泥河湾盆地石沟遗址B区发掘报告

REPORT ON THE EXCAVATION OF THE EARLY PLEISTOCENE SHIGOU SITE B IN NIHEWAN BASIN, NORTHERN CHINA

2014年，泥河湾盆地石沟遗址出土了丰富的石制品和动物化石。本文报道石沟遗址B区的发掘概况及对整个遗址的化石埋藏学和古生物学研究成果。石沟遗址动物化石种类有蛙类、鸟类、直隶狼、猎豹（未定种）、猛犸象（未定种）、黄河马、泥河湾披毛犀、中国羚羊、山东绵羊（相似种）、古中华野牛等，在探方外50m处还发现了古麟。石沟遗址的动物化石代表了迄今在小长梁断层上盘所发现的含大哺乳动物属种最丰富和化石保存最好的动物群。石沟的猎豹上颌化石确认了现生猎豹属在早更新世即已在我国北方出现；早期猛犸象腓骨化石是我国的首次报道；黄河马的新材料提供了该种幼年和老年个体的牙齿特征，以及证明其具有纤长的第三掌、蹠骨；古麟是在阳原盆地（狭义泥河湾盆地）的首次发现。石沟动物组成以马类和犀类为主，骨骼部位以牙齿和四肢远端为主；年龄结构反映了以幼年、老年个体居优的自然死亡特征；遗址的形成主要受短距离季节性流水作用，与古人类及食肉动物的关系不显著。根据古麟和黄河马的地史分布及与周边遗址的地层序列对比，初步推断石沟动物群时代约为1.6Ma，与黄土-古土壤序列的S23相对应。动物群组合显示当时在泥河湾一带主要是稀树草原环境，湖边湿地发育。

Shigou Site（40°13＇53.8＂N, 114°40＇19.6＂E; 830m above sea level）, which was discovered in 1996, is one of the earliest Paleolithic sites in Nihewan Basin. It is located in Cenjiawan Village, Datianwa Town, Yangyuan County, Hebei Province. In 2014, an excavation was conducted by the joint team of Hebei Normal University and Institute of Vertebrate Paleontology and Paleoanthropology, Chinese Academy of Sciences. This site consists of two trenches（SG-A/SG-B）, with area of 22m2 and 13m2 respectively. More than 364 bones, as well as hundreds of stone artifacts were unearthed. This paper is a report on the excavation of SG-B and research on the fossils of both SG-A and SG-B. Shigou fauna consists of the following taxa： Frogs, Aves, Canis chihliensis, Acinonyx sp., Mammuthus sp., Equus huanghoensis, Coelodonta nihowanensis, Gazella sinensis, Ovis cf. shantungensis, Bison palaeosinensis and Palaeotragus sp. Nihewan Basin, which is located in the transition zone between North China Plain and Inner Mongolian Plateau, is mainly filled with Pleistocene lacustrine deposits. In the east margin of Nihewan Basin, south to the Sanggan River, there are quite a number of Early Pleistocene Paleolithic and paleontologic sites. This area was cut by the Xiaochangliang Fault; Shigou Site bears the most abundant fossils among the sites on the hanging-wall block. The fossil layer comprises mainly greyish-yellow fine sand with a thickness of 1.4m; the deposit is quite cemented in the upper part, while laminar structure developed in the lower part. A comprehensive taphonomic study was conducted in Shigou Site. The bones of Shigou fauna are mainly composed of teeth and the distal portion of limb bones, while the axial part is quite scarce; only few bones are still in articulation. 27 individuals can be recognized from the Aves and mammals. The age profile is dominated by the juvenile and senium individuals, which indicates an attritional mortality of the animals. About 76.3% of the bones are slightly weathered, while the fresh and heavy weathered bones account for 12.2% and 11.6% respectively. The rose diagram reflects a nearly south-north water flow; the sediments are not well sorted, mixed with coarse sands and cobbles, indicating a short transport distance. On the bone surface, human modification was undetected, and the carnivore modification is few（4.1%）. Therefore, we can tentatively infer that Shigou site was a jumble of hydraulical process, rather than a human site or carnivore den. Shigou fauna is also of paleontological, biostratigraphical and palaeoenvironmental significance. The cheetah maxilla confirms the appearance of the genus Acinonyx in North China as early as Early Pleistocene. The milk cheek teeth and metapodials of Equus huanghoensis are the first time to know; these metapodials are also among the slimmest ones of Pleistocene equids. Although most of the Shigou mammals are common Early Pleistocene elements, Palaeotragus sp. is a survived taxon of the Pliocene fauna and the only known record of Equus huanghoensis in Nihewan Basin dated back to 1.6Ma; in addition, the SG fossil layer is also at the similar elevation with Majuangou Ⅲ （1.66Ma）. Therefore, the age of Shigou site could be around 1.6Ma, which is significantly older than Shanshenmiaozui Site and Xiaochangliang Site. Shigou fauna indicates a steppe landscape, with woodland and swamp around the lake. The faunal composition is consistent with the relatively warm and moist period, perhaps corresponding to the S23 stage of the loess-paleosoil sequence.