Cretaceous growth strata in terrigenous basins in the East Yangtze Block: A response to Early Cretaceous extension in Southeast China

Abstract

Cretaceous syntectonic growth strata in terrigenous basins in Southeast China have scarcely been reported in previous studies. This work focusses on the growth strata of the Early Cretaceous red beds in the East Yangtze Block (EYB), especially in the Huangshan Basin in southern Anhui Province, to help determine the Late Mesozoic tectonic domain and the precise timing of the initiation of extensional tectonics in Southeast China. Field observations show that the dip angles of the red conglomerate‐bearing sandstones from the lower part of the Huizhou Fm. vary from 49° to gentle dips towards the basin centre and that the visible and estimated thickness within a single bed increases slightly downward from the upper to the lower part. These characteristics indicate that the sedimentary area of the Early Cretaceous Huizhou Formation (Fm.) has undergone an extensional process with the expansion and deepening of the sedimentary basin by rotation of the border surface (limb) and thus deposited the extension growth strata simultaneously with (or closely after) the 139 Ma Shiling volcanic activity. Caused by a NW‐SE‐oriented extensional stress field since ca. 140 Ma, a model in which NE‐SW‐oriented tectonic lines transform to E‐W‐trending tectono‐magmatic belts by intersecting and inheriting the previous E‐W‐trending tectonic fabrics is established in the present work. Consequently, these phenomena are influenced by Palaeo‐Pacific Plate rollback and the inheritance of a structural framework from the regional basement strata and deformation series.