Palaeoecological significance of ichnofossils from the early Cambrian succession of the Spiti Valley, Tethys Himalaya, India

摘要

The diverse assemblage of ichnofossils recorded from the Early Cambrian succession of the Kunzum La Formation in Spiti basin ranges in age from the Chiungchussuian stage of the Lower Cambrian to the Maochuangian stage of the Middle Cambrian. The trace fossil assemblage is dominated by Cruzana, Skolithos and partially by the Nerites ichnofacies, showing behavioural diversity from suspension to deposit feeders. Distribution of the observed ichnofacies variation is attributed to the availability of oxygen and nutrient influx. lchnofossil studies of this area further indicate that the benthic pallaeocommunity was dominated by annelids or similar worm-like animals living predominantly within the sediments, while the trilobites were trailing on the sea floor. The inferred palaeoecological distribution of ichnofossil assemblage is based on modern analogue of ocean slope and shelf zones. The litho and ichnofacies association indicates anaerobic to dysaerobic trends of the ichnofauna from Nereites to Skolithos ichnofacies. Three distinctive lithofacies association have been recognized and the stratigraphic disposition reflects a general upward coarsening of the sediments.