SEDIMENT WAVES AND OTHER EVIDENCE OF PALEO-BOTTOM CURRENTS AT 2 LOCATIONS IN THE DEEP ARCTIC OCEAN

Sediment waves and other evidence of strong paleo-bottom current activity were observed in the deep Arctic Ocean during the 1967 through 1970 drift of Fletcher's Ice Island (T-3). On the crest of the Alpha Cordillera, between depths of 1100 and 2500 m, a blanket of sediment waves approximately 100 m thick overlies the 200-800 m thick sequence of stratified sediments which cover the basement topography of the cordillera. Maximum wave amplitudes were 55 m, with 1000 m wavelength. These waves were observed over an area of approximately 30,000 km2. In one instance a fortuitous loop in the drift track showed that at least two of these waves parallel the 150°W meridian. Many sediment cores and camera stations indicate that these sediment waves are themselves blanketed by at least several meters of pelagic lutite and ice-rafted detritus, and show that the wave-forming process has been inactive since at least mid to Upper Pliocene times (3.0-3.5 m.y. B.P.). However, nepheloid layer and current measurements suggest that the present bottom circulation, while too weak to produce such waves, might be capable of producing the drastic change in regimen represented by these waves if current speeds were increased considerably. Such a regimen probably existed for a certain period prior to the development of the present Arctic ice-cover. At a second location, buried waves appearing seismically as two sequences of hyperbolic echoes, were observed in a 300 m thick zone, 550 m beneath the 3260 m deep Mendeleyev Abyssal Plain. This zone in turn overlies at least another 1500 m of horizontally stratified sediments. Adjacent to this plain, by the Mendeleyev Fracture Zone, other evidence for strong current activity was found, in the form of a depositional scarp apparently maintained by current scour, a zone of present day bottom erosion, and a network of relict abyssal channels. These waves may mark various stages of 'commotion in the ocean' such as those suggested by Berggren and Hollister (1977) for the Pliocene, Cretaceous, or perhaps even earlier. Such drastic changes in the sedimentological regimen, inherent in the mechanics of plate tectonics, may provide additional clues to the origin of the Amerasia Basin in the Arctic Ocean. © 1979.