62 Loughlin and Hechinger — Unconformity 



strata of the Norfolk County Basin, and evidence both 

 lithologic and structural supporting this correlation has been 

 presented in a paper previously cited.* The evidence pre- 

 sented in the present paper thus correlates the Roxbury 

 conglomerate as Permian, and in this respect accords with 

 conclusions of others who have produced evidence pointing to 

 the glacial origin of a part of the conglomerate, and therefore 

 assign it to the Permian, an age of wide-spread glaciation. 

 Crosbyf for a number of years has suggested that the coarse 

 conglomerates in the Boston Basin were of possible glacial or 

 aqueo-glacial origin. The late N. S. Shaler expressed similar 

 views. 



Mansfield,:}: in his study of the Roxbury conglomerate, 

 concluded that aqueo-glacial conditions probably existed during 

 its deposition. Later, in 1910, Sayles and La Forge§ described 

 localities in Hyde Park and Squantum, Mass., where an upper 

 horizon of the Roxbury conglomerate presented characteristics 

 typical of tillite. Regarding the age of the conglomerate, 

 they say : ic In view of the accumulating evidence of glaciation 

 in many parts of the world in Permian time, it seems a reason- 

 able assumption that if glacial conditions prevailed in eastern 

 New England at some time late in the Carboniferous period, 

 they were contemporaneous with similar conditions elsewhere, 

 and hence that glacial deposits found in the Carboniferous 

 rocks of the Boston region were formed in Permian time." 

 The coarse textures of the conglomerate above the red strata in 

 the Norfolk County Basin and of the Dighton conglomerate in 

 the Narragansett Basin accord with that of the Roxbury 

 conglomerate so far as indications of Permian climate are 

 concerned, though no identification of tillite has been made in 

 them. The unconformity between f ossilif erous "Coal Measures" 

 and Dighton conglomerate demonstrated in the present paper 

 thus furnishes definite structural proof in support of the 

 Permian age of the conglomerates as suggested by Sayles and 

 La Forge. 



Tentative Correlation of Strata in the Three Basiifs. 



The accompanying table summarizes the tentative revision 

 of the stratigraphy of the three basins. The position of the 

 Pondville conglomerate and Wamsutta formation is obviously 



* Loughlin, G. F., this Journal, (4), vol. xxxii, pp. 25-31, 1911. 



•f Crosby, W. 0., Oral communications. Prof. Crosby has alluded to this 

 point at different places in his ''Geology of the Boston Basin." 



:{: Mansfield, G. R., The origin and structure of the Roxbury conglomerate. 

 Harvard Coll. Mus. Comp. Zool., Bull., vol. xlix (Geol. Ser. vol. viii, No. 4), 

 p. 260, 1906. 



§ Sayles, R. W., and La Forge, L. : The glacial origin of the Roxbury 

 Conglomerate, Science, n. s,, vol. xxxii, pp. 723-724, 1910. 



