Abstract:
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.