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A. Adam ¹, L. Nemesi ², B. R. Arora ³

Affiliations
1 Geodeticand Geophysical Research Institute of the Hungarian Academy of Sciences, H-9401 Sopron, POB 5, HU
2 Eotvos Geophysical Institute, H-1145 Budapest, Columbus u. 17-23, HU
3 Indian Instituteof Geomagnetism, Colaba, Bombay-400005, IN

Abstract

After, a methodical overview of the magnetotelluric and telluric methods, the paper with the help of test example from the Pannonian basin (Hungary) illustrates the effectiveness of a combined telluric and magnetotelluric methods in the study of basement structures of deep basins. It is strongly emphasized that in the case of such adeep basin me relation between the gravity map and basin structure may be totally distorted by the crustal-mantle anomalies, first of all by the intrusion of mantle material of high density. Recognising the merits of combined telluric-magnetotelluric method in the exploration of sedimentary basins for hydrocarbon traps, the significance of the application of these methods to Indian sedimentary basins is highlighted. Usefulness of electrical conductance map, derived from these investigations, in demarcating thermally favourable zones of hydrocarbon maturation is envisaged.

Keywords

Geophysics, Sedimentary Basin, Hydrocarbon

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R. P. Tiwari ¹, J. Malsawma ¹, S. J. Sangode ², B. R. Arora ²

Affiliations
1 Department of Geology, Mizoram University, Aizawl - 796009, IN
2 Wadia Institute of Himalayan Geology, 33 General Mahadev Singh Road, Dehradun - 248 001, IN

Abstract

A 560 m thick rock succession of Middle Bhuban Formation (Surma Group) exposed between Bawngkawn and Durtlang, Aizawl, Mizoram has been studied for its magnetostratigraphic attributes. A total of 7 normal and 7 reverse magneto-Zones have been delineated in this section. The GPTS correlated ages of this section lie between -21.77 Ma (at the base) to ∼15.16 Ma (at the top) with a total duration of ∼6.6 Ma. The GPTS event C6n occurring at the stratigraphic level between 146 m to 266 m may be considered for basin wide correlation as it is the longest normal event that has been recorded with greater confidence i. e. better alpha- 95. The average sediment accumulation rate (SAR) estimated for this section is 8.48 cm/Ka. Overall the SAR is higher in the lower part of the section with a spike of 26.8 cm/Ka at <21 Ma. The decrease in SAR to 2.1 cm/Ka at around 18 Ma in the upper part of the section may be investigated for possible hiatus.

Keywords

Magnetostratigraphy, Sediment Accumulation Rate (SAR), Surma Group, Middle Bhuban Formation, Aizawl, Mizoram.

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T. M. Mahadevan , B. R. Arora , K. R. Gupta

Abstract

No Abstract.

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B. R. Arora ¹

Affiliations
1 WIHG, Dehra Dun, IN

Abstract

No Abstract.

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A. K. Mahajan ¹, Subash Chandra ², V. S. Sarma ², B. R. Arora ³

Affiliations
1 School of Earth and Environmental Sciences, Central University of Himachal, Dharamshala 176 207, IN
2 CSIR-National Geophysical Research Institute, Uppal Road, Hyderabad 500 007, IN
3 Ministry of Earth Sciences, Government of India, New Delhi 110 003, IN

Abstract

Geophysical studies using multichannel analysis of surface waves (MASW) and high-resolution electrical resistivity tomography (HERT) have been jointly carried out on an experimental basis in the field. The motive is to study shallow subsurface features (i.e. faults traces, cavities and palaeo-channels) in the foothill zone of Northwest Himalaya. These techniques have shown their potentiality in successfully identifying shallow (0-24 m) fault traces and dissolution features/palaeo-channels. Depending on the sensitivity of the MASW and HERT techniques, geophysical signatures of the subsurface features were recorded and further resolved with the help of synthetic simulation. The synthetic simulation of 2D electrical response has been carried out over the initial model for subsurface fault traces as well as palaeo-channels. The initial model has been refined iteratively to bring the synthetic response close to the field response and hence the final refined model is considered to be the true representation of the subsurface.

Keywords

Fault Traces, High-Resolution Electrical Resistivity Tomography, Multichannel Analysis of Surface Waves, Synthetic Simulation, Palaeo-Seismology.

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Koushik Sen ¹, Ruchika Sharma ¹, B. R. Arora ¹, Vikram Gupta ¹

Affiliations
1 Wadia Institute of Himalayan Geology, 33, GMS Road, Dehradun - 248 001, IN

Abstract

Anisotropy of Magnetic Susceptibility (AMS) and seismic wave velocity studies of some paramagnetic Himalayan granitoids show good correlation between magnetic fabric anisotropy and P wave velocity (Vp). Vp shows strong positive correlation with magnetic lineation (L) and degree of magnetic anisotropy (P') having correlation coefficient (r) values of 0.93 and 0.89 respectively. Both Vp and Vs show positive correlation with the SiO₂ content of Proterozoic and Paleozoic granitoids. Velocity of S wave (Vs) shows negative correlation with mean magnetic susceptibility (K_m) having 'r' value of 0.86. The correlation between Vs-K_m, Vp-P', Vp-L also shows >95% probability in Spearman's rank correlation. Based on the results from the present sample size it is suggested that, in paramagnetic granites, Vp is proportional to intensity of deformation and preferred orientation of minerals as well as the mineralogy. On the other hand, Vs is more dependent on the mineralogy alone.

Keywords

Paramagnetic Granites, AMS, Primary Wave, Secondary Wave, Deformation, XRF, NW Himalaya.

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