Abstract

After the last Permian formation of limestone, the Southeast region of Viet Nam was covered with a series of clastic sedimentary rocks of Triassic (Vu Khuc, 2000). This region was classified with the sequential rhythm from coarse to fine, including conglomerate, sandstone, and claystone. According to some previous research, this series of sediments belonged to a molasse facies, the marine sedimentary facies characterized by claystone, siltstone containing lime, arranging in rhythm with conglomerate and sandstone (greywacke, arkose). This paper aimed to more precisely elucidate the sedimentary environment of this debris set, Viet Phuong mine. Regarding the texture of sedimentary rocks (Folk, 1974), the sediment was in the sub-mature stage, the moderate sortting (So = 1.15), the particle shape was nearly square, the kurtosis was from -0.19 to +0.4. For tidal environment, sedimentary structures also contributed to the above theory with the characteristic structures of hering-bone cross stratification, convoluted, Convolute Bedding and Flame structures and the presence of Ichnofacies Asterosoma (Cruziana) and Diplocraterion (Skolithos)…Thus, the sediment of Viet Phuong mine was identified with two types of depositional environments: estuary and tide dominated delta from bottom to top.