214 New York State Museum 



deposited and have yielded numerous fossils. The 

 famous Paleozoic sequence in New York State has been 

 the "standard section" with which the Paleozoic rocks of 

 America have been compared and correlated, although 

 it is now known that this section is far from complete, 

 being interrupted by numerous breaks or erosion inter- 

 vals that are represented by deposits elsewhere. 



The North American continent was outlined in much 

 its present form during the early part of the Proterozoic, 

 and at times was even larger than it is today. It extended 

 for several hundred miles into both the Atlantic and 

 Pacific and was connected then, and for a long time sub- 

 sequently, by dry land with northwest Europe by way 

 of Greenland. There were certain areas of depression, 

 narrow troughs or synclines (called geosynclines from 

 Greek gea, earth), which remained seaways for long 

 periods of geologic time and in which were accumulated 

 heavy deposits of sediments. One of these depression 

 troughs was in the eastern part of the continent running 

 northeast-southwest ; the second in the western part, ex- 

 tending north and south ; and the third was in the middle 

 part of the continent extending roughly east and west. 

 There was an Arctic seaway in the northwest also which 

 partook of the nature of a shallow continental sea, such 

 as Hudson bay today, rather than of a depression trough 

 or syncline. The sediments making up the conglomerates, 

 sandstones and shales (known as clastic sediments or 

 elastics) were derived from the bordering lands. In gen- 

 eral the Proterozoic was a time of continental elevation. 

 During the period of mountain building at the close of 

 the Proterozoic the mainly continental deposits of the 

 medial geosyncline were folded up into mountains (Kil- 

 larney mountains) which divided the interior of the con- 



