准噶尔盆地南缘中下侏罗统含煤层系层序地层及聚煤控制因素

以露头剖面层序地层研究为基础，结合少量钻、测井资料及前人研究成果，分析了准噶尔盆地南缘中下侏罗统含煤层系的层序地层发育特征和聚煤控制因素。准噶尔盆地南缘中下侏罗统含煤层系为1个完整的二级构造层序，内部发育4个三级层序，12个体系域。研究结果表明，弱伸展、缓慢沉降的古构造背景和温湿还原的古气候条件是中下侏罗统成煤的基本条件；二级构造层序相对湖平面变化和三级层序相对湖平面变化速率是聚煤的主控因素。露头出露厚度大、横向分布稳定的工业可采煤层均发育于高位体系域。SQ1沉积时期，二级构造层序的相对湖平面下降，古潜水面整体偏低，煤层主要发育于三级层序相对湖平面上升速率适中的高位体系域下部；SQ3沉积时期为早中侏罗世的最大洪泛期，二级构造层序的相对湖平面上升至最高点，煤层主要发育于三级层序相对湖平面下降且下降速率适中的高位体系域中上部。

Characteristics of Sequence Stratigraphy and Coal Accumulation Controlling Factors of Lower-Middle Jurassic Coal-bearing Series,South Margin of Junggar Basin,NW China

Combined with few well drilling and well logging data, and results of previous studies, sequence stratigraphy characteristics and coal accumulation controlling factors of Middle-Lower Jurassic coal bearing series in south margins of Junggar Basin have been analyzed on the basis of sequence stratigraphic study in outcrops. Middle-Lower Jurassic coal-bearing series in south margins of Junggar Basin can be divided into one complete 2nd order tectonic sequence, where four 3rd order sequences and twelve system tracts were developed inside. The results show that paleo-tectonic setting (weakly extensive and gentle subsidence) and paleoclimate (warm, humid, and reducing condition) were the fundamental conditions for coal-forming in Middle-Lower Jurassic. While, relative lake level changes of the 2nd order tectonic sequence and rate of relative lake level change in the 3rd order sequence were the major controlling factors for coal accumulation. Commercial recoverable coals, which were characterized by large thickness and stably lateral distribution in outcrops, were all developed in highstand system tract (HST). During the depositional period of SQ1, relative lake level of the 2nd order tectonic sequence was descending, leading a lower paleo water table, where the coals were mainly developed in the lower part of HST (ascending rate of the relative lake level in the 3rd order sequence was moderate). The depositional period of SQ3 was the maximum flooding period of Early-Middle Jurassic, when the relative lake level of the 2nd order tectonic sequence ascended to the highest point. coal beds were mainly developed in the middle-upper part of HST (descending rate of the relevant lake level in the 3rd order sequence was moderate).