The stratigraphy of the Bravo Lake Formation starts with a basic section of iron-oxide rich sandstones, psammites, and semi-pelites cover a series of deformed pillow lavas expanding in viscosity towards the west, and volcanic/clastic deposits and ultramafic sills. The lower volcanic section is covered by garnet and diopside bearing calc-silicate layers and finely layered metasediments comprising of course-grained actinolite/hornblende/biotite followed by pelites and semi-pelites that are intruded by separated sills. In the Ridge Lake area, the volcanic belt includes an interlayered series of amphibolite, gabbro, iron formation, sulphidic schist and metasediments.
Geochemical results of pillow lavas and chill boundaries along five transects across the volcanic belt suggest the existence of three chemically different magma types within the Bravo Lake Formation.
Lavas of the volcanic belt display geochemical characteristics similar to modern ocean-island-basalt groups. They range from moderately to intensely fractionated REE-profiles is similar to that from tholeiitic basalts to extremely alkaline lavas in Hawaii.