168 The American Geologist. March, i89i 
well, only, seems to deserve special notice here ; it is located about 
8^- miles southeast of Jamestown, and is commonly known as the 
Weeks or Fentonville well. In this, Carll finds the upper surface 
of the second sand of the Warren oil field at a depth of 276 feet 
below the surface, or 904 feet A. T.* It evidently forms here a 
conglomerate, for it is said to consist of blue sandstone "mixed 
with white pebbles ;" its thickness is given as 30 feet. This corre- 
sponds fairly well with the Jamestown conglomerate, in lithological 
characters, in thickness, and certainly in stratigraphic position.! 
(B). Sub-Conglomerate Beds. — Immediately- beneath the con- 
glomerate, follow gra}' arenaceous shales, containing but little 
calcareous matter, with few or no traces of animal life. These 
grade down into softer and more argillaceous deposits, which in 
turn at a depth of 385 feet, suddenly become hard and calcareous. % 
and so continue for at least 35 feet. Still lower, the soft argilla- 
ceous phase reappears, and throughout the remainder of the Che- 
mung* group, continues with but slight variations. 
PORTA! ;e GROUP. 
The dividing line between the Portage and Chemung groups in 
this section, has, to be sure, been somewhat arbitrarily placed at a 
depth of 950 feet. Yet, that this represents the truth with a fair 
degree of approximation may be judged from the following con- 
siderations : (1). Bits of calcareous matter, apparently of shells, 
were found in the drillings from a depth of 900 feet. Since the 
fauna of the upper Portage is exceedingh* meager, the bed here 
represented is doubtless Chemung. (2). The material at a depth 
*Rept. IIII, 2d Geol. Surv. Pa. 1883, p. 17. 
fBy taking into consideration the elevations of the Pope Hollow 
conglomerate tor its probable equivalent — the Wrightsville conglom- 
erate) as it outcrops at Miller's cliff (1620 ft.), McCoy's (1800 ft.) and 
Pope Hollow (1940 ft.), as given by Carll in Rept. IIII, and by obtaining 
from any reliable map the distances between these three points, its av- 
erage dip will, upon computation, prove to be 23 — feet per mile, S. 18° or 
19° W. 
Assuming that this is the approximate direction and amount of dip 
of the conglomerate in the Jamestown well, its upper surface should 
be found in t he Weeks well at a depth of 984 feet A. T., since the latter 
i> s.4 miles S. 32° E. of the former. This apparent discrepancy can 
be readily accounted for, since, as will be shown farther on, the dip 
becomes greater, and swings gradually to the east as we descend in the 
geological scale. (See " Stratigraphical Deductions.") 
^Probably the representative of the "hard shell " in the Fentonville 
-well. See 2d Geol. Surv. Pa. IIII. p. 17. 
