Oral Paper

         Paleobotany

Late Triassic floras from Guangdong, South China: biostratigraphical context and palaeoenvironmental implications

Presenting Author
Xiaoqing Zhang
Description
Triassic-Jurassic deposits are well developed in Guangdong Province, South China. In particular, the Upper Triassic marine and terrestrial alternating coal-bearing strata yield diverse and abundant plant, ammonite and bivalve fossils. These strata provide a significant reference for the study of palaeoenvironmental variations across the T-J transition and extinction event in the lower latitude regions. In this paper, we review the major progress on Late Triassic floral studies in this area. Specifically, we compare plant assemblages from different fossil sites in central and northern Guangdong which have been dated with marine fauna such as ammonites and bivalves. To date, about 155 species belonging to 57 genera of fossil plants have been reported. In ascending order, four plant assemblages can be recognized in the Late Triassic deposits from the Guangdong area, including the Pachypteris-Lindleycladus assemblage (Early Carnian), the Pterophyllum first common occurrence assemblage (Early-Late Carnian), the Clathropteris-Otozamites assemblage (Late Carnian) and the Danaeopsis first occurrence assemblage (Rhaetian). These assemblages show coordinated taxonomic variation with regards to sea level changes. The Late Triassic flora in Guangdong demonstrats a predominance of Bennettitales and ferns, followed by horsetails, seed ferns, cycads, ginkgos and conifers. In general, the Late Triassic climate in the Guangdong region was mainly humid and warm, either tropical or subtropical. The fossil plant and palaeomagnetic evidence prove that the central and northern Guangdong region was located at approximately the same latitude as it is today and formed the southern coastline of the South China Block during the Late Triassic. Palaeogeographically, the transgression started at the end of early Carnian and the south coastal terrane consisted of a western bay, a peninsula and an eastern bay. During the regression period, post-Rhaetian, the bays evolved into a gulf coastal plain.