摘要
在前寒武纪碳酸盐岩中，最为普遍的是叠层石碳酸盐岩沉积序列，而以潮下相沉积为主的非叠层石碳酸盐岩沉积序列与前者形成了较大的差异；因此，与叠层石碳酸盐岩沉积序列一样，非叠层石序列成为了解前寒武纪复杂多变的碳酸盐世界的重要线索。燕山地区中元古代高于庄组为一套厚度千余米的碳酸盐沉积序列，包括四大部分：第一段（或称为官地亚组）为发育在海侵砂岩上的叠层石白云岩地层；第二段（或称为桑树鞍亚组）为发育少量叠层石的含锰白云岩地层；第三段又称为张家峪亚组，为一套以发育灰岩为主的非叠层石碳酸盐岩沉积序列；第四段以叠层石岩礁和叠层石礁白云岩为特征。延庆千沟剖面的高于庄组第三段的非叠层石碳酸盐岩沉积序列，贫乏叠层石是其基本特点，包含3个三级层序，在三级层序的海侵体系域和早期高水位体系域中，层面上发育席底构造的中层均一石灰岩（隐藻泥晶灰岩）和灰黑色薄层泥灰岩组成若干潮下型米级旋回，晚期高水位体系域则以厚层块状纹理石灰质白云岩和白云质灰岩为特征；三级层序的凝缩段单元则以薄层泥灰岩和泥页岩构成的L—M型米级旋回为特征。因此，每一个三级层序均以一个有序的沉积相序列为特征。高于庄组的分布时限大致为200Ma（1600—1400Ma），考虑到下伏的大红峪组和高于庄组之间的地层间断时限大致为50Ma至100Ma，所以推断高于庄组的堆积作用时限为100Ma（1500—1400Ma）左右，其中高于庄组第一段与第二段的分界线正好处于该组的中部而可以推断该界线的大致为1450Ma左右；因此，高于庄组第三段非叠层石碳酸盐岩沉积序列的发育表明，在1450Ma左右可能发生过一次可以与前寒武纪其他已经被识别出的三次叠层石衰减事件（2000Ma、1000Ma和675Ma）相比拟的又一次叠层石衰
In the long Precambrian, the stromatolitic carbonate succession is very common. But, the non-stromatolitic carbonate succession that is marked by the subtidal deposits forms a strong contrast to the stromatolitic carbonate succession. Both the non-stromatolitic and the stromatolitic carbonate successions are important clues for the further understanding of the evolving carbonate world of the Precambrian. The Mesoproterozoic Gaoyuzhuang Fm. in Yanshan Area is a set of more than 1000m-thick carbonate strata that can be divided into four Members （ or Subformations） ： The first Member （ or the Guandi Subformation） is marked by a set of stromatolitic dolomites overlying a set of transgressive sandstones; The second Member （or the Sangshuan Subformation） is a set of manganiferous dolomites with a few stromatolites; The third Member is chiefly made up of limestones and is characterized by a particularly non-stromatolitic carbonate succession of the Precambrian ; The fourth Member （ or the Huanxiusi Subformation） is composed of a set of dolomites of stromatolitic reefs or lithoherms. The non-stromatolitic carbonate succession making up the third Member of the Gaoyuzhuang Formation at the Qiangou section in Yanqing County of Beijing can further be subdivided into three third-order sequences that are marked by the regular succession of sedimentary facies. In third-order se quences, lots of subtidal carbonate meter-scale cycles made up of the midium-bedded leiolite limestones and the thinbedded marls constitute their transgressive system tracts （TSTs） and the early high-stand system tracts （ EHSTs）, lots of meter-scale cycles made up by the thin-bedded limestones and marls constitute their condensed sections （ CSs）, and thick-bedded to massive dolimitic limestones or lime dolomites make up the late high-stand system tracts （LH- STs）. The time scan of the Gaoyuzhuang Formation is deduced as 200 Ma （from 1600 Ma to 1400 Ma）. An obvious hiatus between the Gaoyuzhuang Formation and the unde
出处
《沉积学报》
CAS
CSCD
北大核心
2008年第4期565-574,共10页
Acta Sedimentologica Sinica
基金
国家自然科学基金会项目(批准号:49802012,40472065)资助
关键词
非叠层石碳酸盐岩序列
高于庄组
中元古代
延庆千沟剖面
non-stromatolitic carbonate succession
Gaoyuzhuang Formation
Mesoproterozoic
Qiangou section in Yanqing
