132 CONTKIBUTIONS TO THE GEOLOGY OF MAINE. [bull. 165 
partly of igneous material, and at the other end of the series there is 
likewise no evident line of separation between the calcite-bearing 
rocks and the gritty, partly calcareous layers in the limestone. 
In size of grain these rocks range from very coarse conglomerate to 
microscopically fine-grained arkoses. All these variations will be 
grouped together and described according to their geographic occur- 
rence as Sheridan sandstone, Chapman sandstone, Mars Hill conglom- 
erate, Mapleton sandstone, and sandstones from other localities. 
SHERIDAN SANDSTONE. 
This series is mentioned in Hitchcock's report 1 by Packard, who 
also 2 describes a smaller section on Fish River Lakes. Bailey 3 has 
also described the beds quite fully and has given a list of the fossils ! 
contained in them. As stated above, these sandstones form one con- 
tinuous series with the volcanic conglomerates of Ashland and Sheri- 
dan, and are interbedded with them. Two parallel sections through 
these rocks were studied, the first on the State road, which follows the 
Aroostook River, the second in the bed of the river itself. 
In the river section the rocks exposed for about 2 miles below the 
Ashland sawmill are argillaceous and arenaceous slates, red, gray, and 
green in color, with an occasional embedded fragment of black slate. 
Interbedded with the slates are thin layers (one-eighth of an inch to 
10 inches) of greenish-gray calcareous material that weathers more 
readily than the slates and resolves itself into a mass of broken crinoid 
stems. These slates strike N. 20°-40° E., and dip SE. <60°, while the* 
slaty cleavage plane dips W. <50°. Succeeding these slates the river 
runs through sandstones and conglomerates for nearly 4 miles, while 
the outcrops along the wagon road repeat and supplement the section 
thus exposed. 
Fine-grained variety. — Of the river outcrops the one about one mile 
west of the east Sheridan line, and known locally as "Alley's grind- 
stone," will be taken as typical for the finer-grained varieties. This 
outcrop is composed of three series of beds, as follows: ' . 
1. A very fine, even-grained sandstone, light gray or almost white in 
places, which attains a thickness of 20 feet and is broken into large 
blocks by cross fractures. Under the microscope a thin section of the 
rock shows quartz in angular and subangular grains, often in inter- 
locking groups, and feldspars which are kaolinized orthoclase and 
fresh-looking plagioclase. The feldspar and quartz constitute about 
90 per cent of the rock, but there are in addition many small fragments 
of slate, a few of igneous rocks of micropegmatitic character, and 
rarely biotite and zircon grains (see PI. VIII). 
1 Agriculture and Geology of Maine, 1861, p. 425. 
2 0p.cit.,p.423. 
a Ann. Rept. Geol. Nat. Hist. Survey Canada, 1887-88, Ft. M, p. 45. 
