o 



DEVELOPMENT OF THE FRAXKLIX GEOSYXCLIXE 19.- 



cially to the concentrated work of the Norwegians (Per 8chei) and the 

 Danes (Lauge Koch) during the past twenty-five years, we are now see- 

 ing far more clearly the general stratigraphic sequence and the broader 

 structural relations of this region. Our knowledge is best for EUesmere- 

 land and northernmost Greenland, where it appears that there is a maxi- 

 mum of deposition exceeding 21,000 feet. The Arctic seas began to 

 spread over the Archean formations in Upper Cambrian times, and thence 

 until the close of the Triassic the sequence is about as complete in the 

 Franklinian geosyncline as in any of the other American trougb;. Upper 

 Cambrian, Ozarkian, and basal Ordovician times are well represented by 

 from 5,000 to 8,000 feet of more or less clastic strata, the rest of the 

 Ordovician and Silurian by about 4,000 feet of limestones, the Devonian 

 by 6,000 feet or more of mainly elastics, while the Carboniferous lime- 

 stones and Triassic shales may considerably exceed 3,000 feet. The 

 strata thicken and becoiKPe coarser toward the north and northwest in the 

 very areas of the most intense folding of the United States Mountains, 

 first made known by Lieutenant Peary. These mountains have peaks up 

 to 8,000 feet and are the northernmost range of the earth, extending 

 from Cape Morris Jesup to Robeson Channel and across it into Grant, 

 Grinnell, and Peary lands. The thinning out of the strata is toward the 

 southeast across Greenland and southward through the Franklin Archi- 

 pelago and the Northwest Territory of Canada, parts of the vast Cana- 

 dian shield. 



It is interesting to note further that northern Ellesmereland (Grant 

 Land) and Peary Land are margined by Archean rocks, and they are to 

 be interpreted as remnants of the borderland that furnished most of the 

 detritals for the Franklinian geosyncline. This old land may be kno\'iTi 

 as Pearya, and how far it extended into the present Arctic Ocean is, of 

 course, unknown. Since the depths of this ocean north of Greenland 

 and the Franklin Archipelago are not nearly as great as farther north- 

 ward, it may have had a breadth of many hundreds of miles. That we 

 are dealing here with a borderland having along its inner side a geosyn- 

 cline whose waters lapped upon the Canadian shield is attested by the 

 position and trend of the United States Mountains and by the further 

 fact that the folding and overthrusting, according to a personal conver- 

 sation with W. Elmer Ekblaw, is away from the Arctic Ocean and toward 

 the southeast. 



Koch^* refers the making of the L^'nited States Mountains to the Cale- 

 bs Lauge Kocb : Stratigraphy of northwest Greenland. Meddel. dansk. geol. Foren., 

 voL 5, no. 17, 1920, pp- 1-78. PreliminatT report upon the geology of Peary Land,. 

 Arctic Greenland. Amer. .Tour. Sci. (5), vol. 5, 1923, pp. 189-199. 



