HR: 11:50h
AN: GP41D-07 INVITED     [PDF]
TI: Astronomical Forcing in Miocene Continental Sediments: Implications for the Geomagnetic Polarity Time Scale
AU: * Krijgsman, W
EM: krijgsma@geo.uu.nl
AF: Paleomagnetic Lab. Fort Hoofddijk Utrecht University, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AU: Abdul Aziz, H
EM: haziz@geo.uu.nl
AF: Paleomagnetic Lab. Fort Hoofddijk Utrecht University, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AU: Hilgen, F
EM: fhilgen@geo.uu.nl
AF: Paleomagnetic Lab. Fort Hoofddijk Utrecht University, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AB: High-resolution magnetostratigraphic and cyclostratigraphic studies have been carried out on cyclically bedded sedimentary successions of Miocene distal alluvial fan to lacustrine deposits in northeast Spain. The magnetic polarity patterns of the composite sections can be correlated straightforwardly to the most recent GPTS of Cande and Kent (1995), providing first order age models. Spectral analyses of the color records in the time domain reveal periodicities for the sedimentary cyclicities close to 23, 41, 100 and 400 kyr, strongly supporting an astronomical origin. Hence, we can determine the astronomical durations of subchrons from the number of sedimentary cycles per polarity interval. Comparison of these results with the GPTS shows significant discrepancies, especially at the upper part of Chron C5n. The duration pattern of our polarity intervals is, however, confirmed by many detailed magnetostratigraphic records from the ocean floor, indicating errors in the reversal ages of the GPTS. In addition, our astronomical tuning provides astronomical ages for all polarity reversals in the interval between 12.9 and 10.6 Ma. Comparison with the GPTS shows that astronomical ages are older by 50 - 100 kyr. Consequently, we demonstrate that astronomical forcing in continental sequences can be a powerful tool to improve the fundamental dating techniques of the geological record.
DE: 1513 Geomagnetic excursions
DE: 1520 Magnetostratigraphy
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting