554 



PROCEEDINGS OF THE ALBUQUERQUE MEETING 



The Monroe formation is Ji strictly marine series succeeding the abnormal (non- 

 marine [Grabau] ) Saliua. It is traceable throughout lower Michigau, west- 

 WAvd into Wisconsin, and eastward through Ohio, Ontario, and into M'estern 

 New York. Where recognizable a strong dividing line separates the lower from 

 the upper part, and in general this division is emphasized by the occurrence 

 of the Sylvania sandstone, a rock of pure quartz grains, and representing, ac- 

 cording to Grabau and Sherzer, an isolian deposit formed under conditions 

 similar to those now found in the Lybian desert. According to this intei'pre- 

 tation, the Sylvania sandstone represents a long time interval the depositioual 

 marine equivalent of which is still unknown. This long interval is further 

 emphasized bj' the entire distinctness of the faunre of the lower and upper 

 divisions of the Monroe. 



The subdivisions recognized so far in the Monroe, with their faunal charac- 

 teristics (determined by Grabau), are as follows: 



I. THE LOWER MONROE 



Proposed name — Bass Islands series. — For this stratigraphic unit the name 

 Bass Islands series is proposed, from the group of islands of that name in west- 

 ern Lake Erie. No other appropriate term seems to be available, though char- 

 acteristic exposures of all the divisions are not found in these islands. 



a. The Greenfield dolomite. — ^This term was proposed by Grabau in 1898, 

 though previously used in a commercial sense, for the dolomite found about 

 Greenfield, Highland county, Ohio, and exposed again in the regions about 

 Ballvllle, in northern Ohio. The name is here accepted for this division, which 

 is characterized by Scliuchertella hydraulica (Whitfield) ; Hindella ? whit- 

 fleldi Grabau ; H. ? rostralis Grabau ; Lejyerditia, etcetera. The faunal zone 

 may be called that of {^chueliertella hijdrauUca. The thickness is 100 feet or 

 more and the formation is the lowest known subdivision of the Monroe. 



6. The TyniocUtee shales and limestones. — This name was proposed in 1873 

 by N. H. Wiuchell for the shales and thin-bedded calcilutytes of the Monroe 

 (Waterlime) series exposed in the creek of that name in Crawford township, 

 Wyandot county, Ohio. The thickness there is something over a hundred feet, 

 but the relation to the overlying and underlying formation is unknown. Its 

 fauna likewise is unknown, and the formation must be considered a tentative 

 division of the Lower Monroe. It is not impossible that it represents in part 

 one or more members recognized elsewhere. 



c. The Put-in-hay dolomites. — This name is proposed for the extensive fossil- 

 iferous series of waterlime exposed on Put-in-bay island, one of the Bass 

 islands, and characterized by the fauna comprising Spirifer ohioensis Grabau, 

 Goniophora duhia Hall, Eurypteriis eriensis Whitfield, and Leperditia. From 

 the abundance of the pelecypod, the paleontologic zone may be called that of 

 Goniophora duhia. Something over a hundred feet of strata is exposed on Put- 

 in-bay island, where the higher beds are in contact with the succeeding zone. 

 The formation is also known from Marion county, Ohio. Its thickness is over 

 100 feet, but the base is unknown. 



d. The Raisin River dolomites. — ^This name is proposed for the highest divis- 

 ion of the lower Monroe exposed in Lucas and Wood counties, Ohio, and in 

 Monroe county, Michigan, especially along the Raisin river. It is perhaps 200 

 feet thick and contains several oolite zones. Its known fauna comprises nearly 



