Dating vertebrate microfaunas in the late Neogene record of Northern China

Abstract

Chinese paleontologists have ordered Neogene strata in time on the basis of their contained fossils, small mammals in particular, but biochronology alone attains limited accuracy in a biogeographically restricted system. The chronology of terrestrial sediments can be refined when sound systematics of the contained fossils is combined with paleomagnetic data. The geomagnetic polarity time scale has proven to be a useful independent reference system for dating the biochronology of continental deposits in North China. Long composites of successive microfaunas, with faunal correlation at times of low endemism, and age estimation through paleomagnetic correlation, yield robust biochronologies that are well constrained in time. The Yushe Basin (Shanxi Province) sequence, which has magnetostratigraphic control, provides a key reference for the late Neogene of North China. Data from Yushe Basin identify the microfauna characteristic at the time of the Miocene/Pliocene boundary in northern China. The assemblage from near the village of Jiayucun strongly resembles the rich microfauna of Ertemte, Inner Mongolia, and occurs at the base of a reversed magnetozone correlated with Chron C3r (early Gilbert Chron), latest Miocene. Successive Pliocene age assemblages from Yushe Basin resemble the Jingle and Youhe local faunas, which were formerly used as reference faunas for North China. Nihewan-like assemblages are correlated with the Matuyama Chron, some being pre-Olduvai Subchron, and therefore Pliocene in age by current definition. Later Pleistocene time is represented in Yushe Basin by fossil sites in loam deposits. The well-known loess sequence of central China, and other Plio/Pleistocene reference faunas yield a date of ca. 1 Ma for a reddish loam microfauna from Yushe Basin.