110 NEW YORK STATE MUSEUM 



in a number of localities in the Appalachian region 1 . The occur- 

 rence of conglomerate beds resting on the limestones from which 

 they were derived, suggested to that experienced observer that 

 the sea bed was raised in ridges or domes above the sealevel, and 

 thus subjected to the action of seashore ice, if present, and the 

 aerial agents of erosion. While no direct connection has been 

 noted between the lower Trenton conglomerate and the youngest 

 limestone bed represented in it, the assumption of the presence of 

 such ridges or domes in the Appalachian region is in accord 

 with our knowledge of the constant movements going on in this 

 region throughout the Paleozoic era, and coincides with the 

 assumption of barriers in this region made by other writers. It 

 is therefore quite possible that the assumed transgressions 

 opened the crest of one of these ridges or domes, and thus laid 

 bare at once to the abrading action of the waves, a series of beds 

 extending from the Cambric to the last deposited Trenton lime- 

 stone, and furnished the various materials for the conglomerate 

 and the caleareo-arenaceous mud of the matrix. These were 

 deposited on the Normans kill shales forming in the deeper water. 

 While the presence of temporary coast lines, or the exposures 

 of the various beds represented by the pebbles, to wave action, 

 caused by the rising of broad ridges to the surface of the lower 

 Trenton sea, may be inferred with some degree of certainty, the 

 great variation in the size of the boulders and pebbles presents 

 some difficulty to these attempts at explanation. Some of the 

 boulders attain a diameter of several feet. The action of coast 

 ice, appealed to by Dawson for the explanation of the lower 

 Sdluric conglomerates near the St Lawrence river and suggested 

 by Walcott as an alternative theory for the origin of some of the 

 Cambric conglomerates, may in the writer's judgment be 

 excluded here on account of the presence of the Trenton fossils, 

 including corals, in the matrix. But it is highly probable that 

 the action of strong tidal or coastal- currents, caused by the ob- 

 lique impact of the waves on the coast, was engaged in spreading 

 the material derived from the coastal or abraded region over a 



i Geol. soc. Am. Bui. 1893. 5:191. 



