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PLIOCENE BIOSTRATIGRAPHIC SEQUENCE IN THE NIHEWAN BASIN, HEBEI, CHINA
- LI Qiang, ZHENG Shao-Hua, CAI Bao-Quan
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2008, 46(3):
210-232.
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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 ~30m(="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-bearing clay at the bottom of the section of Dahonggou in Shixia was named as"Dahonggou Formation"by Chen(1988). At the same time, the~12 m and～7 m thick red clays in the lower part of the Hongya Nangou and Pump Station, respectively, 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 the"Hipparion Red Clay"with 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 upper"Yuxian Formation"and the lower"Huliuhe Formation"by the composition of large fossil mammals. These two formations were respectively correlated to be equal in age to the Pliocene Jingle Formation and the Late Miocene Bahe Formation(Wang,1982). In view of the illegibility of the boundary and the lack of significant differences 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 named "Daodi Formation"and considered of Late Pliocene age(Du et al.,1988). The original sections used for erecting the"Daodi 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 the"Yuxian Fm.", so they suggested that"Daodi Fm."should be abolished and attributed to the"Yuxian Fm.", whereas Cai et al.(2004) retained both"Daodi Fm."and "Yuxian Fm.". The red clay stratum from the first layer at the bottom of the Laowogou section is stillunnamed due to the uniformity of the grain size, the absence of gravels and aquatic animal remains. 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/Pleistocene 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). Judging from the known information, the lower part of the exposed strata in the Nihewan Basin should be attributed to the Late Pliocene Yuxian Formation or some unnamed red clays.These outcrops exist in the Sanggan River Gorge area and on the both sides of the lower reaches of the Huliu River with lithology of aeolian clay, fluvio-lacustrine red clay contained gravels and paludine sandy clay. On the both sides of the lower reaches of the Huliu River, there are 12 localities and sections, in which one or more layers of fossil mammals have been found(Fig.1). The purpose of this paper is to update a faunal list of these mammals based on the review of specimens and their localities, and also an attempt to correlate the other sections to the Laowogou section by comparing their mammalian compositions and lithological strata. Finally,a Late Pliocene biostratigraphic sequence and the environmental changes in the Nihewan Basin are discussed.
