【摘要】 早二叠世下岌岌槽子群发育于博格达弧后碰撞前陆盆地缓坡带,为一套长石含量较高的陆源碎屑岩。古流向、沉积相带分布研究表明,当时的古坡向向南。岌岌槽子群中首次发现大量软沉积物变形构造,包括链环层理、水塑性褶皱、液化沙脉、沙侵蘑菇、碟状泄水构造、球枕构造、流化砾岩、底辟流化砾岩坨、滑混层、同沉积断层等,均是与地震驱动相适配的变形构造。这些变形构造常沿限定的岩层发育,上、下均为未变形的岩层,显示事件变形特征。大量滑混层褶皱枢纽和球枕构造轴面实测结果显示,它们既没有优势方位,其位态也与古坡向无关,进一步证实最有可能的驱动机制是地震。由于古地震活动直接与东天山造山活动密切相关,因此,研究软沉积物变形构造的时、空发育特征能够成为认识天山造山过程和相关盆地发育的一个新视角。更多还原

【Abstract】 The Lower Jijicaozi group of early Permian age consists predominantly of mudstone and siltstone interbedded with sandstone. It was deposited in the distal slope of the Bogda retroarc collisional foreland basin, which developed along with the north Tianshan orogenic belt. Study of palaeocurrents and facies distribution patterns suggest that the slope was then facing south. More abundant and more varied soft-sediment structures than previously recognized in the lower Jijicaozi group were found during this study. They include loop beddings, hydroplastic folds, sand dikes, mushroom-like intrusions of sand or silt, dish-like water-escape, ball-and-pillow structures, fluidization conglomerate, pockets of fluidization conglomerate associated with diapirs, mixed layers, and syndepositional faults, all of which are consistent with seismogenic origin. They were formed in constrained horizons bounded by undeformed strata, suggesting that they are syndepositional. Field survey and statistical analysis of the fold hinges in the mixed layers and the axial planes of the pillow structures indicate that they are randomly distributed without any preferential direction. This observation demonstrates that all are earthquake-induced. As paleo-earthquakes in the Bogda retroarc collisional foreland basin originated during collision of the Tarim and Junggar blocks, our research on seismogenic soft-sediment structures may provide important clues toward understanding Permian formation of the Paleozoic north Tianshan orogenic belt and its related basins.更多还原