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Depositional History of the Chhattisgarh Basin, Central India Constraints from New SHRIMP Zircon Ages A Discussion [查看] P.P.Chakraborty、K.Das、Y.Tsutsumi、K.Horie

In the past 4 decades, extensive field-based studies in unmetamorphosed and mildly deformed Indian Proterozoic basins have produced significant findings in physical sedimentology, in general, and the uniqueness of vegetationless yet biomat-influenced sedimentation patterns, in particular. In comparison,geochronological and geochemical appraisal of the basin fills was limited, rendering the time framework for these basins highly tentative. Use of more and more high-precision instrumental facilities in recent times has provided significant information on time constraints and sediment provenances of these Proterozoic Indian basins (Chakraborti et al. 2007; Malone et al. 2008; Absar et al. 2009). The contribution by Bickford et al.(2011) is a welcome addition to this list. While these contributions have undoubtedly enriched Indian Precambrian geology by adding a new database,the conclusions drawn from this new database have swept the field observations into oblivion in many instances. The contribution of Bickford et al.(2011) is one such example. From U-Pb SHRIMP age determinations of zircon grains from interbedded tuffaceous layers and coarse arenaceous rocks,Bickford et al. (2011) constrained the time domain of Chhattisgarh depositional history (i.e., between ~1400 and ~1000 Ma) and concluded that there had been a change in provenance through Chhattisgarh depositional history.