泥河湾盆地叶沟晚上新世贺风三趾马动物群及其生物地层学意义

A Late Pliocene Hipparion houfenense fauna from Yegou,Nihewan Basin and its biostratigraphic significance

目前对于泥河湾盆地晚新生代地层的年代学认识还存在分歧,基于哺乳动物化石的生物地层学对比结果与基于磁性地层学的年代测定结果存在较大矛盾。生物地层学对比表明,泥河湾盆地桑干河峡谷地带与壶流河下游两岸出露的风成红粘土、含砂砾石河湖相红粘土与沼泽相砂质粘土属上上新统;而磁性地层学研究一般将其归为下更新统。记述了泥河湾盆地叶沟晚上新世贺风三趾马动物群,由丁氏貉Nyctereutes tingi,中华貉N.sinensis,比利牛斯硕鬣狗Pachycrocuta pyrenaica,锯齿虎属(未定种)Homotherium sp.,贺风(近)三趾马Hipparion(Plesiohipparion)houfenense,额鼻角犀属(未定种)Dicerorhinus sp.,麂属(未定种)Muntiacus sp.,山西轴鹿Axis shansius,步氏羚羊Gazella blacki,副驼属(未定种)Paracamelus sp.等9属10种构成。这个动物群的组成与经典的泥河湾早更新世动物群显著不同,是泥河湾盆地内上上新统存在的新证据。在系统记述的基础上,对叶沟贺风三趾马动物群的时代和组成进行了讨论,并对泥河湾盆地晚上新世与早更新世大型哺乳动物群的组合特征进行了归纳,以期对今后泥河湾盆地的地层学研究工作有所帮助。

Currently,there are still different views regarding the chronology of the Late Cenozoic deposits in the Nihewan Basin,which results from the contradiction between biostratigraphic correlations based on mammalian fossils and magnetostratigraphic dating results.Biostratigraphic correlations indicate that the aeolian red clay exposed in the Sanggan River canyon,the fluviolacustrine red clay with sands and gravels,and the sandy clay of swamp facies on both sides of the lower reaches of the Huliu River belong to the Upper Pliocene,whereas the magnetostratigraphic dating usually correlates them to the Lower Pleistocene.In October 2011,a collection of mammalian fossils was unearthed from a block of collapsed deposits at Yegou in the Nihewan Basin,which is about 300 m north of the Laowogou section that is well known for the Pliocene mammalian fossils from its lower part.The Yegou fossils are identified herein as 10 species in 9 genera:Nyctereutes tingi,N.sinensis,Pachycrocuta pyrenaica,Homotherium sp.,Hipparion(Plesiohipparion)houfenense,Dicerorhinus sp.,Muntiacus sp.,Axis shansius,Gazella blacki,and Paracamelus sp.The fauna is quite different from the classic Early Pleistocene Nihewan Fauna in composition and provides new evidence for the existence of the Upper Pliocene in the Nihewan Basin.Based on a systematic description of the fauna,its composition and geological age are discussed,and the compositional features of large mammals of the Late Pliocene and the Early Pleistocene mammalian faunas in the Nihewan Basin are summarized.