| 辽西热河群的时代归属问题 |
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| 引用本文：王东方.1983.辽西热河群的时代归属问题[J].地球学报,5(3):57-64. |
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| 全文下载次数: 1990 |
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| 中文摘要:<正> 目前,我国侏罗—白垩纪陆相地层研究工作虽已取得许多进展,但在地层时代的确定方面尚存在一些根本性的分歧,其中侏罗系与白垩系的界限就是我国生物地层学术界争议最大的问题之一。争论的焦点在于热河群的时代是隶属于侏罗系还是白垩系。本文根据作者等几年来在辽西等地区进行的地质考察、同位素年龄的系统测定、古地磁极的测定,结合生物地层学已积累的资料,综合分析认为热河群的时代应属早白垩世,而不是晚侏罗世。 |
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| ON THE AGE OF THE REHE GROUP IN WESTERN LIAONING |
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| Abstract:In the twenties and thirties of this century, the age of the Mesozoic Rehe Group of the Yan-Liao area was referred to Cretaceous by the American Central Asia Expedition and also by Grabou, Ji Runsen and Yang Zhongjian to that of this group as well as its equivalents Mongyin Group of Shandong and Jiande Group of the coastal area of southeast China. In the first Stratigraphic Conference of China, Guzhiwei and others considered the age of the Rehe Group as Jurassic. During the last 20 years, a great many Cretaceous fossils of Reptilia, Insecta, Ostracoda, and Charophyta and also of plants, spores and pollens have been found in this and other groups, thus furnishing the possibility to correlate them with those of Lower Cretaceous in the Fareast of USSR, Korea, Mongolia and Congo.The fact that the Lowest volcanic formations, the Yixian and Zhangjia-kou formations, of the Rehe Geoup overlie unconformably on the Tuchenzi and Houchen formations containing Chaoyangosarus of Late Jurassic age, a...更多lso suggests the Rehe Group should be of Early Cretaceous in age.The Mesozoic volcanic rocks of this area may be subdivided into three cycles, the Early Jurassic (195-191 m. y. ) , the Late Jurassic (158-149. 5 m. y. by K-Ar and Rb-Sr isochron methods), and the Early Cretaceous Cycle of the Rehe Group (140-137m. y. by Rb-Sr and K-Ar isochron methods). The samples for isotopic dating were collected from the bottom part of the Yixian formation. A total of 126 samples from the volcanic rocks corresponding to the Rehe Group in the areas of Yan-Liao and Da Hingan Mountains have provided a set of K-Ar isotopic datings of 143-95 m. y. from lowest to uppermost of this sequence, thus supporting the Lower Cretaceous age of the Rehe Group. From the Rehe and the Jiande Groups, 8 groups of Rb-Sr isochron ages and 8 by K-Ar isochron method, together with 220 datings of single sample by K-Ar methods, indicate that the age of their lower limite is about 138 m. y. Based on paleomagnetic determination of some oriented samples, the paleomagnetic pole of the Yixian Formation is 140.9° E Lougitude and 45° N Latitude. This closely resembles to that of either Lower Cretaceous or Cretaceous in the Sibiria and the Russian Platform of USSR, North Korea and southern China and obviously differs from that of the Jurassic Eurasia continent. Thus, the paleomagnetic pole data also support the Lower Cretaceous age of the Rehe Group. |
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