The Character of Brunhes-Chron Paleomagnetic Secular Variation at High Latitudes: Results from IODP Expedition 323-Bering Sea (Invited)
Abstract
IODP Expedition 323 (Bering Sea Paleoceanography) has recovered 1,017 meters of replicated Brunhes-Chron paleomagnetic secular variation (PSV) from the Bering Sea region (50.7°N to 60.1°N). Six sites have complete Brunhes PSV records, two at medium resolution (Site U1341 - 10.6 cm/kyr, Site U1340 - 16.0 cm/kyr) and three at high resolution (U1339 - 23.1 cm/kyr, U1343 - 23.7 cm/kyr, U1344 -34.6 cm/kyr). We expect to develop high-resolution Brunhes paleomagnetic chronostratigraphies from all of these sites. Initial PSV records from Holes U1341A, U1343A, U1344A, and U1345A (0-400 ka only) provide a consistent picture of the character of Brunhes PSV at high latitude. The inclinations average higher than axial-dipole expectation (positive D I anomaly), which is consistent with other results from this latitude band. The angular dispersion is comparable to other published results. The inclinations tend toward axial-dipole expectation at high relative paleointensity (as noted at lower latitudes) and tend toward 90° as paleointensities diminish. This seems appropriate given that the sites are located nearby and between the two most significant/persistent high-latitude flux lobes in the Northern Hemisphere. Declinations tend toward east or west as inclinations approach 90°, presumably pointing toward the dominant flux lobe at that time. One unexpected result is the apparent total absence of Brunhes paleomagnetic field excursions in this region near the flux lobes, even though our preliminary data from Matuyama-aged sediments indicate they are common during reversed polarity.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMGP23C..03L
- Keywords:
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- 1560 GEOMAGNETISM AND PALEOMAGNETISM / Time variations: secular and longer