Crustal structure of Bengal Basin and Shillong Plateau: Extension of Eastern Ghat and Satpura Mobile Belts to Himalayan fronts and seismotectonics

2008 ◽  
Vol 14 (3) ◽  
pp. 523-534 ◽  
Author(s):  
R.P. Rajasekhar ◽  
D.C. Mishra
Keyword(s):  
Crustal Structure ◽  
Bengal Basin ◽  
Shillong Plateau ◽  
Eastern Ghat

Seismicity, gravity, and tectonics of northeast India and northern Burma

1976 ◽  
Vol 66 (5) ◽  
pp. 1683-1694
Author(s):  
R. K. Verma ◽  
Manoj Mukhopadhyay ◽  
M. S. Ahluwalia
Keyword(s):  
Large Scale ◽  
Bouguer Anomaly ◽  
Northeast India ◽  
Eastern Himalaya ◽  
Basic Material ◽  
Bengal Basin ◽  
Seismic Zone ◽  
Shillong Plateau ◽  
Eurasian Plate ◽  
High Seismicity

abstract Practically the whole of northeastern India and northern Burma is characterized as an anomalous gravity field as well as an area of high seismicity. The Bouguer anomaly in the region varies from +44 mgals over Shillong Plateau to −255 mgals near North Lakhimpur in Assam Valley. Isostatic anomaly (Hayford) varies from +100 to −130 mgals in these areas. Over Arakan-Yoma and the Burmese plains, the isostatic anomalies vary from −20 mgals to −100 mgals. Regions of high seismicity in the area include the eastern Himalaya (including Assam syntaxis), Arakan-Yoma including the folded belt of Tripura, Irrawaddy basin, Shillong Plateau, Dauki fault and the northern part of Bengal basin. The abnormal gravity and seismicity are related to large scale tectonic movements that have taken place in the area mostly during the Cretaceous and Cenozoic times, due to interaction of the Indian, Tibetan, and Burmese plates. The high seismicity indicates that the movements are continuing. The seismic zone underlying Burma is approximately V shaped and dips toward the east underneath Arakan-Yoma. Most of the intermediate-focus earthquakes in Burma underlie the area characterized by negative isostatic anomalies, indicating the probable existence of a subduction zone underneath the Arakan-Yoma and the Burmese plains. The Shillong Plateau has a history of vertical uplift since Cretaceous times. Provided this statement is true, the uplift of the plateau preceded Himalayan tectonics starting 20 to 30 m.y. before continental India made solid contact with the Eurasian plate. The plateau is characterized by large positive isostatic anomalies as well as high seismicity. The positive isostatic anomalies may be due to intrusion or incorporation of basic material from the mantle into the crust underlying the Plateau. These intrusions may have taken place through deep seated faults such as the Dauki and could be responsible for its uplift as well.

Slab deformation in the Bengal basin due to uplift of the Shillong Plateau and the Indo-Burmese Ranges since the Pliocene, constrained by a Dynamic Topo-Tomographic technique

2020 ◽  
Author(s):  
Raghupratim Rakshit ◽  
Robert James Wasson ◽  
Devojit Bezbaruah
Keyword(s):  
Mantle Convection ◽  
Plate Tectonics ◽  
Bengal Basin ◽  
Dynamic Topography ◽  
Shillong Plateau ◽  
Total Change ◽  
Deep Basin ◽  
The Past ◽  
The North ◽  
Shelf Region

<p>Earth’s topography is mainly controlled by the structures associated with density differences of the lithosphere and the crust. This is related to isostatic topographic processes which work in association with mantle-induced deformation that together leads to dynamic topography. In this study, the dynamic topographic model of Rubey et al. (2017) has been used. The model links sedimentary basin evolution with plate tectonics and mantle convection to deliver a quantitative framework to understand the combined roles of mantle convection and subduction processes in time and space. Dynamic topography is different from surface topographic variations and this difference can be used to explain past deformation. In the Bengal basin, sedimentation began in a deep basin and shelf region that endured continuous subsidence, and then became involved with crustal adjustments due to collision and uplift of the Himalayas and later on the Indo-Burmese Ranges (IBR). In this study, the dynamic topographic changes have been used to understand the past deformational history and plate dynamics beneath the Bengal Basin and IBR. The model has been run in a cloud-computing environment using the global mantle convection code TERRA along with the plate reconstruction Gplates software to reproduce dynamic topographic variations. In such conditions the shelf zones are the dynamic topographic representation. The results for Bengal basin region, 22.5° to 24.5°N latitude and 91.5° to 93.5° E longitude for the past 20Ma, showed that high sedimentation in the subducting basinal setting caused rising dynamic topography from 20 to 5 Ma continuously. A negative trend (i.e. subsidence) is seen for the past 5Ma. Moreover, when total change in subsidence in the last 5Ma is considered, it has been observed that the northern front of the Bengal Basin steeply plunged towards the north at a time when the Shillong Plateau was uplifted. While there has been overall subsidence of the region both the Shillong Plateau and IBR rose. Present day seismic tomographic study indicates the presence of denser magmatic mass beneath Shillong Plateau which might also be linked with Indian oceanic plate subduction. The Dynamic Topo-Tomographic Model suggests that slab bending associated with subduction caused detachment of the denser material zones and change in the slab setting above which the thick sedimentary column is stacked. The rise of the rigid Shillong Plateau caused a deformational front in the sedimentary zone, south of the Plateau, resulting in a steep plunging dynamic topography. </p>

Upper Mantle deformation patterns beneath norteast India from Shear-wave splitting analysis

2020 ◽  
Author(s):  
Jyotima Kanaujia ◽  
Ganpat Surve ◽  
Nava Hazarika
Keyword(s):  
Shear Wave ◽  
Upper Mantle ◽  
Plate Boundary ◽  
Shear Wave Splitting ◽  
Northeast India ◽  
Bengal Basin ◽  
Plate Boundaries ◽  
Shillong Plateau ◽  
Crust And Upper Mantle ◽  
Wave Splitting

<p>Telesesimic earthquake data recorded at eight seismograph stations across the northeast India are analysed for shear-wave splitting from core-refracted XKS phases (collectively PKS, SKS and SKKS). Shear-wave splitting parameters, derived from the analysis provide information about seismic anisotropy and deformation of the crust and upper mantle beneath each seismograph stations site. The results point towards the presence of complex and highly anisotropic crust and upper mantle beneath northeast India. Being surrounded by two seismically active plate boundaries, to the north by India-Eurasia collision plate boundary and to the east by Indo-Burman subduction plate boundary, the crust and upper mantle beneath the northeast India has been assumed to have complex deformation pattern. This present study provides an evidence for this assumption. According to station locations, we have one station BONG situated near the Main boundary thrust (at India-Eurasia collision zone), one station NAMS and eastern syntexis Himalaya, five station AZWL, SILS, DIPH and NKCR at Indo-Burman subduction plate boundary, one station SHLS and Shillong plateau bounded by Oldham Fault, Dauki Fault and Kopli fault, and one station AGAR at the boundary of Bengal basin. The direction of anisotropy is nearly E-W at BONG, NE-SW in the Indo-Burman subduction zone, nearly N-S on Shillong plateau and NW-SE at eastern syntexis of Himalaya. Source of anisotropy in the Himalaya collision boundary is result of lithospheric deformation due to finite strain induced by collision. In Shillong plateau and Indo-burman subduction boundary, source of anisotropy seems to be the asthenospheric flow-related strain which is also in harmony with the absolute plate motion (APM) of the Indian plate in a no net reference frame.</p>

Crustal structure of the west Bengal basin, India from deep seismic sounding investigations

1992 ◽  
Vol 111 (1) ◽  
pp. 45-66 ◽  
Author(s):  
K. L. Kaila ◽  
P. R. Reddy ◽  
D. M. Mall ◽  
N. Venkateswarlu ◽  
V. G. Krishna ◽  
...  
Keyword(s):  
Crustal Structure ◽  
West Bengal ◽  
Deep Seismic Sounding ◽  
Bengal Basin ◽  
The West ◽  
Seismic Sounding

BOUGUER GRAVITY AND ITS GEOLOGIC EVALUATION IN THE WESTERN PART OF THE BENGAL BASIN AND ADJOINING AREA, INDIA

Geophysics ◽  
1973 ◽  
Vol 38 (4) ◽  
pp. 691-700 ◽  
Author(s):  
S. K. Choudhury ◽  
A. N. Datta
Keyword(s):  
Gravity Anomalies ◽  
Main Line ◽  
Bengal Basin ◽  
Bouguer Gravity ◽  
Shillong Plateau ◽  
Peninsular India ◽  
Early Tertiary ◽  
Bouguer Gravity Anomalies ◽  
Adjoining Area ◽  
Darjeeling Himalayas

The Bouguer gravity anomalies in the western part of Bengal Basin and part of eastern Bihar, India, can be explained in terms of basement relief which controls the thickness of the Gondwanas. This relief, however, has no influence on structure within the sedimentary section overlying the Gondwanas. During Gondwana times, the Bengal Basin continued further north at least up to Purnea, but in early Tertiary times, the continuity was interrupted by a basement feature passing through Jangipur and Malda. The main line of connection between peninsular India and the Shillong Plateau may be through the Rajmahal hills and the Darjeeling Himalayas.

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