塔里木盆地顺托果勒地区早中志留世震积岩——高分辨构造事件的记录

在塔里木盆地塔中隆起与满加尔坳陷结合部——顺托果勒地区的深钻井岩心中,发现了大量早中志留世软沉积变形构造。其中主要包括液化砂岩脉、液化角砾岩、触变底劈构造、触变楔、负载构造、球-枕构造和复合混插构造等。通过系统地观察软沉积变形构造的岩石组成、构造形貌及样式、垂向分布的循环性、横向分布的延展性、沉积环境及与古活动断裂的关系,确定其为震积岩。结合该区断裂早中志留世的发育特征,推测发震断裂主要可能是塔中隆起与满加尔坳陷结合部的北东向走滑逆冲断裂以及北西向剪切拉张断裂。在早志留世柯坪塔格组沉积时约4 Ma中最少发生了26次古地震事件(震级M5)。这些古地震记录不仅反映了研究区志留纪构造的活动性,也是弥补主构造运动中高频次构造事件脉动性、循环性的重要证据,为重建中古生代的古构造提供新的线索。

Seismites in the Early and Middle Silurian Strata of Shuntuoguole Area in Tarim Basin: Records of High-resolution Tectonic Events

A lot of soft-sediment deformation structures (SSDS) in deep drilling cores are recognized in the Early and Middle Silurian strata of the Shuntuoguole area which is a conjunction of the Tazhong uplift and the Manjiaer depression in the Tarim Basin. The SSDS include liquefied sand veins, liquefied breccias, thixotropic diapirs, thixotropic wedges, load cast structures, ball - pillow structure deformation structures and complex plunge sediment mixture structures. The lithological composition, the structural morphologies and styles, the sequences of vertical distribution, the extensions of horizontal distributions and the sedimentary envoirment of soft sediment deformation structures are analyzed, and the relationship between the activity of the paleo-faults to the SSDS are discussed. These soft-sediment deformation structures are determined as various seismites. Combined with the faults in the Early and Middle Silurian strata in this area and adjacent areas, the authors hold that the seismogenic faults may be mainly the NE-trending strike-slip thrust faults and the smaller NW-trending extensional faults. There occurred at least 26 times paleo-earthquake events (with magnitude more than 5) during about 4 Ma of the deposition of the Kepingtagh Formation in Early Silurian. These paleo-earthquake records reflect the tectonic activities of Shuntuoguole area and its adjacent areas, complement the evidence of high-resolution tectonic events of the main tectonic movements with the pulsation and circularity, and provide the new clues for reconstruction of paleo-tectonics.