Goosly Lake is an approximately square-shaped stock of about 3x3 km which cuts early Mesozoic lavas and pyroclastic rocks. The rocks of the stock vary from gabbro to syenomonzonitic varieties. The former consist essentially of plagioclase, augite, pseudomorphs after olivine and accessories. Accessory feldspathoidal minerals are described as occurring in some samples of the gabbro, with no further details. The syenomonzonite contains in addition K-feldspar and some quartz. Two other similar, but smaller, bodies occur 13 and 25 km west-southwest of the Goosly stock, but petrographic details are not available. Church (1970, p.123) suggests that the stocks are the source of the extensive Tertiary volcanics of the area.