The Triassic-Jurassic(Tr-J) boundary marks a major extinction event,which(～200 Ma) resulted in global extinctions of fauna and flora both in the marine and terrestrial realms.There prevail great challenges in determining the exact location of the terrestrial Tr-J boundary,because of endemism of taxa and the scarcity of fossils in terrestrial settings leading to difficulties in linking marine and terrestrial sedimentary successions.Investigation based on palynology and bivalves has been carried out over a 1113 m thick section,which is subdivided into 132 beds,along the Haojiagou valley on the southern margin of the Junggar Basin of the northern Xinjiang,northwestern China.The terrestrial Lower Jurassic is conformably resting on the Upper Triassic strata.The Upper Triassic covers the Huangshanjie Formation overlaid by the Haojiagou Formation,while the Lower Jurassic comprises the Badaowan Formation followed by the Sangonghe Formation.Fifty six pollen and spore taxa and one algal taxon were identified from the sediments.Based on the key-species and abundance of spores and pollen,three zones were erected:the Late Triassic(Rhaetian) Aratrisporites-Alisporites Assemblage,the Early Jurassic(Hettangian) Perinopollenites-Pinuspollenites Assemblage,and the Sinemurian Perinopollenites-Cycadopites Assemblage.The Tr-J boundary is placed between bed 44 and 45 coincident with the boundary between the Haojiagou and Badaowan formations.Beds with Ferganoconcha(?),Unio-Ferganoconcha and Waagenoperna-Yananoconcha bivalve assemblages are recognized.The Ferganoconcha(?) bed is limited to the upper Haojiagou Formation, Unio-Ferganoconcha and Waagenoperna-Yananoconcha assemblages are present in the middle and upper members of the Badaowan Formation.The sedimentary succession is interpreted as terrestrial with two mainly lake deposit intervals within Haojiagou and Badaowan formations,yielding fresh water algae and bivalves.However,the presence of brackish water algae Tasmanites and the marine-littoral facies bivalve Waagenoperna from t
Biostratigraphy and chronostratigraphy are common means of subdividing rock strata. The biostratigraphic succession and chronostratigraphic scheme are regarded as the basis for the subdivision and correlation of regional and global stratigraphic units. This paper reviews research on the biostratigraphy and chronostratigraphy carried out in the Jiangnan Slope Belt, South China since 1978, and, in particular, the biostratigraphic succession and chronostratigraphic scheme developed in the last decade. The updated biostratigraphic succession of South China includes 36 biozones, the base of each of which is defined by the first appearance of a single taxon (index fossil), and a poorly fossiliferous interzone. The updated chronostratigraphic scheme of South China comprises 4 series and 10 stages, embracing 3 global chronostratigraphic units, the Guzhangian Stage, Furongian Series, and Paibian Stage, and 2 GSSPs, all of which are erected in northwestern Hunan and 2 International Tie Points recognized in sections also in northwestern Hunan and each was accepted by the International Subcommission on Cambrian Stratigraphy for defining the base of the global stage. The biostratigraphic and chronostratigraphic systems are recognized as Chinese standards both domestically and worldwide. Future research is suggested for improving the two sets of stratigraphic standards.
