川西南地区晚震旦世微生物岩及其对桐湾运动Ⅰ幕的响应

发布时间：2018-06-12 01:18

本文选题：四川盆地 + 震旦系　；参考：《岩石学报》2017年04期

【摘要】：利用震旦纪灯影期沉积较为连续的乐山市峨边地区先锋剖面灯二、灯三段的沉积特征与地球化学特征,分析该时期的沉积环境,探讨存在争论的桐湾运动Ⅰ幕的起始时限。通过对先锋剖面灯二、灯三段地层进行实测,发现灯二段下部为富微生物岩沉积特征,上部为菌藻类减少的贫微生物岩沉积特征,灯三段为蓝灰色、深灰色泥岩沉积,与灯二段的突变接触关系明显。灯二段原岩的地球化学分析结果表明该时期为海水沉积环境,岩石类型为潮坪亚相沉积的白云岩,并可分为两大类与8小类。δ~(13)C在灯二段内部出现了明显负异常,依据δ~(13)C与海平面的变化及微生物的关系,认为桐湾运动Ⅰ幕应起源于灯二段内部富藻层-贫藻层之间。该构造抬升事件是造成海平面下降,古海水温度降低,古盐度降低,沉积环境转变,微生物数量减少,灯二段富藻-贫藻转变,δ~(13)C负异常的主要因素。
[Abstract]:Based on the sedimentary and geochemical characteristics of the second and third member of the Pioneer Section of the Ebian area of Leshan, where the Dengying period of the Sinian was relatively continuous, the sedimentary environment of the period was analyzed, and the time limit for the initiation of the controversial first episode of the Tongwan movement was discussed. By measuring the strata of the second and third sections of the Xianfeng section, it is found that the lower part of the second member of the section is characterized by the sedimentary characteristics of the rich microbe, the upper part of the section is the sedimentary characteristic of the depleted microbe rock which is reduced by bacteria and algae, and the third member of the lamp section is composed of blue-gray and dark gray mudstone deposits. The sudden contact relation with the second stage of the lamp is obvious. The geochemical analysis results of the original rocks of the second member of the Chang Chang show that this period is a seawater sedimentary environment, and the rock type is dolomite deposited in the tidal flat subfacies, and can be divided into two categories and eight subclasses. There are obvious negative anomalies in the interior of the second member. Based on the relationship between 未 ~ (13) C and sea level change and microorganism, it is concluded that the first episode of Tongwan movement originated between the rich and poor algal layers in the second stage of the lamp. The tectonic uplift event is the main factor causing the sea level to fall, the paleo-seawater temperature to decrease, the paleosalinity to decrease, the sedimentary environment to change, the microorganism quantity to decrease, the algae-rich algae-poor algae transition in the second stage of the lamp, the 未 ~ (13) ~ (13) C negative anomaly.
【作者单位】：中国石油大学地球科学学院;油气藏地质及开发工程国家重点实验室成都理工大学;成都理工大学沉积地质研究院;
【基金】：中国地质调查项目(1212011220762) 国家自然科学青年基金项目(41602107)联合资助
【分类号】：P534.31;P618.13

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