320 TRANSACTIONS OF THE [APRIL 5^ 



processes of momitain makiiijr, and the liigh abrupt slopes ancJ 

 their regnlaily succeeding valleys are due to the unequal sub- 

 aerial erosion of the two rock series. About 300 feet from the 

 eastern edge of quartzite above noted, the softer sandstones, here- 

 very coarse and containing pebbles of granulite and feldspar^ 

 come in contact with the Archsean rocks of the Blue Eidge.. 

 These are here unmistakably of the older Archa?an, consisting of 

 quartz-syenite and granulite ; ])oorly bedded, but well lamin- 

 ated. The two are widely unconformable. 'J'he sandstone con- 

 glomerate dips 45° N. W."^, with strike N. 40° E. T lie Arch a^aii. 

 has dip G5° E. ; strike X. 5° E. Professor C. H. Hitchcock has- 

 alluded to this contact in Proc. Amer. Inst. Min. Eng., anci 

 records his opinion that the Archfean as here exposed is the same 

 as much of that of the Green Mountains. It may be added 

 that these quartz-syenites, etc., arc of wide distribution in the 

 Highlands of New "Jersey and New York. 



The question naturally arises: To what geological epoch are- 

 these soft, clayey, variegated sandstones to be referred ? The 

 only information I was able to obtain along the section above 

 described is that they conformably underlie the vitreous quartz- 

 ites, which would appear to be Potsdam, and that they uncon- 

 formably overlie the older Archrean, and are composed of the ma- 

 terials of its disintegration. 



We visited another contact of the Archaean with a basal Silurian 

 rock in Doe River srorge, Eastern Tennessee. The constiuctioii 

 of the E. T. & W. N. 0. Pt. R. to the Cranberry Iron Mine has 

 opened this magnificent canon to travellers. It is several miles 

 in length, and the vertical walls of quartzite rise to heights of 

 500-700 feet above the turbulent waters of the stream. This 

 quartzite is thickly bedded, and contains many pel)l>les of quartz- 

 and much feldspar in grains of variable size, which is in places 

 abundant enough to make the rock an ai'kose. At the contact, the 

 Archsean, as exposed on the southern side of the stream along the 

 railroad cutting, is a pegmatite, with no bedding nor lamination, 

 and evidently a segregated mass. The quartzite has strike N. 42° 

 E., and dip 65° N. W. 500 fee teast of this contact the Archaean is 

 a hornblendic gneiss and syenite, much contorted, but dijiping on 

 the average about vertically. Near by, these rocks are intersected 

 by an eight-foot trap dyke, composed of very fine-grained, dark- 

 colored rock, weathering with a conspicuous slaty cleavage like 

 that in the Highlands of the Hudson. From this point to Roan 

 Mountain station the trap dykes are numerous, and certain areas 

 of light-colored, massive Archjean rocks are seen; at this station 

 the rocks are, however, again laminated. No well-bedded nor 

 highly micaceous crystalline rocks were seen along this section^ 

 and the series may probably be referred to the same age as that 



