Magnetization processes of sedimentary rocks
Sedimentary rocks constitute an important component of our paleomagnetic archives that are used both for tectonic reconstructions and for magnetostratigraphic reconstructions. In most basins, sedimentary rocks record the geomagnetic field as sediments are being deposited through a process known as detrital remanent magnetization. However, in an increasingly large number of studies, we find that magnetization was acquired long after deposition due to either oxidizing or reducing fluids flowing through permeable rocks or sedimentary layers. These post-deposition magnetizations provide useful information about fluid migration but may also leed to erroneous interpretation when they are underestimated or unrecognized.
I work on both oceanic and continental basins using either cores recovered by the International Ocean Discovery Program (IODP) or geological outcrops. In some cases, the anisotropy of magnetic susceptibility of the rock indicates the fluid flow direction.
Alternation of red and green laminae in IODP Core U1502A-9-R1 previously interpreted as resulting from climatic cycles (Ferré et al., 2023).
Escalante National Monument canyon, Utah showing alternation of red and tan strata. Some of the reddish colors and magnetization originate from post-depositional iron-rich fluid flow (Ejembi et al., 2020).
Conceptual model of oxidizing and reducing fluid flow in the ocean floor of an oceanic basin and application to the South China Sea, after Fisher, A. T., & Wheat, C. G. (2010). Seamounts as conduits for massive fluid, heat, and solute fluxes on ridge flanks. Oceanography, 23(1), 74–78. doi.org/10.5670/ocean og.2010.63