Deep Crustal Signatures in India and Contiguous Regions from Satellite and Ground Geophysical Data
- Muawia Barazangi and
- Larry Brown
Published Online: 15 MAR 2013
Copyright 1986 by the American Geophysical Union.
Reflection Seismology: The Continental Crust
How to Cite
Qureshy, M. N. and Midha, R. K. (1986) Deep Crustal Signatures in India and Contiguous Regions from Satellite and Ground Geophysical Data, in Reflection Seismology: The Continental Crust (eds M. Barazangi and L. Brown), American Geophysical Union, Washington, D. C.. doi: 10.1029/GD014p0077
- Published Online: 15 MAR 2013
- Published Print: 1 JAN 1986
Print ISBN: 9780875905143
Online ISBN: 9781118670118
- Seismic reflection method—Congresses
Topography and Bouguer anomalies show an inverse relationship in the Indo-Ganga-Brahmaputra basin and Himalaya-Hindu Kush region. The Indo-Ganga-Brahmaputra basin, devoid of any prominent closure on the Bouguer anomaly map, exhibits a −100 mgal closure on the Airy-Heiskanan map. The positive isostatic anomaly over the Himalaya can be explained by two possible intracrustal mass distributions that could represent either a remnant of the Neo-Tethys floor or large-scale igneous intrusions into the crust from the mantle. We thus suggest that the isostatic compensation in the Himalaya and the Indian shield is nearly complete. The correlation of Moho depths derived from the empirical relationship between crustal thickness and elevation with the depths determined from Deep Seismic Sounding (DSS) provides support for this contention. The steep gradient on the regionalized isostatic anomaly map of the area indicates that the Main Mantle Thrust (MMT), which is located west of the Nanga Parbat, may represent a direct continuation to the Main Central Thrust (MCT), which is located farther east. Likewise, the northern gradient of the isostatic anomaly map is correlated with the Northern Main Suture (NMS) in the Kohistan and Himalaya-Tibet regon. That prominent lineaments, some dating back to the Precambrian, such as the Narmada-Son rift, Godavari graben, and Gandak-Karakorum, show up conspicuously on both groundand satellite-based gravity and magnetic maps suggests a genetic relationship between the near-surface and deep controlling stuctures. The Magsat vertical field (Z) map shows a positive anomaly (4 to 8 nT) over the southern Indian shield and a negative ENE-trend ing anomaly (−4 to −8 nT) over the northern shield, with the Narmada-Son line marking the transition zone. The negative magnetic anomaly over the Ganga-Himalaya area suggests a possible rise of geotherms in this region. There is growing evidence to show that some blocks in the Indian continent, such as the Aravali ranges, Narmada rift, Shillong plateau, and Godavari graben, are associated with recent tectonic activity, suggesting that the Indian shield is not as stable as normally thought and that it may be passing through a phase of rejuvenation.