34 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



ity, near Germanton, is a conglomerate of angular fragments of 

 granite and gneiss, containing roots of silicified tree-stems penetrat- 

 ing and branching in the deposit. The stems are very abundant just 

 above the conglomerate, so abundant as to suggest that they are 

 remains of an ancient forest. Most of them are prostrate and occa- 

 sionally one finds the roots converted into lignite. The great 

 abundance of stems near Germanton in Stokes county impressed 

 Kerr, who says "the public road being in a measure obstructed by 

 the multitude of fragments and entire trunks and projecting stumps 

 of a petrified Triassic forest; and similar petrifactions are abundant 

 in the Deep River belt, occurring in this as in the other among the 

 sandstones near horizons of the coal." 



Stone's examinations led him to assign a thickness of about 

 7,800 feet to the deposits within the Dan River area, where the 

 mass rests on Archean gneiss. The zone of carbonaceous shale with 

 coal is 250 feet thick and just below it, at about 1,000 feet from 

 the base, is conglomerate with subangular fragments, which is absent 

 from the northern portion of the area. The roots and bark of the 

 silicified stems within this mass in some cases have been converted 

 into lignite. Shafts have been sunk in many places but usually only 

 black shale has been found. At one place, 37 inches of such shale 

 with much coal was found. The Leakesville deposit is insignificant 

 and its area is but a few square rods. 



Triassic rocks are exposed in very many localities west from 

 the 105th meridian to the coast but they appear to be without coal 

 in both the United States and in the Dominion of Canada. 



Mexico. — But coal is present in Triassic deposits of the Santa 

 Clara field on the eastern border of Sonora, Mexico. Dumble'*'' 

 has given brief notes respecting the locality. The Rheetic age of 

 the deposits was recognized by Newberry and Fontaine after study 

 of the plant remains. The region has been disturbed greatly by ig- 

 neous rocks, which have metamorphosed the coals. The heavier 

 sandstones are uniform and are moderately coarse conglomerate 

 grits, which have a few fragments of silicified wood and occasional 

 imprints of stems. The shales and finer sandstones are excessively 



*^ E. T. Dumble, " Triassic Coal and Coke of Sonora, Mexico," Bull. 

 Geol. Soc. Amcr., Vol. X., 1900, pp. 10-14. 



