摘要
本区更新统自上而下有茆塘、潘集、桃园三个哺乳动物群,分别与萨拉乌苏、周口店、泥河湾(狭义)动物群相当。通过古地磁、热释光、氨基酸、铀系法测年,并结合气候地层对比,上、中、下更新统底界可分别定为0.13、0.7、1.8Ma左右。上新统/中新统的分界线与地中海地区的Piacenzian/Messinian分界线基本一致,其年龄在4.5Ma左右。
Quaternary system spreads widely in the Huaibei Plain of Anhui Province and the Pliocene-Pleistocene strata are well developed in the western part of the area. Abundant data have been obtained of palaeogeomagnetism, palaeontology, heavy minerals, clay minerals, oxides, heat release luminescence, amino acid, uranium-series dating methods and so forth. These data provide not only reliable evidences for stratigraphic division, but also informations of palaeoclimatic development. Based on preliminary studies, the lower boundary ages of late, middle, early Pleistocene series, and Pliocene series have been determined, to be about 0.13ma, 0.7ma, 1.8ma and 4.5ma respectively. Four stratigraphic units, namely, Maotang Formation(upper and lower members), Panji Formation(upper, middle and lower members), Taoyuan Formation(upp-er, middle and lower members) and Changshenggou Formation(upper and lower members),have been recognized in the light of lithology, biocoenosis and age determination data.
1. Upper Pleistocene Maotang Formation (Q3m)
This formation is 12.80 to 27.90m thick and contains Palaeoloxodon nau-manni huaihoensis and Bubalus youngi etc. (Fig. 1) in the upper member, which belong to Maotang fauna and correspond to Salawusu fauna. Age of the fossi-liferous stratum is 0.07*0.003ma by uranium-series age method. The bottom boundary of the lower member is about 0.13ma in age according to heat release luminescence data and comparisons of climatic stratigraphy.
2. Middle Pleistocene Panji Fm. (Q2p)
It is 33.25 to 63.88m thick, containing Megaloceros (Sinomegaceros) pach-yosteus, Cervus (Pseudaxis) grayi and Sus lydekkeni etc. in the middle member, which belong to Panji Fauna and correspond to Zhoukoudian Fauna. The bottom boundary of the formation, about 0.7ma in age, lies slightly above the boundary between B and M in the palaeogeomagnetic polarity time scale.
3. Lower Pleistocene Taoyuan Fm. (Q1t)
This formation is 4.05 to 61.25m thick, containing Equus sanmeniensis and Eucladoccrus boulei etc. in the lower part of the upper member, belonging toTaoyuan fauna and corresponding to the Nihewan fauna (in narrow sense). The fossiliferous stratum is 0.895ma in age by amino-acid method. The bottom boundary of this formation is located in the Olduvai normal polarity subchron and is about l.8ma in age.
4. Pliocene Changshenggou Fm. (N2ch)
This formation is 6.27 to 82.89m thick, made up of the upper and lower members. The two members are different from each other in lithology. The bottom boundary of the upper member is situated slightly below M/G boundary and is about 2.5ma in age. The bottom boundary of the lower member lies between Sidufiall and Thvera normal polarity subchrons and is about 4.5ma in age.
2.5ma in the area is an important boundary of palaeoclimatic evolution from moist-pleasently cool to semiarid-warm, while strata above or below 1.8 ma boundary are micropalaeontologically similar in the west part of the study area, and the Pliocene series (1.8 to 4.5ma) are commonly absent in the center and east parts of the area. The l.8ma boundary, however, is fundamentally consistent with Vrica boundary-stratotype between N and Q, which has been recognized by International Commission on Stratigraphy and International Union of Geological Science, and thus should be authoritative and convenient for international exchanges. Authors, for this reason, consent to take the l.8ma-boundary as the lower boundary of Quaternary. In this case, the time limits of the Miocene (24-5ma), Pliocene (5.0-l.8ma) and Pleistocene (1.8-0.01ma) are relatively harmonious. It is well known that if the l.8ma-boun-dary is used in China, a number of familiar formations, such as Nihewan Fm. (in narrow sense), Haiyan Fm. in Yushe and the 4th member of Yuanmou Fm., may belong to Quaternary system, while Youhe Fm., Jingle Fm., Mazegou Fm. in Yushe, Gaozhuang Fm. and the other three members of Yuanmou Fm. in Yunnan should belong to Pliocene series. This can be easily accepted by most geologists and palaeontologists.
出处
《海洋地质与第四纪地质》
CAS
CSCD
北大核心
1991年第2期89-96,共8页
Marine Geology & Quaternary Geology
关键词
地层
划分
第四纪
下限
更新世
stratigraphic division the lower boundary of Quaternary the Huaibei Plain
