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Particle age distributions and O 2 exposure times: Timescales in bioturbated sediments
Author(s) -
Meile Christof,
Van Cappellen Philippe
Publication year - 2005
Publication title -
global biogeochemical cycles
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.512
H-Index - 187
eISSN - 1944-9224
pISSN - 0886-6236
DOI - 10.1029/2004gb002371
Subject(s) - bioturbation , geology , total organic carbon , biogeochemical cycle , diagenesis , continental shelf , particle (ecology) , sedimentary rock , mineralogy , oceanography , sediment , geomorphology , geochemistry , environmental chemistry , chemistry
A stochastic particle tracking approach is used to compute particulate age distributions and oxygen exposure times (OETs) in bioturbated marine sediments. Simulations representative of abyssal plain, continental slope, and continental shelf sediments indicate that within the mixed zone, the variability in particle age is of the same order of magnitude as the average age itself. This spreading of particle age by bioturbation complicates the interpretation of sedimentary archives. The results further show that average and median ages of particle‐bound constituents undergoing decay during early diagenesis deviate from those of inert tracers. Similarly, OETs depend on the biological mixing and biogeochemical reactivity of particulate constituents. Hence ratios of the O 2 penetration depth ( L O2 ) and the linear sedimentation rate (ω) may not offer reliable measures of actual OETs. Taking into account biodiffusional particle mixing and preferential degradation of organic matter under oxygenated conditions, the stochastic model predicts a global inverse relationship between the burial efficiency and the OET of organic carbon in ocean sediments. The relationship, however, differs significantly from that proposed by Hartnett et al. (1998), who used O 2 penetration depths divided by linear sedimentation rates ( L O2 /ω) to estimate OETs.