Strike-slip origin of Cretaceous Mazhan Basin, Tan-Lu Fault Zone, Shandong, east China

The Mazhan Basin, Shandong Province, China, is located between the main fau lts, F-3 and F-4, of the Tan-Lu Fault Zone. It is an elongated basin more t han 60 km in length and 8 km in width and contains a series of typical cont inental sediments (the Upper Cretaceous Wangshi Group). This series was div ided into three sedimentary facies associations: conglomerate facies associ ation; sandstone facies association of alluvial fan to lake margin environm ent; and siltstone facies association of lacustrine origins. Their zonal di stribution pattern may represent a contemporaneous heterotopic facies due t o a lateral facies change from margins to axis of the basin. Their stratigr aphic sequence becomes younger northward along the boundary faults. This su ggests that the depocenter of the fan-lake system tends to migrate northwar d along F-3. From the asymmetric features (i.e. basin shape, lithofacies di stribution, facies change) the Mazhan Basin can be explained by progressive subsidence at the Tangwu releasing bend of F-3 with sinistral strike-slip movement. Judging from the fission track (FT) ages from the Wangshi Group, it was concluded that a sinistral strike-slip movement along the main fault , F-3 of the Tan-Lu Fault in Shandong, has lasted until the Late Cretaceous . Its displacement is estimated to be larger than the migrated distance, 60 km, of the depocenter of the Mazhan Basin.