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

S. K. Gupta ¹

Affiliations
1 Central Soil Salinity Research Institute, Karnal - 132001, IN

Abstract

Hydraulics of flow in cavity wells can be aproximated to unsteady state flow in spherical coordinates. The equation proposed by Chauhan et al (1975) can be used for non-leaky aquifer conditions placing the piezometer at a distance exceeding 20 times the radius of the cavity. Solutions to the equation can be found graphically by match point technique or using inverse 'lerfc' function. Solutions are yet to be developed for finite radius wells in leaky aquifer conditions or when source boundaries are present.

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S. K. Gupta ¹, P. Sharma ¹

Affiliations
1 Physical Research Laboratory, Ahmedabad 380 009, IN

Abstract

Radiocarbon dates of around 18 Kyr for palaeosols in Kashmir, indicative of warm-humid climate, have been an enigma as this period is regarded as the last glacial maximum (LGM) globally. In case of aeolian deposits such as loess in Kashmir, which can be assumed to have been exposed to solar radiation before deposition, thermoluminescence (TL) method is also being used for estimating the period since burial. Until a few years ago, when only limited number of measurements were available, it was believed that the dates of Kashmir palaeosols by the radiocarbon and TL methods were apparently not in agreement with each other.

In this note, we use all the available organic fraction radiocarbon and TL dates for the top two palaeosol horizons (S9 and S10) from Kashmir loess-palaeosol sections and show that the dates obtained by the two methods are concordant within the limits of uncertainties of the two methods.

Keywords

Radiocarbon Date, TL Date, Loess, Kashmir.

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K. Pandarinath ¹, Sushma Prasad ¹, S. K. Gupta ¹

Affiliations
1 Physical Research Laboratory, P. O. Box No. 4218; Navrangpura, Ahmedabad - 380 009, IN

Abstract

The crystallinity of the clay mineral illite, which is a climatically sensitive parameter, was studied for palaeoclimatic inferences from a core raised from Nal Sarovar in western India. The changes in crystallinity of illite in the top 3m of the core showed that the climate was wetter than present from ∼6.3-4.6 ka BP and was followed by a relatively dry phase which has continued up to the present. These palaeoclimatic observations are largely similar to those obtained from δ¹³C and C/N ratio variations in the top 3m of the core. From the deeper (>3m) section, a wet spell around 50 ka BP was identified in an otherwise continuous spell of aridity between 7 and 73 ka BP. The presence of a red bed dated to -50 ka BP (depth 1285-1324 cm) also suggested that the climate was wet followed by dry conditions during this period.

This interpretation of palaeoclimatic changes deciphered from the Nal Sarovar core differs in some detail from the Rajasthan palaeoclimatic record and that available from south India.

Keywords

Palaeoclimate, Crystallinity Index, Clay Minerals, Late Quaternary, Rajasthan.

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K. C. Joshi ¹, Y. P. Sharda ², Jaya Singh ¹, S. K. Gupta ¹, P. Pande ¹

Affiliations
1 Geological Survey of India, Lucknow - 226 024, IN
2 Geological Survey of India, Delhi -110 062, IN

Abstract

Seismic microzonation studies in Delhi have been carried out solely on the strength of the geotechnical data available with the Geological Survey of India. The main derivative products of the exercise include the shear wave velocity and predominant frequency maps on 1,50,000 scale. These maps are based on the N value data of subsurface soil columns, mostly down to a depth of 30 m, as observed at 121 Bore-Hole sites, in addition to the depth to bedrock, and other geological and geomorphological information.

The different ground response parameters, e g shear wave velocity and predominant frequency have been estimated by using empirical relationships developed elsewhere, especially m California, USA Although the tenacity of the qualitative/ semi quantitative results is yet to be affirmed, the maps, by and large conform to the effects of the past near and far events, such as the 1905 Kangra, 1960 Delhi and 1999 Chamoli earthquakes.

The amplification of the ground motion being the inverse function of impedance contrast between the underlying hard rock and the overlying soft sediments in Delhi, where the underlying rock is represented by quartzite, practically, the relative values of shear wave velocity of the soft sediments indicate the likely amplification - the low velocity promoting higher amplification A maximum ground motion amplification of 12 5 times and a minimum of 5 times, when assuming the damping as zero, has been estimated However, the actual amplifications are bound to be less because the soil does dampen the ground motions The predominant frequency map prepared on the assumption of simplified subsurface configuration, provides a generalized picture of the range of frequencies expected to get amplified -the amplification governed by the shear wave velocity of the soil cover there.

Keywords

Seismic Microzonation, Geotechnical Studies, Site Amphfication Effects, Delhi Area.

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D. D. Bhattacharya ¹, S. K. Gupta ¹

Affiliations
1 Geological Survey of lndia, Lucknow, IN

Abstract

No Abstract.

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G. S. Thakur ¹, H. U. Usmani ², S. K. Gupta ¹

Affiliations
1 Department of Applied Geology, Dr. H.S. Gour University, Sagar - 470 003, IN
2 Department of Geology, Govt. P.G. College, Chhatarpur - 471 001, IN

Abstract

No Abstract.

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