PROCEEDINGS 



OF THE 



AMERICAN PHILOSOPHICAL SOCIETY 



HELD AT PHILADELPHIA 

 FOR PROMOTING USEFUL KNOWLEDGE 



Vol. LI October-December, 1912 No. 207 



THE FORMATION OF COAL BEDS. 



III.^ 



By JOHN J. STEVENSON. 



(Read November i, 19 12.) 



The Rocks of the Coal Measures. 



Coal beds, Devonian, Carboniferous, Mesozoic and Tertiary, 

 alike, are associated with shales, sandstones and, in many cases, with 

 calcareous beds, the last often containing a marine or a fresh-water 

 fauna. Interior or limnic basins frequently bear close resemblance 

 to paralic or coastal basins, so that distinction between the types 

 becomes arbitrary in some great areas. In the Indiana-Illinois field, 

 wide invasions of the sea appeared again and again throughout 

 practically the whole period of accumulation. On the other hand, 

 the Appalachian basin, almost land-locked during most of its history, 

 experienced few invasions and those, of comparatively small extent, 

 were confined to the earlier periods ; in the later stages, the whole 

 region was practically limnic. 



Study of reports by observers in the several countries makes 

 certain that conditions needed for formation of coal beds were to 



'Part I. appeared in these Proceedings, Vol. L., pp. 1-116; Part II. in 

 same volume, pp. 519-643. 



PROC. AMER. PHIL. SOC, LL 207 A, PRINTED DEC. I3, I9I2. 



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