鄂尔多斯盆地中部二叠系山西组和下石盒子组构造沉降定量恢复及沉积响应

Tectonic subsidence reconstruction and sedimentary responses of the Permian Shanxi and Lower Shihezi Formation in central Ordos Basin

关键词:  鄂尔多斯盆地  山西组  下石盒子组  构造沉降  定量恢复  沉积响应

Key words:  Ordos Basin  Shanxi Formation  Lower Shihezi Formation  tectonic subsidence  quantitative reconstruction  sedimentary response

摘要:

本文利用回剥技术,定量恢复鄂尔多斯盆地中部二叠系山西组和下石盒子组的构造沉降量,并探讨其沉积响应特征。结果表明,山西组的构造沉降量为30~95m,具有中部构造沉降大、向南北两侧减小的趋势,北部构造沉降较南部的大。主沉降中心位于研究区中部,次级沉降中心位于西北部,构造沉降速率为(6~20m)/Ma,具有与构造沉降量一致的分布特征;下石盒子组的构造沉降量为75~110m,总体继承了山西组的沉降中心。但中部的沉降中心向东迁移,范围也有所扩大,构造沉降速率为(9~14.5m)/Ma,其分布特征与构造沉降量一致。在研究区南、北和中部差异构造沉降的背景下,主要发育河流、三角洲和滨浅湖相沉积类型,北部的河流-三角洲沉积体系规模比南部的大,湖盆范围对应着中部的构造沉降中心。研究结果不仅深化了该地区构造沉降方面的认识,还为该时期沉积特征研究提供了重要手段。

Abstract:

The present paper focuses on the quantitative tectonic subsidence reconstruction and sedimentary responses of the Permian Shanxi and Lower Shihezi Formation in central Ordos Basin by using a back stripping method. The tectonic subsidence thickness of the Shanxi Formation ranges from 30 to 95 m, with a maximum subsidence thickness in the central area and gradual decrease towards both the north and south. The secondary subsidence center appears in the norwestern part, with the tectonic subsidence rates from 6 to 20 m/Ma. The tectonic subsidence thickness of the Lower Shihezi Formation ranges from 75 to 110 m, with the tectonic subsidence rates of 9 to 14.5 m/Ma in the central area. Controlled by the differential tectonic subsidence rates, the sedimentary facies types comprise the fluvial, delta and littoral and shallow lake facies, and the fluvial and delta depositional systems have greater scales in the north than in the south. The results of research in this study not only improve our knowledge of tectonic subsidence but also offer an important tool for the research of sedimentary characteristics in the study areas.