鄂尔多斯盆地上三叠统延长组长8段液化柱及相关软沉积物变形

The Liquefied Pillars and Other SSDS of the 8th Member of the Upper Triassic Yanchang Formation in the Ordos Basin

笔者在鄂尔多斯盆地上三叠统延长组长8段的岩芯中首次识别出液化柱变形构造,本文从三维空间研究其宏观与微观特征。赋存液化柱的长8段的多个层位的岩芯中均发现有软沉积物变形构造,如液化流动变形、水塑性变形及脆性变形等,广泛分布于盆地不同地区的钻井岩芯中,并在垂向上重复出现。结合长8段的沉积环境和构造背景分析,笔者认为长8段的液化柱与软沉积物变形系地震触发。晚三叠世鄂尔多斯盆地以南秦岭地震造山运动与盆地沉陷是长8段软沉积物变形的构造背景。根据地震触发软沉积物变形构造的时空分布,鄂尔多斯盆地在长8段沉积的地质时期已受控于秦岭造山带动力机制的控制,而不是传统认为的仅在长8段沉积末期。

The deformation structure of liquefied pillars was first identified in the cores from the 8th member of the Upper Triassic Yanchang Formation in the Ordos Basin. Both the macroscopic and microscopic characteristics of the liquefied pillars were studied in this paper. Soft sediment deformation structures （SSDS）, such as the liquefied SSDS, hydroplastic SSDS and some brittle SSDS, have been found not only in many different sections of the cores from the 8th member of the Yanchang Formation, but also in other cores collected from other areas in the basin. And they present repeatedly along the cores. Basing on the sedimentary environment and tectonic background, the authors propose that the triggering mechanism of the liquefied pillars and these SSDS is the earthquakes originating from the Qinling orogenic process since the late Triassic. Analysis of the temporal and spatial distribution of these seismic SSDS suggests that the Ordos Basin had been controlled by the dynamic mechanism of the Qinling Mountains orogenic belt throughout the entire deposition period of the 8th Member of the Yanchang Formation, but not only in the late period of the 8th Member of the Yanchang Formation.