Paleomagnetism of Eocene volcanic rocks, Talkeetna Mountains, Alaska

Journal Article · Thu May 10 00:00:00 EDT 1990 · Journal of Geophysical Research; (United States)

DOI:https://doi.org/10.1029/JB095iB05p06737· OSTI ID:5073694

Panuska, B C ^[1]; Stone, D B; Turner, D L ^[2]

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1. Mississippi State Univ., State College (United States)
2. Univ. of Alaska, Fairbanks (United States)

Previous paleomagnetic studies of Eocene rocks deposited in the Talkeetna Mountains on the northern edge of the combined Peninsular, Wrangellia, and Alexander terranes (the southern Alaska superterrane (SAS)) yield a paleolatitude of 76{degree}N, while Late Cretaceous rocks on the southern edge of the SAS record a 32{degree}N paleolatitude. At face value, these drastically different paleolatitudes imply that Wrangellia moved 44{degree} to the north in only 20 m.y., requiring a northward component of velocity of about 24 cm/yr. Alternatively, the discrepancy might be explained by postulating an unrecognized tectonic boundary separating the two localities, allowing different emplacement ages. The authors have tested the unrecognized tectonic boundary hypothesis by sampling Eocene volcanic rocks deposited near the southern edge of the SAS in the Talkeetna Mountains. The data set comprises measurements from 97 oriented cores collected from 26 lava flows and two tuffs distributed over a distance of 50 km. A primary remanence is indicated by positive fold tests and penecontemporaneous intrusion tests. Age control is provided by nine new K-Ar whole rock age determinations ranging from 38.8 to 53.6 Ma. The mean paleomagnetic pole calculated for this study is not significantly different from the pole derived from the Eocene flows to the north and gives a paleolatitude of 78{degree}, thus ruling out the hypothesis of an unrecognized suture accommodating major post-Eocene displacement. This result has prompted a reevaluation of the data. The bulk of the evidence suggests northward displacement from lower latitudes; however, the error limits are such that the dramatic velocities previously postulated are not required.

• OSTI ID: 5073694
• Journal Information: Journal of Geophysical Research; (United States), Vol. 95:B5; ISSN 0148-0227
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ALASKA
MOUNTAINS
PALEOMAGNETISM
AGE ESTIMATION
ARGON ISOTOPES
CRETACEOUS PERIOD
EOCENE EPOCH
GEOLOGIC MODELS
GEOMAGNETIC COORDINATES
LAVA
ORIENTATION
POTASSIUM ISOTOPES
SAMPLING
TECTONICS
TUFF
VOLCANIC ROCKS
ALKALI METAL ISOTOPES
CENOZOIC ERA
COORDINATES
DEVELOPED COUNTRIES
FEDERAL REGION X
GEOLOGIC AGES
IGNEOUS ROCKS
ISOTOPES
MAGNETISM
MESOZOIC ERA
NORTH AMERICA
ROCKS
TERTIARY PERIOD
USA
580000* - Geosciences