Late Pleistocene paleomagnetic secular variation from the Sea of Galilee
Publication: Geophys. Res. Lett. 2002, V29(21) (pdf file)
Abstract
Stable magnetization of laminated lacustrine Lisan Formation show typical paleomagnetic secular variation and a possible geomagnetic field excursion. Samples were recovered from two trenches (OH1 and OH2) at the southwestern shore of the Sea of Galilee, a graben within the Dead Sea Transform system. The age of the recorded section is constrained by 14C ages from the Ohalo II paleolithic site at the top of the section, and assuming a 0.9 mm/yr deposition rate between 29-28 ka and 22-23 ka. The angle between the two site mean paleomagnetic directions is 21°, but retilting the beds to horizontal reduces it to 7°, indicating pre-folding, probably depositional magnetization. Aberrations of field directions at one locality, where VGPs deviate >40° from the geographic north, and low NRM intensities between 29-28 ka and 25-24 ka, are contemporaneous with the Mono Lake Excursion. If the correlation is correct, the new data support the hypothesis that the excursion was global, justifying its utilization as a chronological datum.
Location map of the Ohalo sampling site. The faults (solid lines) are part of the Dead Sea Transform system. An anticline (double arrow) that is exposed in Ubediya as well as seismic reflections across the Kinarot Valley [Rotstein et al., 1992] appears to affect the Ohalo area. back to top
Exploratory trench OH1 in the Ohalo II site. Photograph is from the Ohalo excavation web page
A. Characteristic declinations (circles) and inclinations (diamonds) in the Ohalo sections OH1 and OH2. Prominent aberrations appear between -215 m and -215.5 m and between -216.4 and -217 m (relative to mean sea level). B. Low intensities of Natural Remanent Magnetization at the bottom coincide with the aberations.
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The mean directions are compared to the GAD (0°/52°) and to retilted OH1 (open symbol). Equal angle projection shows the OH2 poles from -216 to -214 m. The Mono Lake Excursion may be recorded where the VGPs deviate by more than 40° from GAD.
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