INTRODUCTION. 9 
the granite, as described above, the data used have been largely the 
results of area! mapping, for folio publication, by E. S. Bastin, 
C. W. Brown, and the writer, and of general reconnaissance by the 
writer, assisted by Mr. Bastin. In the more northern areas the work 
by H. E. Gregory and the earlier mapping by C. T. Jackson and 
C, H. Hitchcock have been utilized to supplement this recent work. 
Mr. Brown also contributed the results of recent observations in the 
vicinity of Mount Katahdin. 
GEOLOGIC RELATIONS. 
Wherever the granites of Maine have been studied in any degree of 
detail, their relations are plainly those of intrusion into part, at 
least, of the adjacent formations. Evidence that the granite is the 
younger rock is found in the tendency shown by some of the granite 
areas (see PI. I) toward elongation in a northeast-southwest direc- 
tion, parallel to the general trend of the main structural features of 
the region, but more conclusive evidence is found in the fact that the 
granite actually cuts across the bedding of the sedimentary rocks 
and has in some localities produced in them a very considerable 
amount of alteration. Bordering the granite in Franklin County, 
for example, and in some other parts of the State, are andalusite 
schists which plainly represent sedimentary strata metamorphosed 
by the granite. In many regions, as will be described later, the 
granite masses are bordered by gneisses which are formed by a 
lit-par-lit injection of sedimentary schists by granitic material. 
Thus the general relations throughout the State point to the granites 
being relatively the younger rocks. 
The feature which is perhaps the most significant in the geologic 
relations of the granites to the other rocks of the State is the great 
contrast between the sharpness of certain granite borders and the 
indefinite character of others. In the vicinity of Bluehill and Brooks- 
ville, for example, in Hancock County, the contact is absolutely 
sharp, pure granite being succeeded within a foot by schists unmixed 
with granite. Along such sharp borders, too, the granite usually 
preserves its normal texture up to the very contact, and the sur- 
rounding rocks show almost no effects of contact metamorphism. In 
striking contrast to this are the broad contact zones which charac- 
terize most of the granite masses lying farther westward. In the 
Rockland region, for example, the Sprucehead-Clark Island granite 
area is bordered on the northwest by a zone, 3 to 4 miles in width, 
in which sedimentary slates and schists are intimately associated 
with injection gneisses, basic granites, fine-grained granite, pegma- 
tite, diorite, gabbro, and diabase. These igneous rocks were plainly 
derived from the granitic magma and are most abundant in those 
portions of the contact zone which lie nearest to the areas of pure 
granite. A granite area near South Penobscot, in Hancock County, 
