Latitudinal shift of Pacific hotspots during the late Cretaceous and early Tertiary

Abstract

Two frames of reference, the geomagnetic field and hotspots, have been widely used to measure the past motions and interactions of lithospheric plates. Several studies have found that these reference frames have undergone as much as 19–22^° of relative motion, often called true polar wander (TPW), in the past 200 Myr^1–4. Moreover, it also appears that this offset did not accumulate at a uniform rate. Some evidence suggests that spurts of TPW can occur at rates as high as 1–2^° per Myr^3–5. Rates even an order of magnitude less could pose serious problems for tectonic studies based on the hotspot reference frame because velocities of this magnitude cannot be considered insignificant compared to those of the plates. Unfortunately, the imprecision of most palaeomagnetic data is such that large error bounds are common for many estimates of TPW rates. In this report, we present a record of TPW derived from Pacific palaeomagnetic data that are relatively well constrained in age and palaeolatitude. They show that offset between the two reference frames accumulated at ∼0.3° per Myr^–1 from late Cretaceous to early Tertiary.