华北板块西南缘义马盆地中侏罗世沉积相及古地理

摘要

The Yima basin located on the southwestern margin of the North China plate is the sole recoverable Mesozoic coal field in Henan. Exemplified by the Middle Jurassic coal measures, the stratigraphic division, sedimentary facies and palaeogeographic analysis are made on the basis of lithological, geochemical and sedimentological data. The Middle Jurassic coal measures belong to the Aalenian-Bajocian, when four sedimentary facies are developed, including the alluvial fan, braided stream, delta and lake facies. The Aalenian-Bajocian sedimentary facies and palaeogeographic maps are constructed with the aid of the single factor and multifactor mapping methods. The palaeogeographic units tend to display the variations of the alluvial fan, delta and lake facies, and represent a retrogradational process in the Yima basin throughout the coal-forming periods.%义马盆地位于华北板块西南缘，是河南省境内唯一可采的中生代煤田，位置特殊。为了揭示其中侏罗世阿林期-巴柔期的沉积相及其古地理演化特征，运用矿物岩石学、地球化学、沉积学及岩相古地理等方法，以义马盆地中侏罗世含煤岩系为例，进行地层划分及沉积相和古地理研究。研究结果表明，研究区中侏罗世含煤岩系属阿林期-巴柔期，该时期主要发育冲积扇、辫状河、三角洲、湖泊等4种沉积相。利用单因素分析多因素综合作图法，以成煤期为节点，定量恢复了阿林期-巴柔期的古地理特征，从成煤期前到成煤期后，各优势古地理单元变化明显，具有冲积扇-三角洲-湖泊的变化规律，整体上是一个退积过程。