Application of seismic and sequence stratigraphic concepts to a lava-fed delta system in the Faroe-Shetland Basin, UK and Faroes

摘要

Detailed seismic stratigraphic analysis of 2D seismic data over the Faroe-Shetland Escarpment has identified 13 seismic reflection units that record lava-fed delta deposition during discrete periods of volcanism. Deposition was dominated by progradation, during which the time shoreline migrated a maximum distance of ~44km in an ESE direction. Localised collapse of the delta front followed the end of progradation, as a decrease in volcanic activity left the delta unstable. Comparison with modern lava-fed delta systems on Hawaii suggests that syn-volcanic subsidence is a potential mechanism for apparent relative sea level rise and creation of new accommodation space during lava-fed delta deposition. After the main phase of progradation, retrogradation of the delta occurred during a basinwide syn-volcanic relative sea level rise where the shoreline migrated a maximum distance of ~75km in a NNW direction. This rise in relative sea level was of the order of 175-200m, and was followed by the progradation of smaller, perched lava-fed deltas into the newly created accommodation space. Active delta deposition and the emplacement of lava flows feeding the delta front lasted ~2600 years, although the total duration of the lava-fed delta system, including pauses between eruptions, may have been much longer.