铜川地区瑶曲延长组剖面砂质碎屑流砂体识别及成因

Identification and genesis of sandy debris flow sandbodies in Yaoqu Yanchang formation,Tongchuan area

鄂尔多斯盆地南部铜川地区延长组剖面发育深水沉积,砂体成因复杂.通过野外地质调查开展砂体结构及沉积机制的研究,以分析砂体成因.结果表明:铜川地区瑶曲延长组长7剖面发育砂质碎屑流砂体,砂体为灰色、褐灰色块状细砂岩,砂体层理不发育,粒序继变不明显,中部可见"漂浮状"的泥质团块或凝灰质团块,底部滑动面明显,有别于浊积砂体.坡折带上未固结充足的砂体及高频的地震活动为形成砂质碎屑流主要因素.

Deep water sediments are developed in Yanchang Formation section of Tongchuan area,southern Ordos Basin.Through field geological survey,the study of sand body structure and sedimentary mechanism is carried out to analyze the genesis of sand body.The results show that:Sandy clastic flow sand body is developed in chang7 section of Yaoqu Yanchang Formation in Tongchuan area.The sand body is gray and brownish gray massive fine sandstone.The bedding of sand body is not developed and the grain sequence is not obvious.There are"floating"argillaceous or tuffaceous masses in the middle and obvious sliding surface at the bottom,which is different from turbidite sand body.The unconsolidated sand body and high frequency seismic activity are the main factors for the Formation of sandy debris flow.