Late Cretaceous paleolatitude of the Hawaiian Hot Spot: New paleomagnetic data from Detroit Seamount (ODP Site 883)

Abstract

Paleomagnetic data from Detroit Seamount of the Emperor seamount chain (northwestern Pacific Ocean) provide a direct way to estimate the latitudinal position of the Hawaiian hot spot in the Late Cretaceous (75–81 Ma), providing important constraints on geodynamic models for Hawaiian plume motion. Crystalline basement of Detroit Seamount was sampled at four drill sites by Ocean Drilling Program (ODP) Legs 145 (Sites 883 and 884) and 197 (Sites 1203 and 1204). Here we report detailed thermal and alternating field (AF) demagnetization data collected from basalt lava flows recovered at ODP Site 883. Most samples showed two nearly antiparallel components of natural remanent magnetization (NRM). AF demagnetization was often insufficient to separate the magnetization components; therefore thermal demagnetization data were used to define their directions. Both magnetization components are chemical remanent magnetizations (CRMs) carried by single‐domain to pseudo‐single‐domain titanomaghemite produced by low‐temperature oxidation of titanomagnetite. Rock magnetic experiments suggest that the normal polarity component is a CRM which pseudomorphs the primary thermal remanent magnetization (TRM) of parental titanomagnetite. In contrast, the reversed polarity component is a CRM self‐reversed with respect to a primary TRM [Doubrovine and Tarduno, 2004]. Inclination data analysis of characteristic remanence (normal polarity component) results in the five distinct inclination groups and an average inclination of 57.7°−13.8°+12.3° (95% confidence limits quoted). The angular dispersion of paleomagnetic directions suggests that the Site 883 basalts adequately average paleosecular variation and that the inclination average represents the time‐averaged geomagnetic field. Combining all available paleomagnetic data from the four sites on Detroit Seamount, a revised paleolatitude of 34.4°−5.8°+3.2° was calculated. This estimate is significantly north of the present latitude of the Hawaiian hot spot (∼19°N), suggesting that the hot spot moved southward from Late Cretaceous to Paleogene times (81–47 Ma) at rates of ∼33–67 mm/yr. If the inclination results from ODP Site 883 represent the best estimate among the data available from Detroit Seamount, rates at the higher range of values are favored. Because such rates are comparable to the velocities of lithospheric plates, the new data from ODP Site 883 present a strikingly different view on hot spot stability.