REPORT OF THE DIRECTOR I92C—2I IIQ. 



Eria can still be traced until Triassic time. As Holtedahl (1920, p. 2 1) 

 points out, this part of the crust had through long geologic periods 

 the tendency to rise; but like the eastern part of Appalachia it has 

 now sunken deeply. Suess, clearly recognizing the connection of 

 the Armorican folds in the Bretagne with the Appalachian folds in 

 America ■ — ■ with their northeast bend in Gaspe and Newfoundland — 

 drew the northern shore line of the Poseidon along this sunken 

 Devonian mountain range (see Suess, 1911, p. 102) and derived 

 the northern Atlantic ocean from the breaking down of the Paleozoic 

 continental mass of " Atlantis." 



While the great unconformity of the Cambrian and later Paleozoic 

 overlapping formations upon the Precambrian is clear evidence that 

 the Cambrian sea invaded upon an old land mass that had undergone 

 considerable, if not in some parts enormous denudation, it is still 

 possible that some of the Precambrian rocks are marine deposits 

 that, if they contained fossils and could tell their story would show 

 the Precambrian continent of North America to have been invaded 

 by the neighboring oceans, the same as after the Precambrian. No 

 less an authority than Walcott has, however, steadily maintained 

 that all the Precambrian sediments on the continent are nonmarine; 

 and he seems to be supported by abundant evidence from various 

 sources. There is further clear proof of shallow water origin of the 

 sedimentary beds of the Precambrian in ripple marks, mud cracks, 

 the lithology, etc., as far west as the Inyo range in California (Knopf 

 & Kirk, 191 8, p. 23), and in the immensely thick (37,000 feet 

 according to Walcott) Belt terrane which formed in a relatively 

 narrow Precambrian geosyncline within the continent (W. H. 

 Emmons & F. C. Calkins, 19 13, p. 29), as well as in the Proterozoic 

 beds in Utah (F. L. Ransome & H. S. Gale, 1915, p. 169), and 

 generally in the Rocky mountain plateau region. To this evidence 

 of shallow water origin must be added that of direct land formation. 

 The latter is seen in the successive great unconformities of which 

 at least four are fully recognized; in the well-known discovery of 

 glacial beds (bowlder conglomerate or tillite) of Proterozoic (Lower 

 Huronian) age in Canada by Coleman, and in the observation of 

 proofs of land-formed rocks by our best authorities of the American 

 Precambrian. To cite a few examples, Leith (i9i3,p-333) suggests 

 that " the unconformity at the base of the Cambrian was developed 

 by a process of cut and fill," and that " the common occurrence of 

 late Precambrian terrestrial sediments is more than a coincidence, 

 but is related to the development of the basal Paleozoic uncon- 

 formity." Lane (191 1, p. 32) states that after discussions with 



