Philippine Sea Plate motion since the Eocene estimated from paleomagnetism of seafloor drill cores and gravity cores

Abstract

Current models of Philippine Sea (PHS) Plate motion assume a general and large northward shift since the Eocene. In order to constrain better the age and amount of this northward shift, we have conducted a paleomagnetic study on drill and gravity cores, respectively, taken from the seafloor of the northern part of the PHS Plate. The core samples consist of sedimentary rocks or semi-consolidated sediments, and their ages, as estimated from microfossils and strontium isotope ratios, range from the Eocene to late Miocene. The results of stepwise alternating-field and thermal demagnetization experiments revealed that 19 sections at 17 sites out of 58 sections at the 29 sites examined yielded mean paleomagnetic directions with a 95% confidence limit (α 95) of <25 • , and 14 sections at 13 sites have α 95 < 15 •. An estimation of the amount of the northward shift at each site was obtained from the difference between the paleolatitude and the present latitude. This estimation revealed that the northern part of the PHS Plate was located near the equator at 50 Ma and that the majority of the northward shift took place between about 50 and 25 Ma. Very little northward movement occurred after 15 Ma. Based on our data, together with the available paleomagnetic information suggesting clockwise rotation of about 90 • since the Eocene and the requirements from geometry with the surrounding plates, we present a model in which the PHS Plate rotated 90 • clockwise between 50 and 15 Ma on the Euler pole near 23 • N, 162 • E, although it is impossible to specifically determine the Euler pole position.

Depositional setting, provenance, and tectonic-volcanic setting of Eocene–Recent deep-sea sediments of the oceanic Izu–Bonin forearc, northwest Pacific (IODP Expedition 352)

“…The resulting tectonic reconstruction implies >2000 km of rollback of the downgoing Pacific plate, a low-angle 'soft collision' of the Philippine Sea plate with the Eurasian plate, and the arrival of the Izu-Bonin arc at southernmost Honshu by early Miocene (20 Ma). Palaeomagnetic data from drill and gravity cores from the West Philippine Basin (Sdrolias et al 2004;Yamazaki et al 2010), from Leg 195 (Richter and Ali 2015), and from Expedition 352 (Reagan et al 2015;Sager et al 2017), combined with the known seafloor spreading fabric (Hilde and Lee 1984) confirm that this area was located close to the equator at 50 Ma. Major northward movement took place from 50 to 25 Ma but apparently little movement after 15 Ma, according to Yamazaki et al (2010).…”

“…After 15 Ma, the Neogene IBM arc relocated to near its present position (Taylor and Fujioka et al 1992;Hall et al 1995;Yamazaki et al 2010;Mahony et al 2011), during which there was copious supply of tuffaceous sediment from the Izu-Bonin forearc, as drilled during Expedition 352 (Reagan et al 2015) and elsewhere (e.g. Amami Sankaku Basin; Arculus et al 2015c).…”

“…First, the 'retreating slab' model which is based on palaeomagnetic data indicates substantial northward drift of the Izu-Bonin arc from near the equator, coupled with major clockwise rotation since c. 50 Ma (Shih 1980;Haston and Fuller 1991;Hall et al 1995;Hall 2002;Yamazaki et al 2010; Figure 18(a)). Based largely on land palaeomagentic evidence from Palau, Guam, Saipan Chicijima, and Anijima, the Philippine Sea plate rotated 84°clockwise (Hall et al 1995;Deschamps and Lallemand 2002;Hall 2002).…”

Philippine Sea Plate inception, evolution, and consumption with special emphasis on the early stages of Izu-Bonin-Mariana subduction

“…Any rotational component of the plate is hard to extract since the deep-sea cores are not oriented and most azimuthally oriented paleomagnetic data are from plate boundary zone islands, potentially subject to local rotations. Based on drill cores obtained in the ADO region, Yamazaki et al (2010) considered that most of the northward shift was accomplished between about 50 and 25 Ma with very little northward movement after 15 Ma. They also present a model in which the PSP rotated 90°c lockwise between 50 and 15 Ma around an Euler pole near 23°N 162°E.…”

Boninite and boninite-series volcanics in northern Zambales ophiolite: Doubly-vergent subduction initiation along Philippine Sea Plate margins

“…This gap was addressed by Wu et al (2016) southern Eurasia reveals that the Philippine Sea Plate was bordered by Cretaceous oceanic crust (the East Asian Sea) in its western margin. Paleomagnetic data derived from sites in the Philippine Sea Plate shows northward translation concomitant with clockwise rotation (Hall et al, 1995;Richter & Ali, 2015;Yamazaki et al, 2010) (Fig. 10a).…”