Paleomagnetism of Palawan, Philippines

Paleomagnetic studies have been carried out on Palawan and on the island of Busuanga to the north. Results from the Cretaceous Espina Basalts of the C alatuigas Ophiolite in the South Palawan Block (SPB) pass a fold test, yiel d normal and reversed directions wi;th a magnetic intensity and AF demagnet ization characteristics consistent with a primary TRM. The mean direction i s 293.9 degrees and an inclination of 5.8 degrees, with a k of 37.7 and an alpha(95) of 12.6 degrees. This suggests that these ophiolites have moved n orthward and rotated counterclockwise by 66 degrees +/- + 13 degrees with r espect to the geocentric axial dipole (GAD) field. It also suggests that th ey were obducted from the south. Paleomagnetic directions from the Jurassic Busuanga Cherts and the Cretaceo us Guinlo Formation from the island of Busuanga in the North Palawan Block (NPB) and from the Guinlo on the main island of Palawan are similar, fail r egional fold tests, and have AF demagnetization characteristics consistent with secondary magnetization. Their inclinations are statistically indistin guishable at a 95% significance level, but variation in declination suggest s differential local rotation about a vertical axis. The paleolatitude is c omparable to that of regions of pervasive Cretaceous remagnetization in the South China borderland and may reflect similar remagnetization, consistent with the NPB's proposed South China origin. (C) 2000 Elsevier Science Ltd. All rights reserved.