| 鄂尔多斯盆地西缘奥陶系拉什仲组深水水道沉积类型及演化 |
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| 引用本文： | 李华,何幼斌,冯斌,郝烃,苏帅亦,张灿,王季欣.鄂尔多斯盆地西缘奥陶系拉什仲组深水水道沉积类型及演化[J].地球科学,2018,43(6):2149-2159. |
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| 作者姓名： | 李华 何幼斌 冯斌 郝烃 苏帅亦 张灿 王季欣 |
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| 作者单位： | 1.长江大学地球科学学院, 湖北武汉 430100 |
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| 基金项目： | 国家自然基金项目41472096湖北省教育厅科学研究计划中青年人才项目Q20171308长江青年基金2015cqn26国家自然基金项目41502101湖北省创新群体基金2015CFA024 |
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| 摘 要： | 深水水道沉积是深水区重要沉积类型之一，对其形成机制研究不仅能提高深水沉积认识，还能为油气勘探提供帮助.以露头资料为基础，对鄂尔多斯盆地西缘奥陶系拉什仲组深水水道形成机制进行了详细研究.拉什仲组岩性以灰绿色页岩及砂岩为主，另见少量的粉砂岩及砾岩.槽模、交错层理、粒序层理及变形构造等发育.总体反映深水沉积环境，重力流沉积较为发育.其中，深水水道沉积极为典型.根据形态、结构及沉积方式等，将研究区深水水道沉积划分为限制型和非限制型水道沉积.前者包括复合型及垂向加积型水道沉积，后者由迁移型及孤立型小水道沉积组成.复合型水道沉积厚约7.5 m，岩性以粗砂岩为主，底部见砾岩，水道轴部沉积、次级水道及水道-堤岸复合体沉积发育，可分为早期、中期和晚期.垂向加积型水道沉积宽为12.4 m，厚为1.3 m，宽深比为9.54，以中砂岩及细砂岩为主，水道内部以层状砂岩充填为主.迁移型水道沉积宽为6.9~12.3 m，厚为0.23~0.73 m，宽厚比14.11~53.48，以中-细砂岩为主，具有明显的北西向迁移特征；孤立型小水道沉积宽为0.5~0.6 m，厚为0.15~0.25 m，宽厚比为2.4~3.33，多为细砂-粉砂岩组成，透镜状，规模小.重力流爆发初期，能量高，侵蚀作用强，发育复合型及垂向加积型水道沉积；重力流中-后期，能量逐渐降低，迁移型水道沉积开始发育；在重力流后期及末期，其能量进一步降低，发育孤立型小水道沉积.而在空间位置上，复合型及垂向加积型水道沉积多发育在斜坡中上部，中部及下部发育迁移型水沉积道，斜坡脚及深海盆地以孤立型小水道沉积最为发育.
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| 关 键 词： | 水道 浊流 拉什仲组 奥陶系 鄂尔多斯盆地 石油地质 |
| 收稿时间： | 2017-12-11 |
Type and Evolution of Deep-Water Channel Deposits of Ordovician Lashizhong Formation in Western Margin of Ordos Basin |
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| Abstract: | The deep-water channel sedimentary type is one of important sedimentary types in the deep-water zone. Research on the mechanism of deep-water channel not only can improve acquaintance of deep-water deposits, but also is helpful to oil and gas exploration. Mechanism of the deep-water channel of the Ordovician Lashizhong Formation in western margin of the Ordos basin was detailedly worked based on outcrop. The lithology of Lashizhong Formation consists of greyish-green mudstone and sandstone and few siltstone and conglomeration with flute cast, cross bedding, graded bedding and deformation structure, which suggests deep-water environment. Gravity flow deposits are well developed. The deep-water channel deposits are also typical. It is found in this study that the deep-water channel deposits could be divided into confined and non-confined channels, based on the morphology, structure, and sedimentary style. The former includes complex and vertical aggradation channel deposits. The latter can be subdivided into migrational channel and isolated small channel deposits. The lithology of complex channel deposits is coarse sandstone and conglomeration in the bottom, containing channel axis deposit, secondary channel and channel-levee system deposits, with 7.5 m in width, which could be divided into developmental, mature and decline phases. The vertical aggradation channel deposits are bedded medium and fine sandstone, with 12.4 m in width, 1.3 m in thickness, and the width-to-thickness ratio of 9.54. The migrational channel is medium to fine sandstone with northwestward migration. The width is 6.9-12.3 m, the thickness is 0.23-0.73 m, and width-to-thickness ratios range from 14.11-53.48. The isolated small channel deposits consist of fine sandstone and siltstone, lenticular shaped, small scale with 0.5-0.6 m in width, 0.15-0.25 m in thickness, and the width-to-thickness ratios of 2.4-3.33. The complex and vertical aggradation channel deposits develop when gravity flow outbreaks. Its energy is usually high with strong erosive power. The migrational channel deposits develop when gravity flow is in middle to later phases when their energy is damped. And the isolated small channel deposits develop during last phase of gravity flow. Its energy further decreases. In the spatial position, the complex and vertical channel deposits usually develop in the middle-upper part of slope. Migrational channel deposits form in the middle-lower slope, and isolated small channel deposits commonly grow in toe of slope and deep-water basin. |
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