CLARK: TACONIC REVOLUTION. 161 
states that those strata are folded, and that the folding took 
place during the Appalachian revolution. 
In describing the events of early Palaeozoic time as shown by 
the structure within the Raritan quadrangle, the authors recog- 
nize an epeirogenic uplift and withdrawal of the sea at the close 
of the Ordovician, but continue as follows: "It is believed that 
the early Palaeozoic strata of neighboring regions were some- 
what deformed at this time, but this has not been demonstrated 
for the northern New Jersey region."^ 
Virginia, — In 1892 Darton announced the discovery of fossils 
in the so-called 'Archaean' rocks of the Virginian Piedmont.^ 
They were found in one of the isolated belts of slates which are 
included within the older crystalline rocks of that region. The 
slate in which they occur is very fissile, and it was only by hunt- 
ing among blocks in which slaty cleavage and stratification 
coincided, that the fossils were discovered. Walcott, to whom 
they were referred for identification, decided that they belonged 
to the "Trenton- Lorraine or upper portion of the Ordovician fauna. 
. . . the slates are to be correlated with the Lorraine or Hudson 
series." The slate overlies a sandstone, below which is an altered 
conglomerate. No overlying rocks are known at either this slate 
belt of Arvon or at any of the others in Virginia. It is impossible 
from this evidence alone to assign a date to the metamorphisra 
of the slate. If the fossils are to be relied upon, all that we can 
say is that the slate was metamorphosed after the Upper Ordovi- 
cian, but we have no means of telling how long after, although 
presumably it antedated the Triassic. Here again, this locality, 
upon which Dana placed so much importance, loses its signifi- 
cance as evidence for Taconic folding. 
Conclusion. 
A survey of the whole field in which the Taconic Revolution is 
supposed to have been operative, has failed to show any positive 
evidence of folded and eroded Ordovician rocks unconformably 
overlain by younger strata, with the exception of a few outcrops 
lU. S. Geol. Surv., Oeol. Atlas, Itaritan folio, no. VM, p. 2. 1«.)14. 
^Darton, N. H. Amer. Joiirn. Sci, ser. A. vol. 44, p. .■)()-.')2, 1S92. 
