The Reef showing is located 23 kilometres south-southwest of Vernon between Wood Lake and Clark Creek.

In this area, east of the Okanagan Valley fault zone, sedimentary and volcanic rocks of the Devonian to Triassic Harper Ranch Group are in probable fault contact with metamorphic rocks. Middle Jurassic granitic plutons intrude Shuswap Terrane metamorphic rocks. Eocene Penticton Group and Miocene Chilcotin Group volcanic and sedimentary rocks cap areas of older rock.

In the Penticton Group, an agate-rhyolite bed contains abundant yellow-orange chalcedonic carnelian(?) agate within pyroclastic flow rocks, possibly representing a sinter. The bed is about 5 metres thick and extends over an area of at least 600 by 300 metres. The bed, part of the informally named Trepanier Rhyolite, unconformably overlies monzonite and granodiorite, and underlies Penticton Group felsic tuffs and Miocene fluvial sediments and basalt flows.

In 1977-79, Union Oil Company explored the Miocene sediments for uranium. Geological mapping, hydrogeochemical, radiometric, airborne magnetometer and drill programs were conducted.