Reconstructing the Mesozoic-early Cenozoic evolution of northern Philippines: Clues from palaeomagnetic studies on the ophiolitic basement of the Central Cordillera

Abstract

The first reliable palaeomagnetic data from the Cretaceous to Eocene ophiolitic basement rocks in the Philippines are presented. A total of 12 drill core sites from five localities in the Central Cordillera in northern Luzon, Philippines were sampled. Eight drill core sites were from pillow basalts, and four were from diabase feeder dykes. Combining the characteristic remanent magnetization direction from these sites gives a mean in situ direction of Dec = 162.2°, Inc = -21.4° (α95 = 17.0°, k = 21.1) and a tilt-corrected direction of Dec = 159.3°, Inc = -12.5°, α95 = 6.0°, k = 162.5. Along with other lines of palaeomagnetic evidence, this clustering suggests that the magnetization is primary and that the ophiolitic basement rocks of the Central Cordillera formed at subequatorial latitudes (6.3°N ± 3.1°). This information further suggests that the basement rocks of northern Luzon were formed close to where the island was during the early Cenozoic. These rocks could represent relicts of the proto-Philippine Sea Plate. © 2009 The Authors Journal compilation © 2009 RAS.