鄂尔多斯盆地东部奥陶系风化壳岩溶古地貌特征及综合地质模型

Karst Paleogeomorphology and Comprehensive Geological Model of the Ordovician Weathering Crust in the Eastern Ordos Basin

密切结合勘探实际,以钻井、测井等地质资料为主要依据,以鄂尔多斯盆地东部奥陶系风化壳为对象,以多学科的地质理论与技术方法为指导,结合盆地构造演化,通过对奥陶系不整合侵蚀面上下地层组合情况的深入分析,把印模法与残厚法结果有机结合,深入探讨了奥陶系风化壳古地貌恢复的方法思路及其古地貌发育特征,探索了古地貌恢复的新方法——综合法,建立了解释和恢复古地貌单元属性的综合地质模型。研究结果表明:盆地东部奥陶系侵蚀不整合面上下的地层组合可以分别被划分为上薄下薄、上厚下厚、上厚下薄、上薄下厚4种基本型式以及上次厚下次薄、上次薄下次薄、上次薄下次厚、上次厚下次厚等8种子模型;相应的古地貌解释包括了岩溶高地、岩溶斜坡、岩溶盆地3个二级古地貌单元以及残丘、台地、残台、阶坪、沟谷、浅洼、深洼等11个三级古地貌单元。岩溶高地出现于研究区西南角,分布局限;岩溶斜坡占据了研究区的大部分,其主力地貌单元为斜坡台地与斜坡阶坪;岩溶盆地位于研究区东部,其主力地貌单元为盆地浅洼。

Combineing closely the practical exploration and guided by multidisciplinary geological theory and technology,a comprehensive geological model has been set up to explain and restorepaleogeomorphology unit attributes of the Ordovician weathering crust of eastern Ordos basin. Meanwhile,according to drilling and logging geologic data,authors also combine basin tectonic evolution with results of ＂impression method＂organic integration and results of ＂residual thick method＂,discuss the methods and thinking of Ordovician weathering crust paleogeomorphology restoration,and its ancient landscape development characteristics through in-depth analysis of the stratigraphic combination under and above Ordovician unconformity erosion surface,and explore a new method of palaeogeomorphologic reconstruction-＂synthetic method＂.The research results show that the stratigraphic combination,under and above Ordovician unconformity erosion surface in the eastern of Ordos basin,can be divide into four basic types including＂up thin down thin＂,＂up thick down thick＂, ＂up thick down thin＂,＂up thin down thick＂,and eight sub models which were＂up relative thickening down relative thinning＂,＂up relative thinning down relative thinning＂,＂up relative thinning down relative thickening＂, ＂up relative thickening down relative thickening＂,etc.The corresponding paleogeomorphology explanation includes three two-level paleogeomorphology units as karst highland, karst slope,karst basin,and eleven three-level paleogeomorphology units including monadnock, tableland,residual tableland,level terrace,cheuch,shallow depression,deep depression etc.The Karst highlands occurs restrictively in the southwestern research area.The Karst slope occupies most of the study area where the main paleogeomorphology units were slope tableland and slope level terrace.The Karst basin is located in the eastern study area and the main paleogeomorphology units include basin shallow depression.