RUSSIAN JOURNAL OF EARTH SCIENCES VOL. 7, ES5004, doi:10.2205/2005ES000180, 2005

Conclusions

[53]  Evidence from geomorphologic, marine geologic and paleoclimatic studies leads us to conclude that the Sea of Okhotsk has been glaciated by a marine "back-arc" spillover sector of a highland ice sheet on the North Pacific Rim. This conclusion is supported, at least partly, by a sedimentation model, based on research on Sakhalin Shelf and in Deryugin Deep [Wong et al., 2000]. The grounded ice sheet became a floating ice shelf that spread over the Kurile Basin and was buttressed by the submarine Kurile Island Arc. The last Okhotsk ice sheet was of Late Pleistocene age. It could have existed during both Early and Late Weichselian (Wisconsin) time, and, in accord with the arguments of Braitseva et al. [1968], and of Ono and Naruse [1997], the earlier of the two stages could be a little more extensive than the later stage.

[54]  The Sea of Okhotsk is a close neighbor of Beringia, and its new glacial image lends additional credence to our concept of Beringian glaciation [Grosswald, 1998b; Grosswald and Hughes, 1995, 2002; Hughes, 1995; Hughes and Hughes, 1994; Hughes et al., 1991]. Also, it is consistent with the North Pacific paleogeography implied by the ODP Leg 145 drilling results and, more specifically, with the Late Pleistocene oceanographic changes in the Sea of Japan, in the offshore zone of eastern Honshu Island, and on the Islands of Japan themselves [Grosswald, 2002; Oba et al., 1991; Okada, 1980]. Among other things, the concept of the glacial Sea of Okhotsk accounts for the fact that dropstones became most abundant during the Ice-Age in the North Pacific, in particular, in sites seaward from the Sea of Okhotsk. We conclude that an ice sheet in the Sea of Okhotsk, along with the Beringian ice sheet, was a major source of icebergs, meltwater, and ice-rafted debris supplied to the North Pacific Ocean during the Ice Ages. Icebergs would have calved from the Kurile and Bering ice shelves after they rode over the Kurile and Aleutian Island Arcs and squeezed through their straits.

[55]  We make one final observation. Asians crossed a stormy ocean passage to Australia 60,000 years ago, but did not cross the Beringian land bridge into North America in significant numbers until after 12,000 years ago, even though the west wind was at their back and the land bridge was presumably wide and teeming with game. Perhaps that presumption is wrong. Perhaps ice sheets on the North Pacific Rim blocked the land bridge, as we repeatedly suggested.


RJES

Citation: Grosswald, M. G., and T. J. Hughes (2005), "Back-arc" marine ice sheet in the Sea of Okhotsk, Russ. J. Earth Sci., 7, ES5004, doi:10.2205/2005ES000180.

Copyright 2005 by the Russian Journal of Earth Sciences

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