16 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.