Jyotiranjan S Ray
Articles written in Journal of Earth System Science
Volume 110 Issue 3 September 2001 pp 185-190
40Ar-39Ar analyses of one alkali pyroxenite whole rock and two phlogopite separates of calcite carbonatites from the Sung Valley carbonatite-alkaline complex, which is believed to be a part of the Rajmahal-Bengal-Sylhet (RBS) flood basalt province, yielded indistinguishable plateau ages of 108.8 ± 2.0Ma, 106.4 ± 1.3Ma and 107.5 ± 1.4Ma, respectively. The weighted mean of these ages, 107.2 ± 0.8 Ma, is the time of emplacement of this complex. This implies that Sung Valley complex and probably other such complexes in the Assam-Meghalaya Plateau postdate the main flood basalt event (i.e., the eruption of tholeiites) in the RBS province by ∼10Ma.
Volume 115 Issue 1 February 2006 pp 1-2
Volume 115 Issue 1 February 2006 pp 149-160
The Vindhyan Supergroup of India is one of the largest and thickest sedimentary successions of the world. Deposited in an intra-cratonic basin, it is composed mostly of shallow marine deposits. It is believed to have recorded a substantial portion of Proterozoic time and therefore, likely to contain valuable information on the evolution of the atmosphere, climate, and life on our planet. It also contains some of the most disputed fossils of earliest animal life. Despite their importance, the absolute age of these rocks had remained unknown until recently. In this work I evaluate all the recent chronological information and discuss their implications. From the present findings it appears that the issues surrounding the age of the Lower Vindhyans in the Son valley are now resolved, whereas problems with the age of the Upper Vindhyans and that with the stratigraphic correlations remain to be answered.
Volume 128 | Issue 8
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