Taphonomy of spores and pollen in Gondwana Sequence of India

Abstract

Theoretically only few sedimentary rocks are devoid of spores and pollen; however, it is the taphonomic factors viz., necrolysis, stratinomy and diagenesis, that make them barren, impoverished or polleniferous. Therefore, high fossilization potential of spores-pollen from predominantly terrestrial and complex package of sediments spaning from Early Permian through Early Cretaceous has been utilized to build a comprehensive data-base on the Gondwana palynostratigraphy and also to assess their loss by taphonomic factors. Advent of Gondwana sedimentation witnesses glacio-fluvial-lacustrine environments and rare marine transgressions during Asselian-Sakmarian Talchir Formation. Adverse effect of moraine transport on preservation of spores-pollen from boulder bed matrix of Talchir Formation is evident. In the subsequent Permian Sub-period, depositional conditions favour the formation of enormous coal deposits. Low grade coals, shales and fine-grained sandstones normally contain less degraded spores-pollen from the Upper Gondwana red beds of Lower Triassic Panchet Formation and Intertrappean beds of Lower Cretaceous Rajmahal Formation are interpreted to have undergone chemical and thermal diagenesis, respectively. Spores-pollen from sediments deposited under anoxic and alkaline conditions (with high contents of pyrite, siderite and phosphorites) show that their preservation is related to syn- and post-depositional conditions. Whereas, sediments influenced by plate movement and tectonic activity in Peri-Gondwana Tethyan Himalaya have spores-pollen showing the effect of post-depositional diagenetic factors.