4IO A. C. LANE 



anticlinal rather narrowly, for it is relatively thin at Britton, Ann 

 Arbor, Mount Clemens, absent at New Baltimore, though present at 

 Port Lambton and Marine City, and absent at St. Clair, but present 

 at Port Huron. 



Grabau and Sherzer are inclined to consider it aeolian. But the 

 way the grains of sand occur in the dolomite or limestone as in Port ' 

 Lambton (and in a series of records like those at Marine City [Vol. VJ, 

 we find it shading into the dolomites) its fairly regular variation in 

 thickness, similar at similar situations' on the Cincinnati anticlinal, 

 growing thicker to the line of thickness above mentioned, suggest 

 that if they were wind-transported they were water deposited. Of 

 course, near the outcrop it may be more aeolian. Lithologically it 

 is a pure (99 per cent) quartz sand of the highest grade of glass sand 

 as white as sugar. The nearest like it of recent sands that I have 

 found is one from Florida. Its extreme freedom from iron is not 

 characteristic of desert sands. On the other hand, it seems to have 

 a characteristically fresher water (stronger in sulphates) than the beds 

 below. 



The disconformity with the beds below which Grabau mentions 

 is not marked, though there are red sandy-looking beds at about that 

 horizon in a few wells. The disconformity above is most marked 

 and, as Grabau has pointed out, a new fauna appears of puzzling 

 affinities. It seems that in many places during the whole time of the 

 Lower Monroe and the Middle Devonian the American continent 

 was out of water, and the disconformity marking this period of emer- 

 gence is the well-defined and accepted line between the Silurian and 

 Devonian. This applies to Milwaukee and western Michigan. But 

 the great basin of Lower Michigan was not lifted altogether out of 

 water. The warping which caused the emergence lifted up the 

 Wisconsin land-mass and also the Cincinnati anticlinal, and the 

 Sylvania sandstones were formed as emergent sandstones along a 

 shore not altogether unlike those from Chicago around to New 

 Buffalo today. It was partly aeolian, but there is reason to think 

 that much of the wind-blown sand found its final resting-place under 

 the water, building a sandy shelf out from the shore. 



I Compare Dundee, 60 to 253; Morton Salt Co., 65 to 262; Solvay, 95 to 415; 

 Wallaceburg, 100 to 1,100; Port Lambton, 50 to 1,250. 



