滨岸-浅海混合沉积对海平面与气候变化的响应--以塔里木盆地巴麦地区石炭系为例

陆源碎屑-碳酸盐混积作用发生的环境特征尚不明确，导致对混积岩分布规律认识不足。以塔里木盆地巴麦地区石炭系为例，通过薄片观察、矿物组成分析、主微量元素分析，对沉积环境和古环境特征参数进行了研究。研究区混积岩发育在障壁滨岸、碳酸盐岩局限台地和开阔台地。利用与混积强度相关性极好的Ti、Rb、K和Al的含量，将混积岩定量划分为4级。利用Na/Ca比值、Na含量分析了古盐度特征，Mn/Fe比值和Sr含量分析了古水深，用V/（V+Ni）比值反映了氧化还原条件，并利用Ti/Al，Mg/Sr反映了古气候特征。研究结果表明Ⅱ级以上混积均发生在湿润气候下，而干旱气候无明显混积，并且混合沉积大部分发生在海平面下降阶段。碳酸盐岩开阔台地的混积强度仅达I级，障壁滨岸和碳酸盐岩局限台地的混积强度较高，发育Ⅲ级和IV级高度混积岩。不同沉积环境的混合沉积均对古气候变化与相对海平面变化具有良好的响应，是详细的古环境变化记录。

Shoreline-neritic Mixed Sedimentation Response to Sea Level Change and Paleoclimate: A case study from Carboniferous in Tarim Basin

The characteristics of siliciclastic-carbonate mixed sedimentary environment still remains unknown, resul-ting in poor understanding of distribution of mixed rock. In this study, the sedimentary environments and environmen-tal parameters of Carboniferous in Bamai area, Tarim Basin are deeply studied, using observation of thin sections, measurement of minerals composition, and elements composition. The mixed rocks were deposited, carbonate restrict-ed platform and open platform. The concentrations of Ti, Rb, K, Al are used to divide the degrees of mixed sedimen-tation into four levels due to their good relationship with the degree of mixing. The salinity was reflected by Na content and Na/Ca. The depth of water was reflected by Mn/Fe and Sr content. The redox condition was reflected by V/( V+Ni) . And, the paleoclimate was analyzed from Ti/Al and Mg/Sr. The result of geochemical indices shows the mixed sedimentation beyond II level occurred at humid climate, while there was no obvious mixing at arid climate. Mean-while, most mixed sedimentation accompanied by sea level fall. On the open platform, there was only I level mixed sedimentation, while III-IV level mixed sedimentation developed on the barrier coast and restricted platform. The mixed sedimentation in each depositional environment can record the change of sea level and paleoclimate.