HR: 14:10h
AN: GP33E-03 INVITED    [Abstracts]
TI: The effect of flocculation on DRM direction and intensity
AU: * Mitro, R
EM: ritayan_mitro@yahoo.com
AF: Scripps Institution of Oceanography, UCSD, La Jolla, CA 92093-0220, United States
AU: Tauxe, L
EM: ltauxe@ucsd.edu
AF: Scripps Institution of Oceanography, UCSD, La Jolla, CA 92093-0220, United States
AB: Sedimentary rock records, being relatively more continuous than igneous records, are indispensable for studying past geomagnetic field variations. Sedimentary paleointensity studies rest upon the basic assumption that detrital remanent magnetization (DRM) is linearly related to the ambient field in which sediments acquired magnetization and paleosecular variation studies assume that the magnetization is parallel to the geomagnetic field. Yet, DRM is complicated. Factors other than the magnetic field such as particle size, shape, nature of sediments, hydrodynamic forces etc all affect how sediments get magnetized. In light of the many factors affecting DRM the key assumptions of linearity and parallelism are open to question. Inclination error has been known since the very early days of sedimentary paleomagnetism, yet the mechanisms that control it are poorly understood. Moreover, it has recently been suggested that even linearity may not always hold true. One of the most important control on DRM is now thought to be flocculation. Its role in controlling DRM magnitude has been explored but its influence on the directional properties of DRM is virtually unknown. In a series of laboratory experiments in different field and flocculation states we have confirmed the strong non-linearity of certain sedimentary systems. In addition, we have discovered a marked dependence of inclination error with the field strength and flocculation state. Our findings have serious implications for paleosecular variation studies using sediments, in particular from low salinity environments, such as fresh water lakes in which very small changes in salinity could result in very large changes in flocculation state and DRM acquisition.
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting