82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 64 



Lipalian ' time immediately preceding: the Cambrian period, have 

 been discovered on the North American continent or elsewhere so 

 far as known.^ 



Diastrophism. — The most important diastrophic movement within 

 the Cordilleran area in Proterozoic time was the formation and 

 gradual deepening- of the great geosyncline extending from the 

 Gulf of Mexico north to the Arctic Ocean. This geosyncline was 

 broader when the Algonkian sediments of the Grand Canyon, Llano, 

 Needle Mountain, Uinta and Black Hills ' series were being de- 

 posited than at the beginning of Cambrian time. Indeed, it is 

 highly probable that it extended eastward to central Texas, Colorado 

 and South Dakota where a depression connected it across the upper 

 Mississippian region with the Lake Superior depression. 



Narrowing of the Cordilleran sea. — Before the Lower Cambrian 

 transgression into the Cordilleran area a diastrophic movement 

 began which resulted in a broad geanticline which raised the areas 

 of the Grand Canyon in Arizona, Needle Mountain in Colorado, 

 Uinta in Utah, the Black Hills of South Dakota, and the present 

 site of the Rocky Mountains, above the horizon of wide sedimentary 

 deposition and subjected the region affected by the uplift to erosion 

 during Lower and Middle Cambrian time. This uplift* narrowed 



^Smithsonian Misc. Coll., Vol. 57, 1910, p. 14 (footnote). 



Lipalian (Xeina -\- a\s) is proposed for the era of unknown marine sedimen- 

 tation between the adjustment of pelagic life to littoral conditions and the 

 appearance of the Lower Cambrian fauna. It represents the period between 

 the formation of the Algonkian continents and the earliest encroachment of 

 the Lower Cambrian sea. 



^ In this connection the theory of Chamberlin and Salisbury on the cause 

 of the disappearance of the coastal or fringing deposits should be carefully 

 considered by the student. Their conclusion is that "The theoretical continental 

 fringe of sediments has been borne downward and thrust landward by each 

 general deformation, and has crept outward and downward with each relaxa- 

 tion. The whole series is to be regarded as present in the continental shelf and 

 the coast border tract, but as largely concealed by this combination of disturb- 

 ing processes. When the great depth of the ocean-basins at the edge of the 

 continental shelf is considered, it is obvious that the volume of sediment 

 required .to build the shelf seaward is large in proportion to the extension of 

 the shelf, and hence the fringing zone is not very broad." (Geology, Vol. 

 3, 1906, p. 529.) 



^ Bull. U. S. Geol. Survey, No. 360, 1909, pp. 45, 46. 



■* This movement began some time before the Lower Cambrian transgression, 

 but how long we have no means of determining, as it is not until the beginning 

 of the Upper Cambrian that we find transgressing Cambrian deposits. It also 

 undoubtedly raised the Sierran geanticline west of the Cordilleran area and 

 kept this barrier intact throughout Cambrian time. 



