788 



SCIENCE. 



[N. S. Vol. n. No. 50. 



east of the Mariposa slates and intersects 

 a belt of amphibolite schist. 

 . In the granite of the West Point are a 

 are numerous gold-quartz veins, the ores of 

 which contain a larger per cent, of sul- 

 phurets than the ores of the Mother Lode 

 mines, and such ores are called base. 



The serpentine areas contain clrrome-iron 

 deposits at numerous points. 



The tuffs overlying the gravels at Mokel- 

 umne Hill, Valley Springs and other points 

 have been found to make good building 

 stone. Sandstone quarries are marked in 

 the foot hills in beds of Tertiary age, and 

 the deposits of the same age near lone 

 afford large quantities of clay for pottery, 

 and of coal. 



FOLIO 12, ESTILLVILLE, KENTUCKY- VIRGINIA- 

 TENNESSEE, 1894. 



This folio consists of 5 pages of text by 

 M. E. Campbell, geologist, a topographic 

 map of the district (scale 1:125,000), a sheet 

 showing the areal geologj^ another showing 

 the economic geology, a third of structure 

 sections, and a fourth giving a columnar sec- 

 tion north of Clinch River and another 

 south of that river. 



The territory represented by the folio is 

 located principally in southwestern Vir- 

 ginia, though the southern portion extends 

 into Tennessee and the northwestern por- 

 tion into Kentucky. Its area is 957 square 

 miles, four-fifths of which is in the Appa- 

 lachian Valley and one-fifth in the Cumber- 

 land coal basin. 



The surface features are quite varied. In 

 the ApJ)alachian Valley they consist of a 

 succession of narrow ridges separated by 

 equally narrow vallej^s, trending in a north- 

 east and southwest direction. In the coal 

 basin the ridges are less regular, but higher, 

 reaching in two cases an elevation of over 

 4,150 feet above the sea level. 



The region is almost entirely within the 

 drainage basin of the Tennessee River. The 



principal tributaries of this sti'eam are 

 Holston, Clinch and Powell rivers, each of 

 which is a stream of considerable impor- 

 tance. The Kentucky portion of the terri- 

 tory is drained by the headwaters of the 

 Cumberland River. 



The geologic structure of the region is 

 complicated. In the Appalachian Valley the 

 rocks have been squeezed, in a northwest 

 and southeast direction, until they have 

 been forced into great folds. These are gen- 

 erally overturned toward the northwest, 

 and have in manj' cases been compressed to 

 such an extent that they have broken, allow- 

 ing one limb of the fold to be thrust over 

 the other. These faults are of frequent oc- 

 currence in this region. Sixteen or seven- 

 teen can be counted on the geologic map. 

 In the coal basin the folding is less severe, 

 and the result is a broad basin in which dips 

 are prevailingly light, and in many places 

 the rocks are horizontal. 



The intense folding of the strata has 

 brought to the surface all of the geologic 

 formations from the Carboniferous to the 

 Cambrian. On lithologic grounds these are 

 divided into twenty-two separate and dis- 

 tinct formations. As a result of the original 

 folding and subsequent erosion, these for- 

 mations show at the surface in long, narrow 

 outcrops of limestone, shale or sandstone,, 

 which in the various folds are repeated over 

 and over again. It is this repetition of the 

 hard beds that gives rise to the numerous 

 ridges which are such conspicuous features 

 of Appalachian topography. In the coal 

 basin the rocks are nearly horizontal, and 

 hence they show in outcrop around the 

 fla.nks of the mountains, or irregularly over 

 the less rugged portions. 



The mineral resources of this region are 

 important, though at present but slightly 

 developed. A belt of marble, varying con- 

 siderably in composition and appearance, 

 outcrops along the northern side of Clinch 

 Mountain. Iron ore occurs in many parts 



