| 滇西保山地块中-晚二叠世地层划分、对比的现状和问题 |
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| 引用本文：金小赤,黄浩,沈阳,王义昭.2008.滇西保山地块中-晚二叠世地层划分、对比的现状和问题[J].地球学报,29(5):533-541. |
| DOI：10.3975/cagsb.2008.05.01 |
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| 基金项目:科技部科技基础性工作专项(编号:2006FY120300-9); 中国地质调查局项目(编号:1212010611801) |
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| 中文摘要:保山地块中 晚二叠世沉积由于上部镁质碳酸盐的大量出现和相应的低化石含量以及历史和人为原因，在地层单元划分和时代认定方面，仍处于相对粗放的状态，存在较多的不确定性。根据当初填制１∶２０万地质图时所建岩组的情况，涉及中 晚二叠世地层的组在保山地块北部自下而上有丙麻组、大凹子组和河湾街组，南部有永德组、沙子坡组和河湾街组，西南部有曼里组和沙子坡组。当时填图工作的如下不足给中晚二叠世地层的对比和划分留下了隐患：①未能对北部的河湾街组下部二叠纪有孔虫进行认真研究，而根据一些瓣鳃动物化石将该组时代定为中三叠世；②在南部所建的永德组，既包括下部的红色杂色碎屑岩又包括上部的泥质灰岩；③把在某一层段所见化石的时代看成是整个岩组的时代，忽视了岩组的厚度及其相应时代跨度的大小，特别是那些以前尚未发现化石的部分。通过对区调资料的研读和野外观察，我们现在所理解的岩组对比情况是，西南部的曼里组、南部永德组下部的红色、杂色碎屑岩段和北部的丙麻组相当；西南部的沙子坡组相当于南部的永德组上部的灰岩段和沙子坡组、也相当于北部的大凹子组加上河湾街组的大部（“破灰岩”）；南部的河湾街组大致相当于北部保山幅和泸水幅中河湾街组的顶部灰岩、白云质灰岩段（有时亦称上段，常出露不全或缺失）甚至还有上覆大水塘组的一部分。 |
| 中文关键词:云南 保山地块 二叠系 划分对比 |
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| Subdivision and Correlation of Mid-Late Permian Successions of the Baoshan Block,Western Yunnan:Status and Problems |
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| Abstract:Due to the rapid increase of magnesium carbonate and scarcity of fossils in the upper part of Middle-Late Permian sediments, as well as some historical and artificial reasons, the subdivision and correlation of successions of the said periods on the Baoshan Block remain uncertain. During the mapping course of geological maps of the scale of 1∶200,000 some 20 years ago, a number of formations were erected. Those comprise Middle-Late Permian sediments are the Bingma, Daaozi and Hewanjie formations in northern part of the Baoshan Block, the Yongde, Shazipo and Hewanjie formations in southern part, and the Manli and Shazipo formations in southwestern part. The shortcomings of the work at that time, which resulted in confusion in subdivision and correlation of the Middle-Late Permian sediments are: ①the Hewanjie Formation in the northern part was assigned to the Middle Triassic based on some bivalves, while the Permian foraminifers in its lower part were not properly studied; ②the Yongde Formation erected in the southern part included not only the red and variegated clastics in the lower part but also argillaceous limestones in the upper part; ③age indicated by fossils found in some beds were treated as the age of the whole formation, while the thickness of the formation and the corresponding temporal span were neglected. Scrutiny of the mapping data and extensive fieldwork permit us to make following interpretations: 1) the Manli Formation of the southwestern part, the lower part of the Yongde Formation in the southern part and the Bingma Formation in the northern part can be well correlated; 2) the Shazipo Formation of the southwestern part can be correlated with the limestones in the upper part of the Yongde Formation plus the Shazipo Formation in the southern part, and with the Daaozi Formation and the most of the Hewanjie Formation ( "Cracked limestone" ) in the northern part; 3) the Hewanjie Formation in the southern part can be correlated with the limestones and dolomitic limesones (often not well exposed or absent) in the top part of the Hewanjie Formation or even some of the overlying Dashuitang Formation in the northern part. |
| keywords:Yunnan Baoshan Block Permian subdivision and correlation |
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