7 Undergraduate Research I (Posters)

Wednesday, 12 May 2021
11:25 AM - 12:30 PM
Mackay School of Earth Sciences & Engineering Room

PALEOMAGNETIC DATA FROM THE CARBONIFEROUS BAIRD FORMATION, EASTERN KLAMATH MOUNTAINS, CALIFORNIA

Paper number: 7-5
Program: Theme Sessions
Time: 11:45 AM – 11:50 AM

Authors

Abstract

The tuffs and volcaniclastic strata of the Carboniferous Baird Formation in the Eastern Klamath mountains were formed as part of an emergent island arc system whose paleozoic kinematic history remains enigmatic. The Baird Formation occurs in a sequence of Devonian to Jurassic strata recording several pulses of arc eruptive activity This project uses paleomagnetic data from three sites in the Baird Formation as a means to further constrain the rotational and translational history of the Eastern Klamath terrane (EKT). Sites contain varying lithologies and include silicic ignimbrites, andesitic tuffs, and tuffaceous siltstones and mudstones. All samples were collected from outcrops using a gasoline powered portable drill. Prior to extraction, the samples were oriented with a Pomeroy device and their core azimuths were measured using both a magnetic and sun compass. Samples were stored in a magnetically shielded room to allow viscous magnetizations to decay before measurement.

Alternating field demagnetization of sample NRM up to 12nT, followed by thermal demagnetization up to as high as 660°C produced stable magnetic directions of dual polarity and identified magnetite as the primary remanence carrier in all sites. Results from two sites revealed single component, northwest trending primary directions with 20-30° downward inclinations, following tilt correction. A modern overprint was detected. A third site revealed multicomponent magnetizations and a southward trending magnetite-carried direction with a 20-30° upward inclination. The inclinations of these obtained directions were found to be consistent with the Carboniferous magnetic field of the North American craton and reveal minor dextral rotation relative to the craton. The stable directions produced from these three sites thus likely record primary Carboniferous magnetizations, making the Baird Formation a very suitable paleomagnetic data source for constraining post-Carboniferous regional EKT tectonics.

Geological Society of America Abstracts with Programs. Vol. 53, No. 4

doi: 10.1130/abs/2021CD-363233

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