库车前陆盆地前渊带层序地层分析--以白垩系卡普沙良群为例

库车前陆盆地的白垩系由卡普沙良群(自下而上包括亚格列木组、舒善河组、巴西盖组)和巴什基奇克组组成.盆地北部克孜勒努尔沟的白垩系亚格列木组和巴什基奇克组底部均发育一大套泥石流沉积,表明白垩系卡普沙良群为一期构造活动幕的产物,为一个完整的二级层序,根据沉积演化特征可将其细分为7个三级层序.亚格列木组与舒善河组之间,扇三角洲平原相突变为滨浅湖相沉积,且舒善河组滨岸沙坝微相持续稳定发育,反映前陆盆地楔顶带的发育抑制了构造活动期源于造山带的粗碎屑的供给,使前渊带的沉积物供给速率趋于稳定.此外,克孜勒努尔沟卡普沙良群地层厚度远大于前缘隆起带,与上、下地层呈整合或平行不整合接触.研究表明,克孜勒努尔沟卡普沙良群为一套临近造山带的前渊带沉积.

Sequence Stratigraphy of the Foredeep in Kuqa Foreland Basin,Xinjiang:An Example from the Cretaceous Kapushaliang Group

The Cretaceous in Kuqa foreland basin, Xinjiang is composed of Kapushaliang Group(successively including Yageliemu Formation, Shushanhe Formation and Baxigai Formation), overlying Bashenjiqike Formation. Based on the detailed sequence stratigraphic investigation of Kezileluergou section in the north of the basin, a completed second-order sequence in Kapushaliang Group has been identified by two masses of debris flow at Yageliemu Formation and the bottom of Bashenjiqike Formation, respectively, which was the response to a renewed tectonic episode. Kapushaliang Group can be divided into 7 third-order sequences by sedimentary evolution. Fan delta plain facies in Yageliemu Formation abruptly transfer to shore facies and shallow-lake facies in Shushanhe Formation, and shore sand-bar micro-facies consistently developed in Shushanhe Formation. This suggests the wedge of foreland basin restrained the supply of coarse clastic from the north orogenic belt so as to keep supply-rate of sediment relatively steady in the period of tectonic activity. Additionally, Kapushaliang Group at Kezileluergou section is far thicker than that in the forebulge, and it contacts parallel-unconformally with its underlying formation and conformally with its overlying formation. Above all, Kapushaliang Group at Kezileluergou section is deposited at foredeep close to the orogenic belt.