TITLES AND ABSTRACTS OF PAPERS 61 



SOME HISTORICAL EVIDENCE OF COASTAL SUBSIDENCE IN NEW ENGLAND 



BY CHARLES A. DAVIS 



(Abstract) 



During the summer of 1913 the writer found at many points near Boston, 

 Massachusetts, various kinds of evidence that there has been a definite, pro- 

 gressive, and measurable elevation of the high-tide level vs^ith regard to the 

 coastline since the settlement of the coastal region by white men. 



Taken in connection with the structure of the salt marsh peat beds of the 

 same localities, which are in some places more than 20 feet thick, built up 

 entirely of the remains of plants which grew only at the mean high-tide level, 

 as already reported by the writer, this steady elevation of the high tides can 

 only be interpreted to mean a subsidence of the coast in the region reported 

 on. 



Presented in abstract from manuscript. 



Discussion 



Prof. A. W. Geabau : Could the examples cited not be explained by settling 

 of the marsh itself and the condensation of the peat, owing to the oxidation 

 of the carbon. 



Dr. J. W. Spencer: On the Island of Saint Eustatius, in the West Indies, 

 foundations of stone buildings (which were constructed before 1781) were ob- 

 served standing out in the sea. The question arose whether the land has 

 sunken since 1781 or the coast has been washed away, leaving the foundations 

 of commercial structures which had been built below sealevel. 



Prof. W. M. Davis: The problem of coastal change or coastal stability re- 

 quires for its satisfactory settlement the consideration of all kinds of evidence. 

 Mr. Davis has just presented a kind of evidence that indicates a slight sub- 

 sidence in the Boston district ; but Professor Johnson has previously presented 

 another kind of evidence — and to my mind stronger evidence — derived from a 

 study of Nantasket Beach at the entrance to Boston harbor, which shows long- 

 continued stability. As long as these two kinds of evidence remain unrecon- 

 ciled the problem can not be regarded as solved, and it is quite as much Mr. 

 Davis's responsibility as any one else's to bring about a proper reconciliation. 



In Mr. Davis's references to the depths at which salt marsh deposits have 

 been found, he did not specify their location with respect to the form of shore- 

 line and to the changes that it has suffered in recent centuries. This is of 

 particular importance with respect to the deposits at such depths as 20 feet. 

 In the absence of such specification the bearing of his facts on the solution 

 of. the problem can not be properly appreciated by his hearers. 



Prof. William H. Hobbs : We have had presented evidence of so conflicting 

 a nature that it would seem to be possible to explain them by movements of 

 sections of coast independent of neighboring sections. In studies which I made 

 in Malta during February, 1913, it was found that this island of less than 100 

 square miles gave a vertical movement in opposite direction and, measured in 

 feet, characterize the eastern and western coasts. 



