SUCCESSIVE DEPOSITS IN THE APPALACHIAN REGION 429 



through the greater part of Richmond time. Marine deposition con- 

 tinned to the north, as shown by the Lorraine and Richmond beds of 

 Quebec, to the west, as shown by the presence of the Lorraine and Rich- 

 mond faunas in a continuous sedimentation series (Hudson) in the Lake 

 Huron region, and to the south, as shown by continuance of the Sevier 

 shale of Virginia and Tennessee into the red Bays sandstone overlying it. 

 Ulrich in his correlation tables 43 makes the Bald Eagle the exact equiva- 

 lent of the Oswego sandstone without giving reasons for this correlation. 



Aside from the fact that a formation of sandstone over a thousand feet 

 thick in one section can hardly be the exact equivalent of another bed of 

 similar sandstone only 100 feet thick, we have shown that in the east the 

 sandstone begins earlier and rests on lower beds than in the northwest. 

 In Bald Eagle Mountain it rests on lowest Pulaski, if not Frankfort ; in 

 the Buffalo and Pulaski region it is post-Lorraiue. 



The probable extent of this fan must have rivaled that of the Huang 

 Ho or Yellow River of China of today. Not counting the Appalachian 

 folds, the distance from the easternmost outcrop to its disappearance in 

 the northwest is more than 200 miles. Add to this the amount of its 

 former eastward extent, removed by comparatively early Siluric erosion, 

 and we get in the neighborhood of 250 or 300 miles as the radius of the 

 fan. Of course, this radius was not necessarily the average radius. It 

 seems far more likely that the deposit was a long and relatively narrow 

 one. No doubt, too, some of the material of this delta was removed and 

 redeposited during the succeeding period of red sedimentation, which 

 seems to have followed almost without change in the relative position of 

 land and sea, except perhaps an increased elevation of the mountains 

 supplying the sediment on the east, as will be more fully explained after 

 the character of these deposits has been considered. 



A fact of interest in this connection is the finding of remains of 

 Eurypterids in the Trenton shales of New York. Good specimens have 

 been found in the Schenectady shale of the Mohawk Valley by the New 

 York State Survey, but though they are well preserved no entire speci- 

 mens have been discovered. They are associated with gTaptolites to be 

 sure, but the beds in which they occur also contain mud cracks, 41 and 

 apparently represent a surface swept over only occasionally by the sea, 

 which spread seaweeds and graptolites over it as seaweeds and hydryoids 

 are spread over our mud flats at the present time. 



The possibility that the Eurypterids were swept into this area by the 



43 Bull. Geol. Soc. Am., vol. 22, No. l\, pi. 27. opp. l>. COS. 



a Private communication by Doctor Ruedemann, 



