Upper Siwalik mammalian faunas of India and associated events

Abstract

Tatrot and Pinjor mammalian faunas are well known from the Chandigarh and Jammu regions of India. The Pinjor Formation of the type area in the Chandigarh region has been dated by magnetostratigraphy and ranges from 2.48 to 0.63Ma. The pre-Pinjor beds of the Upper Siwalik Subgroup are referred to as the Saketi Formation and are characterized by the presence of the Tatrot Fauna. These are well exposed in the type area of the Pinjor Formation. The Pinjor Mammalian Fauna marks the end of the record of the Siwalik vertebrate faunal succession since the overlying Boulder Conglomerate Formation, the youngest formation of the Siwalik Group, is devoid of fossils. About 49 mammalian taxa are restricted to the Pinjor Formation. The Saketi beds are differentiated from the Pinjor beds by 30 Tatrot taxa. In the Jammu region, the Nagrota Formation of the Upper Siwalik Subgroup contains both the Tatrot and Pinjor faunas; however both faunas are not as well developed as compared to those of the Chandigarh region. The extinction or migration of the Pinjor Mammalian Fauna began near the Olduvai subchron (i.e. near Neogene\\Quaternary boundary). However, in the Parmandal-Utterbeni (Jammu) and Patiali Rao (Chandigarh) sections, the fauna survived well after the Olduvai subchron, and extinction in various sections ranges in age from 1.72 to 0.6Ma. Near the Olduvai subchron, the last phase of the Himalayan orogeny was marked by initial deposition of the Boulder Conglomerate Formation and was probably one of the reasons for the gradual extinction of the Pinjor Mammalian Fauna. Two biostratigraphic interval-zones, Elephas planifrons Interval-Zone (3.6–2.6Ma) and Equus sivalensis Interval-Zone (2.6–0.6Ma) are also recognized on the basis of mammalian fossils and magnetostratigraphy. Twenty-five taxa made their first appearance in the older zone whereas forty-eight taxa are restricted to the younger zone.