GREGORY.] 
ANJ>KSITES. 
113 
IIOBART III LI, ANDESITES. 
This hill is an isolated mass of andesito forming 5t prominent feature 
in the landscape to the west of Presque Isle Village. It is situated 
partly in Mapleton Township and partly in Chapman Township, and 
is surrounded entirely by low, poorly drained swamps and forest lands. 
It is visited only for lumber and tan bark, which are secured in limited 
quantities during the winter season. The hill is about li miles long 
and three-fourths mile wide, and rises quite abruptly above the plain 
to a height of 300 feet as a single well-defined mass without branches 
or outliers (see PL III, B). The sides are everywhere steep, and 
in places present cliffs 40 to 50 feet high. The top is bare only 
where fire has recently destroyed the vegetation. The talus slopes 
present a confused mass of large and small blocks of andesite, which 
entirely conceal all outcrops except where cliffs are exposed. On the 
west and north sides numerous bowlders of red sandstone and con- 
glomerate are piled along the slope and mingled with the volcanic 
material. These were traced to their parent ledges scarcely a half 
mile to the north, and the bowlders serve to cover the contact of the 
Andesites. 
Fig. 4.— Section on Mapleton-Presque Isle road. 
andesite with the Mapleton sandstone. Specimens collected from 
various places on the hill show but slight differences in composition 
and texture, except the rock from the northwest corner, which is a 
breccia of andesitic fragments and seems to be situated along a fault 
line. Here, as at Edmunds Hill, no actual contact between formations 
was observed, but the sedimentaries were traced to the very base of 
the hill, and the facts indicate that the hill is a remnant of a lava flow. 
SOUTH MAPLETON ANDESITES. 
In addition to the prominent hills of andesite just mentioned, there 
are some ten or twelve less conspicuous outcrops in the fields in the 
southern part of Mapleton Township to the north and the south of 
the Mapleton-Presque Isle road. They usually occur as narrow ridges, 
and seem to be remnants of lava flows which once occupied former val- 
leys, and are now left standing because of the erosion of the sedimen- 
taries on both sides. The accompanying cut (fig. 4) illustrates the theo- 
retical position of the andesite outcrops along the Mapleton-Presque 
Isle road. 
Bull. 165 8 
