58 The American Geologist. January, 1903. 
Structural Details in the Green Mountain Region and in Eastern New 
York. By. T. Nelson Dale. Bulletin of the United States Geo- 
logical Survey, No. 195. 
This is the second paper published by Mr. Dale under this title; 
the first paper appeared in the Sixteenth Annual Report of the U. S. 
Geol. Survey. (Pt. I., 1896, pp. 549-570.) Like the first publication 
the second is not a systematic exposition of the geology of the dis- 
tricts named, but a discussion of geologic details collected in the 
course of the exploration and mapping of seven U. S. Geological Sur- 
vey sheets. These are the Castleton, Pawlet, Equinox and Ben- 
nington sheets in western Vermont- The Greylock sheet of north- 
western Massachussetts and the Berlin and Tracy sheets in north- 
eastern New York. 
The formations underlain by Pre-Cambrian gneiss, include the sed- 
imentary series of the Algonkian, Cambrian and Ordovician — schists, 
quartzytes, slates, marbles, limestone and dolomytes. The intense dy- 
namic action to which they have been subjected has given rise to both 
open and close folding and in some cases, to faulting and shearing. 
As an exceptional occurrence, however, a recumbent isocline is de- 
scribed at Dorset, Vt., on the Pawlet sheet, a little southwest of Green 
Peak. Here also is shown a tendency to pinched folding which is more 
fully developed to the north on the Castleton sheet, at Pittsford. Some 
of the folds have suffered elongation so that the beids are thinned 
along the limbs and thickened at the crest. 
Perhaps the most noticeable feature of this locality is an over- 
thrust fault which begins at Pittsford and extends south for about 
ten miles to the town of Clarendon. The tangential force has been 
of sufficient intensity to produce a thrust fault whose strike is nearly 
north and south. The relation of the faulted beds is well shown on 
Boardman Hill north of Clarendon where Cambrian quartzyte on the 
east side of the fault is in contact with Upper Ordovician schists of 
the west side. There are two excellent plates which show how the over- 
turned major folds of the Cambrian quartzyte are plicated by minor 
folds. In Arlington at Roaring Brook on the Bennington sheet, shear- 
ing accompanies folding. The shear is indicated by borings of the 
Scolithus which were originally perpendicular to the bedding but are 
now deflected many degrees from verticality. 
The remainder of the paper is for the most p<irt devoted to the 
discussion of the lithologic character of some of the formations, as 
well as to their structural relations. The Vermont marble is not a 
pure crystalline limestone, but is made up of coarse grained calcitj 
marble interbedded with a fine grained rock which, by chemical anal- 
ysis, was proved to be a dolomyte. . Since both marble and dolomyte 
have undergone the same pressure, the difference in grain must be 
due, either to a difference in their behavior under pressure or to a 
difference in the original sediments. The Ordovician schists of the 
region are more interesting ; the constituents are muscovite, quartz, 
chlorite, magnetite and albite feldspar with which are associated 
