TAPHONOMY OF SMALL-MAMMAL FOSSIL ASSEMBLAGES FROM THE MIDDLE MIOCENE CHINJI FORMATION, SIWALIK GROUP, PAKISTAN

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This study focuses on taphonomy of small-mammal remains from the Lower Siwalik Chinji Formation in the stratotype area. From a stratigraphic interval about 20m thick that extends laterally for 12km, we prospected in all sedimentary facies for small-vertebrate concentrations. Thirteen sites were documented, most from facies representing abandoned floodplain channels. Screen-washed samples varied in richness, with sites yielding 0-256 identifiable small-mammal teeth. The sediment matrix ranged from fine conglomerate to silty clay. Based on sedimentological and taphonomic criteria, we propose that all concentrations were primary biological accumulations, in some instances with secondary fluvial reworking. Vertebrate predators were the probable agents of accumulation. The taxonomic composition of small-mammal assemblages varied little among sites; variation in lithology had no effect on the frequency of specimens at the family level. A mixture of arboreal, burrowing, and terrestrial small mammals was present; most species were terrestrial herbivores. Based on large and small mammals from the lower Chinji Formation, a seasonal woodland with riparian areas of forest was the likely vegetation.
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