Evidence for shock provides insight into the formation of the central elevated area in the Dhala impact structure, India

Abstract

The central elevated area is a postimpact morphological landmark in the otherwise flat eroded remnant of the Dhala impact structure, India. Its base is the Bundelkhand granitic complex followed by beds of Dhala and Kaimur Formations. The beds of the Dhala and Kaimur Formation present typical sedimentary textures and structures such as cross-bedding. The grains are angular, sorting is moderate to poor, and brittle-ductile deformation of the protolith is still preserved in some grains. This reveals a short distance of transport. Detailed microscopy and U-stage measurements confirm planar deformational features (PDFs) oriented (0001) and {10-13} in few quartz grains. Based on these facts, it is suggested that the quartz with PDFs was shocked, ejected out of the crater, and deposited near the crater cavity. Reworking of the ejecta blanket redeposited these quartz grains to their present location. Relatively few shocked grains in the rocks favor a postimpact fluvial process over impact resurge.

On the Emplacement of the Impact Melt at the Dhala Impact Structure, India

“…Within the Dhala impact structure, there are six isolated outcrops of impact melt rocks. Over the past 15 years, the shock deformation structures, lithology, radiometric dating, petrology, and geochemistry have been well defined (e.g., Agarwal et al, 2020;Pati et al, 2008Pati et al, , 2010Pati et al, , 2015Pati et al, , 2017Pati et al, , 2019Singh et al, 2021aSingh et al, , 2021b. However, the emplacement mechanism of impact melt is not well understood.…”