GLOBAL RESURGENCE OF CORAL-REEF ECOSYSTEM AFTER THE LATE DEVONIAN MASS EXTINCTIONS

The largest metazoan (stromatoporoid-coral) reef ecosystem of the Phanerozoic, which flourished in the middle Palaeozoic, collapsed and disappeared during the late Devonian Frasnian-Famennian (F-F) and Hangenberg mass extinction events, respectively. The Mississippian has been viewed as a metazoan “reef gap”, dominated by microbial reefs and mud mounds often labeled as Waulsortian. Recent studies recognized a variety of metazoan reef types in the Mississippian (Visean stage). However, these Visean skeletal reefs vary in age and composition, and it is unclear when metazoan reef ecosystem recovered and whether a single evolutionary lineage for reef ecosystems appeared after the late Devonian extinction events.

In this study, abundant coral bioconstructions were reported in late Visean strata of the South China Block, possibly indicating that the proliferation of coral-reef ecosystem during this time. To test this hypothesis, the age, abundance, composition and distribution of global late Devonian to Mississippian skeleton- and microbe-dominated bioconstructions were systematically reviewed and quantitatively reconstructed. This analysis shows that no Tournaisian skeletal bioconstruction has been documented in the aftermath of the disappearance of stromatoporoid-coral reefs during the Hangenberg extinction. Skeletal reefs first appeared with low abundance in the early Visean, and then their abundance slightly increased during the middle Visean. However, the reef ecosystem was still dominated by microbes, with the few skeletal reefs built majorly by bryozoans and corals during this time. Their distribution is largely limited to between the palaeoequator and 20° S latitude. In late Visean times, skeletal reefs dramatically increased in abundance and were constructed mainly by corals, which have replaced microbial reefs and became dominant in marine ecosystem. The distribution of coral bioconstructions expands to between 40° latitude on both sides of the palaeoequator and occurs widely in Europe, Asia, North America, North Africa and Australia. Hence, the temporal and spatial evolution of the Mississippian skeletal reefs suggest that global resurgence of coral-reef ecosystem was present during the late Visean after the late Devonian mass extinctions.