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Quaternary alluvial fans in the Gobi of southern Mongolia: evidence for neotectonics and climate change
Author(s) -
Owen L. A.,
Windley B. F.,
Cunningham W. D.,
Badamgarav J.,
Dorjnamjaa D.
Publication year - 1997
Publication title -
journal of quaternary science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.142
H-Index - 94
eISSN - 1099-1417
pISSN - 0267-8179
DOI - 10.1002/(sici)1099-1417(199705/06)12:3<239::aid-jqs293>3.0.co;2-p
Subject(s) - geology , alluvial fan , quaternary , alluvium , sedimentology , holocene , geomorphology , alluvial plain , paleontology , sedimentary rock
Alluvial fans in southern Monglia occur along a group of narrow discontinuous mountain ranges which formed as transpressional uplifts along a series of strike‐slip faults. They provide information on the nature of neotectonic activity in the eastern Gobi Altai range and on palaeoclimate change. Alluvial fan formation was dominated by various geomorphological processes largely controlled by climatic changes related to an increase in aridity throughout late Quaternary times. Their sedimentology shows that initially they experienced humid conditions, when the sedimentary environments were dominated by perennial streams, followed by a period of increasing aridity, during which coarse fanglomerates were deposited in alluvial fans by ephemerial streams and active‐layer structures were produced by permafrost within the alluvial fan sediments. With climatic amelioration during early Holocene times, the permafrost degraded and fan incision and entrenchment dominated. Sedimentation was then confined to the upper reaches of the fans, adjacent to steep mountain slopes, and within the entrenched channels. The alluvial fans have been neotectonically deformed, faulted and their surface warped by small thrust faults that propagate from the mountain fronts into their forelands. Localised uplift rates are in the order of 0.1 to 1 m Ka −1 . © 1997 John Wiley & Sons, Ltd.