New geophysical results from the south-western Eurasian Basin (Morris Jesup Rise, Gakkel Ridge, Yermak Plateau) and the Fram Strait

Abstract

The international multi-ship expedition ARCTIC'91 was able to collect a seismic transect between the Morris Jesup Rise and the Yermak Plateau. These conjugate plateau structures in the south-western part of the Eurasian Basin bound one of the slowest mid-oceanic spreading ridges in the world, the Gakkel Ridge. The seismic data reveal a sedimentary cover that is thin relative to the age of the oceanic crust at 83°N, 10°E and 85°N, 15°W. Close to the plateaus, thicker sequences are evident (Morris Jesup Rise, 500 m; Yermak Plateau, 1500 m). The seismic lines on the Morris Jesup Rise reveal only a thin sedimentary cover of 0.2 s TWT. In contrast, a layer with a thickness of almost 0.9 s TWT (1300 m) was found on the northernmost tip of the Yermak Plateau. The topography of the oceanic basement is very rough along the seismic lines, as could be expected at a slow spreading ridge. Depth variations of more than 1000 m are typical. Hydrosweep swath mapping provides the first detailed 3-D image from the Arctic mid-ocean ridge system at 87°N, 60°E and 84°N, 0°.