3D seismic analysis of the West Shetland Drift system: Implications for Late Neogene palaeoceanography of the NE Atlantic

摘要

Detailed seismic stratigraphic analysis of the West Shetland Drift, located on the Shetland Margin of the Faeroe-Shetland Channel, has been undertaken using commercial 3D seismic data. Emphasis was placed on the interpretation of a significant plastered contourite drift body, the West Shetland Drift-Slope section, with the aim of reconstructing the palaeoceanographic regime of the West Shetland slope during the past 5 Ma. Although limited in areal extent, the West Shetland Drift Slope section provides a key record of the depositional environment and bottom current activity on the West Shetland slope during the Late Neogene. The drift body was divided into three seismic-stratigraphic units and depositional processes responsible for each unit were interpreted, resulting in proposal of an evolutionary model in which a mixed downslope-alongslope depositional system was succeeded by alongslope current derived contourite drift deposition during the Early Pliocene to Mid-Pleistocene. During this time SW flowing alongslope currents impinged upon the West Shetland slope between the basin floor and a mid- to upper slope position. The final stage of deposition consisted of slope wedge progradation associated with Mid- to Late Pleistocene glaciation. Contourite deposition on the West Shetland Slope was punctuated by periods of glaciation activity, during which alongslope current activity appears to have been disrupted, suggesting a link between alongslope current activity and glaciation. Detailed mapping of key, smaller scale features, including a spectacular bottom current sediment wave field and iceberg ploughmarks, both of which were identified for the first time during this study, was instrumental in constraining the palaeocurrent regime, and would not have been possible without the high spatial resolution of the 3D seismic data. This study therefore highlights the efficacy of 3D seismic data as a tool for large scale spatial and temporal analysis of contourite drifts palaeoceanographic research.