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PLIOCENE BIOSTRATIGRAPHIC SEQUENCE IN THE NIHEWAN BASIN,HEBEI,CHINA

2008; Linguagem: Inglês

1000-3118

Qiang Li,

Geology and Paleoclimatology Research

A sequence of fluvio-lacustrine and paludine deposits with thickness over 150 meters occurs in the Nihewan Basin, Hebei, China(Yuan et al.,1996;Min et al., 2006). A series of～30 m (=90 feet)thick red homogeneous clay exposured near the Sanggan River Gorge (=Shixia)was originally considered as the weathering matter of the base rocks(Barbour et al., 1926). Due to the absence of fossils, its age once was speculated to belong to the Pontian (Teilhard and Piveteau, 1930)or the Late Miocene Baodean(Black et al.,1933). However, a sequence of～30 m thick red gravel-beating clay at the bottom of the section of Dahonggou in Shixia was named asDahonggou Formationby Chen(1988). At the same time, the～12m and～7 m thick red clays in the lower part of the Hongya Nangou and Pump Station,respec- tively, were also included into this Pliocene formation.A series of 20～30 m thick redish or yellow-redish alternating sandy clay and gravel beds are exposed in the Luanshigedagou near Hongya village.Yielding Hipparion and Chilotherium,this deposit was considered to belong to theHipparion Red Claywith a Pliocene age (Huang et al., 1974). The sequence of～45 m thick red clay containing sandy gravel and lens of calcareous nodules in the Huabaogou near Xiyaozitou village was divided into the upperYuxian Formationand the lowerHuliuhe For- mationby the composition of large fossil mammals.These two formations were respectively cor- related to be equal in age to the Pliocene Jingle Formation and the Late Miocene Babe Forma- tion(Wang, 1982).In view of the illegibility of the boundary and the lack of significant differ- ences in the fossil faunas between these two formations, Zhang et al.(2003) incorporated them both in the Late Pliocene Yuxian Formation.A series of fluvio-lacustrine and paludine deposits exposed on the both sides of the Huliu River were namedDaodi Formationand considered of Late Pliocene age (Du et al.,1988). The original sections used for erecting theDaodi Fm.are located in the Laowogou near Daodi, the Nangou near Hongya, the Jiangjungou near Xiyaozitou, the Hougou near Qijiazhuang, the Yuanzigou near Yuanzi, the Xiaoshuigou near Qianjiashawa, the Lianjiegou near Beimajuan, the Niutoushan(=Pulu)near Pulu and the Danangou near Dongyaozitou. Zhang et al.(2003) figured that these short sections all belong to theYuxian Fm.,so they suggested thatDaodi Fm.should be abolished and attributed to theYuxian Fm.,whereas Cai et al.(2004) retained bothDaodi Fm.andYuxian Fm..The red clay stratum from the first layer at the bottom of the Laowogou section is still unnamed due to the uniformity of the grain size, the absence of gravels and aquatic animal re- mains. Based on the limited fossil mammals,the age of this stratum was thought to be the late Middle or early Late Pliocene(Zhang et al., 2003; Cai et al., 2004). The Pliocene/Pleisto- cene boundaries, on the other hand, have already been established in the Laowogou, Donggou, Taiergou and Niutoushan sequences (Cai et al., 2004; Zheng et al., 2006; Min et al., 2006; Cai et al., 2007).