used to study uplift and the influence of emplacement of large igneous provinces on source-to-sink systems.Deposition during the Danian is marked by a switch from quiescent carbonate and chalk platforms to strongly progradational clastics at the onset of uplift in the hinterland. This results in the first third-order pulses of clastic input in the ESP and in the adjacent Viking Graben, which correspond to sediments of the Maureen (Upper Danian – Middle Selandian) and Lista Formations (Upper Selandian to Middle Thanetian). These systems are dominated by sediment gravity flows in channel-lobe complexes, and are separated by a top Selandian Unconformity. From Thanetian to early Ypresian, multiple fourth order cycles of relative sea-level change can be recognized in shelfal sequences dominated by normal and forced regression. These include a broad domain of forced regressive to normal regressive shelf-margin – scale clinoforms (Dornoch Formation “Highstand” – sequence D1) that are correlated to an Upper Thanetian Unconformity in the proximal platform and systems of channelized sediment transport in the basin. This is followed by a set of rapidly prograding, flat trajectory clinoforms with wave-dominated shoreline delta geometries and considerable deposition in inner shelf, prodelta lobes (D2 – D4). These systems are interdigitated with a larger shelf-margin – scale clinothem of seemingly coeval age in the southern ESP, closer to the Piper Shelf. In the central ESP, close to the Beryl Embayment, basement reactivation during the Paleocene created structural highs that controlled estuarine or lagoonal - like systems during the Dornoch - Beauly cycles, which ended after significant clinoform progradation beyond the ESP and into the Viking Graben, although the exact nature of these clinoforms (sequence D5) is still unknown. The final sequence B1 is marked by the progressive onlap advance towards the continent (including coastal plain aggradation and backstepping) and eventually complete transgression of the Dornoch-Beauly shelf, which helped preserve erosional landscapes developed during the Dornoch progradation and also the posterior tidal invasion of the shelf. In the south, transgressive deposits are almost 200 ms thick (150 – 200 m) in some seismic profiles, but in the northern ESP shelf often only a single reflector of this same age is identified (< 40 ms). This highlights the marked influence of both tectonic tilting/doming and differential sediment supply versus accommodation rates along strike in the ESP, which are interpreted as a direct result of the activity of the Icelandic Plume in the continent.