Meso-Cenozoic peak-age events and their tectono-sedimentary response in the Ordos basin

Abstract：An integrated analysis of the distribution of the apatite and zircon fission track ages and its relation to coarse clastic sediments and stratigraphic unconformity provides the chronological constraint on the Meso-Cenozoic tectonic events and their sedimentary response in the Ordos basin. The Indosinian tectonic event mainly occurred at 230-190 Ma with two statistic peak ages (195 and 215 Ma). On the southwestern margin of the basin there occur Late Triassic coarse clastic molasse-like deposits, which have a disconformable contact with the overlying strata. The Yanshanian tectonic event mainly occurred at 150-85 Ma with three statistic peak ages (145, 120 and 95 Ma) in the mid-late Yanshanian. On the southwestern margin of the basin there occur middle Yanshanian Late Triassic and Early Cretaceous coarse clastic molasse-like deposits and angular unconformity. The Himalayan tectonic event is mainly marked by polycyclic tectonic uplift of the basin at a regional scale, including at least three statistic peak age events at 55, 25 and 5 Ma respectively. The peak age of 145 Ma offered by zircon and apatite fission tracks and its related angular unconformity, overthrusting and regional magmatic activity all indicate a key Meso-Cenozoic tectonic reworking event in the Ordos basin.