The probable direction of impact at Dhala impact structure, India deciphered from microfracture intensity and X-ray diffractometry: a new potential impact direction indicator

Abstract

The most widely used method of determining impact direction employs asymmetric ejecta distribution around the crater. However, the active terrestrial landscape seldom preserves the pristine ejecta blanket, making it challenging for this analysis to be carried out. The deeply eroded Dhala impact structure, formed during the Proterozoic, is devoid of an ejecta blanket. We, therefore, utilize the variation in the full width at half maxima (FWHM) of the quartz (100) peak in X-ray diffraction (XRD) spectra and the P10 microfracture intensity in the monomict breccia to estimate the probable downrange direction of the Dhala impact structure. The monomict breccia rocks of the Dhala impact structure have experienced low shock pressures (< 10 GPa) and are highly fractured, making them the ideal target lithology for our study. Previous studies have used XRD extensively for strain analysis in synthetic materials and rocks. Microfracture intensity acts as an indicator for the degree of fracturing or brittle damage in the rocks, with the maximum shock-induced damage being concentrated in the downrange direction. The results from the XRD are consistent with the microfracture intensity analyses and indicate that the probable direction of impact was from southwest to northeast, with northeast being the downrange direction. Furthermore, we suggest that the degree of fracturing and X-ray diffractometry can be used to identify the downrange direction of an impact crater. Graphical Abstract