GEOLOGY OF SARATOGA SPRINGS AND VICINITY 83 



Mercersburg troughs and farther south.^ Since, however, the 

 Chambersburg Hmestone does not continue in the Levis trough 

 north of Pennsylvania, the conglomerate can not be referred to as 

 constituting a northern continuation or a part of the Chambersburg 

 limestone and it appears that the Atlantic fauna found in the Ryse- 

 dorph Hill conglomerate was able to enter the troughs between the 

 Appalachian barriers from the east in several independent places. 



The conglomerate about Bald mountain, which is here correlated 

 with the Rysedorph Hill conglomerate is clearly bound to the 

 large overthrust plane, for at Bald mountain itself it is asso- 

 ciated with the Bald Mountain limestone, and to the north of it 

 it is even infolded with Georgian shales. As we have already stated, 

 it is here exposed only close to the great overthrust fault and by 

 the latter brought in juxtaposition with the Bald Mountain lime- 

 stone and Georgian rocks. This position is probably due to its 

 greater resistant power as compared with that of the softer shales, 

 which have been ground up. 



Besides this conglomerate, the matrix of which consists, as at 

 Rysedorph hill, largely of sandy lime, there is observed at Bald 

 mountain a breccia of remarkable appearance and thickness. This 

 is seen in plates 12-14 between the Bald Mountain limestone and 

 the Georgian in very irregular masses. It is best exposed on the 

 south face of the quarry, where it reaches 30 feet in thickness in 

 one place and can be easily studied since it descends to the bottom 

 of the quarry. It consists here of an utterly unstratified black mud 

 matrix with numerous unassorted small more or less angular pieces, 

 mostly of the size of a pea or smaller, of limestone, olive grit, 

 chert etc. (see plate 15, which is a photo of a hand specimen). The 

 matrix has the appearance of a thoroughly ground up shale mass 

 and with pebbles floating in it, resembles a tillite. There is, however, 

 no doubt that this mass is the result of the tremendous friction at 

 the base and between the masses of Georgian rocks on top and the 

 Bald Mountain limestone below, which were moved on a nearly 

 horizontal plane. How the top beds of the Bald mountain limestone 

 were torn ofif and incorporated in the shale is well shown in plate 13, 

 where strings of Bald Mountain limestone are seen to reach intq 

 the black mudrock in the process of being torn up. The black soft 



^ Stose, G. W., Mercersburg-Chambersburg folio, Pa. U. S. Geol. Surv., 

 folio 170, 1909. Bassler. R. S., The Cement Resources of Virginia, West of 

 the Blue Ridge. Va. Geol. Surv. Bui. 2, K)09. Ulrich, E. O.. Revision of 

 the Paleozoic Systems, pts. i-.v Geol. Soc. Amor. Bui. v. 22, no. 3. 191 1. 



