A carbonate carbon isotope record for the late Givetian (Middle Devonian) Global Taghanic Biocrisis in the type region (northern Appalachian Basin)
Published:January 01, 2016
James J. Zambito, IV, Michael M. Joachimski, Carlton E. Brett, Gordon C. Baird, Z. Sarah Aboussalam, 2016. "A carbonate carbon isotope record for the late Givetian (Middle Devonian) Global Taghanic Biocrisis in the type region (northern Appalachian Basin)", Devonian Climate, Sea Level and Evolutionary Events, R. T. Becker, P. Königshof, C. E. Brett
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During the Global Taghanic Biocrisis (c. 385 Ma), Middle Devonian faunas worldwide underwent extinction. In the biocrisis type region, the northern Appalachian Basin, biodiversity changes occurred through three bioevents that ultimately resulted in the loss of numerous endemic taxa. Carbon isotope excursions during this biocrisis have been documented in various stratigraphic successions, but never in the type region. Herein, we reconstruct changes in δ13Ccarb from the biocrisis type region and compare these changes to local faunal transitions. An approximately 1.5‰ negative excursion corresponds to the first bioevent, a time of inferred global warming and replacement of most endemic taxa of the mid-palaeolatitude Appalachian Basin by invasive palaeoequatorial taxa. An approximately 2‰ positive excursion is associated with the second bioevent, recognized as a return of the endemic fauna and the loss of invasive taxa. This positive excursion occurs near the Polygnathus ansatus–Ozarkodina semialternans zonal boundary and is recognized elsewhere. Faunal cosmopolitanism associated with the third bioevent corresponds with an inflection in the carbon isotope record from negative to positive trending values, which agrees with a positive carbon record excursion seen elsewhere at the semialternans–Schmidtognathus hermanni zonal boundary. This new carbon isotope record provides an important reference for recognizing this biocrisis in other areas and facies.
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Devonian Climate, Sea Level and Evolutionary Events
The geological and palaeontological records of climate change and evolutionary events reflect Earth’s widely fluctuating climate systems. Past climates hold the clues to understanding future developments. In this context, research on linked climate, biodiversity and sea-level fluctuations of the Devonian contributes to the general knowledge of deep-time climate dynamics. A fruitful co-operation between the International Geoscience Programme IGCP 596 and the International Subcommission on Devonian Stratigraphy (SDS) addressed the complex succession of climate-linked Devonian global events of varying magnitude. The primary goal of IGCP 596 was to assess mid-Palaeozoic climate changes and their impact on marine and terrestrial biodiversity using an interdisciplinary approach. The focus of SDS includes a revision of the eustatic sea-level curve and the integration of refined chrono- and biostratigraphy with modern chemo-, magneto-, cyclo-, event- and sequence stratigraphy. This enabled the much improved dating and correlation of abiotic perturbations, evolutionary changes, organism and ecosystem ranges. Results by 37 authors are presented in 14 chapters, which cover the entire Devonian.