Paleomagnetism of Jurassic volcanic rocks in southeastern Arizona and North American Jurassic apparent polar wander

Thesis/Dissertation · Tue Jan 01 04:00:00 EST 1985

OSTI ID:6935691

May, S R

The Corral Canyon sequence in the Patagonia Mountains is a 650 meter thick homoclinal sequence consisting of interbedded volcaniclastic red-beds, welded ash-flow tuff, and lavas. Rb/Sr isotopic analysis of eight whole rock tuff samples yields an isochron age of 171 +/- 3 Ma. Welded tuffs in the Corral Canyon sequence possess a stable, primary magnetization carried in both magnetite and hematite that defines a paleomagnetic pole at 61.8/sup 0/N, 116.0/sup 0/E. Paleomagnetic study of the Canelo Hills volcanics welded tuff member also yields a stable, primary magnetization throughout a stratigraphic thickness of 600 meters. Various aspects of the paleomagnetic data indicate that discordance of the Canelo Hills volcanics pole is probably due to acquisition of remanent magnetization during a period of non-dipole behavior of the geomagnetic field. Dispersion of paleomagnetic directions suggests that the welded tuff member represents at most two cooling units and can be interpreted as a caldera-fill sequence. A revised Jurassic APW path differs significantly from available paths and has important implications for North American plate motion and paleolatitude. The spatio-temporal progression of reliable Jurassic paleopoles, in conjunction with Triassic and Early Cretaceous poles, is well described by paleomagnetic Euler pole analysis. The APW path is divided into three tracks, separated by two cusps. These cusps represent changes in the direction of North American absolute plate motion and can be correlated with global plate motion and intraplate deformation events at approximately 200-210 Ma and 150 Ma. Finally, the APW path presented herein predicts more southerly Late Triassic and Jurassic paleolatitudes for North America than have been suggested by previous authors.

• Research Organization: Arizona Univ., Tucson (USA)
• OSTI ID: 6935691
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
580100* -- Geology & Hydrology-- (-1989)
AGE ESTIMATION
ALKALI METALS
ALKALINE EARTH METALS
ARIZONA
ELEMENTS
FEDERAL REGION IX
GEOLOGIC AGES
GEOLOGY
ISOTOPE RATIO
JURASSIC PERIOD
MAGNETISM
MESOZOIC ERA
METALS
NORTH AMERICA
PALEOMAGNETISM
PLATE TECTONICS
RUBIDIUM
STRATIGRAPHY
STRONTIUM
TECTONICS
TUFF
USA
VOLCANIC REGIONS