Evidence From Bathymetry and Gravity Data for Accretion of Benham Rise to Eastern Luzon


Milsom, J.1, Barretto, J.A.2, Aguda, N.R.1 and Bringas, D.2

1Department of Earth Sciences, Hong Kong University; Gladestry Associates, UK
2National Mapping and Information Authority



Benham Rise is a shallow submarine feature in the West Philippine Basin accreted to Eastern Luzon since the Early Miocene. High quality multi-beam swath bathymetry data reveal two important features of Benham Rise. First, Benham Rise is morphologically connected to Eastern Luzon along the Bicol and Palanan Saddles. Second, it is a very shallow bathymetric feature whose boundary with the West Philippine Basin is clearly defined by a significant change in sea floor morphology at water depths greater than 5000 m. Bouguer gravity anomalies also demonstrate that Benham Rise is accreted to Eastern Luzon. Bathymetric features, including the two saddles, which are strongly expressed in the free-air anomaly map, have little or no expression in the Bouguer anomaly map. This means that the thickness and density of the accreted material control the gravity signature and not merely water depth.


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