Late Paleozoic to Liassic reefs and shelf carbonates, forming at the time of accretion and dispersal of Pangea, are specific because of the frequency of reef types other than framework reefs, the importance of microbial contribution, an increase of bio-erosional control, the probable invention of algal/coral symbiosis, and the occurrence of major evolutionary crises of reef biota partly connected with extinction events.
The data base is biased with regard to time intervals and geographic regions. The use of reef distribution in paleoclimatic reconstructions is strongly dependent on paleomaps available. The current three-step processes model describing the evolution of Mesozoic reefs must be modified.
Important constituents of Pangean shelf and reef biota include algae, sponges, and corals exhibiting distinct changes in taxonomic composition, diversity, skeletal mineralogy, and the contribution to reef-building. Reef evolution is characterized by the development of various reef types with different time ranges during accretion and dispersal times of Pangea. Changes in the composition of reef biota with regard to taxa and guild membership are evident during the Permian and Triassic. Reef gaps might have existed during the Early Triassic and perhaps also during the lowermost Early Jurassic. Crucial questions concerning reef evolution in the time of Pangea concern the mode of biotic changes; the lack of Paleozoic holdovers in Triassic reef biotopes and the Scythian reef gap; the coincidence of the late Triassic reef crises with other major modifications of paleogeography, paleoceanography, and climate during the Carnian; and the meaning of the apparently synchronous end-Triassic reef extinction.
Both biological and nonbiological processes depending on paleoclimate and paleolatitudes and connected with sea-level changes of different orders should have been active in the control of the evolution of reefs. The latitudinal distributional patterns of Late Paleozoic reefs, however, might not necessarily reflect low-latitudinal warm-water regions as would be derived from recent distributional patterns. Control of reef development, especially by water temperature and light, may have been different for the various types of reef mounds and reefs originating during Pangean times as compared with Holocene coral reefs. Comparisons of distribution patterns of ancient reefs and global circulation models could help in understanding climatic shifts (as indicated by apparently different paleolatitudinal maxima of Carboniferous to Triassic reefs), in testing long-lasting factors that might have limited reef distribution (e.g., storm tracks, high precipitation areas) as well as in interpreting biogeographical patterns on the shelves around Pangea.
Prerequistites for the use of Permian and Triassic reefs in the interpretation and reconstruction of the Pangean paleoclimate are the improvement of the paleontological data base; the critical evaluation of climate sensitivity, especially of Late Paleozoic reef organisms; carbonate grain associations; and the transformation of reef-derived data into proxy data that can be used in quantitative modeling
