Browsing by Author "Rupa Ghosh"

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100 kyr sedimentary record of Marginal Gangetic Plain: Implications for forebulge tectonics
(Elsevier B.V., 2019) Rupa Ghosh; Pradeep Srivastava; U.K. Shukla; R.K. Sehgal; I.B. Singh
The Gangetic Foreland is a consequence of continent-continent collision and formation of the Himalayan thrust and fold belt. In the more distal part of the peripheral Gangetic foreland basin, the Late Quaternary sedimentary architecture analysis from 17 stratigraphic successions together with optically stimulated luminescence dating (OSL) divulge interaction of peripheral bulge tectonics and climate over the past ~100 kyr. These sections exhibit three sedimentary packages formed under different environmental conditions. Detailed vertical and lateral sedimentary architecture delineates nine lithofacies that are grouped into three facies associations, (i) flood plain facies association, (ii) channel facies association, and (iii) interfluve facies association. The basal package-I, >114 ka old, was deposited by sandy meandering channels and overlying to this with a hiatus of ~30 ka is package-II, ~80–54 ka, deposited by gravelly rivers. The sediments of both the packages-I, II are derived from rocks exposed in the peripheral bulge region. Overlain package- III, deposited by small meandering channels, consist of the sediments derived from the Himalaya. The results indicate that the duration of 80–54 ka was a period of forebulge uplift when gravelly fans prograded basinward. Below the fan sediments lies a peripheral bulge unconformity marked by regionally significant pedogenic horizon. This pedogenic horizon qualifies as to be termed as peripheral bulge uncomformity. After 54 ka, the fine Himalayan sediments onlap the cratonic sediments implying rather a stable forebulge tectonics coupled with fluctuating climatic conditions, occasionally bringing micaceous gray coloured sand-silt of Himalayan origin. © 2019 Elsevier B.V.
Constraints of lithostratigraphy on the landscape evolution in response of erosion, climate and tectonics in the Marginal Ganga Plain, India
(Elsevier Ltd, 2021) Rupa Ghosh; Uma Kant Shukla; Pradeep Srivastava; Anupam Sharma
The Marginal Ganga Plain (MGP) exhibits up to 160 m thick fluvial sedimentary record of the Late Quaternary forebulge dynamics. The mineralogical composition of sediments from forty boreholes reveals three major depositional sequences (DS1, DS2, and DS3) and four sequence boundaries Sb1, Sb2, Sb3 and Sb4 representing where different tectonic and climatic conditions exercised parental control. These sequence boundaries are demarcated by the shift in facies architecture. The Sb1 sequence boundary is locally developed over the basement rocks. The lowermost DS1 represents a thick floodplain and low sinuosity channel association at > 114 ka under stable landscape. This DS1 indicates a low rate of sedimentation and High Accommodation Systems Tract (HAST), characterized by positive > 1 A/S (Accommodation to Sediment) ratio. The sequence boundary Sb2 lies between DS1 and overlying DS2 implies a regional unconformity in the MGP and negative A/S ratio. Further, laterally extensive asymmetrical DS2, developed between ~ 80–54 ka with an erosional base overlies the DS1 and represents Low Accommodation Systems Tract (LAST) with A/S < 1. The Sb3, present between DS2 and DS3 denotes a sharp transition in facies architecture. The DS3 made up of the interfluves sequence shows an upward fining sequence deposited by vertically aggrading minor channels developed after 54 ka and is characterized as HAST where A/S > 1. The Sb4 represents the top surface of the DS3 and is currently getting degraded by ravinement processes. The varying pattern of alluvial architecture in the MGP defines variable A/S ratio and infer forebulge tectonic signature shaping the fluvial landscape. © 2021 Elsevier Ltd
Discovery of Elephas cf. namadicus from the late Pleistocene strata of Marginal Ganga Plain
(Geological Society of India, 2016) Rupa Ghosh; R.K. Sehgal; Pradeep Srivastava; U.K. Shukla; A.C. Nanda; D.S. Singh
We describe an elephant skull recovered from a cliff section of Dhasan river of Marginal Ganga Plain. The dental morphology and cranial features of the skull have been compared with the known species of Elephas from the Indian subcontinent. Although it shows very near resemblance to Elephas namadicus, but being an isolated specimen its specific identity cannot be proclaimed with certainty. As such, the specimen is provisionally referred as E. cf. namadicus. The Optically Stimulated Luminescence ages place this find at ~56 ka BP. This is the first chronologically well constrained report of E. cf. namadicus from the Ganga Plain. © 2016, Geological Society of India.
Stable Isotopic studies of the herbivorous mammals from the Marginal Ganga Plain, India: implication for the palaeo-environmental reconstruction
(John Wiley and Sons Ltd, 2022) Sakshi Maurya; Rupa Ghosh; Ramesh Kumar Sehgal; Pradeep Srivastava; Uma Kant Shukla; Abhishek Pratap Singh; Shushanta Sarangi
The reconstruction of palaeo-vegetation and dietary habitat from vertebrate molar fragments from the Marginal Ganga plains (MGP) are rare. This study from moderately preserved fossil dentitions of herbivorous mammals collected from the two stratigraphic sections of the MGP presents carbon and oxygen isotope compositions, and provides dietary habits of large mammals in the northern Indian Alluvial tract during the Late Pleistocene. Elephas namadicus recovered from the channelized gravel litho-unit of the Jigni section, previously dated to be 56 ± 5 ka dominantly had a C4 dietary system. It exhibits a swampy grassland landscape rather than a savannah-type forest landscape. Bovini fossil specimens recovered from the upper part of channelized gravel litho-unit dated between 54 ± 10 and 51 ± 5 ka, also favour a C4 dietary system suggesting pure grazers living in open grassland habitat. © 2022 John Wiley & Sons Ltd.