Constraining the minimum age of Daraki-Chattan rock art in India by OSL dating and petrographic analyses

Ongoing work in Daraki-Chattan cave, India, has revealed important Paleolithic rock art (petroglyphs) in the form of cupules. The site is rich in stone tools of Acheulian industry to Oldowan-like industry including several hammerstones. The present investigation concerns a further detailed methodological and complementary approach for dating a quartz-arenite sandstone clast from just above the lowest exfoliated cupule, combining surface luminescence chronology with petrography. The optically stimulated luminescence equivalent dose profiles versus depth from quartz were studied to date this clast. Two different dose-depth profiles were measured spanning to 28 mm depth, one natural depth profile and one for a sample following exposure to daylight for nine months. Equivalent dose versus depth profiles indicate bleaching in several millimeters. Varied spatial luminescence response, its effect on the luminescence-depth profiles and interpretation to circumvent minor anomalies are fully discussed in terms of non-luminescent/dull faint minerals, coating, and inhomogeneous distribution of feldspars. Thin section analysis was performed using both optical and cathodoluminescence microscopy. The former indicates mineral origin, distribution and size with dominance of monocrystalline quartz grains that makes rock type classified to a typical quartz sandstone (arenite); the latter identifies blue-and dull cyan-luminescent quartz crystals and recognizes luminescent minerals centers. Three additional micro-samplings were performed for X-ray and scanning electron microscopy analysis on specific points of the profile for minerals and chemical elements. The method followed and dose profiles from the present buried sandstone, suitably discussed, provided an average date for at least two burial sun exposure histories of the fallen stone piece of around 46 ka and 71 ka before current era, providing a constrained terminus post quem for the exfoliated clast from the cave wall with petroglyphs.