Anomalous Late Jurassic motion of the Pacific Plate with implications for true polar wander

Abstract

True polar wander, or TPW, is the rotation of the entire mantle-crust system about an equatorial axis that results in a coherent velocity contribution for all lithospheric plates. One of the most recent candidate TPW events consists of a ∼30 • rotation during Late Jurassic time (160-145 Ma). However, existing paleomagnetic documentation of this event derives exclusively from continents, which compose less than 50% of the Earth's surface area and may not reflect motion of the entire mantle-crust system. Additional paleopositional information from the Pacific Basin would significantly enhance coverage of the Earth's surface and allow more rigorous testing for the occurrence of TPW. We perform paleomagnetic analyses on core samples from Ocean Drilling Program (ODP) Site 801B, which were taken from the oldest available Pacific crust, to determine its paleolatitude during the Late Jurassic and Early Cretaceous (167-133 Ma). We find that the Pacific Plate underwent a steady southward drift of 0.49 • -0.74 • My −1 except for an interval between Kimmeridgian and Tithonian time (157-147 Ma), during which it underwent northward motion at 1.45 • ± 0.76 • My −1 (1σ ). This trajectory indicates that the plates of the Pacific Basin participated in the same large-amplitude (∼30 • ) rotation as continental lithosphere in the 160-145 Ma interval. Such coherent motion of a large majority of the Earth's surface strongly supports the occurrence of TPW, suggesting that a combination of subducting slabs and rising mantle plumes was sufficient to significantly perturb the Earth's inertia tensor in the Late Jurassic.

Jurassic Monster Polar Shift Confirmed by Sequential Paleopoles From Adria, Promontory of Africa

“…The mean rate of polar motion calculated using the well‐dated (U‐Pb perovskite) Ontario (Kent et al, ) and Ithaca (Van Fossen & Kent, ) kimberlites poles from North America is 1.9°/Myr. The Jurassic monster shift was common to the assembled continents, now including parauthocthonous Adria of northwest Africa, and most probably represents an episode of TPW, a rotation of the whole Earth about a pivot on the equator located, in this case, in the region off western Africa and that may have been triggered by an abrupt mass anomaly, such as the break‐off and sinking into the mantle of a subducting slab. An episode of TPW in the Late Jurassic is compatible with the only available contemporaneous data from the Pacific oceanic realm (Fu & Kent, ). The Jurassic monster shift controlled the first‐order depositional architecture of several sedimentary basins worldwide through synchronous and rapid variations of paleolatitude of sign and magnitude that depend on the position relative to the equatorial Euler pivot. The geocentric axial dipole assumption at the basis of these paleolatitude estimates remains valid for TPW, as a mechanism to account for the Jurassic monster shift, insofar as the geodynamo in the fluid outer core will tend to align with the rotation axis (due to the Coriolis effect) providing a stable reference frame for paleolatitude estimates even as the whole mantle‐lithosphere rotates.…”

New paleomagnetic pole for the Upper Jurassic Chon Aike Formation of southern Argentina (South America): Testing the tectonic stability of Patagonia with respect to South America, and implications to Middle Jurassic-Early Cretaceous true polar wander

“…12b). The track between 180 and 140 Ma of the running mean APW path for South America does not support the huge shift suggested by Kent and Irving (2010), Kent et al (2015) and Fu and Kent (2018).…”

“…A TPW event, by definition, should be detectable in all tectonic plates and would involve a displacement about an Euler pole located close to the equatorial plane (Marcano et al, 1999). Recently, Fu and Kent (2018) performed an analysis on core samples of the Pacific ocean basin and suggested that large amplitude TPW occurred as recently as the Late Jurassic, however further paleomagnetic experiments on both Fig. 9.…”

Pacific‐Panthalassic Reconstructions: Overview, Errata and the Way Forward

“…Because of the high Pacific plate velocities and NR due to the entire Pacific-Panthalassic Basin rotating systematically clockwise before 83.5 Ma (Figure 8b inset diagram) Figure 13). Pacific LIPs, when reconstructed, are located near vertically above the surface-projected (Fu & Kent, 2018). Another dip-corrected volcanic latitude estimate from ODP Site 801C (Wallick & Steiner, 1992) has a slightly higher southerly latitude and marked V WS .…”