Fossile Riffe als Klimazeugen in Australien

Summary

First true coral reefs in Australia appear in the Silurian of northern Queensland. The reef belt then advances to the south and reaches its maximum in the Middle Devonian. In the Upper Devonian and Lower Carboniferous reef-building activity is again restricted to the north. Reefs are unknown from the Upper Carboniferous until the middle Tertiary. The southern limit of the reef belt advances along the west coast, possibly since the Miocene and reaches its extreme southerly position (32° S. lat.) in the late Pleistocene, probably the last Interglacial. Since then it has moved northward to 29° N. lat. In the east the Great Barrier Reef reaches southward as far as 24° N. lat. and no more southerly reefs of Pleistocene or Recent age are known. The significance of these facts for the theory of continental drift is difficult to assess. The Pleospongia („Archaeocyathinae“) of the Cambrian are not reef-builders and their distribution could be satisfactorily explained by assuming that they were restricted to the temperate belts in both hemispheres. Conditions in the Middle Devonian with their extraordinary expansion of reef-building organisms require special explanation, but before a shift of the Australian continent relative to the climatic belts is accepted, it is neccessary to study the very irregular course of the limits of the present reef belt. Comparing marine faunas of similar latitudes today one may encounter differences perhaps not less profound than those between Devonian faunas in comparable belts.