Sedimentation model of gravel-dominated alluvial piedmont fan,Ganga Plain,India |
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Authors: | U K Shukla |
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Institution: | (1) Department of Geology, Banaras Hindu University, Varanasi, 221005, India |
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Abstract: | The Piedmont Zone of the Indo-Gangetic Plain contains numerous, laterally coalescing small alluvial fans. The Latest Pleistocene–Holocene
30 km long Gaula Fan can be divided into gravelly proximal fan (0–14 km down-stream), gravel-sand rich mid fan (14–22 km)
and sand–mud dominated distal fan (22–30 km). The fan succession is composed of two fan expansion cycles A and B. Separated
by an undulatory erosional contact of regional extent, cycle A is characterized by river borne clast-supported gravelly deposits,
and the overlying fan expansion cycle B by matrix-supported gravely debris flows. The main process behind fan development
has been lateral migration of channels over the fan surface probably due to rapid sedimentation caused by increased sediment
supply, and the fluctuating water budget in response to changing climate. The water laid expansion cycle A represents a humid
phase. The debris flow deposits of expansion cycle B suggest a dry phase. Approximately between 8 and 3 Ka, cycle B also indicates
a phase of tectonic instability in the Siwalik Hills forming the mountain front. The tectonic activity caused incision of
rivers into the fan surface, and in turn resulted in reduced fan-building activity. At present the fan surface is accreting
by sheet flow processes. |
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Keywords: | Quaternary-Foreland basin Ganga Plain Piedmont Fan Sedimentation |
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