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Fingerprinting of Mass Transport Deposits Using High-resolution XRF Core Scanning

Description: 

Earthquake-triggered mass transport deposits (MTDs) are used in subaqueous paleoseismology to investigate earthquake cycles in seismically active regions. Distinguishing earthquake-triggered MTDs from MTDs triggered by fires or floods is a critical step that allows subaqueous sediments to function as natural seismographs, constraining earthquake recurrence and regional seismic hazard. Confidently attributing an MTD’s triggering mechanism in lake and fjord sediments can be challenging. To address this, we apply geochemical analysis alongside petrophysical measurements of sediment cores to examine depositional processes in these aqueous environments. We employ X-ray fluorescence (XRF) core scanning as a non-destructive approach to rapidly measure a suite of elements at high spatial resolution . The XRF downcore data reveal clear compositional variations within MTDs that distinguish them from the background sediments. These variations reflect shifts in provenance, mineralogy, sorting, grain size, and/or event-induced changes related to redox conditions.

This study integrates high-resolution XRF core scanning with petrophysical properties to investigate the provenance of MTDs in fjord sediments from Prince William Sound, Alaska, located along the Alaska-Aleutian subduction zone_, and lake sediments from Lake Whatcom, Washington, situated in the Cascadia subduction zone. Both study sites contain MTDs triggered by earthquakes, marked by sharp basal contacts. In Prince William Sound, this transition is captured by increases in quartz and alumina-silicate (Si) and decreases in the small-grained silt fraction (i.e., K). In addition, a synchronous decrease in redox-sensitive elements (e.g., Mn) suggests that subaqueous MTDs are likely to result in bottom-water anoxia. In contrast, land-derived MTDs (e.g., landslides, debris flows, floods) are likely to introduce fresh organic matter and shift the bottom water to more oxic conditions. This study explores the geochemical signature of MTDs at two different sites to reconstruct the processes and impacts of earthquake-triggered mass-wasting events.

Session: Subaqueous Evidence for Earthquakes, Coseismic Landslides, Tsunamis and other Cascading Hazards [Poster]

Type: Poster

Date: 4/15/2026

Presentation Time: 08:00 AM (local time)

Presenting Author: Drake M. Singleton

Student Presenter: No

Invited Presentation: 

Poster Number: 165

Authors