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We explore time series of magnetic susceptibility (χ) and anhysteretic remanent magnetization (ARM) in settings of rapid sediment accumulation rate (SAR) with the goals of partitioning exogenic forcings from autogenic processes and to better understand how these magnetic signals are encoded in sedimentary archives. Environmental signals of periodic external forcings commonly operate at Milankovitch frequencies, but in rapid SAR settings autogenic processes including channel avulsions and delta lobe switching both shred high-frequency external forcings, or even impart their own quasi-periodic signals. We measure χ using both a hand-held KT-10 magnetic susceptibility meter and a lab-based Kappabridge KLY-3s, and ARM in the < 2 mm size fraction using a GSD-5 alternating-field and a 2G superconducting magnetometers, with all results mass normalized to SI units. We focus on 40 samples collected at 25 cm intervals from 10 m of propagating foresets in a Gilbert delta of the Provo stage of Lake Bonneville at High Creek, Utah. A luminescence-based age model in this delta establishes a mean SAR of 8 cm/yr and terrestrial cosmogenic nuclide concentrations of both delta sediment and alluvium in the source indicates modern and paleoerosion rates (E) ranging from ~60-100 m/Myr (0.006-0.01 cm/yr). Periodicities of 18 and 33 yrs in the rock magnetic time series are greater than twice the compensation time for these foresets where peaks in χ and ARM are positively correlated with fine-grained matrix. We interpret a positive correlation between E and χ as driven by stripping of soil-mantled hillslopes that harbor greater concentrations of magnetic minerals than the underlying bedrock. The encoding of the environmental signal, here interpreted as autogenic cascading of sediment on foreset surfaces, is primarily set by the SAR and depositional processes, which are decoupled from E. Nevertheless, the strength of the magnetic signal in our sedimentary archive varies with E which can be more widely explored as a E-proxy when locally calibrated. These results offer insight into how to isolate the impact of quasi-periodic tectonic forcings on stratigraphic archives at sub-Milankovitch frequencies, where autogenic processes dominate depositional processes but which also encode critical human-dimension natural hazard information. 

Rapid sediment accumulation rates (SAR) in a fan delta situated on the rapidly uplifting footwall of the Taormina normal fault in NE Sicily preserves a rare record of earthquakes and base level change for a tightly coupled source to sink system. We use this sedimentary archive to reconstruct the kinematics and slip history of the fault and further an understanding of how tectonic forcing across various scales are encoded in stratigraphy. A revised luminescence-based age model indicates that ~82 m of the Pagliara fan-delta foreset facies was deposited in ~11 ka at a mean SAR of ~0.74 cm/yr during MIS 7. Syn-depositional terrestrial cosmogenic nuclide (TCN) determined paleoerosion rates of 0.91±0.12 mm/yr and 1.31 ±0.61 mm/yr are similar to published modern erosion rates for the Pagliara basin of 0.97 ±0.11 mm/yr. At the stratigraphic scale, a time series of magnetic susceptibility (c) sampled at 1 m intervals in the foresets displays four ~2,800 yr / 20 m-thick cycles of growing c, bounded by sharp decreases that do not coincide with changes in sediment texture. The c of the low-grade metamorphic bedrock in the source is 20-100 times weaker than the c of rubified soils mantling the hillslopes, which is comparable to the c of the delta sediments. We propose that large, bedrock-cored landslides quasi-periodically deliver weak c sediment to the delta that dilutes a c signal otherwise dominated by the stripping of soil-mantled hillslopes. We propose that centennial-scale recurrence interval earthquakes are most capable at triggering a basin-scale landslide only after channel incision has increased relief of hillslopes to the threshold condition, which requires millennia to achieve. At the landscape scale of delta geometry and location, the Pagliara delta accumulated in a hanging wall basin that has since been inverted. We reconstruct the history of base level fall for the delta from an inversion of fluvial topography and apportion that record to its rock uplift, delta deposition, and eustatic components. We show that footwall uplift has been unsteady over the past 600 ka ranging from -1 to 3 mm/yr. The integration of our stratigraphic- and landscape scale observations furthers our understanding of the natural hazards related to normal fault earthquakes and their impact on sediment dynamics in this steep, active tectonic setting.