Detrital composition of Lower-Middle Jurassic sandstones from Huangshi, Hubei: Implication for provenance types and geotectonics

Abstract

The detrital modes of the sandstones from the south basin of Dabie (大别) orogenic belt during the Early-Middle Jurassic are complex due to multiple supplying. Detrital compositions of medium-coarse sandstones from the Lower-Middle Jurassic, Huangshi (黄石), show three main provenances: recycled ororgen, volcanic arc (arc orogen), and continental block on the bases of the Dickinson discriminating diagrams of modal composition and analysis of sandstone petrofacies. Combined with sparse published paleocurrent data, geotectonic setting of the study area, and the unpublished detrital zircon age data, the positions of the main provenances are inferred as follows: coastal orogenic belt (COB) in the East China provided detritus as the recycled orogen provenance; Dabie orogenic belt (DOB) to the north was the source of volcanic arc (arc orogen) materials; and the continental block clasts were likely from the uplift of the Yangtze basement (UYB) (Jiangnan (江南) uplift). Six sedimentary cycles are recognized in the studied section, one in Wuchang (武昌) Formation, and five in Huajiahu (花家湖) Formation. During the deposition, the three main provenances play different roles. The quantitative petrofacies analysis revealed distinct changes of the effect from each source, that is, 61.9% (Cycle I)→54.5% (Cycle III)→50% (Cycle IV)→57.9% (Cycle V)→14.3% (Cycle VI), 14.3% (Cycle I)→21.2%( Cycle III)→40% (Cycle IV)→36.8% (Cycle V)→14.3% (Cycle VI), and 23.8% (Cycle I)→24.2% (Cycle III)→10% (Cycle IV)→5.3% (Cycle V)→71.4% (Cycle VI) from COB, DOB, and UYB, respectively. The results show that (1) COB behaved in considerable activation during the Early Jurassic but weakened in the Middle Jurassic; (2) the vigorous tectonic uplift of DOB initiated in Middle Jurassic; and (3) UYB was in stabilization basically from the Early to Middle Jurassic.