Abstract
Microbial-sponge reef mounds of the Carnian, Late Triassic, Maantang Formation crop out along the northwestern margin of the Sichuan Basin in South China. Samples from three mounds have been investigated and their ostracod assemblages are here described for the first time. Thirty-three species are present, distributed into 19 genera, including five newly described species:Carinobairdiacabralaen. sp.,Hiatobairdia senegasin. sp.,Hiatobairdiazhengshuyingin. sp.,Hungarella gommeriin. sp,Pontocyprella goussardin. sp. While most of the encountered genera are already known from the Carnian stage worldwide, the Maantang assemblages are precursors in providing the oldest occurrences of the family Schulerideidae, typical of the Middle and Late Jurassic of Europe, and of the genusCarinobairdia, which was until now restricted to the Norian-Rhaetian interval. These records demonstrate the underestimated importance of the easternmost Tethys in the early Mesozoic evolution of marine ostracods. Some important Jurassic European taxa might have originated on the eastern margin of the Tethys during the Carnian, migrated to the western Tethys later during the Late Triassic and diversified there up to the record known for the European Jurassic. Microbioerosion trace fossil analysis of associated brachiopod shells revealedOrthogonum giganteumas the sole identifiable ichnotaxon and represents the first record of this ichnospecies in Triassic strata. The complete absence of microborings produced by phototrophic trace makers points towards aphotic depths for the deposition of the Maantang Formation, providing independent evidence suggesting that typical shallow water ostracods (Carinobairdia, Schulerideidae) radiated in relatively deep settings.
Highlights
Comprehensive research on Triassic marine ostracods has been carried on mainly in the 1960s and 1970s and established the baseline of our understanding of their global distribution (Kristan-Tollmann, 1988)
To fill in this gap, we report on the first assemblages of ostracods of Carnian (Late Triassic) age from siliceous sponge-microbe reef mounds of the Maantang Formation of Sichuan Province, South China
During the Late Carnian, a hexactinellid-thrombolite reef mound tract developed along the northwestern margin of the Sichuan Basin, at the transition between the Chuan Dian Shelf in the east and the SongpanGanzi deep marine Trough in the west, which was connected with the Tethys
Summary
Comprehensive research on Triassic marine ostracods has been carried on mainly in the 1960s and 1970s and established the baseline of our understanding of their global distribution (Kristan-Tollmann, 1988). Our knowledge of the emergence of Mesozoic taxa is largely dominated by westernTethys localities and the importance of the eastern-Tethys might be underestimated, as was already hypothesized by Bate (1977) and Lord (1988) To fill in this gap, we report on the first assemblages of ostracods of Carnian (Late Triassic) age from siliceous sponge-microbe reef mounds of the Maantang Formation of Sichuan Province, South China. During the Late Carnian, a hexactinellid-thrombolite reef mound tract developed along the northwestern margin of the Sichuan Basin, at the transition between the Chuan Dian Shelf in the east and the SongpanGanzi deep marine Trough in the west, which was connected with the Tethys These mounds were discovered during geologic mapping in 1974–1976 (Wu et al, 1977) and have been studied thoroughly since This occurrence is in line with other fossil groups such as crinoids (Hagdorn, 2011) and microbioerosion trace fossils reported here: they provide an important support to the assumption of Bate (1977) and Lord (1988) that ancestral stocks of Jurassic lineages might have been introduced into the northwest Europe from the eastern Tethys during the Late Triassic
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
