Biotic collapse

Biotic extinctions of varying magnitudes are associated with many era boundaries (see Section 1.5.5), and there are often accompanying excursions in the carbon isotopic record. Such isotopic excursions reflect environmental events of sufficient size to have an impact on the global carbon cycle. However, it is not always easy to determine whether the excursion was the result of the extinction event (due to biotic collapse), is attributable to some other consequence of the event leading to the extinction or may even be largely unrelated to the extinction event. The problems associated with interpretation of isotopic excursions are demonstrated by three important boundary events in the following subsections. 

Fig. 6.29 Idealized representation of C isotopic gradients for marine carbonate under normal photosynthesizing conditions (e.g. modern ocean), after biotic collapse (Strangelove ocean) and for dominance of microbial respiration in surface waters (after Hsii McKenzie 1990).

Emery, K. F., L. E. Wright, and H. Schwarcz (2000), Isotopic analysis of ancient deer bone Biotic stability in collapse period maya land use,. Archaeol. Sci. 27(6), 537-550. 

Twitchett R.J., Looy C.V., Morante R.,Visscher H., Wignall P.B. (2001) Rapid and synchronous collapse of marine and terrestrial ecosystems during the end-Permian biotic crisis. Geology 29, 351—4. 

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