226 J. Barrett — Tipper Devonian Delta of the 



show that on the east not only did the strata once extend many 

 tens of miles, but that the sources of erosion were not nearby. 

 The evidence contained in the formations of the Green Pond 

 Mountain outlier shows that the Upper Devonian deposits 

 were there of fluviatile origin and of materials brought from a 

 distance. The structure as well as the composition point to 

 the present syncline being a mere fragment of the original 

 deposit, downfolded and downfaulted, and thereby preserved 

 from erosion. The Green Pond Mountain axis was conse- 

 quently not an isolated bay but its sediments were originally a 

 part of the general Paleozoic mantle thinning to the eastward 

 and in that direction were commonly of coarser texture. In 

 the Upper Devonian it was part of a broad piedmont gravel 

 plain, a continental bajada of low grade skirting the mountains 

 of Appalachia ; a gently inclined and graded plain, sensitive 

 to climatic and diastrophic changes. 



Following this part on the character and original limits of 

 the Upper Devonian sediments, is given a discussion of the 

 volume and sources of the material. It is concluded that 

 Appalachia was not confined to the limits of the present conti- 

 nental shelf. The shelf in fact is to be regarded as in consid- 

 erable part an aggradational terrace built out in post-Jurassic 

 time. The foundations of Appalachia are buried some thou- 

 sands of feet beneath it, extend beyond it, and doubtless slope 

 gradually for an unknown distance toward and beneath the 

 basin of the Atlantic Ocean. In Upper Devonian times the 

 mountains which rose above these foundations stood on the 

 eastern side of the Appalachian system. 



Indications Given by the Strata of Former Extension. 



Faunal Relationships and the Possible Seaways. 



According to Schuchert, the Upper Devonian faunas of the 

 Appalachian geosyncline show a connection with the Atlantic 

 province and in his Paleogeography he has located a strait 

 across northern New Jersey as the channel of ingress.* The 

 existence of an Upper Devonian seaway in this locality, how- 

 ever, seems impossible. In the first part was developed the 

 evidence showing that the Upper Devonian of this region 

 must be regarded as continental in origin. Furthermore the 

 sediment appears to have come from lands in this direction. 

 In the search for an available connection with the north 

 Atlantic faunas we must look for a passage around either the 

 southern or northern end of Appalachia. A southern route 

 would not be a direct one for the migration of North Atlantic 



*Bull. Geol. Soc. Am., xx, p. 545, pi, 77, 1910. 



