HR: 11:05h
AN: GP41D-04 INVITED     [PDF]
TI: Shallowed vs. Concordant Paleomagnetic Inclinations in Asian red Beds: Tectonic Implications
AU: * Dupont-Nivet, G
EM: gdn@geo.uu.nl
AF: Utrecht University-Paleomagnetic laboratory, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AU: Martin-Hernandez, F
EM: fatima@geo.uu.nl
AF: Utrecht University-Paleomagnetic laboratory, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AU: Dekkers, M J
EM: dekkers@geo.uu.nl
AF: Utrecht University-Paleomagnetic laboratory, Budapestlaan 17, Utrecht, 3584 CD Netherlands
AU: Kodama, K
EM: kpk0@lehigh.edu
AF: Lehigh University; Dept. of Earth and Environmental Sciences, 31 Williams Drive, Bethlehem, PA 18015 United States
AB: Anomalously low paleomagnetic inclinations are often recorded in Asian red beds. Based on the available age control, most Tertiary sections show low inclinations while inclinations concordant with the paleomagnetic pole of Eurasia are generally recorded in Cretaceous red beds. This inclination pattern hinders tectonic interpretations but may also yield important constraints on the development of the Indo-Asia collisional system. To better constrain the reliability of the paleomagnetic record, we investigate the rock magnetic and petrologic signature in samples from 21 stratigraphic sections collected north of the Tibetan plateau. In addition to classic thermal demagnetization of NRM, IRM acquisition curves in fields up to 8 T were used to characterize magnetic mineralogy. Magnetite and hematite bearing samples can both be affected by inclination shallowing. AMS reveals a characteristic sedimentary fabric regardless of the degree of inclination shallowing. Separation of the paramagnetic from the ferromagnetic contribution of the anisotropy is performed according to Hernandez and Hirt (2001) technique. In samples with shallowed inclination, the anisotropy of the ferromagnetic fraction mimics the sedimentary fabric of the paramagnetic fraction. Determination of AAR using both the thermal themagnetization of Tan et al. (2002) protocol as well as a high-field IRM protocol involving IRM acquisition in 13 Tesla fields to erase the magnetic history of previous steps (Kodama and Dekkers, submitted) was carried out on representative samples with shallowed and with concordant inclinations. We hope that the distinct properties of the analyzed sediments will provide us with tools to discriminate red beds affected by inclination shallowing from sediments recording the correct paleomagnetic inclination from which paleopole positions can be confidently calculated
DE: 1520 Magnetostratigraphy
DE: 1525 Paleomagnetism applied to tectonics (regional, global)
DE: 1527 Paleomagnetism applied to geologic processes
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2003 Fall Meeting