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

R. Sinha ¹, B. C. Raymahashay ¹

Affiliations
1 Engineering Geology Group, Department of Civil Engineering, Indian Institute of Technology, Kanpur - 208016, IN

Abstract

The Sambhar lake of central Rajasthan, located between Ajmer and Jaipur, is a hypersaline lake. The present study focuses on the mineralogy of the lacustrine sediments of this region. X-ray diffraction patterns of shaflow auger hole samples show a broad pattern of fluctuation in vertical profiles. It is apparent that rock weathering in the catchment area supplies a flux of clastic minerals like quartz, feldspar and mica during the wet period. This is followed by an evaporite sequence of carbonate-sulfate-chloride in dry climate. Thus, an abundance of calcite indicates the beginning of evaporation, while later stages are characterized by the dominance of thenardite and finally of halite.

Keywords

Sedimentology, Sediment Geochemistry, Clay Minerals, Evaporites, Saline Lake.

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Chhaya Sharma ¹, M. S. Chauhan ², R. Sinha ³

Affiliations
1 Department of Geology, University of Lucknow, Birbal Sahni Institute of Palaeobotany, Lucknow - 226 007, IN
2 Birbal Sahni Institute of Palaeobotany, Lucknow - 226 007, IN
3 Indian Institute of Technology, Kanpur - 208 016, IN

Abstract

Pollen analysis of a sediment core from Priyadarshini Lake (Core S3), East Antarctica, has revealed the climatic oscillations in the region since Holocene. Three pollen zones have been identified on the basis of recovered pollen taxa and varying frequencies. Between 10,000 and 9,000 yr BP, cold and dry climate prevailed in the region as reflected by the dominance of grasses, Acritarch and very low frequencies of Cosmarium - a fresh water alga. The lake was probably shallow and smaller in dimension during this period. Between 9,000 to 2,400 yr BP, relative increase in grasses is witnessed though in fluctuating frequencies. Cosmarium also exhibits a distinct increasing trend, whereas Acritarch declines considerably. This overall change in the assemblage reflects the onset of warm and moist climate and the lake had a wider expansion during this phase on account of amelioration in climate than witnessed before. Between 2,400 and 1,000 yr BP, relatively reduced frequencies of grasses, coupled with total disappearance of Cosmarium, demonstrate that the climate changed once again to cold and dry. However, 1,000 yr BP onwards, marked increase in grasses coupled with exceedingly high values of Cosmarium implies that the climate ultimately turned warm and moist.

Keywords

Palynology, Holocene, Climate Changes, Priyadarshini Lake, Antarctica.

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R. Sinha ¹, M. R. Gibling ², S. K. Tandon ³, V. Jain ¹, A. S. DasGupta ¹

Affiliations
1 Engineering Geosciences Group, IIT Kanpur - 208 016, IN
2 Departrnent of Earth Sciences, Dalhousie University, Halifax, Nova Scotia, B3H 355, CA
3 Departmen of Geology, University of Delhi, Delhi - 110 007, IN

Abstract

Floodplain deposits are exposed in an about 29 rn high cliff section at Kotra along the Betwa river, a tributary of the Yamuna river at the southern margin of the Gangetic Plains. The Betwa is a peninsular river originating in the Bundelkhand Craton parts of which are exposed as bedrock close to the sectipn. The Betwa river is incised and bordered by an extensive zone of badland (dissected into gullies). The.stratigraphic units comprise pedogenized floodplain muds and reworked carbonate grayels that fill small plains-fed channels. Gully, fills of mud and gravel mark extensive degradational surfaces that divide the section into discontinuity-bounded units, currently of unknown'duration and age. Closely spaced discontiquities low in the section may mark a former interfluve level, after which a thick floodplain succession accumulated up to the level of the modem clifftop. Presence of prominent discontinuities and thick floodplain deposits in the cliff sections suggest that the late Quaternary history of the southern plains is marked by cycles of channel incision and floodplain degradation and alluviation.

Keywords

Quaternary, Allostratigraphy, craton-Sourced river sedimentation, Betwa river, Gangetic plain, Uttar Pradesh.

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R. Sinha ¹, V. N. Sastry ², G. Rajagopalan ³

Affiliations
1 Engineering Geology Group, Indian Institute of Technology, Kanpur - 208 016, IN
2 Bhabha Atomic Research Centre, Bombay, Mumbai, IN
3 Birbal Sahni Institute of Paleobotany, 53 University Road, Lucknow, IN

Abstract

Data on geochemical analysis of sediment cores obtained from Lake Priyadarshini, Schirmacher Range, Eastern Antarctica is presented. Elemental distribution in vertical profiles has been correlated with the redox cycles which provide information about depositional environment. Very low sedimentation rate is inferred in the periglacial environment of Antarctica with a very limited sediment supply. A ¹⁴C age of ∼8 kyr indicates that the lake formed in early Holocene as a result of major deglaciation after the end of the last glacial period.

Keywords

Lacustrine Sedimentation, Geochemistry, Holocene, Radioisotopes, Antarctica.

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R. Sinha ¹, S. K. Tandon ²

Affiliations
1 Department of Civil Engineering, IIT, Kanpur - 208 016, IN
2 Department of Geology, Delhi University, Delhi - 110 007, IN

Abstract

No Abstract.

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R. P. Gupta ¹, R. Sinha ², M. S. Roohani ¹

Affiliations
1 Department of Earth Sciences, University of Roorkee, Roorkee-247 667, IN
2 Engineering Geology Group, Department of Civil Engineering, IIT, Kanpur - 208 016, IN

Abstract

In the Himalayas, snowmelt runoff makes a dominant contribution to the total annllal stream flow. An early prediction of the amount of runoff to be derived from the snow pack is, therefore, of great importance for proper management of water resources. The area selected for the present investigation is the Punjab Himalayas comprising three major catchments of the Beas, Ravi, and Chenab rivers. Landsat imageries have been used to map snow cover in these three catchments. Data from a number of discharge gauging stations on the Beas, Ravi and Chenab rivers have been used to yield snowmelt runoff. Unique relationships between satellite snow cover and snowmelt runoff have been obtained for each of the sub-catchments. The studies show that geomorphometric parameters have a systematic influence on the relationship between snow cover area and subsequent runoff. The relationships are interpreted for their physical implications.

Keywords

Geomorphology, Geohydrology, Satellite Data, Punjab Himalaya.

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