Because the Pacific plate has moved rapidly, its apparent polar wander path (APWP) shows a large amount of motion since Cretaceous time. This APWP is useful not only for understanding the tectonics of the Earth's largest plate, but also for comparison with other plate tectonic reference frames, such as the hotspots. Roger Larson made significant strides in defining the Pacific APWP with early studies of seamount magnetic anomalies that showed significant northward drift of the plate, by publishing a study of DSDP cores that implied Late Jurassic southward motion of the plate, and by authoring a study on M-anomaly skewness that illuminated the Cretaceous "hook" in the APWP. The Pacific APWP is coming into better focus owing to new paleomagnetic data and data compilations; although, significant questions about the path remain. Recent results confirm ~40° of northward motion since ~123 Ma, but show an irregular amount of northward motion. During one period (94-80 Ma), apparent polar wander was rapid (~1°/Ma) whereas a subsequent time span (80-47 Ma) shows a still-stand. The overall shape of the APWP appears to correspond, however, to the known history of the Pacific plate and its interactions with surrounding plate boundaries. Despite recent advances, significant uncertainties still exist in the shape and details of the Pacific APWP. The chief problem is that paleomagnetic data are limited because the plate is almost entirely covered by ocean. As a result, the APWP is constrained mostly by "non-standard" paleomagnetic data, including azimuthally-unoriented core data and magnetic anomaly inversions (of seamounts and lineation skewness). Important questions that remain to be resolved are: (1) the direction and amount of early southward drift of the plate, (2) better characterization of the period of Late Cretaceous rapid apparent polar wander and the still-stand, (3) better understanding of why Ontong Java Plateau paleomagnetic data are anomalous with respect to other Pacific data, (4) reconciliation of apparent differences between skewness and other paleomagnetic data, and (5) an integration of paleomagnetic data from the south Pacific.
AGU Fall Meeting Abstracts
- Pub Date:
- December 2007
- 1525 Paleomagnetism applied to tectonics: regional;
- 3040 Plate tectonics (8150;
- 8157 Plate motions: past (3040);
- 9609 Mesozoic