THE WANGZUO FISSURE-FILLING AND ITS RECORD OF THE MIDDLE-LATE PLEISTOCENE WARM PERIOD ENVIRONMENT IN BEIJING AREA
Caves and fissure-fillings containing mammalian fossils are critical for studying Pleistocene environments.This study presents the first discovery and analysis of the Wangzuo fissure-filling(39°50′ N,116°05′E;156 m a.s.1.),located in the piedmont area of Wangzuo Town,western Beijing.The surrounding limestone of the fissure has been artificially stripped,and the remaining reddish-brown soil-like filling,rich in mammalian fossils,extends southward along the limestone fissure,with a length exceeding ten meters and a maximum thickness of approximately 3.8 meters.We collected profile samples from the fissure-filling and analyzed their grain size,color,and magnetic susceptibility for paleoenvironmental reconstruction.The results show that the median grain size(Md)ranges from 6.97 μm to 9.31 μm with an average of 8.06μm,the redness(a*)value ranges from 5.07 to 9.92 with an average of 7.14,and the low-frequency magnetic susceptibility(xlf)ranges from 191.02×10-8 m3/kg to 343.02× 10-8 m3/kg with an average of 249.90×10-8 m3/kg.By correlating these findings with the current loess-paleosol sequences in the Beijing area,we determine that this filling primarily belongs to the paleosol layer of the Middle-Late Pleistocene loess-paleosol sequence.Based on variations in median grain size,brightness,redness,and magnetic susceptibility,as well as the stratigraphy of mammalian fossils,we divided the fissure-filling into three layers from bottom to top,corresponding to the early,middle,and late stages of the Wangzuo fissure sedimentation.The Wangzuo fissure-filling formed during a warm period with favorable thermal and precipitation conditions in the Middle-Late Pleistocene.This warm period experienced rapid climate changes,evolving from a prominent warm peak to a relatively milder warm period.The paleoenvironmental proxies and mammalian fossils from the paleosol indicate that the Wangzuo fissure-filling reveals a paleo-warming event in the Beijing area during the Middle-Late Pleistocene.
万方数据
维普
