HR: 1340h
AN: U33A-0024    [Abstracts]
TI: Rapid true polar wander: A quixotic search?
AU: * Cottrell, R D
EM: rory@earth.rochester.edu
AF: Department of Earth & Environmental Sciences, University of Rochester 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Smirnov, A V
EM: alexei@earth.rochester.edu
AF: Department of Earth & Environmental Sciences, University of Rochester 227 Hutchison Hall, Rochester, NY 14627 United States
AU: Tarduno, J A
EM: john@earth.rochester.edu
AF: Department of Earth & Environmental Sciences, University of Rochester 227 Hutchison Hall, Rochester, NY 14627 United States
AB: Studies in the 1960's emphasized that polar wander could be a significant component of apparent polar wander curves. These concerns were assuaged when subsequent tests revealed that polar wander components were very small and overwhelmed by plate motion. Nevertheless, the concept of large and rapid polar wander has been surprisingly resilient. It gained new support in the 1980's when polar wander was defined in a fixed hotspot frame of reference and called ``true polar wander" (TPW). This new TPW was correlated to a wide variety of phenomena, from the rate of geomagnetic reversals to anomalous volcanism, but the linkages often differed sharply between studies. And renewed investigations, including paleomagnetic studies of the Emperor seamounts (ODP Leg 197), have emphasized that hotspot drift can be relatively rapid (over 40 mm/yr). We trace problems in some past and recent TPW hypotheses to an overreliance on the hotspot reference frame. The failure to scrutinize independently the two key components (APWPs and hotspot tracks) in directional space has led to illusory short-term spurts of TPW and overestimates of long-term rates. We review tests that can be used to detect these artifacts. The exclusion of hotspot drift reduces total ``TPW" displacements so that they are near the level of other competing explanations that might account for variation in global paleomagnetic pole positions (e.g. reconstruction uncertainities and inadequate geomagnetic field averaging). This vanishingly small amount of polar wander suggests that locally developing mantle mass heterogeneities may have been naturally balanced by global mantle flow in the post-Jurassic Earth.
DE: 8155 Plate motions--general
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
SC: Union [U]
MN: 2004 AGU Fall Meeting