Possible El Nino-Southern Oscillation-related lacustrine facies developed in southern Lake Poyang during the late Holocene: Evidence from spore-pollen records

摘要

In order to explore the impacts of past climate changes on the origin and evolution of Lake Poyang, the biggest freshwater lake in China, eight periods of palaeoenvironmental changes were constructed to depict the history of climate change over the past 3500 years based on the palynological records and carbon isotopic excursions. The climate regime was associated with the presence of a deciduous and evergreen broad-leaved forest/a mixed needle broad-leaved forest and strong/weak solar variability. Palaeohydrology change reconstructed by the percentage of aquatics and stable carbon isotopes demonstrated that the wet episode was associated with the developed lacustrine facies and enhanced El Nino-Southern Oscillation (ENSO) activities. The presence of the united open lake (Lake Poyang) during 2000-1200 cal. a BP was linked to a long wet period caused by the strong ENSO activities. At the decadal-centennial timescales, climate changes together with the ENSO activities might have played a great role on the regional hydrological condition and sedimentary evolution in southern Lake Poyang. The correlations of the palaeotemperature and palaeohydrology with the multi-proxy data from the Northern Hemisphere all suggest that palaeotemperature change with the monsoon intensity is linked to the solar variations, but palaeohydrology change has a striking consistency with the ENSO activities. The distinct hydrothermal diversification (warm-wet, warm-dry, cold-wet, cold-dry) revealed by the palaeotemperature and palaeohydrology changes will provide important clues about the origin and evolution of Lake Poyang in the Holocene and a better understanding of the interactions between solar radiation, ENSO activity and lake deposition in the middle Yangtze River Valley.