Frýda J, Lehnert O, Frýdová B, Farkaš J, Kubajko M (2021)
Publication Type: Journal article
Publication year: 2021
Book Volume: 564
Article Number: 110152
The Ludfordian (late Silurian) records one of the largest perturbations in the Phanerozoic marine carbon cycling, the mid-Ludfordian positive δ13Ccarb excursion (MLCIEcarb), which occurred in the aftermath of the Lau/Kozlowskii Bioevent (LKB). There are still controversies regarding origin of the MLCIE and its possible causal link(s) with respect to the preceding LKB. Surprisingly, the isotope fractionation of carbon between inorganic and organic carbon pools during the MLCIE was not investigated in detail. To constrain better this parameter of marine C cycle, its linkage to the LKB, and local sulfur cycle, we analysed high-resolution δ13Ccarb, δ13Corg, and δ34Spy records in the Prague Basin (peri-Gondwana) representing one of the most complete records of the MLCIEcarb in the world. Evaluation of these high-resolution δ13Corg and δ13Ccarb records reveals their tight coupling, which in turn indicates the photosynthetic origin of the MLCIEorg via links to primary production and changing rates of organic carbon burial. On the other hand, our data also reveal a short-term decoupling of the δ13Corg and δ13Ccarb records preceding the MLCIE which may have been related to a purported increase in atmospheric pCO2 levels or anoxic event. The peak of the Δ13C anomaly exactly coincides with the LKB and, therefore, for the first time suggests a tight link between the change in marine carbon cycling and the bioevent. Subsequent rapid drop of the Δ13C values (and by inference also atmospheric pCO2) fits well with a rapid cooling and globally documented regression reported for this time interval. Finally, the documented strong coupling of δ13Ccarb and δ34Spy records during the MLCIE points to an intensive microbial sulfate reduction which should increase carbonate alkalinity input, thus contributing to formation of authigenic carbonates and an increase in δ13C values of DIC (and anticipated seawater carbonate saturation). The coupling of δ13Corg and δ34Spy values suggests a global enhancement of organic carbon and pyrite burial likely driven by an expansion of euxinic (anoxic and sulfidic water column) conditions in the oceans. Present study of C and S isotope variations during the MLCIE reveals for the first time a tight link among carbon and sulfur cycling, global cooling, and reorganization of faunal communities and fits well with purported seawater carbonate hypersaturation at the onset and during MLCIE.
Frýda, J., Lehnert, O., Frýdová, B., Farkaš, J., & Kubajko, M. (2021). Carbon and sulfur cycling during the mid-Ludfordian anomaly and the linkage with the late Silurian Lau/Kozlowskii Bioevent. Palaeogeography, Palaeoclimatology, Palaeoecology, 564. https://dx.doi.org/10.1016/j.palaeo.2020.110152
Frýda, Jiří, et al. "Carbon and sulfur cycling during the mid-Ludfordian anomaly and the linkage with the late Silurian Lau/Kozlowskii Bioevent." Palaeogeography, Palaeoclimatology, Palaeoecology 564 (2021).