Rocks exposed in the quarry and in the roads cuts along the highway are feldspar phyric dacites and andesites that are locally flow banded. Neil Church of the BCGS (see Church and Barakso, 1990) has mapped these rocks as part of the Eocene Goosely Lake Formation. The Goosly Lake Formation is the lower part of a thick succession of Eocene flows that unconformably overlie Takla, Hazelton, Skeena and Kasalka Group rocks in the area south of Highway 16.

The Goosely Lake Formation, which regionally is mainly of feldspar phyric trachyandesite, is up to 500 metres thick and is overlain conformably by the Buck Creek Formation. The latter is comprised mainly of brown weathering, fine grained, amygdaloidal andesite and basalt flows. Most of the hills that can be seen to the southwest are capped by gently dipping flows of the Buck Creek Formation. Hills to the northeast are uplifted blocks or Late Triassic and Early Jurassic Takla and Hazelton Group volcanic rocks.

Church reports a 48.8+/-1.8 Ma K-Ar whole rock isotopic age for the Goosley Lake Formation and a 48.2+/- 1.6 Ma K-Ar whole rock isotopic age for the Buck Creek Formation. These ages and lithologic similarities suggest the Goosly Lake and Buck Creek Formations are correlative with the Endako Group.