Asian monsoon weather and climate and lake system changes on the Yunnan Plateau during the Late Holocene inferred from sclerochronological isotope patterns of gastropod shells and sediments from Xingyun and Fuxian lakes (Yunnan, China).
Final Report Abstract
The Yunnan Plateau represents a key region for studying weather and climate processes triggered by and coupled with Asian monsoons´ dynamics, particularly with respect to the Indian Summer Monsoon. Previously some dendro-climatological studies have successfully focused the second half of the last millennium however there is a lack of palaeo-weather records of older periods of the Holocene and beyond. The main goal of this pilot study was to explore and establish shells of the aquatic viviparid gastropod Margarya as a Holocene palaeo-weather archive for the Yunnan Plateau. Shells of a subrecent and a mid-Holocene specimen from the Lake Xingyun basin were sub-sampled sclerochronologically by micro-milling 263 and 365 times respectively. The aragonitic shell samples were analysed with regard to δ18O and δ13C. The hydrological changes triggered by atmospheric seasonality are clearly archived in the shells, the mid-Holocene Margarya shell e.g. exhibiting three full summer monsoon rain fall cycles. The temporal resolution of isotope data is ca. 3 days and thus has the potential to exhibit even extreme short-term events such as typhoons. Respective isotope data possibly indicating typhoon rain fall will have to be reproduced before a conclusion can be reached. In general, the results show that Margarya is a suitable palaeo-weather archive and likely other viviparid gastropods too. A semi-follow-up project is in the planning phase and may focus the climate variability including extreme events under which Yunnan Plateau Bronze Age/Dian culture settlements developed. Another related project to be submitted will focus the Early Oligocene early Icehouse weather and the changes of weather patterns during the Plio-Pleistocene transition with the aid of sclerochronological isotope patterns from east and central Asian viviparid shells.
