Paleomagnetic age and palaeobiological significance of hominoid fossil strata of Yuanmou Basin in Yunnan

Abstract

The two sections containing hominoid fossils in the Yuanmou Basin, Yunnan Prov-ince have been studied by means of magnetostratigraphy. The results are as follows. The Xiaohe section records over 8 polarity zones corresponding to Cande-Kent95 time scale, including C3Br.1n, C3Br.1r, C3Br.2n, C3Br.2r, C4n.1n, C4n.1r, C4n.2n and C4n.2r, attaching to Late Mio-cene. This section comprises two layers of hominoid fossils: the lower layer (the 1st layer in fig. 4) which records the lower portion of C4n.2r with paleomagnetic age of 8.20—8.10 Ma and the upper layer (the 16th layer in fig. 4) which records C3Br.1r with paleomagnetic age of 7.20—7.15 Ma. So the age of hominoid fossils in the Xiaohe section is about 8.20—7.15 Ma. The Leilao section records over 11 polarity zones corresponding to Cande-Kent95 time scale, including C3Br, C3Br.1n, C3Br.1r, C3Br.2n, C3Br.2r, C4n.1n, C4n.1r, C4n.2n, C4n.2r, C4n.3n and C4n.3r, attaching to Late Miocene. This section also consists of two layers of hominoid fossils: the lower layer (the 3rd layer in fig. 3) which records C4n.2r with the age of 8.20—8.10 Ma and the upper layer(the 19th layer in fig. 3) which records the middle portion of C3Br with the age of 7.15—7.1 Ma. So the age of hominoid fossils in the Leilao section is about 8.20—7.10 Ma. Sedimentary environments reflected in both sections are extremely similar, and the ages of hominoid fossils are of correspondency. The age of the lower and upper fossil layers is 8.20—8.10 Ma and 7.20—7.10 Ma respectively, which probably imply that hominoids living in Xiaohe and Leilao basins have uniform activity areas. There were hominoids activities all along during 8.00—7.00 MaBP in this field.