510 STEVENSON— THE FORMATION OF COAL BEDS, [^'ov. i, 



pelian origin for the black limestone of Hun and F. Kaisin had done 

 the same for the Dinant marbles. De Dorlodot agrees with Renier 

 that the limestone is marine but dissents from the opinion that 

 it is a coast deposit. The conditions and stratigraphical relations 

 had led him to believe that it was deposited far from shore, for the 

 deposits are not local, they are extensive and their lithological char- 

 acter suggests deep-sea origin. 



According to de Dorlodot, Renier's decision in favor of shore 

 deposit depends upon the presence of terrestrial plants and of 

 sapropelic matter in the limestone; but presence of remains of ter- 

 restrial plants is irrelevant, for A. Agassiz found them far from 

 shore and in deep water off the Pacific coast as well as in the Gulf 

 of Mexico. Sapropel deposits can be formed along coasts only in 

 lagoons or in bays protected against movement of the waves. 

 ■Proximity to the coast is not possible, for action of the waves would 

 cause continuous oxygenation of the water. The deep sea would 

 be most favorable to accumulation. He supports his opinion by 

 reference to carbonaceous shales of the Toarcien, asserting that 

 their geographical extent is proof that they were not deposited in 

 isolated bays, while their fauna proves deposit in the maximum of 

 immersion — and those shales contain remains of land plants. The 

 fact that deep sea soundings in our day show no sapropelian de- 

 posits is not final. The problem is not to explain why the old 

 marine rocks are so rich in kaustobiolithic materials, but why 

 modern deep sea deposits are so poor. The problem may be stated 

 in another way. How is aerobian life possible in great depths of 

 the ocean so as to cause destruction of the organic matter which 

 the plankton must afford? This is explained by the bottom-creep 

 of oxygenated water from the poles ; in the Black sea, which is 

 beyond the influence of that creep, there are only anaerobic organ- 

 isms in its depths. Sapropelic character does not prove shore 

 origin — it rather tends to establish and at times to demonstrate 

 deposition at distance from the shore and at great depths. De 

 Dorlodot believes that the limestones under consideration were de- 

 posited far from the coast and in calm water. 



It is difficult to discover the force of this reasoning and equally 



