Late-Quaternary Diluvial Floodstreams in the mountains Of Altai And Tuva
by
Alexei N. Rudoy
Tomsk State Pedagogical University, Pr. Komsomolsky - 75, Tomsk, Russia, 634041

The first domestic works on geological and geomorphologic consequences of giant basin ice-dammed lakes outbursts in Altai were published some 20 years ago (Butvilovskiy, 1982; Rudoy, 1984). Using the methods of quaternary geology, geomorphology and paleoglaciology, it was found that during glacial Pleistocene such lakes occupied all the intermontane depressions of the Altai-Sayany mountain region, reaching their maximums almost simultaneously with glacial expansion maximums. Using the methods of simulation, magnitudes of thawed flow from glaciers of lake basins mountain frames in late Würm were estimated. Finally it was ascertained that a thawed flow had been increasing simultaneously with a glaciation area, and, for example, in basin of the Upper Chuya - the greatest in Altai Chuya intramontane depression, had exceeded the nowadays thawed flow 30 times (Rudoy, 1981; Rudoy and others, 1987). Thus a full basin filling to the highest lake terraces level took no more than 100 years, and then its catastrophic evacuation followed. It took the ice-dammed lake of Kurai no more than 30 years to be filled. Filling duration of Hubsugul and Darhat late quaternary ice-dammed lakes was of the same order (Grosswald, 1987, 1989). It seems that a filling and catastrophic evacuation period of basin ice-dammed lakes for about a hundred years was common to all of Siberian mountain territories that is quite clear taking into consideration similar hydroclimatic and orographic conditions of the region nowadays and in Pleistocene alike.

Outbursts of ice-dammed lakes both in Altai and in Tuva produced powerful glacial superfloods (diluvial floodstreams) with flow volume exceeding 106 m3/s. The greatest flow power was determined for a Chuya-Kurai floodstream (about 13 thousand yeas ago), it's volume was more than 18 million m3/s (Rudoy, Baker, 1993; Grosswald, Rudoy, 1996).

These regular repeating deluges did a great destructive and accumulative work that resulted in fact that all main flowing valleys of Tuva and Altai (Upper Yenisei, starting from outburst channels in Darhat basin and lower throughout Kyzyl, Chulyshman, Biya, Katun, Chuya, Argut) appeared to be severely transformed relative to the initial ones. The surfaces deformed by diluvial floodstreams were called "scablands" by analogy with well-known territory of Channeled Scabland in North America. The territories of scablands, in the broad sense of the notion, were being formed by processes of diluvial destruction (erosion and evorsion) and diluvial accumulation. The territory of Columbia basaltic plateau in America was named scabland (Channeled Scabland) by a floodstream discoverer J.H.Bretz primarily due to pioneer interpretation of diluvial forms destructive groups - coolie-channels, "kettle holes" and others. In Altai and in Tuva, on the contrary, the comprehension of true geological role of quaternary glaciers, gigantic ice-dammed lakes and their regular outbursts came with the discovery and research of diluvial accumulation forms - giant current ripple-marks and diluvial swells and terraces. By now such forms are determined in all valleys mentioned above.

International expeditions of the last decade showed that diluvial formations peculiar to mountain and plain regions of America and Eurasia must be characteristic of all territories that experienced a quaternary glaciation. The results of these expeditions has greatly stimulated appearance of general scientific conclusions and the newest theories about role of quaternary ice-dammed lakes and seas and diluvial streams in Northern hemisphere on the whole (Grosswald, 1999; Ancient Floods..., 2002, Rudoy, 2002). The comprehension of principal appropriateness of diluvial processes on the Earth that has been reached in the end of the previous century resulted in much more detailed and argued interpretation of history of other planets surface development: Mars, in particular (Mars paleoglaciology and geomorphology, Komatsu, Baker, 1999; Rudoy, 1999).

References

Baker V.R., Benito G., and Rudoy A.N. 1993. Palaeohydrology of late Pleistocene Superflooding, Altay Mountains, Siberia. Science, 259, 348-350.

Grosswald M.G., and Rudoy A.N., 1996. Quaternary Glacier-Dammed Lakes in the Mountains of Siberia. Polar Geography, 20, 180-198.

Rudoy A.N. 1998. Mountain Ice-Dammed Lakes of Southern Siberia and their Influence on the Development and Regime of the Runoff Systems of North Asia in the Late Pleistocene. In G. Benito, V.R. Baker, K.J. Gregory, eds., Palaeohydrology and Environmental Change, Chichester, John Wiley & Sons Ltd., 215-234.

Rudoy A.N. 1999. Earth analogues of the Channels on Mars. In The 30th Vernadsky-Brown Microsymposium on Comparative Planetology, Moscow, October1999, 91-92.

Rudoy A.N., and Baker V.R. 1993. Sedimentary effects of cataclysmic Late Pleistocene glacial outburst flooding, Altay Mountains, Siberia. Sedimentary Geology, 85, 53-62.

Rudoy A. N. 2001. Glacier-dammed lakes and geological work of glacial superfloods in the Late Pleistocene, Southern Siberia, Altai Mountains. J. Quaternary International, 87, In Press.

Date received: April 26, 2002