142 CONTRIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165. 
The data at hand for the determination of the succession of the rocks 
in the limestone series are very meager. The extremely disturbed con- 
dition of the rocks and the scarcity of fossils make a final interpretation 
of their age and structure at present impossible. The many cuts 
along the line of the Bangor and Aroostook Railroad give a better 
opportunity to determine the composition and position of the different 
beds than has heretofore been afforded. 
Structure. — As seen in the field the limestone masses never present 
angles, but have their corners rounded off, and contain small sink 
holes in limited areas. The beds are very thin, usually from a frac- 
tion of an inch to a few inches in thickness, and rarely several feet. 
They are distorted and folded to an extreme degree along axes which 
run approximately northeast. The folds are at times 15 to 20 feet 
broad, but commonly are merely minute twists and plications, several 
of which may occur within a few feet. The apices of the folds are 
often enormousty infolded and distorted on an almost microscopic 
scale. In one place thirteen complete miniature anticlines were 
counted, the total length of which was 9 inches from apex to apex, 
but was over 3 feet measured along the beds. In addition to the folds, 
there are countless faults, but always, so far as observed, on a small 
scale. Slickensides are formed in nearly every outcrop, and in places 
take the form of a succession of approximately parallel grooves along 
which movement has taken place. The grooves are n ow occupied by 
flattened columns of arenaceous limestone. 
The average strike of the strata is about N. 60° E. in the southern part 
of the area, and N. 30° E. in the northern part. The dips are usually at 
high angles. Since folding has taken place the beds have been slated 
by planes running about northeast, which often nearly coincide with the 
bedding and are always more prominent than the bedding planes. 
Unusual caution is therefore required in taking measurements of dip 
and strike. Other sets of cleavage planes are present, and often serve 
to cut the strata into rhombs. 
PetrograjjJiy. — The exposed rock surfaces are coated with a thin, 
yellowish-white weathered zone. Owing to the varying amount of 
impurities in the beds the rock takes on a banded appearance, which 
is much intensified where metamorphism has been active. The rock 
itself is quite uniform throughout its whole extent and is of a typically 
grayish-black color, becoming a lighter gray in the more sand}^ beds. 
It is extremely dense, and under the highest powers reveals masses of 
exceedingly fine-grained calcite arranged in layers which vary slightly 
in size of grain. Quartz and fragments of mica and iron are also 
occasionally present. 
Heavy beds of limestone. — Heavy beds of limestone, sometimes 10 
feet and more in thickness, are found with the typical thin-bedded 
variety, especially between Presque Isle and Fort Fairfield and in the 
