Rapid Sagging of the Barents Shelf over the Last 15-16 ka

摘要

A number of sedimentary sequences have been identified in the Barents shelf from investigations of the upper part (100-150 m) of the geologic section, including sea drilling and continuous seismoacoustic profiling. The uppermost sequence is represented mostly by clayey and silty-clayey material, which is consolidated only incipiently and therefore recognized easily in the seismic records. The sole of this sequence marks an unconformity caused by a long period of a subaerial regime, fluvial drainage, and a break in sedimentation. The timing of the last transgression is based on radiocarbon datings of foraminifers, mollusk shells, and other organic remains from poorly consolidated sediments. This transgression was of a tectonic rather than a gla-cioeustatic nature. The sagging proceeded with spatially varying amplitude and rate, and both parameters generally increased from the present-day shallow-water areas toward the deep sea, where the rate of subsidence was 1.4-3.0 cm/yr, i.e., 1-2 orders of magnitude greater than the rate of sedimentation. These phenomena explain why the subaerial landforms that preceded the last marine transgression are well preserved in deepwater shelf areas. It is suggested that the sagging, which caused this transgression, was merely a particular stage of oscillations of the western Arctic margin of Eurasia that lasted from the late Miocene to Quaternary and were genetically or paragenetically related to the evolution of the Arctic oceanic basins.