THE SILURIAN SECTIONS 541 



large stems of Mariacrinus, and more rarely Stromatopora. The 

 corals continue downward and into the Rosendale waterlime (for 12 

 inches), here a bed 9 feet thick. Below are 3 feet more of thin- 

 bedded, poor, water limestone with local beds of chert; the basal 

 transition zone, 12 inches thick, is sandy, with the coarsest sand at 

 the bottom. 

 The Lower Cobleskill is again well seen at the falls of the Rondout at 

 High Falls, followed beneath by the Rosendale cement beds, about 20 

 feet thick. 



Binnewater sandstone. North of Binnewater station this formation has a 

 thickness of from 32 to 35 feet. It is a coarse-grained, gray, dense 

 quartzite, easily distinguished from the formations above and espe- 

 cially below, and consists in the main of cleanly washed, regularly 

 bedded, thin sandstones, with interbedded green to black shales that 

 vary in thickness up to 4 inches. The strata are commonly rippled, 

 with the wave crests from 1 to 2.5 inches apart. Near the middle of 

 this member were seen sun-crackings. The uppermost 5 feet are 

 somewhat cross-bedded and with the coarsest sand ; a few Halysites 

 occur, linking the formation faunally with the Cobleskill cement beds. 



Farther north on the Wallkill Valley Railroad at the north end of Red 

 Rock siding is another and better exposure of the Binnewater sand- 

 stone, with a complete transition zone into the cement beds of the 

 Cobleskill. Here the upper beds of the Binnewater sandstone have 

 far more lime and the terminal 3 feet have the undescribed Favosites 

 globuliformis (Vanuxem) and Stromatopora. 



At High Falls the Binnewater thin-bedded grayish sandstone is fully 

 exposed and has a thickness of about 25 feet, though Brown gives it 

 as 50 feet and Hartnagel as 15 feet, differences that are due to de- 

 limitations in a continuous series .of sediments. Here it is also rip- 

 pled, has more calcareous cement, is thinner bedded, and has zones of 

 intraformational pebbles of waterlime-like rock (now leached out, 

 leaving cavities ) , showing that near by impure limestones were form- 

 ing and being torn up by the storm waves of this shallow sea. 



Probable break. 



Silurian. Cayugan series. 



High Falls shale, about SO to 90 feet thick. Best seen along Rondout 

 River below High Falls, New York, where there is no clearly devel- 

 oped transition zone nor easily determined hiatus between it and the 

 higher Binnewater sandstone. The upper 10 feet of the High Falls 

 shale is a sandy and very impure blue water limestone that is mucb 

 sun-cracked. This passes unbroken into brick-red shales, full of small 

 leached cavities and with much intraformational shale conglomerate, 

 interbedded with an occasional blue shaly waterlime (more or less 

 sun-cracked) zone, which together have an estimated thickness of 30 

 feet. Then come evenly bedded, dark blue, very hard, calcareous 

 sandstones about 12 feet thick. Below occur from 30 to 40 feet of 

 mainly red shales, interbedded with green ones. These rest on the 

 Shawangunk formation. 



