Post-Miocene sedimentation at the continental rise of Southeast Greenland: the interplay between turbidity and contour currents

Abstract

Southeast Greenland continental rise depositional sequences have been studied by means of high-resolution reflection seismic data. Major depositional features of this glaciated margin have been compared with comparable seismic architectures at the Antarctic margin. Two seismic units with an estimated age of early to mid Pliocene and mid Pliocene to Recent have been analysed in detail. It is concluded that episodic turbidity currents interacting with more continuous contour currents have controlled the location and architecture of the sedimentary mounds found off Southeast Greenland. In the early Pliocene turbidite sediment input significantly surpassed the amount of sediments reworked and transported by southbound contour currents. As a result an overbank deposit developed, oriented perpendicular to the continental slope at the proximal part and parallel to the continental slope in the distal part where the effect of the turbidity processes decreased. Contour current action further resulted in a southward migration of the overbank deposit. From the mid Pliocene, a relatively stronger impact of the contour current on the sedimentation pattern is observed, suggesting a relative decrease of downslope sediment transport processes. Stronger contour current activity may have been related to generally enhanced North Atlantic deep-water circulation. This resulted in formation of elongated contourite deposits trending parallel to the continental slope both in proximal and distal settings. The morphology and seismic expression of the sedimentary mound structures at the Southeast Greenland margin display several features also observed at the Antarctic margin. It is concluded, however, that the sedimentary mounds in the latter area formed in a different way, which is principally attributed to persisting contour current activity off Antarctica during glacial stages, when currents off Southeast Greenland had virtually ceased.