Seamount paleomagnetism and Pacific Plate tectonics

Author(s): Sager, William Warren
Source: 489p. Institution: University of Hawaii at Manoa, Honolulu, HI, United States
Note: In English. Doctoral dissertation
Summary: Thirty-four new seamount paleomagnetic models are presented in this study, doubling the amount of reliable seamount paleomagnetic data available from the Pacific, making it possible to re-interpret the apparent polar wander path (APWP) of the Pacific and to examine the temporal distribution of volcanism in the Line Islands and Musicians Seamounts. Paleomagnetic results from twenty-six dated seamounts were combined with Pacific paleomagnetic data from other sources to calculate seven mean paleomagnetic poles representing the Eocene, Maastrichtian, Campanian, Santonian, Turonian, Albian, and Barremian. The agreement of the seamount VGPs with the other paleomagnetic data is generally quite good, indicating that the seamount results are relatively free of any bias that might result from demagnetization or secondary magnetization components. The APWP begins near Greenland along the Late Jurassic DSDP Site 307 polar circle and moves more than 20° southward to the Barremian and Albian poles. Between the Albian and the Campanian it turns to the north and then to the east to form a mid-Cretaceous loop before trending northward to the geographic pole in the Late Cretaceous and Tertiary. The rate of APW along the segments that form this loop are very high, and in one spurt from about 91 to 81 Ma. the paleopole appears to move over 22° in only 10 Ma. Within the resolution of the data, the timing of the fast APW appears to be coincident with the Cretaceous Quiet Time. The north Pacific paleomagnetic poles are compared to the positions predicted for them by a Pacific plate/hotspot motion model and a large discrepancy during the Early and Late Cretaceous is noted. These differences could be caused by true polar wander, varying long term nondipole geomagnetic field components, or by an inadequate model of plate/hotspot motion. The implications of the paleomagnetic data for each of phenomena is discussed and it is concluded that although true polar wander and non-dipole components probably have some effect on the APWP, most of the rapid APW is due to plate motion. It is noted that a number of equatorial DSDP sediment paleocolatitudes record paleomagnetic poles significantly closer to the geographic pole than do the rest of the paleomagnetic data. These discrepant data show excellent agreement with the few south Pacific paleomagnetic data available, and it is suggested that the discrepancy may have a tectonic cause. Seamount paleomagnetism gives some interesting insights into the processes of volcanism in the Line Islands and the Musicians Seamounts. The VGPs of Line Islands seamounts indicate that there was volcanic activity in the chain during both the Late Cretaceous and the Eocene. Few reliable ages are available for Musicians Seamounts, but the VGPs from these edifices are very consistent and so a magnetic age has been assigned to each volcano by the position of its VGP along the APWP. The paleomagnetic data indicates that volcanism occurred in the Musicians from the Santonian-Turonian to the Maastrichtian. The magnetic ages are inconsistent with all proposed models for the formation of the Musicians, but show a general younging trend from west to east.
Year of Publication: 1983
Research Program: DSDP Deep Sea Drilling Project
Key Words: 12 Stratigraphy, Historical Geology and Paleoecology; 18 Geophysics, Solid-Earth; Age; Albian; Barremian; Campanian; Cenozoic; Cretaceous; Cretaceous Quiet Time; Eocene; Line Islands; Lower Cretaceous; Maestrichtian; Mesozoic; Musicians Seamounts; Oceania; Pacific Ocean; Paleogene; Paleomagnetism; Plate tectonics; Polar wandering; Pole positions; Polynesia; Santonian; Seamounts; Senonian; Stratigraphy; Tectonophysics; Tertiary; Turonian; Upper Cretaceous; Volcanism; Volcanology
Record ID: 1984028246
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from U. S. Geological Survey, Hawaiian Volcano Observatory, United States

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