The Tibetan Plateau is the key to understanding the East Asian and Indian summer monsoons because of(i) its role in initiating and maintaining monsoon circulations and(ii) its high sensitivity to monsoon variations.One related question is how long-term chemical weathering processes respond to monsoon change.As bivalved arthropods,the chemistry of freshwater ostracod shells provides valuable information about lake water chemistry.Due to distinct difference between the ~(87)Sr/~(86)Sr ratios of seawater and freshwater,the stratigraphic~(87)Sr/~(86) variations of ostracod fossils have been successfully used to trace the transitional marine-lacustrine environment.However,only one work has focused on ostracod ~(87)Sr/~(86) ratios to evaluate changing conditions in a truly lacustrine or freshwater system.We provide the first coherent,high-resolution chemical and ostracod Sr-O isotopic records of early to mid-Pleistocene climate variations and chemical weathering processes related to changes in the Indian monsoon system from the central Tibetan Plateau.Between 2.01 and 0.95 Ma,lake water chemistry was dominated by a high proportion of carbonate weathering related to Indian monsoon variation,resulting in relatively low and constant ostracod ~(87)Sr/~(86) but obvious fluctuations in Mg/Ca,Sr/Ca and δ~(18) O associated with at least six mild to warm climatic cycles.The increase in ostracod ~(87)Sr/~(86)across the mid-Pleistocene transition(MPT) highlights a change in catchment weathering patterns induced by increased glaciation and strong seasonality on the plateau,rather than in climate-enhanced weathering intensity,with an increased weathering of ~(87)Sr-rich minerals potentially induced by marked extensive glaciation and strong seasonality in the central plateau.Across the MPT,a significant increase in ~(87)Sr/~(86) and frequently fluctuating ratios of ostracod Mg/Ca,Sr/Ca and δ~(18)O are coincident with increases in both Chinese loess grain size and Arabian Sea lithogenic flux.This correlation indicates an increased glaciation and a strong monsoon seasonal contrast over the plateau across the MPT.Both plants and fauna immediately responded to the MPT shift. The Tibetan Plateau is the key to understanding the East Asian and Indian summer monsoons because of (i) its role in initiating and maintaining monsoon circulations and (ii) its high sensitivity to monsoon variations. One related question is how long-term chemical weathering processes respond to monsoon change. As bivalved arthropods, the chemistry of freshwater ostracod shells provides valuable information about lake water chemistry. Due to distinct difference between the ~ (87) Sr / ~ (86) Sr ratios of seawater and freshwater, the stratigraphic ~ ( 87) Sr / ~ (86) variations of ostracod fossils have been successfully used to trace the transitional marine-lacustrine environment. Although only one work has focused on ostracod ~ (87) Sr / ~ 86 ratios to evaluate changing conditions in a truly lacustrine or freshwater system. We provide the first coherent, high-resolution chemical and ostracod Sr-O isotopic records of early to mid-Pleistocene climate variations and chemical weathering processes related to changes in the Indian monsoon system from the central Tibetan Plateau. Bathween 2.01 and 0.95 Ma, lake water chemistry was dominated by a high proportion of carbonate weathering related to Indian monsoon variation, resulting in relatively low and constant ostracod ~ (87) Sr / ~ ( 86) but significantly fluctuations in Mg / Ca, Sr / Ca and δ ~ (18) O associated with at least six mild to warm climatic cycles. The increase in ostracod ~ (87) Sr / ~ (86) across the mid- Pleistocene transition (MPT) highlights a change in catchment weathering patterns induced by increased glaciation and strong seasonality on the plateau, rather than in climate-enhanced weathering intensity, with an increased weathering of ~ (87) Sr-rich minerals potentially induced by marked extensive glaciation and strong seasonality in the central plateau. Cross the MPT, a significant increase in ~ (87) Sr / ~ (86) and frequently fluctuating ratios of ostracod Mg / Ca, Sr / Ca and δ ~ 18 are coincident with in both Chinese loess grain size and Arabian Sea lithogen icflux.This correlation indicates an increased glaciation and a strong monsoon seasonal contrast over the plateau across the MPT.Both plants and fauna immediately responded to the MPT shift.