First observation of microspherule from the infratrappean Gondwana sediments below Killari region of Deccan LIP, Maharashtra (India) and possible implications

摘要

A rare occurrence of a microspherule has been found in the infratrappean sediments, encountered below 338?m thick Deccan volcanic cover in KLR-1 scientific borehole, drilled in the epicentral zone of the 1993 Killari earthquake (Maharashtra, India). Palynological studies of the sediments indicate their age as Early Permian (Asselian, 298–295?Ma) for deposition. Transmission electron microscope studies reveal that the spherule from the infratrappeans, is having a similar composition to that of the Neoarchean amphibolite to granulite facies mid crustal basement. The spherule is non-spherical in nature, containing mostly FeO (10.70?±?0.20?wt.%), CaO (13.8?±?0.5?wt.%), Al2O3(7.78?±?0.30?wt.%), MgO (6.47?±?0.3?wt.%), SiO2(47.46?±?0.50?wt.%), TiO2(2.47?±?0.3?wt.%), K2O (1.89?±?0.20?wt.%), and Cl (0.33?±?0.05?wt.%). Since the Fe composition of the spherule is almost same as the basement rock (10.5?wt.%), and the chlorine content is also in the same range as the basement (0.04–0.24?wt.%), it would suggest possibility of an extraterrestrial impact over the Indian terrain during the erstwhile Gondwana sedimentation period that may be associated with the Permian–Triassic mass extinction, the most severe one in the Earth's history.