Age of the Laschamp excursion determined by U-Th dating of a speleothem geomagnetic record from North America

Ioan Lascu; Joshua M Feinberg; Jeffrey A Dorale; Hai Cheng; R. Lawrence Edwards

doi:10.1130/G37490.1

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Age of the Laschamp excursion determined by U-Th dating of a speleothem geomagnetic record from North America

Journal article

Peer reviewed

Age of the Laschamp excursion determined by U-Th dating of a speleothem geomagnetic record from North America

Ioan Lascu, Joshua M Feinberg, Jeffrey A Dorale, Hai Cheng and R. Lawrence Edwards

Geology (Boulder), Vol.44(2), pp.139-142

02/2016

DOI: 10.1130/G37490.1

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Abstract

The Laschamp geomagnetic excursion was the first short-lived polarity event recognized and described in the paleomagnetic record, and to date remains the most studied geomagnetic event of its kind. In addition to its geophysical significance, the Laschamp is an important global geochronologic marker. The Laschamp excursion occurred around the time of the demise of Homo neanderthalensis, in conjunction with high-amplitude, rapid climatic oscillations leading into the Last Glacial Maximum, and coeval with a major supervolcano eruption in the Mediterranean. Thus, precise determination of the timing and duration of the Laschamp excursion would help in elucidating major scientific questions situated at the intersection of geology, paleoclimatology, and anthropology. Here we present a North American speleothem geomagnetic record of the Laschamp excursion that is directly dated using a combination of high-precision (super 230) Th dates and annual layer counting using confocal microscopy. We have determined a maximum excursion duration that spans the interval 42.25-39.70 ka B.P., and an age of 41.10+ or -0.35 ka B.P. for the main phase of the excursion, during which the virtual geomagnetic pole was situated at the southernmost latitude in the record. Our chronology provides the first age bracketing of the Laschamp excursion using radioisotopic dating, and improves on previous age determinations based on (super 40) Ar/ (super 39) Ar dating of lava flows, and orbitally tuned sedimentary and ice-core records.

absolute age

carbonate rocks

Cenozoic

chronostratigraphy

Crevice Cave

dates

Geochronology

magnetic excursions

magnetostratigraphy

Missouri

paleomagnetism

Perry County Missouri

Pleistocene

Quaternary

Quaternary geology

sedimentary rocks

solution features

speleothems

Th/U

United States

upper Pleistocene

Details

Title: Subtitle: Age of the Laschamp excursion determined by U-Th dating of a speleothem geomagnetic record from North America
Creators: Ioan Lascu - University of Cambridge
Joshua M Feinberg - University of Minnesota
Jeffrey A Dorale - University of Iowa
Hai Cheng - Xi'an Jiaotong University
R. Lawrence Edwards - University of Minnesota
Resource Type: Journal article
Publication Details: Geology (Boulder), Vol.44(2), pp.139-142
DOI: 10.1130/G37490.1
ISSN: 0091-7613
eISSN: 1943-2682
Publisher: Geological Society of America (GSA)
Language: English
Date published: 02/2016
Academic Unit: Earth and Environmental Sciences
Record Identifier: 9984229178402771

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