255 / 2022-03-30 22:36:13

鄂尔多斯盆地西南缘上奥陶统平凉组岩石特征及沉积环境

浊流沉积；海底扇；深水斜坡；平凉组；上奥陶统；鄂尔多斯盆地

In order to study the petrological characteristics and sedimentary environment of the Upper Ordovician Pingliang Formation in the southwest margin of Ordos Basin, the petrological characteristics, sedimentary facies division, sedimentary environment analysis and dictating factors of the study area were studied by using sedimentology theories and methods based on outcrops, paleontology and grain-size analysis data. The result shows that:(1) The Pingliang Formation in the study area can be divided into four facies and two facies associations. Facies 1 of sandstone with massive bedding indicates turbidites. Facies 2 of sandstone with parallel bedding reflects low density turbidites. Facies 3 of siltstone with parallel bedding represents distant turbidites. Facies 4 of mudstone with horizontal bedding points to deep water autochthonous sediments. Facies association 1 is proximal lobe deposition, and facies association 2 is distal lobe deposition; (2)Based on an analysis of the lithologic character, sedimentary structure, palaeobiologic fossils and grain size parameters, it is believed that the sedimentary environment of Pingliang Formation in the study area is mainly deep-water slope environment; (3)The sedimentary facies of Pingliang Formation in the study area is submarine fan, which can be further divided into two subfacies: middle fan and lower fan, and two microfacies: proximal lobe deposition and distal lobe deposition; (4)Gravity flow deposits are developed in Pingliang Formation in the study area, which is mainly controlled by the change of the relative sea level, tectonic movement and source supply.