The Winneba concession lies along the south western end of the Winneba-Kibi volcanic belt of Ghana. The main part of the N. E. trending 'volcanic belt' in the Winneba area consists of metavolcanic and volcaniclastic units (greenstones) but there are fairly wide zones of quartzitic, micaceous schists and the distinctive Mumford Series of coarse clastic units. The geology of the concession is dominated by Cape-Coast-type granitic and migmatite intrusives comprising largely foliated biotite and/or muscovite bearing granite and granodiorites with pegmatite, quartz and aplite veining.
Birimian sediments outlined to the southwest comprise phyllite, schist, tuffs and greywacke. North-east-trending metamorphosed intermediate to mafic volcanics commonly termed "greenstones" are metamorphosed and sheared to actinolote schist, hornblende schist, and amphibolites and intruded by Dixcove intrusives. The latter, unlike the Cape-Coast granites are Hornblende-bearing and are generally massive. Minor "Munford System" rock groups comprise siltstone, quartzite, greywacke and sandstone. The immediate coastal area, between the coastal towns of Nakwa and Saltpond, is underlain by the Amisian coarse clastic units of Jurassic- Cretaceous age and Recent sediments are largely confined to lagoonal areas adjacent to the main perennial rivers.