Late Quaternary stratigraphic development in the lower Luni,Mahi and Sabarmati river basins,western India |
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Authors: | M Jain S K Tandon S C Bhatt |
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Institution: | (1) Risoe National Laboratory, DK-4000 Roskilde, Denmark;(2) Department of Geology, Delhi University, 110 007 Delhi, India;(3) Department of Geology, Bundelkhand University, Jhansi, UP, India |
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Abstract: | This study reviews the Quaternary alluvial stratigraphy in three semi-arid river basins of western India i.e., lower Luni
(Rajasthan), and Mahi and Sabarmati (Gujarat alluvial plains). On the basis of OSL chronologies, it is shown that the existing
intra-valley lithostratigraphic correlations require a revision. The sand, gravel and mud facies are present during various
times in the three basins, however, the fluvial response to climate change, and the resulting facies associations, was different
in the Thar desert as compared to that at the desert margin; this makes purely lithostratigraphic correlations unviable. It
is further shown that the rivers in the Thar desert were more sensitive to climate change and had small response times and
geomorphic thresholds as compared to the desert-margin rivers. This is illustrated during the early OIS 1, when the Luni river
in the Thar desert was dynamic and showed frequent variations in fluvial styles such as gravel bedload braided streams, sand-bed
ephemeral streams and meandering streams, all followed by incision during the early Holocene. The coeval deposits in Sabarmati,
however, only show a meandering, floodplain-dominated river.
Late Quaternary alluvial deposits in these basins unconformably overlie some older deposits that lack any absolute chronology.
Based on the facies types and their associations, and the composition and architecture of the multistoried gravel sheets in
the studied sections, it is suggested that older deposits are of pre-Quaternary age. This hypothesis implies the presence
of a large hiatus incorporating much of the Quaternary period in the exposed sections |
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Keywords: | Late Quaternary lithofacies luminescence chronology stratigraphic correlation fluvial response climate change |
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