Cretaceous paleomagnetic apparent polar wander path for the pacific plate calculated from Deep Sea Drilling Project and Ocean Drilling Program basalt cores

摘要

The apparent polar wander path (APWP) of the Pacific plate still has many uncertainties owing to the fact that paleomagnetic data are difficult to obtain for oceanic plates. After more than three decades of coring by the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP) there are now a large number of reliably dated basalt cores recovered from the Pacific plate and this provides an opportunity to determine paleomagnetic poles based on igneous rock samples, considered by many scientists to be the most reliable data type. Cretaceous Pacific plate basalt core data were compiled, corrected using a standard technique, divided into groups based on age, and combined to calculate five mean paleomagnetic poles with ages of 80, 92, 112, 121, and 123 Ma, the latter two being for two different coeval regions. In all pole analyses, the lack of azimuthal orientation for cored samples leads to large uncertainties in pole locations along a nearly east-west direction. This difficulty was mitigated by using declination data from magnetic anomaly inversions of dated Pacific seamounts for azimuth constraint. The two nearly same-age poles were calculated because paleocolatitudes from Ontong Java Plateau (OJP) are discordant compared to those from other Pacific locations. I interpret the discordant OJP results to indicate that the plateau is on crust that had an early history as an independent plate. The other poles (80, 92, 112, and 123 Ma) fall on a northeast-trending line that suggests slow apparent polar wander during the Early and mid-Cretaceous, followed by rapid polar wander between 92 and 80 Ma. Comparison of the 123 Ma pole with previously published paleomagnetic data of Jurassic age implies southward apparent polar wander followed by a turnaround. Because the 123 Ma pole is the farthest from the geographic pole, it implies the turnaround happened near that time and that the Pacific plate has moved similar to 40 degrees northward since then. The 80 Ma pole stands similar to 17 degrees from the geographic pole, indicating that similar to 60% of the northward drift occurred prior to that time and similar to 40% afterwards. (c) 2006 Elsevier B.V. All rights reserved.