Taphonomy and palaeoenvironment of the middle Eocene rodent localities of northwestern Himalaya, India

Abstract

In northwestern Himalaya, the middle Eocene rodents are known from the Upper Subathu Group in Jammu and Kashmir and Himachal Pradesh (India) and from the coeval Kuldana Formation in Pakistan. Most of the localities in these areas represent more or less the same timeframe but their faunal compositions differ considerably and also some of them are lithologically dissimilar. The bone assemblages from some of the productive middle Eocene rodent localities of Jammu and Kashmir were analysed applying the standard techniques of taphonomic data collection and interpretation to reconstruct their taphonomic histories and palaeoenvironment. The petrography of the rodent-bearing matrix was also studied and used in the taphonomic analysis. The analysis has revealed markedly different taphonomic histories for two of the most prolific localities thereby partly explaining the differences in their faunal composition and demonstrating that taphonomy can be an important aid to biostratigraphic interpretations. The East Babbian Gala (EBGL) rodent assemblage was initially accumulated in the mammalian predator scats. For the accumulation of Sindkhatuti (SKL) bone assemblage, the nonpredator agents are held responsible and a catastrophic mortality is indicated. The taphonomic data from West Babbian Gala (WBGL), Chenpur (CPL), Tattapani (TTPL) and Triyath-Barakh Road (TBRL) localities is inadequate to identify with certainty mode of accumulation of their assemblages, which is best ascribed at present to an attritional mortality and fluvial accumulation. The palaeoenvironmental reconstructions suggest fluvio-deltaic conditions at the time of deposition of the rodent-yielding uppermost part of the Subathu Group. They further indicate that the shoreline of the Tethys Sea was close to the site of deposition of the Middle Eocene rodents and other land mammals. These interpretations are supported by other associated vertebrate groups which also include marine mammals, Cetacea.