Abstract

Stratigraphic units have been formed in a specific condition and geological history. The sedimentary properties such as grain size, roundness, chemical composition, especially the presence of biofossil will significantly help geoscientists reconstruct the environmental condition of an area on the Earth surface. The Hạ Lang Area, where was deposited by the Middle-Upper Paleozoic sedimentary formations, which were formed during the Early - Lare Devonian and they are typically characterized by sedimentary composition and fossil. These are the basis for interpretation of the paleogeography of these formations.