23 



Medina formation. — Thickness 60 to 70 feet (18.3 

 to 21 .3 m.). 



Upper massive, quartzose, whitish, cross bedded 

 sandstones. Gray band of authors. From 8 to 

 10 feet (2.44 to 3.05 m.) thick. 

 Reddish and greenish bedded sandstones, much 

 cross bedded and channeled. From 12 to 15 feet 

 (3.65 to 4.57 m.) thick. Arthrophycus harlani 

 — 2 feet (.61 m.) beneath top — and Lingula 

 cuneata. Thin bedded, reddish sandstones, with 

 red shale partings and at least one zone of 

 storm-rolled mud balls. From 35 to 40 feet 

 (10.7 to 12.2 m.) thick. In the upper part of 

 these sandstones occurs the typical Medina 

 marine fauna. 



Gray sandstone with green shale partings. Thick- 

 ness 5 feet (1.5 m.). Poor Medina fossils. 



Disconformity and irregular contact, seen best along 

 the Grand Gorge trolley line. 



Cataract formation. — To be seen on each side of the 

 small tunnel on N.Y.C.R.R. Thickness about 

 51 feet (15.5 m.). 



Upper dark green shales, 4 feet (1.2 m.) thick. 

 Thin bedded , green to yellow magnesian and argil- 

 laceous limestone, in lenses abounding in Helopora 

 and fragments of Lingula. Thickness 3 feet 

 (.91 m.). 



Middle green shales, 10 feet (3.05 m.) thick. 

 Thin bedded argillaceous magnesian limestones, 

 2 feet (.61 m.) thick. 



Helopora common, Leperditia, Whitfieldella and 

 fragments of Lingula. 

 Lower green shales, 7 feet (2 . 1 m.) thick. 

 Basal or Whirlpool (Grabau) sandstone. Thick- 

 ness 25 feet (7.6 m . ) . 



Hard, heavy bedded, gray, somewhat coarse, 

 cross-bedded sandstones. Thin bedded in upper 

 5 feet (1.52 m.). No fossils. 



Disconformity with irregular contact in places. 



Ordovician. 



Queens ton (Grabau. Synonym Lewiston, Chad wick). 



Brick-red sandy shales. Exposed for 115 feet 

 (35.0 m.). No fossils. In Ontario in equivalent 

 strata occur fossils of Richmondian age. 



