32 SMITHSONIAN INSTITUTION 



Northeast of Napanoch on Rondout Creek the dip steepens to 50 

 degrees or more to the northwest. The lower half of the exposed 

 section abounds in marine fossils, but the upper half contains many 

 fossil land plants. Nevertheless, a thin zone of Upper Hamilton 

 marine fossils exposed at the top of Honk Falls gave a clue to the 

 thickness in this valley, approximately 3,200 feet. 



The dip of the beds lessens northeast of Napanoch to an average 

 of about 5 degrees, and the outcrop widens. The upper part of the 

 Hamilton changes to unf ossiferous, red, argillaceous sandstone and 

 greenish, coarse or conglomeratic sandstone well shown around 

 Ashokan Reservoir. Between these continental beds and the lower 

 fossiliferous marine Hamilton rocks west of Kingston about 300 feet 

 of bluish sandstone or "blue-stone" intervene. This rock, now called 

 Ashokan sandstone, was extensively quarried about 40 years ago and 

 formed the basis of the once flourishing "blue-stone" industry. 



From Kingston nearly to Albany approximately the same sequence 

 prevails: a lower part of about 1,000 feet of fossiliferous marine 

 sediments (Bakoven and Mount Marion), then 300 feet of "blue- 

 stone" succeeded by a great thickness of red-beds (Kiskatom) diffi- 

 cult to date because of absence of marine fossils. 



An important part of this investigation was the determination of 

 the thickness of red-beds belonging to the Middle Devonian in the 

 mountains west of Catskill. In the absence of marine fossils, resort 

 had to be made to comparison with other sections. The studies be- 

 tween Port Jervis and Kingston showed a continuously thickening 

 sequence northeastward toward Albany, exactly the condition dis- 

 covered on the north side of the Catskills between Susquehanna 

 Valley and Albany. Therefore the section at Catskill must be at least 

 as thick as that at Napanoch, where 3,200 feet of Hamilton sediments 

 are known. Considerable thickening occurs northeast of Napanoch; 

 hence it is concluded, on the basis of known rate of thickening that 

 the Hamilton beds west of Catskill are much in excess of 3,200 feet, 

 perhaps as much as 500 feet, putting the top of the Hamilton near the 

 well-known Mountain House between 2,100 and 2,200 feet. 



The results of this investigation thus corroborate the findings of 

 1932 on the north side of the Catskills. They also show that the 

 marine beds of Stroudsburg and Port Jervis gradually change north- 

 eastward to nonmarine beds about Catskill. The northeastern por- 

 tion of the Catskills is a great delta deposited from old highlands 

 to the northeast. The delta sends out fingers of continental sediment 

 into the marine beds west of the Catskills. 



