DIASTROPHISM AND THE FORMATIVE PROCESSES 317 



International Geological Congress at Toronto in August, 19 13, and 

 is presented here because it was undertaken as a part of the series 

 of studies now appearing under the title " Diastrophism and the 

 Formative Processes." 



For brevity in designating the various diastrophic disturbances, 

 my father has found it convenient in his lectures to use such terms 

 as the following: Ordovicides for foldings or strong diastrophic 

 movements which took place either at or near the close of the 

 Ordovician period; Silurides for like movements at or near the 

 close of the Silurian period; and similarly, Devonides, Carbonides, 

 and Permides for movements connected with the closing stages of 

 the Devonian, Carboniferous, and Permian periods. For move- 

 ments near the close of the Mississippian, or Lower Carboniferous 

 period, the term Cuhnides is used in place of a more cumbersome 

 derivative from the name Mississippian. These terms will be used 

 in this paper. 



CAMBREDES ? 



The Proterozoic era seems to have closed with profound dias- 

 trophic movements in most parts of the world where satisfactory 

 identifications have been made. At the close of the era the sea was 

 quite generally withdrawn into the deep basins. The Paleozoic era 

 which followed commenced with advancing seas in which the Cam- 

 brian sediments were laid down unconformably, for the most part, 

 upon eroded and trunkated Proterozoic strata. During the Cam- 

 brian period there appears to have been a general, but more or less 

 fluctuating, advance of the sea up to the close of what is usually 

 classed as Upper Cambrian. Following this, in the debatable 

 ground that lies between the well-recognized Upper Cambrian and 

 the undoubted Ordovician, evidence of some diastrophic movements 

 appears, but, so far as present data go, these movements do not seem 

 to be of the decided class to which this paper chiefly relates. Rather 

 widespread unconformities occur near this horizon in various parts 

 of the Mississippi and St. Lawrence basins, but they are not of 

 such a nature as seriously to affect the genera] paralleHsm of the 

 Cambrian and Ordovician systems.' There are discordances be- 



^ Chamberlin and Salisbury, Geology, II (igo6), 311-12; Ulrich, "Revision of the 

 Paleozoic System," Bull. Geol. Sac. Am., XXII (1911), 614-16, 626-28; Schuchert, 

 " Paleogeography of North America," ibid., XX (1910), 522-29. 



