49 s A. W. GRABAU PALEOZOIC DELTA DEPOSITS OF NORTH AMERICA 



tary to the Salina basins was probably three times the area of these States, 

 or more, and from the remnants of the Niagaran beds left in some localities 

 its thickness averaged at least 500 feet, and may have approached 1,000 feet, 

 not to speak of the underlying marine Ordovicic strata. Thus at least 15 sncb 



salt beds could be obtained from the Niagaran beds, a large part of which are 

 known to have been eroded during Salina time. It is probable that half this 

 amount of salt is mure than sufficient to form all the salt beds of the Salina 

 basins of New York. Michigan, and Ontario. 



'"On the basis of the salt content of modern marine deposits the amount of 

 available salt might easily be considered as live times greater than that given 

 by the above calculations. 



"The calcareous beds in the Salina series of New York and Michigan are 

 undoubtedly formed from the lime sand and lime mud derived by the mechani- 

 cal destruction of the older limestones (Niagaran). The magnesian character 

 of some of these beds is accounted for by the partial dolomitic character of 

 the limestones from which they were secondarily derived. The gypsum may. 

 of course, be in part the calcium sulphate of the old sea-water and in part 

 altered limestones of the clastic type. Much of the lime sand and mud re- 

 mained unused, however, until the advent of the Monroe Sea over this region, 

 when it was deposited as stratified elastics in this sea. or on its margins, to 

 form the finely bedded Monroe strata. 



'•Considering the Salina deposits in the light of modern salt accumulations. 

 it becomes apparent that of all the known methods of accumulation, that of 

 the continental fits best the conditions found and explains all the characters 

 of the deposits, which, on the other hypotheses of origin, are difficult or even 

 impossible of explanation. One of the strongest arguments in favor of the 

 marine or estuarine origin of the clastic Salina deposits, the Shawangunk and 

 the Longwood. thus falls to the ground, and we are driven to the conclusion 

 that these deposits could not have accumulated in a body of standing water, 

 marine or estuarine. because, as shown by the contemporaneous deposits in the 

 interior basins, where such seas should have been, there was no such water 

 body in existence. Instead of this there was a desert area, parts of which 

 were flooded momentarily by the infrequent stream, which washed the saline 

 efflorescence from the surrounding highlands and thus brought about their con- 

 centration in a circumscribed desert area" (page St. 



Relation of the Eurypterids to their environment. — It has been, as a 

 rule, tacitly assumed that Eurypterids were marine organism?, at least 

 in the earlier periods of their existence. The only writer who has argued 

 for a non-marine habitat of these organisms was Chamberlin, 93 w 

 study was mainly a philosophical one and which only incidentally con- 

 sidered the indications furnished by the rocks in which the remains are 

 found. Xevertheless. here, as in so many other cases, this brilliant writer 

 and investigator has touched upon the essentials of the problem, which 

 he. for the first time, clearly places before us, and he has pointed out the 



93 T. C Cbamberlin : On the habitat of the early Vertebrates. Journal of Geology, 

 vol. S, 1900, p. 400, 



