12 - The mid-Permian: major changes in geology, environment, and faunas and some evolutionary implications

Summary

Much attention has recently been given to the major biological changes in the Phanerozoic. The emphasis has been on extinctions, whereas the nature of the recoveries by faunas and floras after the times of major extinctions has not been so fully examined. In this chapter, attention is directed to that latter aspect. Emphasis is also placed on relating the biological developments to the geological changes and examining how those relationships interacted with the environment.

The term “mass extinction” is avoided, because it does not accurately describe most, if not all, of the examples of important extinctions during the Phanerozoic. In a detailed context of time and stratigraphy, it is not easy to say that any change was “abrupt” – see, for example, even the Permian–Triassic extinction (Dickins, 1983; Sweet et al., 1992), often rated as the largest within the Phanerozoic (regarding the Precambrian–Cambrian change as outside the Phanerozoic).

Until recently, correlations involving the mid-Permian (in the twofold Permian subdivision based on the Russian type area) have proved difficult, especially because of the worldwide regression and the associated strong tectonic changes (Dickins et al., 1989). The difficulty in making correlations has obscured both the geological and biological changes. A more nearly satisfactory resolution has become possible by considering the geological and biological aspects together, and that has led to the synthesis that is the subject of this chapter.