文摘
We obtained bulk-sediment 未18O and 未13C data from biostratigraphically-constrained Tethyan marine sections at Aghia Marina (Greece), Guri Zi (Albania), and Brumano and Italcementi Quarry (Italy), and revised the published chemostratigraphy of the Pizzo Mondello section (Italy). We migrated these records from the depth to the time domain using available chronostratigraphic tie points, generating Ladinian-Rhaetian 未13C and 未18O records spanning from ~ 242 to ~ 201 Ma. The 未18O record seems to be affected by diagenesis, whereas the 未13C record appears to preserve a primary signal and shows values increasing by ~ 1鈥?in the Ladinian followed by an ~ 0.6鈥?decrease across the Ladinian-Carnian boundary, followed by relatively constant (but oscillatory) Carnian values punctuated by a negative excursion at ~ 233 Ma in the early Carnian, a second negative excursion at ~ 229.5 Ma across the early-late Carnian boundary, and a positive excursion at ~ 227 Ma across the Carnian-Norian boundary. The Norian record is characterized by a long-term decreasing trend and a negative excursion at ~ 216 Ma. Rapid increases and decreases in 未13C have been observed in the Rhaetian, but these may be at least in part due to mixing of different sources of carbonate carbon with different 未13C values. Our Triassic 未13C record has been compared to data from the literature, and a composite 未13C record spanning the last ~ 242 Myr of Earth's history has been generated. This composite record shows a sequence of dated 未13C trends and events that can be used for stratigraphic correlation as well as for a better understanding of the global carbon cycle in the Mesozoic-Cenozoic.
