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synclinal basins over a large area in south central Graham island.
It seems reasonable to suppose that these now separate basins
were formerly part of a small geosyncline of Cretaceous sedi-
ments, occupying the area in central Graham island between
Skidegate and Masset inlets, and perhaps having an even wider
extension.

The surface on which the Queen Charlotte series was
deposited, as evidenced by the varying thickness of the Haida
member, was one of considerable relief, and it is possible that
some of the present highlands of pre-Cretaceous rocks remained
out of water during the depositional period, as suggested by
Clapp!. However, owing to the manner in which the basins
of Cretaceous rocks occur on the pre-Cretaceous hills, and owing
to the large amount of erosion which has taken place, it seems
more probable to the writer that the area was wholly submerged
during the later period of deposition at least. Post-Cretaceous
folding has elevated this area and denudation has stripped much
of the sedimentary veneer from the pre-Cretaceous basement,
leaving the Queen Charlotte series in localized basins.

Numerous dykes and sills, largely of Tertiary age, intrude
the Queen Charlotte series, especially the lower Haida member.
These bodies range up to 50 feet in thickness, and are partic-
ularly abundant in certain places. Some of them have been
faulted, and the intrusive period probably covered a long interval.
They range from dacite to augite andesite in composition.
Following this intrusive epoch came a period of marine sedi-
mentation, in part at least lacustrine or fluviatile, during which
the fossiliferous sandstones, shales, conglomerates, and lignites
af the Skonun formation were deposited. Overlying these
sediments, probably essentially conformably, is a very great
thickness of basaltic flows, tuffs, and agglomerates, termed the
Masset formation. These rocks underlie the greater portion
of Graham island west of Masset inlet and north of Rennell
sound, and are found in the Slatechuck range also. In amyg-
dules in some of the basalt flows is found black tarry matter,
which has led to considerable prospecting for petroleum.

1Clapp, C. H., Geol. Surv., Can., Sum. Rept., 1912.