STEVEySOX, COAL BASIN OF DECAZEVILLE. FRAXCE 281 



The sterility of the intervening deposits should not be overlooked. 

 The whole succession above the Bourran coal bed is exposed in the hill 

 between Domergue and Decazeville and no trace of coal was seen any- 

 where in the section. The interval between the Bourran and the Cam- 

 pagnac is certainly 750 feet along the eastern exposures; the lower por- 

 tion is shown well at Tramont, fragmentary exposures are numerous 

 along the road from Firmy to Cransac and much of the higher portion 

 is shown north from Decazeville. In this great interval, there are few 

 horizons in which traces of coal occur, and those seem to be local. 



In this connection, one must not forget that the series is complete and 

 continuous ; that a borehole at Decazeville would pass through the Bour- 

 ran and Campagnac systems into at least the upper part of the Auzits, 

 seen under the Campagnac coal at a little way east ; that the Campagnac 

 rocks continue to the eastern l)oundary, and that the Campagnac coal bed 

 is far under the Bourran coal bed at the most southerly exposures. In 

 this basin, the coal beds are of independent origin ; they do not come 

 together at the border. 



ORTGIX OF TIIK COAL BEDS 



The only liypothesis thus far ])resented to account for tlie accumula- 

 tion of coal beds in this basin is that the vegetable matter was brought 

 in l)y the streams. Bergeron in ISSS announced that the delta theory, 

 newly proposed by Fayol in his brilliant memoir on Commentry, was 

 fully applicable to Decazeville. Bergeron, Jardel and Picandet, in 1900, 

 were more explicit, as they had better knowledge of the conditions. The 

 Soulier- Abiracs coal bed was formed by the Haute Serre stream; the 

 Campagnac bed was formed at the south by accumulation of vegetable 

 matter brought down by the Lugan and Haute Serre, while at the north, 

 the Pont du Bourran stream contributed the needed material; the com- 

 paratively imimportant Bourran beds at the west are irregular and in- 

 definite because of their proximity to the entering currents, the fine 

 vegetable materials being carried farther east, there to accumulate beyond 

 disturbing influence of the streams. 



The mode in which the coal occurs within the Decazeville is in notable 

 contrast to that observed in the basin of Commentry. Accumulation of 

 coal in important quantity began at a comparatively late time in the his- 

 tory of Commentry, and it was confined to two insignificant areas sepa- 

 rated by the barren zone of Montassiege.^ But at Decazeville the basin 



» For explanation of these references to Commentry, see H. Fayol, "Reunion extra- 

 ordinaire dans I'Allier," Bull. Soc. OSol. de France, 3me. ser., t. 16me.. Separate, p. 12 ; 

 or .1. T. Stevenson. "The coal basin of Commentry in central France," Ann. N. Y. 

 Acad. Sci., vol. xix, pp. 161-204, 1909. 



