EPICONTINENTAL SEDIMENTATION 491 



ing to assume transformation of sediment to a very dense rock 

 induced from below. Finally biogeography and paleobiogeography 

 can hardly do without transoceanic migration paths with more 

 land and shallow water than is now present. Such isthmian or 

 island-arc links have disappeared if they ever actually existed. 



It cannot be claimed that any of these pieces of evidence is con- 

 clusive, but put together they at least suggest that we still lack 

 insight into the nature of the contrast between ocean floor and 

 continental block and do not know whether both or either are 

 permanent. Geophysicists must assist in solving this riddle. They 

 should help in deciding the question whether any of the ancient 

 geosynclines accumulated their sediments on an open oceanic 

 shelf or whether a closer parallel is to be found in inland seas, 

 such as the Persian Gulf. 



It is becoming more fashionable among geologists to admit the 

 possibility of continental drift to account for transoceanic migra- 

 tions. If the theory of Wegener is accepted the problem of con- 

 tinental terraces would have to be reviewed in this new light. 

 Curiously, geophysics in the form of geomagnetic studies has pro- 

 vided the main impetus to this new trend of thought, whereas the 

 stoutest opposition to continental drift has always come from 

 geophysicists. Yet another recent suggestion is of an expanding 

 earth. It is easy to raise objections to such bold speculations, but 

 the bulk of the favorable evidence is sufficient to warn against 

 offhand rejection of these ideas. 



Marine Geology in Aid of Other Branches of Oceanology 



An aspect more difficult to treat is how far other branches of 

 oceanology can profit from geological investigations. Luckily the 

 title of my paper does not oblige me to take it up, but to ignore 

 it entirely would leave a serious gap in the discussion, so I will say 

 a few words. 



The sediments form the only permanent record in the oceans of 

 what has happened in the past. One wants to know how far present 

 current systems, chemistry of sea water, habitats of organisms, 

 meteorological conditions, etc., are permanent and inherent to 



