34 TACONIC PHYSIOGRAPHY. 
material; (2) the Cretaceous sediments and sea cliffs have themselv( 
all been eroded; (3) land barriers at the north and south prevente 
access of the sea in Cretaceous time, in which case we should hav 
Cretaceous lake shore lines; (4) there is some error in the estimate 
amount of the post-Cretaceous elevation. 
The disproportionate amount of erosion called for in Cenozoic tim 
as compared with that in Paleozoic and Mesozoic time, and th 
absence of Cretaceous sedimentation and sea cliffs, seem to call for 
careful restatement of the peneplain theory as far as it applies t 
the Taconic region. 
Whether in consequence of the Ordovician movement alone, o 
because of that and subsequent uplifts, the Taconic region has sui 
fered a vast amount of erosion. It is a deeply dissected upland. A] 
inspection of the map and sections will justify the estimate that th | 
amount of denudation which has taken place between the westen 
foot of the Green Mountain Range and the western limit of the schis 
belt alone is not very much less than the bulk of the present schis-ij 
masses. If to this be added the amount of denudation suffered b; 
the western rim of the Green Mountain Range, the total will be vas 
indeed. This feature is the most impressive one in the region, an! 
continued study serves greatly to increase its impressiveness. 
All the products of this erosion have been transported into tin 
Atlantic, the schist in the form of fine sand, into which it easily dis 
integrates under long-continued mechanical action, and the calcareou 
material mainly in solution. 
PROCESSES OF EROSION. 
Denudation in this region was either general, consisting in tin 
truncation of major anticlines and in the exposure of the limestone 
along the axes of the folds, or special, consisting in the cross.cuttins. 
and the minute sculpture of the truncated folds and in the erosior 
of fault scarps. In a general way it was the effect of the exposure oi 
the rock surface to atmospheric agents. While these were chiefly tin 
action of streams and of ice, the operation of the atmosphere itself 
through its carbonic acid and its vapor of water, should not be over- 
looked, nor should the effects of changes of temperature nor the chem- 
ical and physical effects of vegetation. In view of the lapse of time 
between the close of the Ordovician or the Silurian and the close oil 
the Tertiary, and of the succession of floras which must have flour- 
ished in this region during that interval, the amount of erosion duo 
to plant life alone must have been considerable. 
STREAM EROSION. 
The principal streams of the region (see PL I) include two that 
follow the axes of the folds — Otter Creek, which flows northward 
