Searching for the age of the upper Vindhyan basin, India: A view from paleomagnetism and geochronology

The closure age of the Proterozoic Vindhyan basin is a long-standing puzzle, unresolved due to inconsistencies between paleontological, geochronological, and paleomagnetic data. Some fossil findings from the Upper Vindhyan basin suggest an Ediacaran closure age, Pb-Pb dating of carbonate units yield dates ranging from ∼750–910 Ma, and detrital zircon data generally support a Kleisian (800–1000 Ma) closure age. In this study, we review published detrital zircon data and apply a statistically robust method to estimate the maximum depositional age (MDA) of the upper Vindhyan Kaimur, Bhander, and Rewa groups. Additionally, we present new paleomagnetic data from the folded Bhander sandstones near the Great Boundary fault to establish the primary nature of the Bhander-Rewa paleomagnetic pole. Our analysis reveals an MDA of 945 ± 7 Ma, which aligns closely with the youngest zircon population in the spectra. This MDA also corresponds to the onset of the Delhi Orogeny to the west of the Vindhyan basin; collisional orogenesis in the Central Indian Tectonic Zone to the south; and more distal high-grade metamorphism and collisional tectonism in the northern Eastern Ghats belt providing a geologically meaningful context for the basin closure age. Our paleomagnetic data offers a robust field test for the Vindhyan pole and we demonstrate that proposals for terminal Tonian closure of the basin (∼850–770 Ma) are incompatible with extant paleomagnetic data from India.