HR: 1330h
AN: V32A-0990    [PDF]
TI: The Hawaii-Emperor Bend: Clearly a Record of Pacific Plate Motion Change
AU: * Wessel, P
EM: pwessel@hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822
AU: Harada, Y
EM: harada@scc.u-tokai.ac.jp
AF: School of Marine Science and Technology, Tokai University, 3-20-1 Orido Shimizu, Shizuoka, 424-8610 Japan
AU: Kroenke, L W
EM: kroenke@soest.hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822
AU: Sterling, A
EM: akel@soest.hawaii.edu
AF: School of Ocean and Earth Science and Technology, University of Hawaii, 1680 East-West Road, Honolulu, HI 96822
AB: As most introductory textbooks will point out, the conventional explanation for the $\sim$120$\deg$ change in the trends of the Hawaiian and Emperor chains is a $\sim$60$\deg$ change in plate motion over a fixed plume in the mantle. Recently, however, new paleomagnetic and radiometric age data from the Emperor Seamounts have led some scientists to reject the conventional view of the origin of the Hawaii-Emperor bend in favor of a mobile plume. Yet, at the brink of being explained away as the mere consequence of a drifting plume, the fixed hotspot hypothesis now gains support from newly reported radiometric dates of rock samples from seamounts at the bend which reveal an age much older than expected. Unlike the previous younger age ($\sim$43 Ma), the older age ($\sim$47 Ma) allows the bend to be directly correlated with a period of pronounced, global tectonic reorganizations around Chron 21. Here we present a new Pacific absolute plate motion model, derived from 15 hotspot chains, which does not require hotspot drift in order to satisfy geometric and chronological constraints. By considering this absolute plate motion model with available Pacific paleomagnetic poles we find support for the notion that the spin axis was closer to the Hawaiian hotspot during the formation of the Emperor chain, and this interpretation (polar wander, not hotspot drift) also explains the paleomagnetic latitudes from the Emperor seamounts as well as the lack of coral reefs materials in the drill holes north of Koko Guyot. However, this interpretation is not unique, and drift cannot be summarily ruled out. Yet, if Pacific plumes are drifting then they appear to be moving in unison. Careful examination of the Pacific seafloor reveals additional Pacific trails with bends that appear to be contemporaneous with the Hawaii-Emperor Bend, although conclusive radiometric age data are lacking. Our plate motion model predicts hotspot tracks that fit these bends. Considering all these lines of evidence the fixed hotspot hypothesis is granted a new lease on life.
DE: 1219 Local gravity anomalies and crustal structure
DE: 8121 Dynamics, convection currents and mantle plumes
DE: 8157 Plate motions--past (3040)
SC: Volcanology, Geochemistry, Petrology [V]
MN: 2003 Fall Meeting