Francia O. Olaguera and G.P. Yumul, Jr.

National Institute of geological Sciences, College of Science

University of the Philippines, Diliman, Quezon City

NIGS – UP & UMR 6538, Universitĕ de Bretagne Occidentale, Brest, France


A significance portion of the Zamboanga Peninsula, From Dapitan on the Northeast to zamboanga City on the southeast, was mapped from 1998 to 2001. This resulted into the update of the stratigraphic and structural information about the region. Geological maps, at the scale of 1:50,000, also resulted from these surveys.


Several highlights brought about by the surveys are:


1.        The northwestern continuation of the Cotobato – Sandangan – Daguma Lineament, called the Siayan – Sindangan Sututre Zone, was mapped;

2.        Several ophiolites and ophiolitic masses ( e.g. ,  Polanco, Titay) wre delineated;

3.        Tectonic and sedimentary mélanges (e.g., Gunyan, Tampilisan, bungiao, Limpapa) and their associated broken formations were recognized;

4.        Varied mineral deposits which include volcanogenic massive sulfide, replacement – type base metal, epithermal gold and porphyry copper are present in the area;

5.        New isotopic and paleontological ages were obtained. The data provided rigorous constraints in determining the temporal and spatial relationships of the different rocks formation;

6.        Pyroclastic and lava flows identified during the surveys support the existence of a middle Miocene volcanic arc in the peninsula;

7.        Our data show that Miocene sedimentary sequences from northeast Zamboanga were deposited in the bathyal and shallow marine environments, respectively. This suggests a “ shallowing” of the peninsula from the northeast towards the southwest

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