T014-02
Collision Signatures in the Western Philippines and their Implications on East Asian Geodynamics

Tuesday, 8 December 2020: 16:04
Virtual
Carla Besa Dimalanta1, Rurik San Pedro Austria1, Nathaniel Espedido Parcutela1, Leo Tajapal Armada1, Decibel Villarisco Faustino-Eslava2, Jenielyn Tuando Padrones3, Betchaida Duetes Payot1, Jillian Sibal Gabo-Ratio1 and Karlo Lagera Queaño4, (1)Rushurgent Working Group, National Institute of Geological Sciences, University of the Philippines, Quezon City, Philippines, (2)School of Environmental Science and Management, University of the Philippines, Los Baños, Philippines, (3)Institute of Renewable Natural Resources, College of Forestry and Natural Resources, University of the Philippines, Los Baños, Philippines, (4)Department of Environmental Science, Ateneo de Manila University, Quezon City, Philippines
Recorded Presentation
Abstract:
The present-day geodynamics of the Philippine archipelago are highly influenced by the birth and demise of surrounding marginal basins and their interactions with larger tectonic elements that include Mainland Asia and the Pacific Sea plate. The most extensive remnants of these interactions are the collisional boundaries between the Palawan Microcontinental Block (PCB) and the Philippine Mobile Belt (PMB).

As is generally accepted, the opening of the Oligocene to Miocene South China Sea led to the collision of the PCB with the PMB. This is evidenced by the accretion of ophiolitic materials derived from the proto-South China Sea emplaced onto the various islands along the western Philippines. Additionally, continent-derived sedimentary formations have also been documented on the islands of Mindoro (Lasala Formation) and the western Panay island (Buruanga Peninsula), west of mountain ranges that are believed to have developed consequent to the PCB-PMB collision.

New potential field geophysical data also reveal a sharp contrast between the PCB and the PMB. The PCB displays long wavelength low magnetic anomalies as opposed to the PMB which exhibits short wavelength, high amplitude magnetic anomalies. Estimation of crustal thickness derived from gravity anomalies reveals that the crust beneath the PCB is thicker (~33 km) compared to the eastern side (~20 km). Power spectral analysis of the magnetic data show the varying depths of the Curie surface from 18-32 km. The deepest Curie point depth is observed in the Mindoro-Palawan area consistent with the gravity-derived crustal thickness estimates. Spectral analysis of the regional gravity data, on the other hand, revealed three spectral domains that are interpreted to correspond to the gravity signatures of the mantle, the PCB and PMB.

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