Palaeomagnetic palaeolatitudes of the Ontong Java Plateau from 120 to 55 Ma: implications for the apparent polar wander path of the Pacific Plate

Abstract

We present palaeomagnetic inclinations from Late Cretaceous-Early Tertiary deep-water carbonates obtained during ODP Leg 192 drilling at the Ontong Java Plateau (OJP) for the following periods: magnetochrons C33n (73.6-79.1 Ma), C32 (71.1-73.6 Ma), C27r-C31n (61.3-68.7 Ma) and C25-C26 (55.9-60.9 Ma). Compaction-induced inclination shallowing is considered to be negligible for the OJP sediments examined here because: (i) their palaeomagnetic inclinations are in excellent accord with those recently obtained from underlying OJP basement rocks, (ii) the studied sediments have anisotropy of anhysteretic remanent magnetization fabrics that appear poorly correlated with individual characteristic remanent magnetization inclinations and (iii) in the few cases where we observe a significant difference between our new OJP sedimentary palaeomagnetic data and data from other parts of the Pacific Plate, obtained mainly from seamount magnetization studies and skewness analyses, the sedimentary inclinations are not systematically lower, and therefore, cannot be explained in terms of inclination shallowing. Combining our new data with existing OJP palaeomagnetic data we obtain an internally consistent data set that we interpret to indicate northward motion of the plateau from its formation at similar to 120 Ma until 55 Ma. At 120 Ma the central plateau was located at 24 degrees +/- 4 degrees S. Approximately 45 Myr later (similar to 76 Ma) the plateau is located near 21 degrees S. Our data, therefore, indicate that the OJP was either stationary or exhibited a slow northward latitudinal drift during this interval. In contrast, from similar to 76 Ma until 68 Ma the plateau moved rapidly through approximately 10 degrees of latitude to similar to 10 degrees S. These intervals of slow and rapid motion track similar motions previously proposed for the entire Pacific Plate during the Cretaceous but extends the interval of slow motion into the Late Cretaceous. From 68 Ma until 56 Ma the plateau was again almost latitudinally stationary before moving slowly northward. More direct palaeomagnetic data are necessary to better define Pacific Plate motions during this time interval.