APPLICATION TO THE SYLVANIA SANDSTONE 653 



paucity of fossils. Goodcliild concludes^ "with a tolerable amount of 

 certaint}^^ that any sandstone largely composed of well rounded grains of 

 sand represents a desert sand, and was formed under arid conditions, on 

 a land surface" (page 211). Accordingly he assigns such an origin to 

 the Torridon, Old Eed, and jSTew Eed sandstones of Great Britain. 



In the Lake Erie region the open-sea conditions of the Niagara period 

 were succeeded by those under which there was deposited extensive beds 

 of salt and gypsum, marking the Salina formation and indicating, it is 

 believed, a period of great dessication and aridity of climate,'^^ but with 

 no suggestion of actual emergence of the land. Following the Salina 

 deposits, there succeeds those of the lower Monroe, formed of compacted 

 gypseous, dolomitic slime, free from land detritus, becoming character- 

 istically brecciated, and sometimes conglomeritic, showing ripple-marks, 

 mud cracks, carbonaceous matter, and beds of oolite essentially like that 

 forming about the shores of Great Salt Lake. This certainly indicates a 

 shallowing of the sea at mid-Monroan time and probably a continuation 

 of the arid conditions.'^ The upper Monroe series shows shallow sub- 

 mergence again, passing into the clear, open-sea conditions of the Cor- 

 niferous. There is thus furnished conclusive evidence of a general move- 

 ment in lower Monroe time toward emergence of the land and in upper 

 Monroe time away from emergence. If there is any one place in the 

 geological scale of this region, then, where we may reasonably expect sub- 

 aerial deposits to be found, it is in mid-Monroan time, and here occurs 

 the singular deposit of pure quartz sand, difficult, indeed, to account for 

 on any other than an seolian hypothesis. 



A careful search has been made for field evidence that could not be 

 reconciled with the seolian hypothesis, but so far nothing has been found. 

 Criticisms have been invited from those familiar with the formation, and 

 the following received: If there was a shore near, should there not occur 

 in the sand clastic grains of dolomite, this being the rock on which the 

 deposit rests? Why did not the land surface contribute other material 

 than quartz to the Sylvania formation? Why is the Sylvania not some- 

 what red, as in the case of desert sands today? As to the first of these 

 three queries, it may be said that such clastic grains, if introduced, would 

 be relatively small in amount and soon be ground to powder, in the same 

 way that the Portland cement "cinder" is reduced between quartz peb- 

 bles. In this condition it would be removed by wind action or by perco- 

 lating water in solution, traces of which are abundant in the bed, but 

 probably of much later introduction. Concerning the second question, 



■^1 See Lane in vol. v, Michigan Geological Survey, 1895, part ii, p. 28. 

 ■^2 Geological Survey of Ohio, vol. vii, 1893, p. 15. 



