贺兰山—桌子山地区石炭—二叠系陆表海高精度层序地层模拟与聚煤分析

The High-resolution Sequence Stratigraphy Simulation and Coal Accumulation Analysis of Carboniferous-Permian Offshore Clastic Deposit in Helanshan-Zhuozishan Area

层序地层学的研究不断从盆地规模的层序地层格架和体系域分析向高精度的、微相规模的层序地层分析的方向深化。精细的野外和钻井资料分析表明,贺兰山—桌子山地区的太原组—山西组可划为3个三级层序、6-8个四级层序及20多个准层序。四级层序界面一般是下切的分流河道、潮—河混合水道、近端河口坝或滨面沉积的底部冲刷面,海进初期发育的煤层底界以及盆地方向低水位三角洲前缘底超面等,可以在大范围内追踪,其识别和划分是建立高精度层序地层格架的关键。应用层序地层模拟系统（SSMS）可揭示海平面变化、构造沉降等对层序形成过程的控制。模拟分析表明,对称和不对称的相对海平面变化产生的层序结构存在明显的差异,快速上升后缓慢下降的海平面变化过程可解释区内四级层序的结构特征和聚煤规律。四级层序高水位晚期至海进的转换期有利于形成广泛分布的煤层。

The study of sequence stratigraphy developed continuously from sequence stratigraphy framework and depositional system tract analysis of basin scale to high-resolution and microfacies scale.Refine outcrop and well logging analysis show that there can be divided into 3 3rd order sequences,6-8 4th order sequences and more than 20 parasequences in Shanxi Formation and Taiyuan Formation of Helanshan-Zhuozishan area.The 4th order sequence generally are bounded by incised distributary channel,tide and fluvial mix channel,near mouth bar or scoured base of shoreface deposit,coal base developed on early transgression and delta front baselap surface developed in low stand system tract.These surfacies can be extensively traced in the study area,and their recognition and subdivision are critical factors of high-resolution sequence stratigraphy framework foundation.The sequence stratigraphy simulation applying SSMS system may reveal the control of sea level change and tectonic subsidence on sequence formation process.The simulation results show that symmetrical and non-symmetrical relative sea level change formed obvious different sequence compositions.The fast rise and slow drop process of sea level interpreted the 4th order sequence composition character and coal accumulation regular pattern.The transformation of later high stand system tract and transgression is the most favorable period to form coal deposition widely.