Formation of the Emperor Seamount Lineament by Southward Motion of the Hawaiian Hotspot
Dept. Earth & Environmental Sciences, University of Rochester, Rochester N.Y. 14627, USA
Our work on the Hawaiian-Emperor hotspot track started with paleomagnetic and rock magnetic investigations of basalt core samples recovered by Ocean Drilling Program (ODP) Leg 145 (Rea et al., 1995). These analyses (Tarduno & Cottrell, 1997) led to two conclusions which, at the time, were startling. First, the paleomagnetic data indicated that previous ideas of Pacific plate apparent polar wander based on seamount anomaly modeling were incorrect. Subsequent tests have continued to show that poles derived from seamount anomaly modeling are inconsistent with global paleomagnetic data (see discussion in Cottrell & Tarduno, 2000).
Second, the paleolatitude differed considerably from predictions of the fixed hotspot hypothesis. When viewed with other time-averaged paleomagnetic data (i.e., Kono, 1980) the new results suggested motion of the hotspot at rates of 30 to 50 mm yr-1. Moreover, together with other global paleomagnetic data, the new data suggested motion between hotspot groups (Tarduno & Gee, 1995; Tarduno & Cottrell, 1997). These findings seemed compatible with inferences from studies of plate circuits (see Hawaii Focus Group summary by J. Stock).
The new paleomagnetic data motivated us to prepare a JOIDES proposal, which eventually became ODP Leg 197 (Motion of the Hawaiian Hotspot: A Paleomagnetic Test). The age and paleomagnetic results of this drilling confirmed an age-progressive paleolatitude history, indicating that the Emperor seamount trend was principally formed by the rapid motion of the Hawaiian hotspot between approximately 81 and 47 Ma (Tarduno et al., 2003).
Overall, the paleomagnetic data suggest a much more active role of large-scale mantle flow in controlling the distribution of some volcanic islands. The new data also directly challenge the formulation of true polar wander (TPW, rotation of the entire solid Earth with respect to the spin axis) when defined in a fixed hotspot reference frame. Much of the TPW proposed to have occurred over the last 200 million years may instead record large-scale motion between groups of hotspots (see also Smirnov & Tarduno, 2001; 2002).