Abstract
In order to further understand the full vector excursional details of the geomagnetic field, a paleomagnetic and rock magnetic study of four sites has been conducted at the type locality of Pringle Falls, Oregon where 827 samples were drilled and spaced along a distance of 5 km, for their detailed directional and relative paleointensity studies. The profiles have registered a high-reso- lution (>10 cm/kyr) paleomagnetic record of the excursion (ca. 211+/13 ka) as recorded by diatomaceous lacustrine sediments. Remanence as well as induced magnetization experiments to investigate the reproducibility of the signal throughout the profiles have been conducted. In addition, low-field susceptibility vs. temperature analysis was performed indicating that the main magnetic carrier is pure magnetite (Curie point 575 ℃). The magnetic grain size also has indicated Single Domain-Multi-Domain (SD-MD) magnetite. The demagnetization was done by alternating field (a.f.) experiments, and the mean directions were determined by principal component analyses. In addition, induced magnetic tests were done, such as magnetic susceptibility (x) analyses, saturation IRM, anhysteretic remanent magnetization (ARM70) as well as the normalization of J17.5 mT/ARM70 to attempt to obtain relative paleointensity records of these sediments in question. The results of the induced rock magnetic tests such as the normalization studies indicate a direct correlation between the decrease of the relative paleointensity variations (i.e. lows) with respect to the directional changes. The detailed behavior of the paleosignal is highly consistent, since they are rapidly deposited sediments providing a detailed representation of the paleofield. The dissected VGP paths in 3 different phases are highly internally consistent and are defined by clockwise and anticlockwise loops traveling from the high northern latitudes over eastern North America and the North Atlantic to South America and then to high southern latitudes. They then return to the high northern latitudes through the Pacific and over to Kamchatka. This VGP behavior defines the geomagnetic signature of the Pringle Falls excursion as recorded at the type locality.
Highlights
IntroductionAt the beginning of the identification of the excursion research, it was mistakenly identified as the Blake polarity episode [1] [2]
The discovery of the Pringle Falls excursion took place in the late 1980s
It was after the identification of the characteristic geomagnetic features recorded by the declination and inclination records and the research work done on the chronostratigraphy, geochronology and tephrachronology that documented two sites at Pringle Falls along the Deschutes River in Oregon that the excursion was officially described and established as a geomagnetic feature [3]
Summary
At the beginning of the identification of the excursion research, it was mistakenly identified as the Blake polarity episode [1] [2]. It was after the identification of the characteristic geomagnetic features recorded by the declination and inclination records and the research work done on the chronostratigraphy, geochronology and tephrachronology that documented two sites at Pringle Falls along the Deschutes River in Oregon (see Figure 1) that the excursion was officially described and established as a geomagnetic feature [3]. Subsequent research work was performed to correlate the directional geomagnetic signal from additional profiles drilled (~837 samples) along the Deschutes River spaced along a distance of 5 km, for their detailed directional geomagnetic signature.
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