Journal of Geological Society of India (Online archive from Vol 1 to Vol 78)

Indra Bir Singh ¹, V. N. Bajpai ², A. Kumar ¹, M. Singh ¹

Affiliations
1 Department of Geology, Lucknow University, Lucknow 226 007, IN
2 Department of Geology, Delhi University, Delhi 110 007, IN

Abstract

Gangetic plain shows distinct geomorphic surfaces formed in response to the climatic and base-level changes related to the sea-level fluctuations during Quaternary. Within the major river valleys, a distinct geomorphic surface (T₁) is developed, located about 5-10 m above the present-day flood plain (T₀). Study of these surfaces in the Ganga River valley near Kanpur demonstrates that T₁ -surface channel deposits assigned tentatively the date of the last interglacial (25-30 Ka) show meandering scars and coarser sediments (M₁ = 1.9 φ) than the present-day channel sands. The T₀-surface shows braided channels and finer sediments (M₁ = 3.4 φ). The Ganga River has undergone a river metamorphosis from meandering to braided-type during the last 25,000 years, accompanied by decrease in grain-size, and probable decrease in water budget and increase in sediment load. All the major rivers of the Gangetic Plain, many of them braided-type today, show evidence of having been meandering rivers during last interglacial (25-Ka).

Keywords

Geomorphology, Indo-Gangetic Plain, Ganga Pleistocene-Holocene, Quaternary Geology.

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Suyash Kumar ¹, I. B. Singh ¹, M. Singh ¹, D. S. Singh ¹

Affiliations
1 Department of Geology, Lucknow University, Lucknow - 226007, IN

Abstract

Several meter thick muddy sequences make up the topmost part of upland surfaces in Central Gangetic Plain. Excavations in the river-valley terrace (T₁-surface) of Gomti River show about 4 m thick fine-grained deposits, which are underlain by a meter thick sand body: The sand of such sand bodies is coarser-grained than the present-day Gomti River sand. The sequence is essentially a silty very fine sand, highly mottled due to extensive bioturbation. These muddy successions are deposited by sheet floods of monsoon rains and not linked to flood plain of present-day active river. The high plateau surface (T₂-surface) shows locally a few meter thick channel fill sequences, produced by small channels which have been abandoned. The muddy sediments of upland surfaces show high degree of variability.

Keywords

Fluvial Morphology, Sedimentology, Gomti Alluvial Valley, Quaternary Deposits, Gangetic Plain, Uttar Pradesh.

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