CLARK: TACONLC REVOLUTION. 155 
there is no doubt that the Silurian strata were laid down upon a 
surface of upturned Ordovician strata. None of the uncertainty 
which surrounds the relations of these two systems at Becraft 
Mountain exists at Rondout, as the two following quotations 
show. 
"The Hudson River rocks were upheaved, exposed to erosive 
forces, presumably of the ordinary subaerial kind, and then sub- 
merged to receive the later formations on their worn edges. . . . 
The irregularity of the contact in the Rondout quarry com- 
pletely excludes the possibility of the disagreement of dips in the 
over- and underlying formations being due to a fault, at least at 
this point, for . . . the limestone fits closely into channels worn 
along the strike of the softer sandstone beds, and the two rocks 
are so firmly consolidated that hand specimens can be easily 
obtained showing the line of junction. It is noteworthy that the 
limestone begins immediately with its fully determined cal- 
careous character: there is no band of transitional composition; 
no fragments of the sandstone are contained in the overlying 
rock. The old worn surface was swept clean before the corals 
and crinoids began growing upon it, and their fragments and 
grindings make the first deposit. Some little pieces of crinoid stems 
lie directly on the bare sandstones. ... It is therefore probable 
that this contact [another contact at the end of the quarry rail- 
road in Eddyville] is not the original one, but has been produced 
by faulting or slipping when the rocks were folded. The pos- 
sibility of such slipping is well shown in the deep quarry (Newark 
Lime and Cement Company) a little south of Section I, whcn» 
the Water-lime is folded and slipped so as to be apparently un- 
conformable to itself.^" 
Twenty years after the above extract was written, Van Ingen 
and Clark^ announced that the limestone contained "rounded 
water-worn boulders of sandstone incrusted with fossil bryozoans 
and corals." The rocks of this locality are so generally ami 
complexly faulted, that one suspects that all contacts miy be due to 
'Davis, W. M. The aoncoafortnity at Rotidout, N. Y. Amor, loiirii. 
Sci., ser. li, vol. 26, p. ;i92-;ii);i. 18S3. 
^Van Infxon, Gilbert, and Clark, P. E. Disturbed fossiliforous roi^ks 
in the viinnity of Rondout. N. Y. Rept. N. Y. State I>al. I«)()2, [). 120!)- 
1210. 1903. 
