64 ECONOMIC GEOLOGY OF AMITY QUADRANGLE, PA. 
certain relations which hold good with respect to the individual 
fields. The Washington oil field, the most striking example, is 
located on the eastern flank of the Washington anticline, which it 
follows in this quadrangle for a distance of 5 miles. The field aver- 
ages about a mile in width and in position agrees closely with the 
lower portion of the steepest grade of the anticlinal slope. The 
greater proportion of wells are grouped in a belt about a mile wide 
just above a change in grade from the gentle structural slopes of 
the bottom of the syncline to the steeper slopes of the anticline. 
Along this belt the dip of the rocks i.^ unusually steep — about 200 
feet in a mile. This is the steepest continuous dip in the quad- 
rangle and is greater than usually occurs in Pennsylvania oil fields. 
It will be noticed that the map shows a nose-like projection from 
the axis directly east of the Manifold mine, and that a projection 
of the oil field agrees with this. 
One small area in the Washington (ield — the group of wells west 
of Gambles — shows structural relations somewhat different from 
those in the rest of the field. This area is near the north end ot 
the Washington field, and here the belt bends to the east and oil 
occurs down to the bottom of the syncline. As operations in this 
part of the Washington field ceased long ago, it is difficult to obtain 
data for drawing conclusions regarding the cause of these peculiar 
conditions. It is suggested, however, that if the rocks directly 
below this pool arc dry the oil may have descended from farther up 
the slope, and thus the relations of the field may be accounted for. 
Another peculiar feature 1 of this field is the presence of a number 
of gas wells in the bottom of the syncline north of Linden. Such 
an occurrence is exceptional, as gas is more often present on the 
anticlines. The gas occurs, however, above the oil, as would be 
expected. 
Examples of the anticlinal tendency of gas. — A typical illustration 
of the structural relations of natural gas is afforded by the scattered 
wells lying high up on the Washington anticline in Chartiers and 
western North Strabane and South Strabane townships, where they 
occur over a broad arch in the strata. The Canonsburg gas field is 
a continuation of this belt. 
Perhaps the best illustration of the anticlinal tendency of gas is 
afforded by the Amity anticline, between the Greene County line 
and Kammerer. This anticline is a rather broad arch having gen- 
tle dips at its crest, and along it occur a large number of gas wells. 
Zollarsville field. — The principal gas field of the quadrangle — the 
Zollarsville field — can not be said to hold any definite structural 
position. Instead of occurring high up on the anticline southeasj 
of Deemston, as might be expected, it lies on the west flank of the 
anticline and stretches over nearly the entire synclinal slope between 
