44 STEVENSON— INTERRELATIONS OF FOSSIL FUELS. 



are common features at many places. Sandstones and shales fre- 

 quently contain logs of wood, in such relations as to leave little room 

 for doubt that they are simply stranded material. 



There is, however, ample proof that the sea invaded many places 

 where coal was accumulating. The Lower Oolite of England has 

 beds with great abundance of fragmentary marine shells ; the Liassic 

 sandstone of Austria and Hungary includes layers with many marine 

 mollusks of littoral types; Ammonites was found at one locality, 

 but that does not militate against the conclusion that the water was 

 shallow — if the shell be not drifted, it shows that the genus could 

 exist in shallow water ; the Rhastic of Sweden is freshwater below, 

 but has marine shells in the upper portion, where the coal seams 

 are very thin and impure. The lower beds of the Jura-Trias in 

 Queensland have yielded a few specimens of offshore mollusks. The 

 incidental references to beds with marine fossils do not enable one 

 to determine the extent of areas covered at one time or another by 

 salt or brackish water; but in the Funfkirchen district of Hungary 

 such beds, though few in number, are present in the roof, floor or 

 even partings of several coal seams, recalling the conditions ob- 

 served in southwestern Utah, within the Benton, near base of the 

 Upper Cretaceous, where a coal seam between beds of marine lime- 

 stone has freshwater mollusks in a parting. In any event, these 

 deposits suggest that the areas in which they exist were lowland, 

 close to the ocean level. The shallowness of the water cover during 

 their deposition is so evident that one may well conceive that the 

 invasions were due to diversions of drainage, to shifting>of channels 

 of large streams. How readily such shifting of channel ways may 

 change conditions in a plain country is shown by Featherston- 

 haugh's*^ statement that, in one area, the Arkansas River broke 

 through its banks and converted 30,000 acres into swamp land, kill- 

 ing all the trees. Still more remarkable illustrations exist on the 

 broad plains bordering the Paraguay and other rivers in South 

 America. Many times in sections of coal-bearing rocks, marine 

 deposits are in contact with those of land origin or are separated 

 from them by an inch or two of fine sediment. 



*^ G. W. Featherstonhaugh, "Geological Report of Examination of the 

 Elevated Country between Missouri and Red Rivers," Washington, 1835, p. 84. 



