STEVENSON, COAL BASIN OF DECAZEVILLE, FRANCE 279 



EXTENT OE THE COAL BEDS 



Little can be said respecting the original or even the present extent of 

 the Soulier- Abiracs coal bed; the outcrop marked on the map encloses 

 an area considerably less than two square miles, from most of which ero- 

 sion may have removed the bed. How far the coal extends northward 

 and westward under the Campagnac system has not been ascertained, as 

 the matter has no economic importance and no explorations have been 

 made. The greatest thicloiess is west from the supposed line of the 

 Eaute Serre stream, where there is about 10 feet of coal ; the total amount 

 must be large, as the bed goes under cover with undiminished thickness. 



It is less difficult to determine approximately the extent and distribu- 

 tion of the great Campagnac-Paleyrets-Bouquies coal at the base of the 

 Campagnac system. That bed is practically continuous along the out- 

 crop indicated on the map, though it is said to be lens-shaped at some 

 localities. How far it extends toward the west has not been ascertained 

 in the northern part of the basin ; an exploratory pit in the Bourran mine 

 did not reach it, having been stopped before coming to its place ; but near 

 Cransac the underground workings of the Compagnie des Mines de Cran- 

 sac have been pushed beyond the outcrop of the Couche de Crol, the Bour- 

 ran coal bed. This is clear from all the cross-sections constructed by 

 Saint-Martin, in which the bed shows only the ordinary variations, 

 thinning toward some of the faults, thickening towards others. This bed 

 has been recognized definitely nowhere west from a line connecting Levin- 

 hac at the north with Lugan at the south, but there seem to be good 

 reasons for referring to approximately the same horizon some thin and 

 irregular deposits in the southwest corner. The bed, practically single 

 at the south as the Couche de Eulhe, divides near Eiou Vieux, the inter- 

 vals between the lower benches increasing northwardly in the Firmy re- 

 gion, so that in going by the wagon road from Firmy to Cransac, one 

 crosses the whole series from the main bed down. The dips throughout 

 are conformable in the Campagnac system and conformable also to the 

 underlying Auzits. There is every reason to believe that the Campagnac 

 coal covered much of the region south from Eiou Vieux, that it underlies 

 the Firmy area and that northward from that area it extended to the 

 eastern border. The conditions observed along the comparatively narrow 

 valley of Eiou Mort show that the bed has been removed by erosion there. 

 The presence of Permian in the interior of the basin and its conforma- 

 bility to the Bourran system seems to be a final argument. Permian is 

 present along the eastern border and along the middle of the basin, but is 

 lacking in the intervening space. Its absence is evidence of great erosion 



