Quaternary Geology of the Tumanmyun Hills, Khovsgol,
Justin Brooks, Class of 2001
Department of Geology, Whitman College, Walla Walla, WA 99362
The Jarai Gol, a river located in northern Mongolia, flows eastward
out of a glacial trough and into the Darhad depression. Landforms in
this area reflect a complex history of major late Quaternary processes
(glacial, periglacial, lacustrine, eolian, fluvial, and mass wasting).
This area is, in effect, a microcosm of Quaternary processes in the
whole of the 3500-km2-Darhad depression.
Of primary interest are the
interaction and timing of glacial and lacustrine processes. The Tamanmyun
Hills, two end moraine complexes, record a history of approximately
two glacial advances. The outer moraine complex is composed of two sections
of differing morphology and elevation. Kettles in the higher moraine
section and the inner moraine complex indicate ice stagnation. The lower
moraine section, on the other hand, has a much smoother and more subdued
Shorelines and lake
sediments indicate that a lake filled the Darhad depression at least
once. Wave modification of the outer moraine complex suggests the lake
to be coeval with and/or to post-date moraine formation. Lacustrine
modification may be responsible for the differing outer moraine morphologies.
Shoreline elevations (max of 1660 m) suggest the lake overtopped only
the lower section of the moraine complex (max elev. of 1620 m, base
at 1575 m) but not the higher section. (max elev. of 1680 m) The morphology
of the inner moraine complex suggests there has been no wave modification;
the lake level must have dropped before its construction.
Evidence for periglacial
processes is found as patterned ground. Wind has used the abundant supply
of lacustrine and glacial sediments to deposit large parabolic dunes.
The Jarai Gol incised the moraine complexes, leaving terraces. Oversteepened
slopes enhance mass wasting of incompetent lakebeds.
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