410 abstracts: geology 



The correlation of the granites of this area with those of the Narra- 

 gansett Basin is a problem for the future. Shaler, Woodworth, and 

 Foerste regard the granite of the Narragansett Basin as older than the 

 Carboniferous sediments while the Sterling granite gneiss of the Preston 

 area is intrusive into them. C. E. Siebenthal. 



GEOLOGY.— Pawpaw-Hancock, Md., W. Va., Pa., folio. G. W. Stose 

 and C. K. Swartz. Geologic Atlas of the United States, No. 179. 

 24 folio pp., with maps, views and sections. U. S. Geological Sur- 

 vey, Washington, D. C. 1912. 



The rocks exposed in the area range from Cambrian to Carboniferous 

 and comprise, from the base up, Conococheague limestone, Beekman- 

 town limestone, (Stones River and Chambersburg limestones absent at 

 surface by reason of faulting), Martinsburg shale, Juniata formation, Tus- 

 carora formation, Clinton shale, McKenzie formation, Wills Creek shale, 

 Tonoloway limestone, Helderberg limestone, Oriskany sandstone, Rom- 

 ney shale, Jennings formation, Catskill formation, Rockwood formation, 

 Purslane sandstone, Hedges shale, Myers shale, Pinkerton sandstone. 



The beds are rather strongly folded, the axes striking northeast-south- 

 west, the Cambrian rocks appearing only at the southeastern corner of 

 the area, the Carboniferous in three narrow synclinal bands. The folds 

 are not as continuous as in most parts of the Appalachian province, 

 many of them terminating in the area by plunging or branching. Many 

 complete arches and synclines are exposed in stream banks and in artifi- 

 cial cuts, and are illustrated by half-tone cuts. In the eastern part of 

 the area the folds are overturned, broken, and extensively overthrust. 



The area is crossed from west to east by the Potomac River whose 

 channel is deeply cut in the surrounding upland and is bordered by a 

 series of gravel-covered terraces recording stages of uplift of the land. 

 The highest gravels found are 250 feet above the river level. The up- 

 land is an early Tertiary planation surface on which were developed the 

 great meanders of the Potomac. The Jurassic-Cretaceous peneplain 

 is preserved only on the tops of the highest mountains. Changes in the 

 drainage of the area are discussed. 



The only products of economic importance in the area are glass sand 

 from the Oriskany, extensively mined in the vicinity of Berkeley Springs, 

 W. Va., and natural cement rock, formerly quarried at Roundtop, Md. 



G. W. S. 



