Environmental humidity changes inferred from multi-indicators in the Jianghan Plain, Central China during the last 12,700 years

Abstract

Time sequence of the JZ-2010 profile derived from AMS14C dating and the content of the sediment elements Ti, Rb and Sr, the Rb/Sr values as well as the granularity and the magnetic susceptibility are utilized to reconstruct the environmental humidity changes in the Jianghan Plain since 12,700 cal. BP. The comprehensive analyses of multiple alternative indicators indicate that the regional moisture turned from relatively dry to wet after the Late-Glacial period and reached its optimum until the mid-Holocene. However, the trend was punctuated by several decreased humidity phases. Beginning with the severe dry event approximately 4400–4100 cal. BP, the environment was dry as a whole, with modest humidity from approximately 3900 cal. BP. Humidity changes in the study area are dominated by the East Asian monsoon system, which is under the influence of the gradual southward migration of the ITCZ, driven by the summer solar insolation changes in the Northern Hemisphere due to orbital forcing. As the first attempt to apply Rb/Sr value and Ti concentration in tracing moisture evolution in a region with typical subtropical humid climate, this study highlights the different effects and consequences of the proxies throughout the palaeoenvironmental change process, and the impacts of regional topography that sustained tectonic subsidence since the Cretaceous as well as the southeast tilt that opened the plain to the summer monsoon. Moreover, the fluctuation of magnetic susceptibility is associated with the granularity feature, the reduction–oxidation conditions, and the impact of human factors on the natural sedimentary environments during the historic period in the Jianghan Plain.