scholarly journals Geochemistry and petrogenesis of early Cretaceous sub-alkaline mafic dykes from Swangkre-Rongmil, East Garo Hills, Shillong plateau, northeast India

2004 ◽  
Vol 113 (4) ◽  
pp. 683-697 ◽  
Author(s):  
Rajesh K. Srivastava ◽  
Anup K. Sinha
Keyword(s):  
Early Cretaceous ◽  
Northeast India ◽  
Shillong Plateau ◽  
Mafic Dykes ◽  
Garo Hills

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.

scholarly journals Farms or Forests? Understanding and Mapping Shifting Cultivation Using the Case Study of West Garo Hills, India

Land ◽  
2019 ◽  
Vol 8 (9) ◽  
pp. 133 ◽  
Author(s):  
Kurien ◽  
Lele ◽  
Nagendra
Keyword(s):  
Land Use ◽  
State Government ◽  
Shifting Cultivation ◽  
Northeast India ◽  
Tree Plantations ◽  
Old Growth Forest ◽  
Forest Survey ◽  
Garo Hills ◽  
Government Statistics

Attempts to study shifting cultivation landscapes are fundamentally impeded by the difficulty in mapping and distinguishing shifting cultivation, settled farms and forests. There are foundational challenges in defining shifting cultivation and its constituent land-covers and land-uses, conceptualizing a suitable mapping framework, and identifying consequent methodological specifications. Our objective is to present a rigorous methodological framework and mapping protocol, couple it with extensive fieldwork and use them to undertake a two-season Landsat image analysis to map the forest-agriculture frontier of West Garo Hills district, Meghalaya, in Northeast India. We achieve an overall accuracy of ~80% and find that shifting cultivation is the most extensive land-use, followed by tree plantations and old-growth forest confined to only a few locations. We have also found that commercial plantation extent is positively correlated with shortened fallow periods and high land-use intensities. Our findings are in sharp contrast to various official reports and studies, including from the Forest Survey of India, the Wastelands Atlas of India and state government statistics that show the landscape as primarily forested with only small fractions under shifting cultivation, a consequence of the lack of clear definitions and poor understanding of what constitutes shifting cultivation and forest. Our results call for an attentive revision of India’s official land-use mapping protocols, and have wider significance for remote sensing-based mapping in other shifting cultivation landscapes.

Survey and census of the hoolock gibbon in West Garo Hills, Northeast India

Primates ◽  
1990 ◽  
Vol 31 (2) ◽  
pp. 299-306 ◽  
Author(s):  
J. R. B. Alfred ◽  
J. P. Sati
Keyword(s):  
Northeast India ◽  
Garo Hills

scholarly journals State of tectonic stress in Shillong Plateau of northeast India

2016 ◽  
Vol 95 ◽  
pp. 36-49 ◽  
Author(s):  
Santanu Baruah ◽  
Saurabh Baruah ◽  
Sowrav Saikia ◽  
Mahesh N. Shrivastava ◽  
Antara Sharma ◽  
...  
Keyword(s):  
Tectonic Stress ◽  
Northeast India ◽  
Shillong Plateau

scholarly journals Petrological and geochemical study of the Sylhet trap basalts, Shillong plateau, N.E. India: Implications for petrogenesis

2020 ◽  
Vol 2 (1) ◽  
pp. 01-18
Author(s):  
M. Faruque Hussain ◽  
Md Shofiqul Islam ◽  
Mithun Deb
Keyword(s):  
Partial Melting ◽  
Lithospheric Mantle ◽  
Crustal Contamination ◽  
Northeast India ◽  
Subcontinental Lithospheric Mantle ◽  
Shillong Plateau ◽  
Geochemical Study ◽  
Significant Enrichment

Sylhet Traps exposed along the southern margin of Shillong plateau, Northeast India are subalkaline tholeiitic basalts. The basalts are generally massive but occasionally contain large amygdules of zeolites and chalcedony. Microscopically, some basalts show porphyritic texture with olivine phenocrysts. Phenocryst assemblage of plagioclase ± clinopyroxene ± olivine implies crystallization at shallow level. SEM-EDX analysis shows occurrences of spinel with Ni and Cr within the basalts therefore indicating partial melting of the subcontinental lithospheric mantle as the possible source materials for the basalts. The multi-element plot for the basalts shows two distinct trends: one with significant enrichment of LILE and depletion of HFSE and plot similar to OIB (Type 1) while the other trends are chara cterized by slight enrichment of LILE and negative anomalies at Nb, P and Ti (Type 2). Chondrite-normalized REE patterns for Type 1 basalt shows very high enrichment of LREE and a strong right dip HREE pattern and also plots similar to typical OIB while Type 2 show a slight enrichment of LREE over HREE with small Eu anomaly. The geochemical signatures suggest crustal contamination by plume-derived magma produced by low degree of partial melting for Type 1 basalt. Type 2 basalt was produced by partial melting of subcontinental lithospheric mantle, which may be triggered by plume upwelling.

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