云南元谋小河盆地含古猿化石的主要层位有2个，时代相差约1 Ma。以黄色砂砾石层作为标志层，参考各含古猿化石剖面基底和现代海拔高度，盆内含化石层的晚第三纪地层可以很好的对比，小河盆地蝴蝶梁子剖面、房背梁子剖面相当于豹子洞箐剖面的的中下部。从哺乳动物化石和古地磁资料分析，小河组的地质时代为7.3～8.2Ma。%Hominoid evolution is an important research subject. Since 1986, a skull, lower jaws and a thousand teeth of hominoid have been found in Late Miocene in X iaohe basin, Yuanmou County, Yunnan. These significant discoveries arouse a grea t attentions of anthropologists, paleontologists, geologists and archaeologists , and multidisciplinary research have acquired a lot of advances.rn Xiaohe basin, located about 30 km to the NNW of Yuanmou County, Yunnan, Southwe st China, is a small depression basin with 3.5 km in length and 1.5 km in wid th. The sediments in this basin is composed of brown-red silt clay, siltstone, yellow sandy conglomerates, which contain well-developed lenticuly bodies and ab u ndant Hominoid and other mammalian fossils, named as Xiaohe Formation. The thick ness is 77 m at the Baozidongqing. The depositional environments of the Xiaohe Formation have been regarded as fluvial facies. Actually, a lot of evidences sugg est that sediments are deposited by the density flow, while the fossiliferous bed is braided river facies, especially point bar. There were a lot of different views of correlation about Hudieliangzi, Fangbeiliangzi and Baozidongqing section s in Xiaohe basin based on altitude level of sections now. During the fieldwor k from 1998-1999, we used GPS and level to decide all localities of fossil and section at 1:5000 relief map in Xiaohe basin found before. Used yellow sandy cong lomerate beds as an index, the section of Hudieliangzi and Fangbeiliangzi are co rrelated with the middle and lower part of the Baozidongqing section, absent the upper part of Baozidongqing section because of erosion by fluvial lately.rn Abundant mammalian fossils found in Xiaohe basin except Hominoid are Adcrocuta , Eomillivora, Ictitherium, Indarctor, Thalassictis, Metailurus, Ailurarotos, Go mphotherium, Sinomastodon, Stegolophodon, Acerorhinus, Shansirhinus, Hipparion, Chalicotherium, Tapirus, Hyotherium, Yunnanochaeurs, Dorcabune Moschus et al., this fauna is similar to that of the Lufeng Hipparion fauna, of which geologica l age is consider as Late Miocene. In Xiaohe Hominoid fauna there are some repr esentative elements of Baodeian in North China, such as Eomillivora, Adcrocuta et al., the geological record of these fossils is Late Miocene up to now. The geological age of Baodelian in China is equal to Turolian in Europe and its age is 5.3～8 Ma.Based on Mammalian fossil assemblage and paleomagnetic analysis, the Xiaohe Formation deposited in the Late Miocene, about 7.3～8.2 Ma.
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