540 CHARLES S. PROSSER 



20. The Monroe formation, however, in northwestern Ohio con- 

 contains a light-colored, very quartzose rock, which in 1888 was 

 named the " Sylvania sandstone" by Dr. Orton,^ from the 

 exposure in a quarry about four miles west of Sylvania village, 

 in Sylvania township, Lucas county. The stratum was first 

 described by Mr. G. K. Gilbert in 1873, who referred it to the 

 " Corniferous group" with a thickness of 20 feet,^ although on the 

 accompanying geological map of Lucus county it is apparently 

 the division termed the Oriskany sandstone, and represented as 

 crossing the county from the Michigan state line to the Maumee 

 River on the south. The same terrane was represented in 

 Wood county, south of the Maumee River, 3 and perhaps in some 

 of the other counties of northwestern Ohio. The sandstone 

 thickens as followed to the northeastward in Michigan, and Mr. 

 Sherzer gives it as 50 feet in thickness in Exeter township, 

 Monroe county, the one immediately north .of Lucas county, 

 Ohio ; while still farther north it is given as ranging from 95 to 

 130 feet in thickness.^ On Mr. Sherzer's geological map of 

 Monroe county the " Monroe beds " are represented in five 

 divisions, and the only one to which a geographic designation is 

 given is the Sylvania sandstone. The dolomitic limestones 

 below the Sylvania sandstone are separated by an oolitic bed, 

 which is given as about lOO feet below the sandstone and from 

 20 inches to 2 feet in thickness. ^ 



It appears to the writer that the Monroe formation of north- 

 western Ohio may probably be divided into at least three 

 members. For the upper one the name Lticas limestofie is pro- 

 posed, from Lucas county, which it crosses from north to 

 south. It may be studied at the typical locality in Sylvania 

 township, described by Mr. Gilbert in 1873, where are the 

 extensive quarries of the Toledo Stone and Glass Sand Com- 

 pany and the place now named Silica, or in the banks of the 

 Maumee River bordering Providence township. It includes all 

 the rocks between the top of the Sylvania sandstone and the 



' Rept. Geol. Surv. Ohio, Vol. VI, p. i8. 



^Ibid., Vol. I, Part I, p. 576. ^ Ibid., Vol. II, Part I (1874), op. p. 368. 



t Geol. Stirv. Mich., Vol. VII, Part I (1900), p. 54. 5 Ibid., p. 61. 



