Rapid environmental change of Jingpo Lake in mid-holocene: Inferred from fluvial/lacustrine sedimentary facies transition

The Jingpo Lake is the China’s largest lava-dammed lake, however, the formation age of Jingpo Lake and associated volcanic eruption events are poorly understood and still under controversy. In this study, we obtained a 12.72-m-long sediment core (JP-C) from Jingpo Lake in south Heilongjiang Province, northeast China, and used AMS radiocarbon dating of terrestrial plant macrofossils to provide a robust chronology. This study will focus on the sediments below 954 cm depth. Lithology, multi-proxy analyses and microbiological fossils data reveal rapid transition from fluvial to lacustrine sedimentary environment related to volcanic eruption events. Three stages of sedimentary environment change are documented: (i) Unite 1, fluvial sedimentary facies (below 1,232 cm, prior to _5,120 cal. yr BP); (ii) Unite 2, transition sedimentary facies (between 1,232 and 1,154 cm, from _5,120 to 5,060 cal. yr BP); (iii) Unite 3, lacustrine sedimentary facies (above 1,154 cm, after _5,060 cal. yr BP). Our results suggest that Unite 1 represents fluvial sedimentary facies, while the lacustrine sedimentary facies developed afterwards. Between 1,250 and 1,240 cm intervals, the highest MS values and high amounts of charcoal could be the result of the Jingpo volcanoes eruption at _5,135 cal. yr BP. During and after the volcanic eruptions, the lava flows descending along lowland areas and valleys may block many river valleys and eventually dammed the Mudanjiang River and created Jingpo Lake. Therefore, the core JP-C provides clear evidence that the Jingpo Lake was gradually formed after the Holocene volcanic eruption of Jingpo volcanoes (after _5,135 cal. yr BP). The stabilization of the lacustrine sedimentary environment had formed after _5,065 cal. yr BP.