The geology of the area is described in blad 30 van de geologische kaart van java by Ludwig (1) Folded and faulted dark concretion bearing shales of the widdle miocene Annualatushorizon are overlain by andesitic bearing tuff and breccia amd puntured by contemporaneus (?) plugs, dikes and small stocks of diorite porphyry and andesite.