Initial Report on the Geologic Quadrangle Mapping for Liloy Quadrangle

By Kris Elvis Alferez

The Geologic Quadrangle Mapping for Liloy Quadrangle commenced on April 19, 2018 in the Municipality of Liloy, Zamboanga del Norte. It was conducted by a team composed of three (3) technical personnel from the Geosciences Division. The purpose of the activity is to update the existing Liloy Quadrangle Map that was produced by the Geosciences Division of MGB Region 9 in 1991. Generally, this undertaking is part of the Government’s effort to produce geologic maps for Region 9 (Zamboanga Peninsula). The output will be a technical report and GIS-based geologic maps which are expected to be extremely useful for many practical applications such as in mineral exploration, groundwater resource and vulnerability assessment, geohazard mapping, solid waste disposal site selection, land use planning, and other applications.

The study area is located in Zamboanga Peninsula which lies roughly at the southern part of the Philippine Archipelago chiefly in the island of Mindanao on the western segment. It lies between Moro Gulf on the south and Sulu Sea on the north. Along the coast of the peninsula are lavish bays and islands with varying extents. It is connected to the rest of Mainland Mindanao through an isthmus situated between Pagadian Bay and Panguil Bay. The peninsula falls under the jurisdiction of Western Mindanao (Region IX) consist of three provinces (Zamboanga del Norte, Zamboanga Sibugay and Zamboanga del Sur), and the boundary between the peninsula and mainland is marked by the border between the provinces of Zamboanga del Sur and Lanao del Norte.

Liloy Quadrangle covers the latitude N8° 0’ 0” to 8° 10’ 0”, and longitude E122° 30’ 0” to 122° 45’ 0” is approximately centered in the Municipality of Liloy. From various airports positioned in the peninsula, the target municipalities covered by Liloy Quadrangle are easily accessible via all-weathered national road which serves as the main access throughout the entire peninsula. Far-flung areas can be accessed using a motorbike (locally known as habal-habal) and coastal areas using outrigger boats.

During the course of the activity, the team conducted on the spot megascopic rock identification and sampling of rocks and soil for megascopic, petrographic, paleontologic and physical analyses which are vital information needed for the finalization of technical report. Delineation of lithologic boundaries/geologic contacts and structures were also conducted within the target municipalities. As for initial result, the lithological boundaries and structures from the existing Liloy Quadrangle Map are expected to be modified based on ground validation/field observations conducted.

Karren field with abundant corals and tridachna, indicative of shelfal facies with low siltation in Barangay Punta, Liloy, Zamboanga del Norte
Coastal exposure of pebbly to bioclastic limestone in a muddy to marly matrix which forms several sea notches, it is capped by massive corals mostly of coralline component (porous to sparitic)
Massive outcrop of ultramafic rock which shows fluidal texture of serpentine minerals in Brgy. San Roque, Liloy, Zamboanga del Norte
Boulders of schist along the coastal area showing intense folding and fracturing. Brgy. Malintuboan, Labason, Zamboanga del Norte
A hill that is entirely composed of chert located inside a school in Brgy. Balakan, Salug, Zamboanga del Norte
Exposure of intensely foliated schistic rock, alternating bands of silvery white to brown minerals in Brgy. Pianon, Kalawit, Zamboanga del Norte
Exposure of melange rock composed of silicified chloritized volcanisclastic (andesite), sparitic limestone, ferrigenous chert and ultramafics in Brgy. Barili, Tampilisan, Zamboanga del Norte
Exposure of a highly foliated schist along a creek which is part of the patawag river in Brgy. Malila-T, Tampilisan, Zamboanga del Norte

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