22 NEW YORK STATE MUSEUM 



GARDEAU FLAGS AND SHALE 



Light bluish gray sandstones and flags separated by beds of blue, 

 olive or black shales succeed the Grimes sandstone for about 500 

 feet. In general stratigraphy this formation is much like 

 the Hatch shale and flags, but many of the sandstones and some 

 of the shale beds are thicker than are seen in that formation. It 

 is the surface rock over a large area on these quadrangles, the drift 

 cover of which, except in a few localities, is quite thin, and field 

 outcrops are frequent. Almost innumerable ravines and small gul- 

 lies on the hillsides show rock sections e:nbracing some part of the 

 Gardeau beds. 



Among the best exposures on these quadrangles are : in Reynold's 

 gulf, three miles north of Springwater ; along Calabogue creek- 

 above the mill at Conesus ; the Culberson ravine above the railroad ; 

 the Bradner creek ravine north of Woodville ; and at Stones Falls 

 and Stony brook glen south of Dansville. 



Fossils are rare, but a few brachiopods known in the Ithaca fauna 

 occur in some of the sandstones, and a few lamellibranchs and 

 cephalopods common in the Cashaqua shales are found in soft 

 shales, especially in the upper part of the formation. 



The following is a partial list of the species occurring in the Gar- 

 deau beds : 



Manticoceras oxy Clarke 



Palaeotrochus praecursor Clarke 



Grammysia elliptica Hall 



Leptodesma robustum Hall 



Productella lachrymosa Hall 



P. spinulicosta Hall 



Ambocoelia umbonata (Conrad) 



Atrypa hystrix Hall 



Orthothetes chemungensis Conrad 



Liorhynchus mesacostalis Hall 



Hydnoceras tuberosum Conrad 



Aulopora sp. 



Crinoid stems 



NUNDA SANDSTONE 



(Portage sandstone of early reports) 



A heavy band of light bluish gray sandstone succeeds the Gar- 

 deau flags in central New York. It is a strongly marked feature 

 of the stratigraphy of the region and is of considerable economic 

 value as the source of fine building stone. 



