COASTAL MARSHES OF CAPE COD 743 



and modern date at the same level. He imiuircd what Dr. Davis would offer 

 as an explanation of the failure of the older beaches to show subsidence. 



Prof. A. W. Grabau asked for a statement as to the depth of the peat de- 

 posits in the Lons: Island region and the rate of growth of the salt peat. 



Dr. Davis rei)lled : Two hypotheses may accoinit foi- the lack of apparent 

 accord in the physioiiraphic evidence of the beach and other phenomena <'ited 

 with the botanic evidence of subsidence: (1) Tlie beach |)henomena may not 

 be so old as supposed. (2) They may have been formed by hi<:h storm tides 

 long ago to a level which has been brought down to the present one by sub- 

 sidence, as trees are apparently brought down within reach of tidal waters 

 in the 200 to 500 years of their lives. The greatest subsidence found in the 

 brief studies in Long Island was about 10 feet. The only records showing 

 rate of subsidence found were in the vicinity of Boston at the end of the field 

 season. In two localities the turf of salt marshes along long-established rail- 

 ways was foinid to contain coal cinders from locomotives in the upper ^ or 4 

 inches. One of the lines had introduced the use of coal in its locomotives in 

 1801, and by 1805 had equipped all of its locomotives for burning coal. 



CRITERIA FOR THE RECOGNITION OF ANCIENT DELTA DEPOSITS 



BY JOSEPH BARRELL 



Published as pages 377-446 of this volume. 



ANCIENT DELTA DEPOSITS 

 BY A. W. GRABAU 



(Al)stract) 



After a brief reference to the pre-Cambric or early Cambric delta fan of 

 the Pacific province and the Torridon of Scotland, the following were discussed 

 with especial reference to their stratigraphic and paleontologie characters 

 and their bearing on paleogeography : 



The late Ordovicic and early Siluric fans of the Appalachian region. 



The Shawangunk dry delta fan and its relationship to the Saliua desert. 



The Esopus delta and its relation to the Oriskany deixjsits. 



The early Devonic talus breccia of ^Michigan and western Ontario. 



The Old Ked of Scotland and the Catskill grouj). 



The Pocono, Mauch Chunk, and Pottsville. 



The Triassic fans of America and western Europe. 



MISSISSIPPIAN DELTA IN THE NORTHERN NEW RIVER DISTRICT OF 



VIRGINIA 



BY E. B. BRANSON 



Published, iiiuler tlio title "A Mississippian delta," as pages 447-456 

 of this volume. 



