﻿146 C. D. Walcott — Cambrian System of North America. 



« During the deposition of the Potsdam sand- 



® stone the shore-line was close at hand, and the 



° Adirondack area furnished material for the 



.| formation. Out from the shore-line the mud 



in and sand were mixed, and still farther out, 



£ over the present area of the Georgia section, 



g the shales with interbedded limestones point 



% to deeper, quieter waters. I have yet failed 



M to find in Vermont any Potsdam sandstone 



•« north of Burlington ; and the evidence goes 



13 to prove that the upper portion of the Geor- 



S gia section, with its shales and u lentiles" 



2 of limestone, is equivalent to the Potsdam 

 t§ sandstone about the Adirondacks. 

 g We have now hastily reviewed the princi- 

 '-§ pal sections of the Cambrian under which 

 | all the others now known can be grouped 



3 except those of Braintree, Massachusetts, St. 

 © John, New Brunswick and the southeastern 



1 ~ Newfoundland sections. These are not con- 

 ^ ° nected paleontologically with the more west- 

 § ern section and we distinguish them as the 

 § d Atlantic border sections, and mostly of older 

 2 g date* than the strata of all but the lower 

 J ^ portions of the Wasatch, and perhaps the Ten- 

 be^ nessee sections. As the position of the At- 

 •|m lantic border Paradoxides fauna is determined 

 JicS on paleontologic evidence, the discussion of it 

 a 1i will be taken up later. 



"g'j- In the following table, the writer expresses 



" § | his view of the classification of the various 



o ^^ formations that go to make up the Cam- 



g g a brian system of North America. It is sub- 



J|^ ject to revision in details, but the main 



^ o p divisions are based on paleontologic and 



& stratigraphic data, that I think will render 



"* > them of service in the permanent classifica- 



,& go tion of American Paleozoic rocks. 



'J J o ^ * s not claimed that the arrangement of 



* I £ the formations in the following table is orig- 

 "ij ° § inal with me, as, with some changes in nomen- 



* g j> clature, it is the same as that to be found 

 o on page 46 of the Report of the Geological 



* At St. John, New Brunswick and also in Newfoundland, the higher members 

 of the Cambrian system, containing the later Cambrian faunas are known, but, 

 with our present information, the lower fauna predominates, and the upper faunas 

 will probably prove to be more closely related to the Atlantic than to the interior 

 basin, although we may expect to find a number of species common to each. 



