294 T. N. Dale, Jr.—The Fault at Rondout. 
the hill consists of grit dipping east-northeast at an angle of 
about 45°. These grits form part of the series of clay-slates 
and grits of the Hudson River group.* Unconformably resting 
upon these grits is a series of limestones, dipping at about the 
same angle, but toward the northwest. e grits are non-fos- 
siliferous at this point. The limestones are abundantly fossil- 
iferous. T am indebted to Mr. Lindsley for the following 
measurements of the latter. 
ginning above: No. 9, 20 feet or more, Upper Pentamerus 
limestone. No. 8, 20 feet, Encrinal limestone. No. 7, 15-20 
feet, Delthyris limestone. No. 6, 20 feet Lower Pentamerus 
limestone with chert, Pentamerus galeatus, Crinoids. No. 5, 
feet, Ribbon limestone with Stromatopora concentrica.. No. 4 
15 feet, Tentaculite limestone with Tentaculites trregularis, Le- 
perditia alta. No. 8, 4 feet, limestone with prismatic mud 
cracks. No. 2, 80 feet, Water-lime with Leperditia alta. No. 
1, 6 feet, Encrinal limestone. _ Whatever may be thought as to 
the presence in No. 1 and 2 of N iagara beds, we certainly have 
to do with Lower Helderberg in part of No. 2 and in No. 8 and 
The relative position of the rocks is shown in the accom- 
anying sections. For Section No. 8, I am indebted to Mr. 
Lindsley. The excavations represented in figure 1 were made 
in ne the rock being a hydraulic limestone or “ cement 
rock,” 
ON 
KK 
j \ \S\\ . Y RAIN SVX iw‘ 
Figs. 1 to 3, Lowe Helderberg beds resting unconformably on the Hudson 
River group (fine-lined portion in the figures); 
West, of H. R. east-northeast, 
AN 
\ \ 
A 
WS 
It has been supposed, I believe by Sir William Logan, that 
the great fault which begins near eo. crosses the Hudson 
were powerfully folded and metamorphosed. A period of ay. 
lift and erosion followed ; then a depression and the depositio® 
*See this Journal, III, vol. xvii, 1979 page 57, “On the Age of the Clay-slate> 
" Ba 8 Wee, Ughkeepsic,” by T. Nelson Dale. Jr. > 
___ tPana, Manual of Geology, page 184, 2d edition, 1876. 
