Late Devonian-Early Carboniferous Ostracods in Dushan, Guizhou Province

Ostracods of the Late Devonian-Early Carboniferous are reported for the first time from Qilinzhai section in Dushan, Guizhou, South China. A total of 29 species belonging to 16 genera in 6 superfamilies, including one new species (i.e., Bairdia qilinzhaiensis sp. nov.) are identified and figured from the Tangbagou Formation in the Qilinzhai Section. The ostracod assemblage is dominated by the Order Podocopida (22 species belonging to 10 genera), with fewer Orders Palaeocopida (4 species belonging to 3 genera) and Platycopida (3 species belonging to 3 genera). Based on the characteristics of the ostracod assemblage, combined with previous studies on conodonts and carbon isotopes, the age of the Tangbagou Formation is assigned to the Late Devonian to the Early Carboniferous, and the Devonian-Carboniferous boundary(D-CB) approximately located at 13 meters in the lower limestone-mudstone Member of the Tanbagou Formation. The ecological assemblage of ostracods belongs to the Smooth-podocopid association (i.e., Eifelian Mega-Assemblage), which implies an offshore environment for the Tangbagou Formation. The ostracod assemblage of the Tangbagou Formation shows similarities with contemporaneous assemblages from Russia and Western Europe, suggesting that the transgression beginning in the Early Carboniferous (Tournaisian) facilitated close biogeographic connections between the ostracod faunas of South China and those of the Euramerican regions. The ostracod fauna near the D-CB in the Qilinzhai section may have been influenced by the Hangenberg Event, exhibiting a low abundance and a rapid recovery pattern.