High resolution climatic records of the past ~489 years from Central Asia as derived from benthic foraminiferal species, Asterorotalia trispinosa

Abstract

Many researchers have reported the occurrence of the species Asterorotalia trispinosa as a major constituent in foraminiferal assemblages from different regions, its ecological significance has never been studied. The occurrence of the species A. trispinosa in the Recent benthic foraminiferal distribution on the Ayeyarwaddy Delta Shelf off Myanmar was found to be very conspicuous. The surface distribution of A. trispinosaspecies in the study area, establishes its preference for low salinity. The ecological preferences of A. trispinosa make the species a useful proxy for the delineation of wet and dry periods of the past. The downcore variation in the abundances of A. trispinosa, its reproductive behaviour viz. its MPS and stable isotopic values were analysed, in sediments of the core GC-5 collected at 37 m water depth on the delta front. Downcore variations in the abundance and MPS of A. trispinosa indicate two significant climatic conditions in the study area since 1513 AD; a dry climate prior to 1650 AD and warm and wet climate since 1650 to present. Three major freshwater pulses are recorded in the core at approx. 1675, 1750 and 1850 AD since 1650. The multi-proxy data also support these findings. This high-resolution palaeoclimatic data representing the past 489 years, may be the Asian signatures of the European Little Ice Age.