814 C. SCHUCHERT MEDINA AND CATARACT FORMATIONS 



those higher in the formation. Both of these limestones have small 

 shale pebbles, and as these latter do not come from the Clinton, they 

 are regarded as of intraformational origin. 

 Clinton limestone. Contact sharp with Rochester. Thickness about 15 feet. 

 Seen best at head of Weutworth Street incline. 

 Irondequoit limestone memher. One bed of hard, cavernous, crystalline, 



slightly pinkish, crinoidal limestone. Thickness 4 feet 5 inches. 

 Wolcott limestone memlyer. Seven beds of gray magnesian limestones 

 with shale partings. Thickness (16, 18, 16, 18, 18, 10, 8 inches) 8 

 feet 8 inches. 

 Basal thin-bedded, gray, magnesian limestone. 18 inches thick. At the 

 base it is sandy, glauconitic, and pyritiferous for about 2 inches, 

 then the sand is less abundant, but the glauconite and pyrite continue 

 into the limestone; near the top is an abundance of Pentamerus od- 

 longus (Clinton form). 

 The sharp contact with the Medina, the very different sediments, and 

 the marked faunal difference indicate that the Clinton-Medina con- 

 tact is here broken. 

 Disconformity. Contact sharp between adjacent beds. 



Medina sandstone. Thickness about 12 feet. Seen to best advantage at the 

 head of John street beneath the large road-metal quarry between 

 two stone crushers and back of the covered reservoir building. 

 At the top about 4 feet of thin-bedded light green sandstones, interbedded 

 with sandy shale. Below, a horizon 4 to 6 feet thick of heavy-bedded 

 sandstones, with localized zones of large (2 feet deep) mud-ball (sea- 

 churning) formation. Next lower occur 4 to 6 feet of thin-bedded 

 sandstones, alternating with shales, the basal bed of 1 foot thickness 

 having in abundance Lingula clintoni, a form also found in the 

 Cataract below. The contact between the Cataract and the Medina 

 is. however, a sharp one, as may be seen in plate 14, figure 1. 

 Cataract formation. Thickness about 90 feet. Seen to best advantage be- 

 neath and to the south of the Wentworth Street incline and along 

 the Jolly Cut road. Contact with Medina above is sharp. Cataract 

 green shale below and gray sandstones above. There appears, how- 

 ever, to be no break in sedimentation here. 

 Cahots Head shale inemher. Green shales at the top variable in thick- 

 ness from 6 to 18 inches. These then change below into red shales, 

 and at about 5 feet beneath the top abound in Phwnopora and other 

 Bryozoa. 

 Red argillaceous and sandy beds, 6 feet thick, abounding in Helopora. 

 Red shales with an occasional sandy magnesian limestone, 10 feet seen. 



All of the above beds especially rich in bryozoans. 

 Covered area. Thickness about 30 feet. 



The rest of the Cataract occurs in the Mills and Webb quarry. 

 Manitoidin member. Thin-bedded^ green and reddish, magnesian lime- 

 stone, with much interbedded shale, 20 feet thick. Abounds in Helo- 

 pora and other fossils. 

 Sandstone layer, 4 inches thick. 



Thin-bedded magnesian limestones, without shale partings, 8 feet thick. 

 Fossils are common, among them Helopora, Favosites, and Plectam- 

 honitea tranaversaUs. 



