The Zamboanga Peninsula, which is composed of the provinces of Zamboanga del Sur, Zamboanga del Norte, and Misamis Occidental, is a relatively understudied area. The most recent and intensive geologic investigations of the area were conducted in the 1960s. The area chosen by the authors was the southwestern portion of Zamboanga del Sur with the primary objectives of establishing an updated stratigraphy of the area, as well as verifying its continental affinity as reported by several workers.

Reconnaissance mapping has ascertained the existence of the following formational units: the Pre-Tertiary Tungauan Schist, the Pre-Miocene Bungiao Melange, the Early to Middle Miocene Anungan Formation, the Late Miocene Curuan Formation, the Late Miocene Vitali Diorite, the Pliocene-Pleistocene Mt. Maria Volcanics, and the Quaternary Alluvium.

On the basis of the mineral assemblage comprising the Tungauan Schist, one can establish the continental character of Southwestern Zamboanga Peninsula, as well as its affinity with Sundaland.