NEW GEOPHYSICAL RESULTS FROM THE SOUTH-WESTERN EURASIAN BASIN (MORRIS-JESUP-RISE, GAKKEL-RIDGE, YERMAK-PLATEAU) AND THE FRAM-STRAIT

The international multi-ship expedition ARCTIC'91. was able to collect a seismic transect between the Morris Jesup Rise and the Yermak Plate au. These conjugate plateau structures in the south-western part of th e 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 deg rees N, 10 degrees E and 85 degrees N, 15 degrees W. Close to the plat eaus, thicker sequences are evident (Morris Jesup Rise, 500 m; Yermak Plateau, 1500 m). The seismic lines on the Morris Jesup Rise reveal on ly a thin sedimentary cover of 0.2 s TWT. In contrast, a layer with a thickness of almost 0.9 s TWT (1300m) was found on the northernmost ti p of the Yermak Plateau. The topography of the oceanic basement is ver y rough along the seismic lines, as could be expected at a slow spread ing ridge. Depth variations of more than 1000 m are typical. Hydroswee p swath mapping provides the first detailed 3-D image from the Arctic mid-ocean ridge system at 87 degrees N, 60 degrees E and 84 degrees N, 0 degrees.