The carbonaceous shale of the Miocene (late Burdigalian) Quilon Formation (Kerala Basin, southwest India) were collected and processed to retrieve the microfaunal component. In the present study, the oxygen isotope analysis of the growth bands of the recovered bivalves Pitar (Hyphantosoma) simonnei and Ostrea sp. (both retrieved from the Quilon Formation) is emphasized to help reconstruct the palaeomonsoonal seasonality. The oxygen-isotope record for the specimens of P.(Hyphantosoma) simonnei and Ostrea sp. exhibits regular, high amplitude δ18O cycles caused by the yearly seasonal temperature and monsoonal variations. Based on the number of δ18O cycles,P. (Hyphantosoma) simonnei and Ostrea sp. have been considered to be approximately 2- and 4-year-old, respectively, at the time of deposition. The calculated palaeo- seawater δ18O values between -0.6 to -1.1‰ [for P. (Hyphantosoma) simonnei] allow us to distinguish between the wet and dry seasons. In addition, the two-component mixing model is suggestive of seasonal freshwater discharge of ~70-80% during wet season and ~20-40% during the dry season into the depositional system. This reconstructed palaeo-seasonality clearly indicates presence of monsoon system in the south west of India during the Miocene (late Burdigalian).

You do not have access to this content, please speak to your institutional administrator if you feel you should have access.