A revised Latest Cretaceous and Early Cenozoic apparent polar wander path for the Pacific plate



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Texas A&M University


The apparent polar wander path (APWP) for the Pacific plate during the Late Cretaceous and Early Cenozoic has been constrained primarily by seamount magnetic anomaly inversions and seafloor magnetic anomaly skewness. The reliability of these data types is uncertain and data are too sparse to provide a consistent or detailed APWP. In an effort to refine the Pacific APWP, we collected a larger, more diverse data set that allowed for the calculation of new mean paleomagnetic poles for the latest Cretaceous and Paleogene. We combined four types of data including sediment core paleocolatitudes, basalt core paleocolatitudes, seamount magnetic anomaly inversion declinations, and effective inclinations from magnetic anomaly skewness calculations. This diverse data set yields paleomagnetic poles that are less affected by bias from any particular data type. We found reasonably good agreement between data types and calculated five mean paleomagnetic poles representing the Oligocene (30 Ma), Late (39 Ma) and Early (49 Ma) Eocene, and Paleocene (61 Ma) epochs and the Maastrichtian (68 Ma) stage. Though a significant percentage of the data are from azimuthallyunoriented cores, which do not provide constraint on paleodeclination, a wide distribution of sites and the use of declination data from seamount anomaly inversions gave relatively good control on pole paleolongitude. The large numbers of data in our calculations allow for reasonably compact uncertainty bounds and the overall agreement among most data implies insignificant systematic errors in the data set. The greatest disagreement among data occurs due to a divergence between poles from anomaly skewness and other data types prior to 55 Ma. As a whole, the new APWP implies northward Pacific plate drift. However, this motion is punctuated with a stillstand from the Late Cretaceous (~80 Ma) until the middle Eocene, (~49 Ma). This stillstand suggests a lack of northward Pacific plate motion during this time, counter to most accepted models. This APWP is consistent with paleomagnetic results from the Emperor Chain that indicate the Hawaiian hotspot moved south during formation of the Emperor Chain, but it implies an amount of motion slightly greater than that previously proposed for hotspot drift.