912 WAPPINGER LIMESTONES AND ASSOCIATE STRATA. 
These strata dip away at a very low angle (from 6° to 
10°) from the axis of the mountain ; but the dip of the 
adjoining strata increases rapidly with the distance 
from the mountain, until it reaches the usual angle of 
the Wappinger valley strata, that is, from 30° to 45°; 
with the increasing dip, it also acquires the predomi- 
nant northeast and northwest strike. 
The Olenellus quartzyte has an estimated thickness of 
about one hundred sixty feet, and the associated Olen- 
ellus limestone, one of about seventy-five feet. 
About sixty feet of red shale overlie the Olenellus 
limestone, and over the shale there are about three 
hundred feet of limestone, which, in turn, is surround- 
ed by the prevalent Hudson river shales of the valley. 
We found no fossils in red shale, nor in the higher 
limestones. In the absence of paleontological evidence, 
the more evident stratigraphy of Fishkill mountain 
establishes the presumption that the red shales, belong 
to the Hudson river group, and the upper limestone to 
a post-Potsdam age. 
We examined the strata to the distance of alam two 
miles from the south end of Mt. Stissing, in a south- 
westerly direction. We found them much faulted, so 
that the Olenellus quartzyte is brought again to the 
surface. It was evident that nothing short of a pro- 
tracted and very careful examination would suffice to | 
develop the true stratigraphic relations of that district. 
The succession of the strata in the eastern part of 
Dutchess county, and doubtless of the entire county, is 
probably completely revealed by the acquisition of these 
facts concerning Stissing mountain. It is as follows, 
-beginning with the lowest strata : 
1. The Archean gneiss of Stissing and Fishkill 
mountains, and of other elevations. 
2. The Olenellus group, (Georgia group of Vermont, ) 
96 
