Biological Diversity, Crisis and Recovery in the Phong Son Formation (D<sub>3</sub>-C<sub>1</sub> <i>Ps</i>), Thua Thien-Hue Province, North-Central Vietnam

Abstract

The present of Upper Devonian and Lower Carboniferous sediments and fossils in Hue City, Van Xa area, Huong Thuy District; Thanh Tan, Hien An villages, Dong Lam Quarry, Phong Dien District, Thua Thien-Hue Province has been noted in recent years depend on explosion of limestone underlying the Quaternary cover for cement technology and building. The Phong Son Formation has been established with two members: the underlying Van Xa Member composed of mainly limestone, 280 m thick, containing abundant Famennian brachiopods, crinoids, gastropods; the overlying Hien An Member composed of limestone intercalated with black shale, 210 m thick, containing abundant brachiopods, crinoids, bryozoans, stromatoporoids, corals, trilobites, foraminiferans, gastropods of Latest Famennian-Tournaisian age. Over 1000 macrofossil examples were collected from both the Van Xa Member and Hien An one for analyzing biological diversity, crisis and recovery of all macrofossil group of stratigraphical level of the Phong Son Formation (D₃-C₁ <i>ps</i>). In the Famennian stage, the diversity is related to representatives of phyla Brachiopoda, Cnidaria, Mollusca; belonging to the <i>Cyrtospirifer</i>-<i>Yunnanella</i> Assemblage. In the Tournaisian stage, the recovery and diversity is related to reprensentatives of phyla Porifera, Cnidaria, Arthropoda, Brachiopoda, Bryozoa, Mollusca, and Echinodermata; belonging to the <i>Leptagonia-Phillipsia </i>Assemblage. The crisis at the DCB of the Phong Son Fm is well displayed in phyla Brachiopoda, Cnidaria and Porifera.