The West Philippine Basin, is the

oceanic crust Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumu ...

located underneath the western part of the

Philippine Sea The Philippine Sea is a marginal sea of the Western Pacific Ocean east of the Philippine archipelago (hence the name), the largest in the world, occupying an estimated surface area of . The Philippine Sea Plate forms the floor of the sea. Its ...

. It was formed during the early

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but the ...

epoch. To its southwest is the

Philippine Trench The Philippine Trench (also Philippine Deep, Mindanao Trench, and Mindanao Deep) is a submarine trench to the east of the Philippines. The trench is located in the Philippine sea of the western North Pacific Ocean and continues NNW-SSE. It has a ...

, and to its east is the Kyushu–Palau Ridge. The West Philippine Basin is deeper and older than the eastern basins and has crustal heat-flow values approaching that of old oceanic crust.Sclater, J. G., 1972. Heat flow and elevation of the marginal basins of the western Pacific: J. Geophys. Res., v. 77, p. 5705–5719. It is roughly bisected by the Central Basin Fault zone which comprises a band of high relief running from the northwest corner to the Kyushu–Palau Ridge near 14°N. Characterized by the presence of several submarine plateaus (

Benham Rise The Benham Rise, officially known as Philippine Rise, is an extinct volcanic ridge located in the Philippine Sea approximately east of the northern coastline of Dinapigue, Isabela. The rise has been known to the people of Catanduanes as Kalip ...

and Anami and Oki-Daito Ridges).

Genesis

In terms of origin, two models distinguished:

Trapped oceanic basin

Trapped basin occurs in two stages: Emplacement of an oceanic basin and Individualization/isolation of the oceanic crust from the rest of the basin. It was invoked by Uyeda and Ben-Avraham (1972); Hilde and others (1977) and Hilde and Lee (1984) and suggests West Philippine Basin as a trapped piece of the Pacific Plate. Envisioned a N-S trending transform fault (connecting two ridges, the Kula Pacific Ridge and the Philippine Ridge/Central Basin Fault as turning into a subduction (the proto-Mariana Trench) zone following a change in the Pacific Plate's motion from NNW to WNW during the Eocene. In this model, the basin is originally a part of the Pacific Plate which was isolated during the kinematic reorganization 43 Ma.

Back-arc basin evolution

Formed behind a subduction zone and involves process that creates an extensional regime oriented perpendicular to the subduction zone. First proposed by Karig (1971), shows the WPB as forming by back-arc spreading behind the Oki-Daito Ridge starting the Eocene. Crustal extension within the plate took place successively in the eastern portion of the plate to form the other inter-arc basins. Supporters include: Lewis et al. (1982); Seno and Maruyama (1984), Rangin et al. (1990); Hall et al. (1995); Lee and Lawyer (1995), and Deschamps (2002); Honza and Fujioka (2004); Queano et al. (2006).

References

Oceanic basins of the Pacific Ocean Philippine Sea {{Philippines-geo-stub

Genesis

Trapped oceanic basin

Back-arc basin evolution

See also

References