A vertical borehole has been drilled through 215.8 m of the Monaro volcanic sequence at a location 20 km south of Cooma. The site is on basalt outcrops near the crest of the Main Divide. The core comprises 198.2 m of mafic volcanic and weathered volcanic rocks overlying 8.5 m of lacustrine sedimentary and hyaloclastite deposits and 9.0 m of weathered basement composed of schist and meta‐sandstone. About 55% of the volcanic sequence is weathered; and some of the weathered material may have been originally volcaniclastic. Seven weathering profiles, up to 12.5 m thick have bauxite zones up to 3.5 m thick at the top. Bauxite comprises ∼9% of the sequence. The fresher rocks are mainly alkali basalt flows, up to 27 m thick, but also include a basanite flow at the top of the sequence and two intervals of alkali dolerite between 65.0 and 75.0 m. The deeply weathered nature of many of the flows indicates prolonged periods of intense chemical weathering under wet climatic conditions between lava eruptions.