云南元谋发现的晚更新世哺乳动物群

LATE PLEISTOCENE FAUNA DISCOVERED IN YUANMOU BASIN, YUNNAN

本文记述云南元谋地区首次发现的含化石洞穴堆积。哺乳动物种类均为晚更新世时期的大熊猫-剑齿象动物群成员;代表草原型生态环境;孢粉分析亦呈现出干、凉的稀树草原植被特征;^(14)C年代测定距今16540±1470年。本研究填补了元谋地区晚更新世哺乳动物材料及洞穴堆积的空白,对进一步研究元谋盆地古环境、沉积类型及哺乳动物的生态特征具有重要意义。

In the winter of 1984, a cave-fissure deposit was first discovered in Yuanmou county, Yunnan. Seven species of mammalian fossils were recovered from the locality, i.e. Rodent in-det, Hytrix subcristata, Crocuta ultima, Cervus sp. (1), Cervus sp. (2), Bos (Bibos) sp., Cap-ricornis sp.. These are members of the 'Ailuropoda-Stegodon fauna' which is known from south China during the Late Pleistocene. An age of 16540±1470 B.P. was determined by radiocarbon dating of the samples of fossil bones. The geological age is considered to be the later part of the late Pleistocene as judged from the fauna and the 14C test. Xiao Midi is about 3 km. to the south west of the village of Reshuitangcun of Yuanmou county and is situated on the top of Balan mountain. The maximum altitude is 1466 meters. The cave-fissure deposit was developed in the Kunyan group of the Presinian period. It was formed by the convergence of the shear plane of a conjugated fracture. The cave inclines NW and NNE. The dip angles are 80° and 60° respectively, resulting in an almost vertical fissure cave. The width is 5-8 meters. The inclination is NNE and the thickness is about 20 meters. The deposit is fillded with a series of fragments of redbrown silts, clayey soils and includes some brecia and lesser lime nodules. The wall of the cave is rough but there are no stalactite. The red crust weathering at the top is similar to that of T3, T4, T5 on the Long-chang River in Yuanmou Basin. It is interesting that there are more infant individuals in the mammalian fauna. It raises doubts whether it is related to human activity although human fossils had not been recovered in the site. So it may give a clue as to investigate paleoanthro-pology in future. The mammalian fauna consists of most of Artiodactyla, which reflect grassland-style environment mainly. This cave-fissure deposit was the first one discovered in Yuanmou. It is important because it fills the gap of late mammalian fauna in the area. It is the more recent geologically site in the Yuanmou Basin, being younger than Pliocene and early Pleistocene mammalian localities previously recognized. It also adds to our knowledge of the cave-fissure deposits beside the fluvial and lacustrine facies on the sedimentary face. It proviled new material for study of the palaeoecology and palaeoenvironment in the Yuanmou Basin.