Mid-triassic shallow marine evaporites and a genetic model for evaporation during regional compression (Lower Yangtze Basin, Anhui, China)

Three lines of evidence show that the shallow marine carbonates and sulfates of the mid-Triassic Dongmaanshan Formation of the Lower Yangtze Basin, Anhui, China, were deposited during regional compression. Deposition took place at the onset of collision on the shelf of the Yangtze Block, which was underriding the North China Block. The geological circumstances of this very specific situation are outlined, and a genetic model ("colliding shelf model") is proposed. The model predicts a low probability of rock salt formation. However, halite was precipitated west of the study area.