Full Vector Studies of the Pringle Falls Excursion Recorded at Pringle Falls, Oregon

University Of Hawaii, Honolulu

Investigators

Abstract

The main objective of this proposal is to investigate the relative paleointensity of the lake sediments that recorded the Pringle Falls excursion (ca. 218+/-1o ka) at the original site of Pringle Falls along the Deschutes River in Oregon. Paleomagnetic directions (i.e. Declination and Inclination) as well as the relative paleointensity (i.e. Full Vector) from the Pringle Falls sediments will provide information on the spatial and temporal variability of the Earth's geomagnetic field for the well documented aborted reversal at Pringle Falls which duration is of few hundred years. Due to the fact that there is a real need to obtain detailed records from high-resolution sediments (i.e. high sedimentation rates, at least 10cm/year) in order to have a better understanding of the generation of the field, we propose to study in detail five sections sampled along the Deschutes River with the main objective of understanding the directional behavior as well as the geomagnetic field strength (i.e. relative paleointensity of the sections) recorded before during and after the Pringle Falls excursion in Oregon. The objectives of this proposed study are primarily related to the knowledge of the paleofield variations during periods like reversals and excursions, and the critical time intervals that precede and follow the high resolution (i.e. at least 10 cm/year of sedimentation rates) Pringle Falls excursion (recorded in Oregon) that so far have only been documented from a few sedimentary sequences particularly between 30 to 220 thousand years of the geomagnetic history. Reversal and excursion studies cannot be separated from the surrounding polarity intervals and most records published so far were not long enough to provide complete information. The lacustrine sediments along the Deschutes River sections offer the first exceptional opportunity to document field changes over a time period that includes a polarity episode that lasted a few hundred to, at most, several thousand years, and thus document the field behavior over various time constants. The results of the rock magnetic tests/experiments performed on pilot samples indicate that the sediments in question are suitable for the relative paleointensity studies proposed here. The magnetic results of this proposed research will contribute to the understanding of the structure in the core of the Earth, the core-mantle and the inner and outer core boundaries as well as the related causes of the generation of the Earth's magnetic field.