Formation and evolution of a loess sinkhole in the southern Chinese Loess Plateau

Sinkholes are formed by the collapse of the overlying strata or the subsidence of the ground from cracks or holes in the underlying strata, which are widely developed in the karst and loess regions over southern and northern China. These sinkholes have been explored intensively to infer their climatic and ecological significances, as well as the management of geological disasters. In this study we investigated the Sanyuan (SY) sinkhole in the southern Chinese Loess Plateau to understand how it was formed and evolved. Two 30-m cores were retrieved from the SY sinkhole and a detailed chronological framework was established by applying radionuclides dating for the top 1-m sediments as well as 14C dating for the two 30-m cores. These dating results show that SY sinkhole was formed 23.7 m below the sinkhole surface at ca. 6.0 kyr BP (before 1950 CE). Changes in lithology, sedi-mentation rate, magnetic susceptibility, lightness, and mean grain-size of these two cores reveal that the sinkhole has undergone two-stage evolution. The first stage was characterized by a relatively slow deposition of loess sediments during 6.0-1.9 kyr BP, and the second stage was a rapid accumulating period since 1.9 kyr BP likely affected by human activities. Our results suggest that SY sinkhole can well document the combined influence of climate change and human activities, offering an ideal archive to decipher the natural and anthropogenic im-prints since the mid-Holocene.