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| 基金项目：河北省人民政府特别资助基金项目（Z20177187），河北地质大学校长基金项目（TS2017-001） |
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| 摘要： |
| 以贵州大坡上剖面和广西南边村剖面为基础，介绍了我国泥盆—石炭系界线年龄研究现状。桂林南边村剖面属于斜坡相重力流沉积，牙形类的演化序列有些混乱。虽然前人将泥盆—石炭系界线定在‘56层’与‘57层’之间，但这些 ‘层’号实际上是牙形类采样号。‘55层’—‘58层’是一层介壳灰岩，采集了4个牙形类样品。研究认为，将泥盆—石炭系界线置于该层介壳灰岩内不正确，在理论上也不科学，不能将介壳灰岩中的腕足类化石一分为二，即个体的下部属于晚泥盆世，上部属于早石炭世。用于测年的样品采自‘58层’和‘66层’，明显高于剖面中牙形类Siphonodella sulcata出现的层位，很显然，获得的（361.0±4.1）Ma界线年龄值不可信。贵州大坡上剖面属于深水盆地相沉积，也是我国唯一既产出Wocklumeria动物群又产出Gattendorfia动物群的剖面。刘永清等（2012）在王佑组底部2～4 cm厚的含凝灰岩黑色页岩中采集了1件凝灰岩测年样品，获得了1个锆石U-Pb测定年龄（359.6±1.9）Ma，该年龄值非常接近但又老于国际地层委员会2020年公布的（358.9±0.4）Ma的界线年龄值，表面看来，该年龄值基本可信，也是可接受的，但其误差较大、精度较差，需再次采样加以验证。研究认为，国际地层委员会公布的界线年龄值（358.9±0.4）Ma是可以接受的，而且泥盆纪末期事件层的年龄值在360.0～361.0 Ma区间同样也是可接受的。 |
| 关键词：大坡上剖面 南边村剖面 泥盆—石炭系界线年龄 中国南方 |
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| Abstract: |
| This paper makes an introduction to the dating ages of the Devonian-Carboniferous boundary in South China, based on the Nanbiancun section in Guangxi and the Daposhang section of Guizhou. The Nanbiancun section of Guangxi falls into the slope, gravity flow sedimentary facies, and the conodont sequence is somewhat chaotic. Although the D-C boundary was fixed between ′Bed 56′ and ′Bed 57′, the so called ′bed′ numbers are actually the conodont sampling numbers.′Bed 55′to ′Bed 58′are a single shell-limestone, from which 4 conodont samples were collected. The paper believes that it is unacceptable and unscientific in theory to place the D-C boundary within the shell-limestone. It is unreasonable to separate the brachiopod individuals into 2 parts, that is to place the lower part in the Upper Devonian, and the Upper part in the Lower Carboniferous. The samples used for dating were taken from ′Bed 58′ and ′Bed 66′, which are clearly higher than the occurrence position of Siphonodella sulcata(conodonts) in the profile. It is clear that the D-C boundary age of (361.0±4.1) Ma obtained by them is neither credible nor desirable. The Daposhang section in Guizhou falls into the sedimentary facies of deep-water basin, and it is the only section in China yields both the Wocklumeria Fauna and the Gattendorfia Fauna. Liu et al. (2012) collected a tuff sample for dating from the D-C event bed of 2-4 black shale at the basal part of the Wangyou Formation and obtained a zircon U-Pb concordant age of (359.6±1.9) Ma. This age is close to, but older than the D-C boundary age of (358.9±0.4) Ma given by International Commission on Stratigraphy (2020). Superficially, this age seems credible and acceptable, but its error is huge, and the data is not precise enough to make the final word now. It is necessary to collect again samples from the Daposhang section in order to verify the accuracy of the age. Personally, it is acceptable that the age of the D-C boundary is about (358.9±0.4) Ma, and that the age of the D-C event bed ranges from 360.0 to 361.0 Ma. |
| Keywords:the Daposhang section the Nanbiancun section the age of the D-C boundary Southern China |
| 季燕南，梁蕾，季强.中国南方泥盆—石炭系界线年龄[J].地质学刊,2021,45(1):8-12 |
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