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U-Pb zircon dating and Sr isotope systematics of the Vindhyan Supergroup, India

Jyotiranjan S. Ray, Mark W. Martin, Jan Veizer and Samuel A. Bowring
U-Pb zircon dating and Sr isotope systematics of the Vindhyan Supergroup, India
Geology (Boulder) (February 2002) 30 (2): 131-134

Abstract

The Vindhyan Supergroup of central India, the focus of many paleontological studies, has been reported to contain Cambrian small shelly fossils, Ediacaran fossils, trace fossils, and Proterozoic microfossils and carbonaceous megafossils. New U-Pb zircon and (super 87) Sr/ (super 86) Sr isotopic data from the Lower Vindhyan Supergroup require that the rocks are latest Paleoproterozoic to earliest Mesoproterozoic in age. Two rhyolitic volcanic horizons from the Deonar Formation, between the Kajrahat and Rohtasgarh Limestones and below the unit containing trace fossils, yield U-Pb zircon ages of 1631+ or -5 Ma and 1631+ or -1 Ma. The Kajrahat and Rohtasgarh Limestones of the Semri Group that are below and above the reported Mesoproterozoic trace fossils have (super 87) Sr/ (super 86) Sr ratios of 0.70460 and 0.70479, respectively. The Bhander Limestone from the Upper Vindhyan Supergroup has an (super 87) Sr/ (super 86) Sr ratio of 0.70599, consistent with a Neoproterozoic age for this formation. These results indicate that the Kajrahat Limestone is of latest Paleoproterozoic age and the Rohtasgarh Limestone is of probable Mesoproterozoic age. These findings are in conflict with the report of Cambrian small shelly fossils and fossils of articulate brachiopods in the Rohtasgarh Limestone and argue for a Mesoproterozoic age for the formation that contains the alleged trace fossils. Reports of an Ediacaran fossil Spriggina(?) from the Lower Vindhyan Supergroup from the northern margin of the Vindhyan Basin suggest either incorrect stratigraphic correlation of units or misidentification of this fossil.


ISSN: 0091-7613
EISSN: 1943-2682
Coden: GLGYBA
Serial Title: Geology (Boulder)
Serial Volume: 30
Serial Issue: 2
Title: U-Pb zircon dating and Sr isotope systematics of the Vindhyan Supergroup, India
Affiliation: University of Ottawa, Ottawa-Carleton Geoscience Centre, Ottawa, ON, Canada
Pages: 131-134
Published: 200202
Text Language: English
Publisher: Geological Society of America (GSA), Boulder, CO, United States
References: 25
Accession Number: 2002-014640
Categories: StratigraphyGeochronology
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, geol. sketch map
N23°49'60" - N24°40'00", E79°00'00" - E82°30'00"
Secondary Affiliation: Massachusetts Institute of Technology, USA, United States
Country of Publication: United States
Secondary Affiliation: GeoRef, Copyright 2019, American Geosciences Institute. Reference includes data supplied by the Geological Society of America, Boulder, CO, United States
Update Code: 200206
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