Summary of Discussion 



Professor Yonge stated his experience on the Barrier Reefs off Queens- 

 land, where the coral grew in confused masses, and, under heavy seas, 

 it was broken up and piled up on the reef, and on other parts of the 

 Barrier the reverse took place, and broken material formed submarine 

 talus slopes. In answer to a question concerning light-penetration. 

 Dr. Emerj- stated that some measurements had been taken, and that 

 light seemed to be effective 150 to 180 ft. in the lagoon, and apparently 

 this was the same outside the reef. 



Dr. P. Marshall remarked that the distribution of organisms and 

 sediments described was very similar to that observed at the Cook Islands. 



MULTIPLE STANDS OF THE SEA IN POST-GLACIAL TIMES 



By Rhodes W. Fairbridge, University of Western Australia 



In his memorable work on the most recent eustatic drop in the level of 

 the sea Daly (1920) reckoned on something of the order of 20 ft. and 

 collected from the world-wide literature, willy-nilly, it might seem, all 

 references he could find to " fairly recent " raised beaches, terraces, and 

 the hke. 



More than adequate evidence is now available to indicate that quite 

 a number of Daly's levels really belonged to a late Pleistocene date 

 (possibl}" Zeuner's " late Monastir " level, approximately 25 ft. in the type 

 area of the Mediterranean) and identified far and wide in the Pacific 

 (see Stearns, 1941, &c.) and other oceans. On the other hand, the various 

 lower figures obtained by many workers have rashly been discredited 

 altogether by the late Professor Douglas Johnson (1933), who decided 

 that all marine erosion surfaces below " hurricane-beach " height were 

 the products of the present cycle of erosion. 



The wide experience of and many papers by Stearns (1941, 1945, &c.) 

 should be sufficient demonstration that in fact some of these lower levels 

 are truly eustatic. Stearns and others attribute them to a mid-Recent 

 stand of the sea at 5 ft. above the present. 



In certain particularly favoured areas, however, it has been possible 

 to recognize not one, but fo2ir distinct stands of the sea in post-Glacial 

 times. Kuenen (1933) found these in the East Indies and placed them 

 at 4-5 m., H-2 m., and |-1 m. above the present sea-level, which con- 

 stitutes the fourth and latest stand. Working independently, the author 

 and C. Teichert have lately found very similar traces in Western x\ustralia 

 (10-11 ft., 5-6 ft., 2-3 ft., and the present zero-level bench). These 

 were first recognized in the Abrolhos Islands (Fairbridge, 1948) and on 

 Rottnest Island (Teichert, 1948), and we have both followed out the 

 evidence together up and down the very stable coast of Western Australia 

 for nearly 1,000 miles. Further evidence from islands and mainlands 

 bordering the Indian Ocean and elsewhere suggests that these indicate 

 truly eustatic sea-levels. This was suggested already over a century ago 

 by Ehrenberg (1834). Comparison with recent studies in Sweden suggest 

 that they have all been completed during the last four thousand years. 

 The highest sea-level appears to correspond with the " Atlantic " phase 

 of climatic optimum (Flandrian stage of Dubois). 



The fact that these terraces are horizontal in attitude and separated 

 from one another by short vertical cliffs, with other evidence, has led to 

 the conclusion that periods of stand-still were protracted, but that changes 



345, 



