PROCEEDINGS OF THE ACADEMY AND AFFILIATED 



SOCIETIES 



THE GEOLOGICAL SOCIETY OF WASHINGTON 



The 294th meeting was held in the lecture room of the Cosmos 

 Club on March 24, 1915. 



SYMPOSIUM ON THE FACTORS PRODUCING CHANGE IN POSITION OF STRAND- 

 LINE DURING PLEISTOCENE AND POST-PLEISTOCENE 



T. Wayland Vaughan: Introductory remarks. Before introduc- 

 ing the speakers, the President of the Society called attention to the 

 geologic importance of the factors producing change in the position 

 of the strand-line, and stated that the subject is perhaps brought more 

 forcibly to the consciousness of those who are studying present-day 

 shore lines. As instances of phenomena which demand explanation, 

 the succession of terraces and the general character of the shore line 

 within the Coastal Plain of the eastern United States between New 

 Jersey and Mexico were mentioned. The so-called "coral-reef" prob- 

 lem was cited as furnishing other instances of phenomena which have 

 not been satisfactorily explained. 



It appears safe to say that the coral-reef platforms are due to plana- 

 tion processes, operating partly above and partly below sea-le"\^el. 

 It has been possible to make correlations in some of the West Indies 

 between the length of geologic time planation processes have been 

 operative and the width of the platform. The deduction that such 

 platforms were formed and have been submerged is so firmly estab- 

 lished tliat it may be accounted a geologic fact. How were they 

 submerged, why do some show vibratory oscillation while others 

 do not, why has there been in some areas marked tilting or warping 

 while in other areas such phenomena are not exhibited, why does the 

 depth of water in the principal atoll and barrier lagoons of the Pacific 

 so nearly accord, and why is the depth on the extensive platforms in 

 the Caribbean Sea and around many of the West Indian Islands the 

 same as on similar platforms in the Pacific? Are there causes of world- 

 wide as well as others of only local effect? If causes of the two classes 

 are operative, how much of the resultant effect is to be assigned to each? 

 The ultimate answer to these questions largely depends upon detailed 

 investigations of numerous tropiotil and sub-tropical areas, but defi- 

 nite results can not be expected unless the fundamental principles 

 involved have been ascertained, and unless these principles are properly 



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