新集矿区早二叠世含煤岩系层序地层划分及聚煤作用

Sequence Stratigraphy and Coal Accumulation of Early Permian in Xinji Mining Area

目的通过建立淮南煤田新集矿区早二叠世含煤地层层序地层格架,探讨其对煤层分布的控制作用。方法主要以下切谷砂体底部冲刷面为层序界面,结合沉积旋回特征,对矿区早二叠世含煤岩系(山西组和下石盒子组)进行层序地层划分。结果将早二叠世含煤岩系从下到上划分为层序Ⅰ、层序Ⅱ、层序Ⅲ3个三级层序及8个体系域,构建新集矿区含煤地层三级层序地层格架。结论在层序地层格架下,煤层厚度变化呈现一定规律,其中层序Ⅲ煤层最厚,总厚度为15.77m;层序Ⅰ煤层较为发育,总厚度为7.42m;层序Ⅱ煤层较不发育,总厚度为5.59m。同一个层序中,海侵体系域煤层厚度最大,高位体系域煤层次之,低位体系域煤层最不发育,其中可采煤层主要发育于泻湖-潮坪沉积环境和近海三角洲平原沉积环境的海侵体系域中。

Objective Through establishing the sequence stratigraphic framework to research its control action on the distribution and thickness variation of coalbeds in Xinji Mining Area.Methods According to the identification of the sequence boundaries represented by incised valley filling sandstone base,combined with the characteristics of sedimentary cycles.Results The sequence stratigraphy of the Early Permian coal seams(Shanxi formation and Lower Shihezi formation)were analyzed and divided into 3 third-order sequences and 8 system tracts from bottom to top,the sequence stratigraphic framework was established.Conclusion Under the sequence stratigraphic framework,the thickness variation of the coal seams shows a certain regularity.The total coal seam is the thickest in SQ3(15.77 m)and the thinner in sequence SQ1(7.42 m),with the thinnest in SQ2(5.59 m).Within the sequence,the thickest coals were developed in the transgressive systems tract,the thicker coals in the high-stand systems tract and the thinnest coals were preserved in the low-stand systems tract.The recoverable coal seans are mainly developed in the transgressive system tracts of the drainage lake-tidal flat sedimentary environment and offshore deltaic plain depositional environment.