基于高精度碳酸盐岩微相的海平面变化曲线分析

精确的海平面变化曲线分析一直是地质学研究的难题和前沿科学问题，原因在于:1）深时沉积记录是全球海平面变化和区域构造沉降的综合响应，如何从沉积记录中剔除区域构造运动对海平面变化的影响尚缺乏手段；2）根据深时沉积记录确定古水深还具有挑战性。晚奥陶世塔里木盆地柯坪地区经历了从盆地—盆缘—陆棚的环境演变，这是对海平面变化最为敏感的环境地带，是开展沉积微相研究的理想地区。对大湾沟剖面上奥陶统进行密集取样分析，基于岩相沉积学、古生物学等手段，划分了广海陆棚及盆地边缘两大相带。详细划分为七个微相:MF1砖/紫红色微生物泥晶灰岩、MF2灰色微生物泥晶灰岩、MF3灰绿色钙质泥岩、MF4灰色生物碎屑—岩屑微角砾岩、MF5灰色含微生物碎屑粉屑灰岩、MF6灰色生物碎屑泥微晶灰岩及MF7深灰色钙质泥岩；重建了上奥陶统坎岭组—印干组海平面变化曲线，提供一套在深时沉积记录敏感带基于高精度微相全球海平面曲线的分析方法。将研究区海平面变化与全球各地区海平面变化曲线进行对比，发现研究区与北美海平面频繁波动极其相似。前人古板块重建恢复结果显示这一时期加里东构造运动已具备全球响应特征，而相似的海平面变化则是由不同区域造山碰撞所导致。

Analyses of the Sea Level Curve Based on High-precision Carbonate Microfacies

The variation of an accurate global sea level curve has always been a difficult and frontier scientific problem in sedimentary geological research. There are 2 reasons: （1） the deep-time sedimentary record is the comprehensive response to global sea level change and regional movement， but accurately eliminating the regional tectonic effect is also difficult； （2） determining paleo-water depth based on deep-time sedimentary records is still being explored. The Kalpin area of the Tarim Basin in the Late Ordovician experienced an environmental evolution from basin to basin margin to shelf， making it highly sensitive to sea level changes and an ideal area for conducting research on sea level changes based on sedimentary microfacies. The study conducted a detailed field investigation and intensive sampling analysis of the Dawangou section. Based on lithofacies sedimentology， paleontology， etc.， the two major facies of the continental shelf and the basin edge were divided， and seven microfacies are distinguished in detail: MF1， brick red /purple microbial micritic limestone； MF2， gray microbial micritic limestone； MF3， gray-green calcareous clay； MF4， gray bioclastic - lithoclastic breccia limestone； MF5， gray bioclastic silty limestone； MF6， gray bioclastic micritic limestone； and MF7， dark gray calcareous clay. Based on advanced microfacies for the sensitive zone of deep-time sedimentary records， the sea level change curve of the Upper Ordovician Kanling and Yingan Formations is constructed， and a set of methods for determining the global sea level curve can be summarized. Our sea level curve is compared with the upper Yangtze region， the southern margin of Ordos， North America， South America， Wales， and the global sea level change， and results indicate that the frequent fluctuations of sea level are similar to North America. The reconstruction plate tectonic results of the study indicate that the Caledonian tectonic movement has global corresponding characteristics during this period. Frequent plane fluctuations are mainly caused by orogenic collisions in different regions.