摘要
类Ｇａｌｏｗａｙｉｎｅｌａ长期以来被当作长兴阶的带化石，是长兴阶底界的标志。江西上高七宝山剖面表明Ｇａｌｏｗａｙｉｎｅｌａ富集层并非像以往认为的那样是稳定的一层，在此剖面上至少有二层：下层在Ｃｌａｒｋｉｎａｌｅｖｅｎｉ带之下，其上下均有典型的吴家坪期的菊石（Ｋｏｎｇｌｉｎｇｉｔｅｓ等）；上层与吴家坪期的牙形刺Ｃｌａｒｋｉｎａｏｒｉｅｎｔａｌｉｓ，Ｃ．ｇｕａｎｇｙｕａｎｅｎｓｉｓ，Ｃ．ｄｅｍｉｃｏｒｎｉｓ，Ｃ．ｌｉａｎｇｓｈａｎｅｎｓｉｓ共存。这一事实表明Ｇａｌｏｗａｙｉｎｅｌａｍｅｉｔｉｅｎｅｎｓｉｓ是吴家坪期的而不是长兴期的。为此建议，长兴阶的底界不用类定义，而以牙形刺Ｃｌａｒｋｉｎａｓｕｂｃａｒｉｎａｔａ和／或Ｃ．ｗａｎｇｉ的首次出现为准。
The first appearance of the genus Equus was regarded as the sign of the lower boundary of the Quaternary, but it has been doubted,even negated,in late years. According to the lower boundary of the Quaternary at 2.5 Ma B.P., which is generally accepted at present, however, the first appearance of the genus Equus in Eurasia is just right identical with the boundary, which is proved by the evidences from the Villafranchian Fauna in Europe, the Nihewan Beds in North China, the Yuanmou Basin in South China, and other profile sections. In Europe, the genus Equus appeared firstly in the Middle Villafranchian whose lower boundary′s age is 2.5 Ma B.P. by the potassium argon dating. In North China, the lower part of the Nihewan Beds is called the Dongyaozitou Formation with a Pliocene fauna; above it, there is the Nihewan Formation with an early Pleistocene fauna. The fossils of Equus sanmeniensis are collected from the bottom of the Nihewan Formation and the age of the bottom is 2.5 Ma B.P. by the amino acid dating. In South China, the Yuanmou Formation in the Yuanmou Basin is divided into two parts: the first part includes a Pliocene fauna in Members 1-2 of the Formation; the second part includes an early Early Pleistocene fauna in Members 3-4 of the Formation. The fossils of Equus yunnanensis occur earlist in Member 3 of the Yuanmou Formation, and the oldest of the member is 2.48 Ma B.P. by the paleomagnetic dating. Some data of the plaeomagnetic dating also proved that the first appearance of the genus Equus is at the boundary of Matuyama/Gauss, 2.48 Ma B.P. in the profile sections of the southeastern Shanxi Province and the Youhe district, Shaanxi Province. The first appearance of the genus Equus was contemporary with many important geological events at about 2.5 Ma B.P., such as the boundary of Matuyama/Gauss in magnetostratigraphy, the loess accumulation′s beginning in China, the appearance of the ice map in the Arctic, and the first strengthening of the neotectonism. The first appearance of the genus Equus at the 2.5 Ma B.P. was not a coincidence. The fall of the sea level, which was caused by the appearance of the ice map in the Arctic, made the bottom of the Bering Strait emerge and connect between Eurasia and North America. The genus Equus, which originated in North America and successed in evolution, spread rapidly into Eurasia and other regions through the landbridge. Therefore, the first appearance of the genus Equus can be regarded as an easily recognized sign of the lower boundary of the Quaternary in the regions, especially in Eurasia.
出处
《地层学杂志》
CSCD
北大核心
1997年第2期100-108,T001,共10页
Journal of Stratigraphy
基金
国家自然科学基金
关键词
TING
依牙形刺
古动物
二叠系
长兴阶
底界
genus Equus, lower boundary of the Quaternary, Qualernary, 2.5 Ma B.P., Eurasia
