The municipality has three (3) rock formations-the Sierra Billiones limestone characterized by massive, cavernous fossiliferous and marly limestone-where sinkhole and channel ways have been developed where must springs have originated. Difficult area for wells when mar51 and massive limestone are encountered. This is dominant in the hinter land barangays. Another rock formation is the Jagna andesite characterized as Posphysitic Andesite where saline intrusion may be present in areas near the coast difficult area for wells. Usually dense in character, hence very difficult for well construction. Springs have low yield and usually dry up in summer months. This is dominant in barangays of Talisay and Linawan. The third rock formation is the Quarternory aluminum. It is generally mud silt, sand and gravel along coastal areas channels, flood plains and inner reaches of river system including raised coral reefs. This is common in areas in Poblacion, Bacong, Virgen, and Candabong along the coast.