鄂尔多斯盆地及周缘地区上石炭统沉积特征

鄂尔多斯盆地及周缘地区上石炭统本溪组(羊虎沟组)沉积特征对于预测其砂体展布、油气勘探具有重要意义。在野外地质考察、岩心观察和薄片研究的基础上,对本溪组(羊虎沟组)进行了岩石学特征、沉积相类型和空间展布规律等方面的研究。本溪组(羊虎沟组)岩石类型主要为灰白色中-粗砂岩和深灰色、灰黑色泥岩、粉砂质泥岩、泥质粉砂岩,夹多层煤、灰岩和泥灰岩;主要发育浅海陆棚、障壁岛、潮坪、潟湖和扇三角洲沉积。鄂尔多斯盆地中央古隆起西部主要发育扇三角洲、障壁岛和潟湖沉积相,东部主要发育扇三角洲、潟湖、障壁岛和浅海陆棚沉积相,中间过渡带主要为潮坪沉积。自北向南依次发育扇三角洲平原、扇三角洲前缘、潮坪、潟湖和浅海陆棚等沉积。总体上来讲,本溪组(羊虎沟组)为一套海陆交互相沉积建造,具有东、西分异的沉积格局。

Sedimentary characteristics of the upper Carboniferous in Ordos Basin and its adjacent areas

Defining the sedimentary characteristics of the Benxi( Yanghugou) Formation of the upper Carboniferous in Ordos Basin and its adjacent areas is of great significance for predicting its sand-body distribution and hydrocarbon exploration. In this paper,the petrological characteristics,sedimentary facies types and spatial distribution of the Benxi( Yanghugou) Formation are studied,based on field geological investigation,core observation and thin section identification. It shows that the Benxi( Yanghugou)Formation mainly consists of gray-white medium to coarse-grained sandstones,dark gray and gray-black mudstones,silty mudstones and argillaceous siltstones, with multiple layers of coals, limestones and marls interbedded with these above-mentioned rocks. In the study area,the shallow sea shelf,barrier island,tidal flat,lagoon and fan delta deposits were mainly developed. The fan delta,barrier island and lagoon mainly developed in the west of the central paleo-uplift,the fan delta,lagoon,barrier island and shallow sea shelf mainly developed in the east of the central paleo-uplift,and the tidal flat mainly developed in the intermediate transition zone. It also shows that fan delta plain,fan delta front,tidal flat,lagoon and shallow sea shelf developed successively from north to south. Generally,the Benxi( Yanghugou) Formation is a set of marine-terrigenous transitional facies with the sedimentary pattern divergence from east to west.