Mid‐Cretaceous to early Tertiary apparent polar wander path of the Pacific Plate

Abstract

Pacific apparent polar wander was delineated for mid‐Cretaceous to early Tertiary time using 22 seamount paleomagnetic poles, 11 paleocolatitudes from azimuthally unoriented cores, five effective inclinations from two‐dimensional magnetic anomaly inversions, and one magnetic lineation relative amplitude datum. Three of the seamount paleomagnetic poles were new data calculated in this study. The apparent polar wander path was defined with six mean poles having ages of 39, 66, 76, 82, 85, and 94 Ma. An alternate path was constructed combining data from two pairs of mean poles (66 and 76 Ma, 85 and 94 Ma) that were statistically indistinguishable. The apparent polar wander path is hook‐shaped with a nearly right angle bend at 82 Ma. Its post‐82 Ma section trends north–south, the pre‐82 Ma part, east–west. The path indicates uneven polar wander. Unresolvable polar motion occurred between 66–76 Ma and 85–94 Ma, suggesting Stillstands. However, the large distances between the 85 and 82 Ma poles (15.2°±3.8°) and 82 and 76 Ma poles (11.3°±2.8°) imply rapid polar wander at rates of 5.1°±1.3°/m.y. and 1.9°±0.5°/m.y., respectively. Both the sharp bend and rapid polar wander occurred at the end of the Cretaceous Normal Polarity Superchron. The mid‐Cretaceous paleomagnetic data show a trend suggestive of southward motion of the Pacific plate that may be the end of a period of southward drift postulated by others to have begun in the Jurassic. The evolution of various features of the apparent polar wander path are discussed in terms of plate motion, true polar wander, and time‐varying non‐dipole geomagnetic fields. We argue that the overall shape of the polar wander path resulted from the change of Pacific plate motion from southward to northward, perhaps brought about by the beginning of the subduction of the plate beneath Asia.