Ichnological study of the Palaeogene sedimentary succession of Botsa, Kohima District, Nagaland, India

The Palaeogene sedimentary succession of the Inner Fold Belt, exposed in Botsa, Kohima District of Nagaland, contains a rich ichnofossil assemblage, with trace fossils being common in the lower part. The present investigation was aimed at establishing the palaeoenvironmental conditions of the Palaeogene sedimentary rocks of the study area. Based on the various parameters, two lithofacies; siltstone-sandstone and mudstone facies have been identified. The trace fossils recorded comprise 10 ichnogenera representing 12 ichnospecies namely, Chondrites intricatus, Diplocraterion isp., Lockeia siliquaria, Monocraterion isp., Nereites isp., Palaeophycus tubularis, Planolites beverleyensis, Scolicia plana, Scolicia prisca, Skolithos verticalis, Thalassinoides horizontalis and Thalassinoides suevicus. Based on integrated lithofacies and trace fossils analysis, an upper shoreface to offshore transition shallow marine palaeoenvironment with fluctuating energy conditions is envisaged for the Palaeogene sedimentary rocks of the study area