MAGNETIZATION ACQUISITION IN FAST DEPOSITED NATURAL SEDIMENTS (TURBIDITES AND HOMOGENITES) AND LABORATORY EXPERIMENTS
MAGNETIZATION ACQUISITION IN FAST DEPOSITED NATURAL SEDIMENTS (TURBIDITES AND HOMOGENITES) AND LABORATORY EXPERIMENTS
French Title: ACQUISITION DE L'AIMANTATION DANS DES SEDIMENTS NATURELS DEPOSES RAPIDEMENT ET DANS LES EXPERIENCES DE REDEPOSITION EN LABORATOIRE
Abstract ID#: 34978
English Abstract:
Turbidites result from rapid depositional processes and are evidently ruled out from paleomagnetic records dealing with time-series. No attention has ever been paid to the magnetization of turbidites which is fully justified if the high level of turbulence governing the depositional processes influences the acquisition of magnetization. In certain conditions like channeled turbidity currents, levées of sediment are generated and then associated with relatively calm although very fast depositional processes. Such conditions will thus govern the subsequent acquisition of magnetization through mechanical lock-in of the magnetic grains. This situation is actually quite similar to what happens during the experiences of artificial redeposition that are conducted in laboratory. Therefore, combining laboratory experiments and studies of natural turbidites could reveal important information on the processes involved in the acquisition of magnetization, especially if the comparison with the overlying hemipelagic sediments does not show any striking difference.
We will present the results of measurements of magnetic remanence, susceptibility, anisotropy of magnetic susceptibility (AMS) performed on four different and relatively recent turbidites. We also scrutinized the evolution of various rock magnetic parameters (ARM, IRM, S ratio, magnetic grain sizes, hysteresis parameters…). The second step is to compare the characteristics of these turbiditic and homogenites levels with the same parameters measured after experiences of redeposition of sediments in laboratory. As expected there is a grain size grading with relatively coarse sediment at the bottom and fine-grained sediment at the top, similarly to what is observed with laboratory redeposited sediments and thus further justifies the comparison. Surprisingly, in most cases the magnetic grain sizes follow a similar pattern, which would imply that magnetic grains were not clustered inside sedimentary particles. These experiments also allow us to test whether magnetization acquisition obeys the same rules as for slowly deposited hemipelagic sediments.
We will present the results of measurements of magnetic remanence, susceptibility, anisotropy of magnetic susceptibility (AMS) performed on four different and relatively recent turbidites. We also scrutinized the evolution of various rock magnetic parameters (ARM, IRM, S ratio, magnetic grain sizes, hysteresis parameters…). The second step is to compare the characteristics of these turbiditic and homogenites levels with the same parameters measured after experiences of redeposition of sediments in laboratory. As expected there is a grain size grading with relatively coarse sediment at the bottom and fine-grained sediment at the top, similarly to what is observed with laboratory redeposited sediments and thus further justifies the comparison. Surprisingly, in most cases the magnetic grain sizes follow a similar pattern, which would imply that magnetic grains were not clustered inside sedimentary particles. These experiments also allow us to test whether magnetization acquisition obeys the same rules as for slowly deposited hemipelagic sediments.