Carbonate verse silicate Sr isotope in lake sediments and its response to Little Ice Age

The87Sr/86Sr ratios of silicate (acid-insoluble, AI) and carbonate (acid-soluble, AS) of the lake sediments from the Daihai Lake, Inner Mongolia, since the last 500 years are measured respectively, indicating that chemical weathering of silicate minerals was in an early stage since the Little Ice Age within the Daihai watershed by combination with mineral constitute, Rb/Sr ratio and CaCO3 content in the sediments. During the Little Ice Age maximum, an evident peak in the87Sr/86Sr ratios of both silicate and carbonate in sediments suggests that a cold climate condition is unfavorable to dissolving radiogenic strontium from silicate minerals. Meanwhile, the variation of87Sr/86Sr ratios of silicate and carbonate also reflects a projected warming climate favorable to intensifying chemical weathering after the Little Ice Age. Consequently, the87Sr/86Sr ratio of both silicate and carbonate in inland lake sediments can be used as an effective proxy of the past climate in single watershed.