PORTAGE AND NUNDA QUADRANGLES 59 



pact layer 3 feet, 6 inches thick by 5 feet, 4 inches' of soft shale 

 mostly dark. 



This sandstone is succeeded at the top of the formation by 19 

 feet, 8 inches of light and dark shales with a few thin flags, overlain 

 by the stratum of light blue gray sandstone 7 feet thick that is the 

 basal layer of the next higher member of the Portage group, the 

 Nunda sandstones. The Gardeau flags and shales are the lowest 

 rocks exposed on the Portage quadrangle in the Oatka creek or 

 Warsaw valley. In the large ravine of Stony creek or Fall brook, 

 y 2 miles southwest of Warsaw 235 feet of these beds are finely 

 exposed below the Erie Railroad. They are, as a whole, noticeably 

 softer than in the Genesee river section and there are fewer sand- 

 stones except at the top of the falls, where a hard stratum 1 foot 

 thick has been denuded of shale for the space of a few square rods, 

 and is locally known as Table rock. It is not, however, in the 

 same horizon as the Table rock at the Lower Portage falls. 



In Gibson's glen, near South Warsaw, 150 feet of the upper beds 

 are exposed, and a somewhat less thickness of the same up to the 

 top of the formation in the ravine of Oatka creek between Newburg 

 and Rock Glen. 



In the Nunda or Cashaqua creek valley the small ravines on the 

 side of East hill opposite Nunda and on the west side below Brooks 

 grove, show partial sections of these beds, and Wildcat gully cuts 

 through the entire formation. 



The upper parts of the rock gullies on the west side of the 

 Canaseraga valley above West Sparta and nearly up to Byersville 

 are in the Gardeau beds, and they are exposed under similar con- 

 ditions on the east side above Groveland station. 



The fauna of the Gardeau beds on these quadrangles is not an 

 extensive one, but it is made specially interesting by the fact that it 

 is composed of several species that first appeared in the Genundewa 

 limestone and were more or less common in the Cashaqua, with 

 additions from the Portage fauna on Lake Erie, and, east of the 

 river, some members of the Ithaca fauna that do not appear in the 

 exposures in the gorge, nor in this horizon further west. 



Fossils except plant remains are usually almost entirely absent 

 from these sandstones on the Portage quadrangle but Table rock in 

 the Fall brook ravine, Warsaw which is in two parts, separated by 

 a thin seam of shale, bears on the surface of the lower part scores 

 of the little lamellibranch Buchiola retrostriata and 

 several other species abundantly. Some flattened concretions in a 



