Persistent shallow magnetic inclination in the past 5 million years with implications for regional tectonics in the Philippines

• Published in: Journal of Asian Earth Sciences: X
• Main Authors: Decibel V. Faustino-Eslava, Hidetoshi Shibuya, Carla B. Dimalanta, Graciano P. Yumul, Jr., Jonathan T. Macuroy
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2021
• Subjects: Paleosecular variation of lavas (PSVL); Shallow inclination anomaly; Luzon; Philippines; Geology; QE1-996.5; Geomagnetic Pole
• Online Access: https://doi.org/10.1016/j.jaesx.2021.100048; https://doaj.org/article/b41e6d0da842484fba83e2cd0ea6fe57

Despite the growing knowledge on geomagnetic paleosecular variations, the region around the Philippine archipelago remains to be a huge data gap in this regard. This work looked into rock magnetic information from <5 Ma volcanic rocks of Luzon Island to provide data for the statistical characterization of the time-averaged field in the region.A total of 21 sites with ages from 1 ka to 4.3 Ma yielded 13 normal, 7 reversed, and 1 intermediate polarity dataset. These were aggregated with previously published work to form a combined dataset of 59 normal + reversed sites with a mean virtual geomagnetic pole at 321.1°E and 83.7°N with α95 = 3.4, and an angular standard deviation of about 14.6°. This amount of scatter is slightly larger than that predicted by Model G but relatively comparable with other near-equatorial regions such as Java and Ecuador. This work is a first examination of paleomagnetic data from the Philippines in relation to the long-term behavior of the magnetic field in this part of Southeast Asia. The long-ranging shallow inclination observed may also have implications on how paleomagnetic data are interpreted for tectonic studies in the region.