| 天津蓟县中元古界高于庄组中臼齿状构造的层序地层位置及其成因的初步研究 |
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| 引用本文： | 梅冥相.天津蓟县中元古界高于庄组中臼齿状构造的层序地层位置及其成因的初步研究[J].古地理学报,2005,7(4):437-447. |
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| 作者姓名： | 梅冥相 |
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| 作者单位： | 1.岩石圈构造、深部过程与探测技术教育部重点实验室 中国地质大学（北京） 北京 100083;2.中国地质大学地球科学与资源学院 北京 100083 |
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| 摘 要： | 天津蓟县剖面的中元古界高于庄组为一套厚度约为1 600m的碳酸盐岩地层，包括四个段：第一段以潮坪相叠层石白云岩为主；第二段主要为含锰白云岩；第三段发育较多的纹理化石灰岩和泥晶灰岩；第四段则以叠层石岩礁（叠层石生物丘和生物层）的发育为特点。根据岩相到岩相序列可在该套碳酸盐岩地层中识别出L-M型、潮下型、环潮坪型米级旋回层序。根据米级旋回层序的有序垂直叠加形式所反映出的沉积相序列可以把高于庄组划分为13个三级层序（SQ1至SQ13），并进一步归为4个二级层序。在以灰岩为主的高于庄组第三段中，其中的第三个三级层序（SQ11）中部的灰岩层中发育臼齿状构造。这种臼齿状构造以特别的形态、富含有机质、易硅化等特点可能表明了前寒武纪碳酸盐岩沉积作用的一些基本特征：第一、在浅水环境中发育叠层石而在较深水环境（中缓坡）中发育臼齿状构造，臼齿状构造就象叠层石一样是一种极为特别的与生物沉积作用相关的沉积构造；第二、在发育叠层石的潮坪环境中有利于发生白云石化作用，发育臼齿状构造的地层则以灰岩为主，这从一个侧面反映了前寒武纪白云岩似乎又不是原生白云岩。实际上，这些特征本身即代表了一些前寒武纪沉积学问题，随着研究的深入对这些问题将会得出更加接近自然事实的答案。
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| 关 键 词： | 臼齿状构造 层序地层 高于庄组 中元古界 天津蓟县 |
| 文章编号： | 1671-1505（2005）04-0437-11 |
| 收稿时间： | 2005-03-04 |
| 修稿时间： | 2005-03-20 |
Preliminary study on sequence-stratigraphic position and origin for Molar-tooth structure of the Gaoyuzhuang Formation of Mesoproterozoic at Jixian section in Tianjin |
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| Mei Mingxiang.Preliminary study on sequence-stratigraphic position and origin for Molar-tooth structure of the Gaoyuzhuang Formation of Mesoproterozoic at Jixian section in Tianjin[J].Journal of Palaeogeography,2005,7(4):437-447. |
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| Authors: | Mei Mingxiang |
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| Institution: | 1 Key Laboratory of Lithospheric Tectonics and Lithoprobling Technology, Ministry of Education, China University of Geosciences, Beijing 100083;
2 School of Earth Sciences and Resources, China University of Geosciences, Beijing 100083 |
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| Abstract: | The Gaoyuzhuang Formation of Mesoproterozoic at the Jixian section in Tianjin is a set of about 1 600 m-thick carbonate strata, which can be divided into four members: The first member is mainly constituted by stromatolitic dolomites; The second member is marked by a set of manganese dolomites; The third member is mainly composed of laminar limestones; The fourth member is a set of stromatolitic-lithoherm dolomites. According to lithofacies and lithofacies succession, several types of meter-scale cyclic sequences, i.e. the L-M type, the subtidal type and the peritidal type can be discerned in the Gaoyuzhuang Formation. There is a regularly vertical stacking pattern for meter-scale cyclic sequences in the third-order sequence. Therefore, the Mesoproterozoic Gaoyuzhuang Formation can be divided into 13 third-order sequences (SQ1 to SQ13) and still be grouped into 4 second-order sequences. The third member of the Gaoyuzhuang Formation that is marked by laminar limestones can be grouped into 3 third-order sequences (SQ9 to SQ11); and the molar-tooth structure is developed in the middle part of the third sequence in the third member of Gaoyuzhuang Formation. Several features of this kind of molar-tooth structure, i.e. the particular configuration, containing abundant organic matter, easy silication etc., reflect some characters of carbonate sedimentation in Precambrian as follows: Firstly, stromatolites are chiefly formed in shallow tidal-flat environment and molar-tooth structures are mainly generated in more deep-water environment of carbonate ramp, therefore, similar to stramatolite the molar-tooth structure is also a kind of biosedimentation structure; Secondly, the shallow tidal-flat environment mainly developed stromatolites is propitious to dolomitization, but in the more deep water environment of carbonate ramp is chiefly formed limestones, both of which might reflect
that Precambrian dolomites are appear not primary dolomites. Actually, these features of Precambrian sedimentation also represent the problem of Precambran carbonate sedimentation. With much more detail study, much more truly solution for these problems will be obtain in the future. |
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| Keywords: | Molar-tooth structure sequence stratigraphy Gaoyuzhuang Formation Mesoproterozoic Jixian Tianjin |
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