The physical mechanisms of geomagnetic field recording in sediments

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Two large-scale natural systems, sedimentation and sea floor spreading, continuously record and archive the changing geomagnetic field. Sedimentary paleomagnetic records attain superior temporal resolution, but their paleofield information is not unambiguous. Numerous geological factors - sedimentation rate, magnetic carrier properties, matrix composition, compac- tion rate, macro- and micro-environment - control mobility, alignment and fixation of magnetic particles. They filter, bias, modulate or randomize the remanence aquisition process and thus the resulting paleofield records. Reversal sections with their typically low field intensities are particularly affected. These signal deformations could be identified and recovered, if the recording mechanism, its controls and filter characteristics were better known. The scientific quest for ever more detailed paleofield data creates a growing need for new signal analysis and validation techniques in magnetostrati- graphy. Separation of field and climate induced signal com- ponents, multi-factorial calibration of paleointensity records and deconvolution of the time averaging lock-in process are increasingly important, yet unresolved tasks.Several new experiments and investigations are proposed to detect and quantify the micro-scale mechanisms of sedimentary remanence acquisition and to develop empirical, statistical and analytical models. Magnetic particle activation by Brownian motion, compaction, pore water flow, bioturbation, microfossil desintegration, adhesive and capillary forces, magnetic interaction, microtectonics and seismicity will be studied on naturally deposited marine surface sediment columns probed by multi-coring. Magnetic particle relaxation in weak ambient fields as a function of various controlled treatments will be magnetically monitored over extended periods from hours to months using SQUID and, if available, MPMS technology. Microscopic methods will be tested for their suitability to visualize magnetic particle distribution.