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

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 190Ma with two peak ages of 195Ma 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 peakages 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 Himalay an tectonic event mainly occurred between 65Ma and 5Ma having peak ages of 55Ma,25Ma and 5Ma.Especially,145Ma peak of fered by zircon and apatite fission track indicated a key tectonic event of the Mesozoic-Cenozoic in Ordos basin.