Concluding remarks

Abstract

The Great Barrier Reef Expedition of 1928-29 and the Royal Society and Universities of Queensland Expedition of 1973 are separated in time by only 44 years. In that period coral reef studies expanded greatly and the geomorphology of reefs and reef areas became a major theme of research. Up to 1928 it is almost true to say that no work had been done on coral islands, and the writings on reefs were almost entirely biological. W. M. Davis’s The Coral Reef Problem appeared in 1928. It was the first book that examined coral reefs from a geomorphological point of view. Davis made extensive use of deductive reasoning, but he did not examine, on the ground, the structure and formation of coral islands, although he travelled widely in coral regions and made great use of charts. He did, however, emphasize and discuss at length the importance of studying reefs in relation to the coast of the land they border. Thus he enlarged on the point, first made by Dana, that drowned valleys imply not only subsidence of the land they traverse but also of the foundation of the reefs in front of that land. This was a major contribution. Two other comments made by Davis are only of subsidiary importance - the unconformable contacts of reefs on the rocks on which they rest, and the disposal of detritus in lagoons, especially in subsiding areas. Davis’s conclusion was that Darwin’s theory of subsidence was the most convincing explanation of the way in which barrier reefs and atolls are formed. He also, rightly, acknowledged the force of Daly’s glacial control theory, but fluctuations of sea level in the Quaternary were regarded as relatively minor incidents in comparison with the much greater subsidence that was necessary to explain deep drowned valleys and the evidence of the Funafuti bore. Incidentally this bore and the much shallower one on Michaelmas Reef were the only ones that were made before 1928. Davis also demonstrated the significance of cliffing in the marginal belts and the general absence of cliffs within reefs in the truly coral seas. In short, up to about 1928 discussions on the origin of coral reefs were wholly theoretical; despite the swing towards Darwin’s hypothesis there were still supporters of the theories propounded by Murray, Agassiz, Gardiner and others.