鄂尔多斯盆地中新生代构造事件的峰值年龄及其沉积响应

Peak Ages and Sedimentary Responses of the Mesozoic-Cenozoic Tectonic Events in Ordos Basin

通过锆石-磷灰石裂变径迹的峰值年龄与地层不整合事件的综合分析,提供了鄂尔多斯盆地中新生代构造事件的年代学约束及其沉积响应特点.印支期构造事件主要发生在230～190 Ma,包含215 Ma±和195 Ma±两个峰值年龄,在盆地西南缘发育晚3叠世粗碎屑类磨拉石建造.燕山期构造事件主要发生在燕山中晚期的150～85 Ma,包含145 Ma±、120 Ma±和95 Ma±3个峰值年龄,在盆地西南缘发育燕山中期的芬芳河组和志丹群的粗碎屑类磨拉石建造.喜山期构造事件主要发生在65～5 Ma,包含55 Ma±、25 Ma±和5 Ma±3个峰值年龄.其中,锆石和磷灰石叠合分布的峰值年龄(145 Ma±),指示了鄂尔多斯盆地中新生代的一次关键性构造变革事件.

Statistic analysis of 131 age data from apatite and zircon fission tracks, combined with the analysis of sedimentary type and stratigraphic unconformity, the peak ages and sedimentary responses of the Mesozoic-Cenozoic tectonic events in Ordos basin has been determined. The Indosinian tectonic event mainly occurred in an age range from 230 to 190 Ma with two peak ages of 195 Ma and 215 Ma. The ages are matched up with a set of Late Triassic molasses deposit on the southwestern margin of the basin during. The Yanshanian tectonic event is dated in an age range of 150~85Ma with three peak ages of 145Ma, 120Ma and 95 Ma. All these ages are associated with 2 Mid-Yanshanian molasses deposits respectively in the southwestern margin of the basin. The Himalayan tectonic event mainly occurred between 65 Ma and 5Ma having peak ages of 55Ma, 25Ma and 5Ma. Especially, 145 Ma peak offered by zircon and apatite fission track indicated a key tectonic event of the Mesozoic-Cenozoic in Ordos basin.