鄂尔多斯盆地南部下白垩统演化改造特征

Geologic characteristic and its evolution and reformation of Lower Cretaceous in southern Ordos Basin

目的研究鄂尔多斯盆地南部下白垩统的地质特征,分析其演化历史及后期改造特点。方法运用野外地质观察、地层展布、沉积特征分析及地层剥蚀厚度恢复等方法进行研究。结果盆地南部下白垩统总体经历了宜君洛河—环河华池期及罗汉洞—泾川期两大沉积旋回,呈一东缓西陡的不对称向斜形态;剥蚀厚度恢复表明其东部、南部最大剥蚀量可达2 000多m。结论早白垩世盆地发育于伸展构造环境,晚白垩世以来遭受了多种形式的后期改造,具东强西弱、南强北弱的剥蚀特点;盆地发育鼎盛时期,原始沉积边界东可达今黄河一带,南在今渭河盆地甚或秦岭北麓,西部超覆于西缘逆冲带之上可与六盘山盆地相通。

Aim To study the geological features and its evolutionary history and late reformation of the Lower Cretaceous in the south of Ordos Basin.Methods Detailed field investigation,stratum distribution,sedimentary characteristics analysis and the erosion thickness restoration are adopted.Results The Lower Cretaceous stratum in the south of Ordos Basin has experienced two sedimentary cycle periods of Yijun Luohe-Huanhe Huachi and Luohandong-Jingchuan,which shows the form of east slow and west steeper,as an asymmetric syncline.The erosion thickness restoration indicates that the most erosion thickness may reach to 2000 meters at the eastern and southern side.Conclusion The Lower Cretaceous stratum basin develops in the extended structure environment.It has suffered various forms of late reformation since the Late Cretaceous,which presents the erosion characteristics with east strong and west weak,south strong and north weak.During the heyday development,the original sedimental boundaries may reach to the area of the Yellow River at east,locate in Weihe River basin or even north margin of Qinling Mountain at south,overlap at the western thrust belt and may be interlinked with the Liupanshan basin at west.