A 1600 year multiproxy record of paleoclimatic change from varved sediments in Lake Xiaolongwan, northeastern China

Abstract

A multiproxy record from Lake Xiaolongwan, northeastern China, reveals distinct stratigraphical patterns in organic carbon, total nitrogen, organic carbon isotope, nitrogen isotope, clastic content and dinocyst concentration, over the past 1600 years. High atomic C/N ratios in the sediment suggest that a large amount of organic matter in the sediments is derived from vascular plants and soil in the catchment. Based on the good agreement between cyclical variations of δ 13 C org in the sediments and the spring drought index from historical documents, we interpret that the variation of δ 13 C org in the sediments is an indicator of humidity or precipitation in the study area. Several notable drought periods with heavier δ 13 C org occurred during AD 490–570, AD 780–990, AD 1360–1450, AD 1590–1670 and the last 150 years. These century‐scale drought episodes correspond to solar activity. It suggests that solar forcing plays an important role for the δ 13 C org variation in the sediments through driving the changes in humidity/vapor pressure deficit. Dinocyst concentration is high during most of the Medieval Warm Period, and low during the European Dark Age and the Little Ice Age. The increase in dinocyst concentration is generally synchronous with decrease of δ 15 N value. The δ 15 N values in the studied lake are most likely influenced by the duration and intensification of lake overturn, which regulates the amount of depleted δ 15 N nutrients (dissolved organic nitrogen and ammonium) and dinoflagellate blooms.