Quantitative statistics of sandy and gravelly wedges in the Longmenshan foreland basin, Sichuan

The sedimentary records of the Upper Triassic-Jurassic strata in the Longmenshan foreland basin, western Sichuan show that from the Early and Middle Jurassic onwards, although the general stratigraphic configuration appears to be tabular, abundant alluvial coarse-grained fragments occur along the margin of the basin on the orogenic side.The sandy and gravelly wedges originated in the north-central segment of the Longmenshan front during the Early and Middle Jurassic, and the migrated southwestwards during the Late Jurassic-Early Cretaceous. The provenance migration is accounted for the strike-slipping of the Longmenshan orogenic belt; this is expressed by the spatio-temporal framework of the sandy and gravelly wedges of varying ages, localities and compositions.