SUCCESSIVE DEPOSITS IN THE APPALACHIAN REGION 433 



chians and progressed outward by overlap. Nor is the upper surface of 

 the red sediments of the Appalachians at the exact horizon of the upper 

 level of the red Queenston shale, for both have probably suffered erosion 

 before the deposition of the succeeding beds. Essentially, however, they 

 are to be regarded as contemporaneous. 



What has been said of the contemporaneity of the red beds of the 

 Appalachians and western New York applies with equal if not greater 

 force to the red beds of the Appalachian region itself. Ulrich thinks that 

 there are two red series in the Appalachians. He would make the 

 "Juniata" of southern Pennsylvania and Maryland, as well as the Bays 

 of the southern Appalachians, of earlier age than the Juniata of the 

 western ridges. I have shown in the preceding pages that the strati- 

 graphic evidence is wholly against such an interpretation in the southern 

 Pennsylvania region, where only a false identifications of horizons could 

 lead to such a supposition. I have, I believe, definitely shown that the 

 Bald Eagle horizon is there represented by the upper marine Martins- 

 burg sandstones, the upper part of which is of late Lorraine and Oswego 

 age. Hence the succeeding red beds are Juniata. As for the Bays sand- 

 stone, I also have paleontological evidence that Ulrich's supposition is 

 incorrect. This will be given further on. If Ulrich's supposition were 

 correct, we would have in the eastern region first red sedimentation, 

 then a great series of white and gray sediments, followed again by red 

 sedimentation. That such is not the case is shown by the fact that no- 

 where in the immediate vicinity of the so-called older red series, nor 

 away from it, is there any indication of i;ed sedimentation beneath the 

 Bald Eagle conglomerate, even though the distance is only a few score of 

 miles. It is inconceivable that if red sedimentation went on near by 

 there should be no trace of such sediment wherever the white conglom- 

 erate and sandstone appear except above it. This can only be interpreted 

 as indicating that red sedimentation followed, but did not precede the 

 sedimentation of the white sand and pebbles, and that wherever the 

 white beds as such are absent and there is no hiatus they are represented 

 by marine sands and clays on which the red beds come to rest. In other 

 words, the red beds overlap the continental portion of the white beds and 

 rest directly on the marine equivalents of the latter. Thus we conclude 

 that there is only one Ordovicic red series in Pennsylvania and Mary- 

 land, namely, the Juniata formation. 



If we now consider the principal sections in eastern and central Penn- 

 sylvania and adjoining regions in which the Juniata beds are exposed, 

 we find considerable variation in the thickness of the deposil a( different 

 points. Beginning again in the westernmost ridges, we have the most 



XXX— Bull. Gbol. Soc. Am., Vol. 24, 1912 



