Paleomagnetism of the Patagonian Plateau Basalts, Southern Chile and Argentina

Authors

Robert F. Butler
Francisco Herve
Francisco Munizaga
Myrl E. Beck Jr., Western Washington UniversityFollow
Russ R. Burmester, Western Washington UniversityFollow
Eduardo S. Oviedo

Document Type

Article

Publication Date

4-10-1991

Abstract

A total of 505 paleomagnetic samples were collected from 65 sites (volcanic flows) of the Patagonian plateau basalts at four locations in southem Chile and Argentina. K/Ar analyses indicate that 38 flows from two locations form a Late Cretaceous group (64-79 Ma), while the remaining 27 flows are Eocene in age (42-56 Ma). Progressive demagnetization indicates that a characteristic remanent magnetization (ChRM) has been successfully isolated from 59 flows. Rock-magnetic prop­erties and analysis of ChRM directions within and between sites allow the secure inference that the ChRM is a thermoremanent magnetization acquired during original cooling. The Eocene flows yield 15 independent samplings of the paleomagnetic field. However, these data fail the reversals test and probably do not adequately average geomagnetic secular variation. The Late Cretaceous flows yield 18 independent samplings of the paleomagnetic field, six of normal polarity and 12 of reversed polar­ity. These data pass the reversals test and have angular dispersion of virtual geomagnetic poles (VGPs) consistent with adequate sampling of geomagnetic secular variation. The mean of these 18 VGPs yields a Late Cretaceous paleomagnetic pole for South America: latitude = 78.7°S; longitude - 358.4°E: A₉₅ = 6.3° (K = 31.6; S = 14.5°). This pole is consistent with similar age poles from North America and Africa when the Atlantic is reconstructed to 70 Ma. Contrary to previous indications, the South American apparent polar wander path does not reach the present rotation axis until after Late Cretaceous time.

Publication Title

Journal of Geophysical Research-Solid Earth and Planets

Volume

96

Issue

B4

First Page

6023

Last Page

6034

Required Publisher's Statement

Copyright 1991 by the American Geophysical Union

Recommended Citation

Butler, Robert F.; Herve, Francisco; Munizaga, Francisco; Beck Jr., Myrl E.; Burmester, Russ R.; and Oviedo, Eduardo S., "Paleomagnetism of the Patagonian Plateau Basalts, Southern Chile and Argentina" (1991). Geology Faculty Publications. 28.
https://cedar.wwu.edu/geology_facpubs/28

Subjects - Topical (LCSH)

Geology, Stratigraphic--Cretaceous; Paleomagnetism--Patagonia (Argentina and Chile); Basalt--Patagonia (Argentina and Chile); Polar wandering--Patagonia (Argentina and Chile)

Geographic Coverage

Patagonia (Argentina and Chile)

Genre/Form

articles

Type

Text

Language

English

Format

application/pdf