Paleoweathering and paleoenvironmental change recorded in lacustrine sediments of the early to middle Eocene in Fushun Basin, Northeast China

Abstract

AbstractDeciphering the long‐term interaction among continental silicate weathering, global climate, and atmospheric CO2 concentrations is helpful in understanding the mechanisms of the Cenozoic climate change and accessing the future climatic and environmental response to anthropogenic carbon emissions. The Eocene, which is characterized by the Early Eocene Climatic Optimum (EECO) and the following global cooling, represents an ideal test case. Here we generate geochemical data of the Eocene lacustrine sediments from the Fushun Basin, northeast China, to explore the regional climatic response to the global climate change. The chemical index of alteration (CIA) and plagioclase index of alteration (PIA) consistently show a gradual, long‐term decrease, indicating a climatic transition from warm and humid to relatively cold and arid during the Eocene in the Fushun Basin. This climatic trend is broadly coincident with the global cooling and decreasing CO2 concentration, implying that the regional climate is closely correlated with the global climate change over geological time scales. Additionally, the extreme silicate weathering and high lake productivity as reflected by relatively positive δ13C values of lacustrine organic matter are associated with the EECO. This consistency may demonstrate that enhanced continental weathering and lake productivity had served as effective sinks to lower atmospheric CO2 across the EECO. Collectively, our new geochemical data add supporting evidence for a long‐term, close coupling among continental silicate weathering, climate, and global carbon cycle during the Eocene.