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Revisiting 228Th as a tool for determining sedimentation and mass accumulation rates

July 12, 2022

The use of 228Th has seen limited application for determining sedimentation and mass accumulation rates in coastal and marine environments. Recent analytical advances have enabled rapid, precise measurements of particle-bound 228Th using a radium delayed coincidence counting system (RaDeCC). Herein we review the 228Th cycle in the marine environment and revisit the historical use of 228Th as a tracer for determining sediment vertical accretion and mass accumulation rates in light of new measurement techniques. Case studies comparing accumulation rates from 228Th and 210Pb are presented for a micro-tidal salt marsh and a marginal sea environment. 228Th and 210Pb have been previously measured in mangrove, deltaic, continental shelf and ocean basin environments, and a literature synthesis reveals that 228Th (measured via alpha or gamma spectrometry) derived accumulation rates are generally equal to or greater than estimates derived from 210Pb, reflecting different integration periods. Use of 228Th is well-suited for shallow (<15 cm) cores over decadal timescales. Application is limited to relatively homogenous sediment profiles with minor variations in grain size and minimal bioturbation. When appropriate conditions are met, complimentary use of 228Th and 210Pb can demonstrate that the upper layers of a core are undisturbed and can improve spatial coverage in mapping accumulation rates due to the higher sample throughput for sediment 228Th.

Publication Year 2022
Title Revisiting 228Th as a tool for determining sedimentation and mass accumulation rates
DOI 10.1016/j.chemgeo.2022.121006
Authors Joseph Tamborski, Pinghe Cai, Meagan J. Eagle, Paul Henderson, Matthew Charette
Publication Type Article
Publication Subtype Journal Article
Series Title Chemical Geology
Index ID 70233496
Record Source USGS Publications Warehouse
USGS Organization Woods Hole Coastal and Marine Science Center