American Geophysical Union Become an AGU Member
Subscribe to AGU Journals		 AGU Home AGU Publications

Read Full Article (file size: 365654 bytes)    Cited by

GLOBAL BIOGEOCHEMICAL CYCLES, VOL. 19, GB3013, doi:10.1029/2004GB002371, 2005

Particle age distributions and O2 exposure times: Timescales in bioturbated sediments

Christof Meile

Department of Marine Sciences, University of Georgia, Athens, Georgia, USA


Philippe Van Cappellen

Department of Earth Sciences–Geochemistry, Utrecht University, Utrecht, Netherlands


Abstract

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 O2 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 O2 penetration depths divided by linear sedimentation rates (L O2/ω) to estimate OETs.

Received 23 September 2004; accepted 16 June 2005; published 24 August 2005.

Keywords: bioturbation; particle age distribution; random walk; oxygen exposure time; organic carbon burial.

Index Terms: 3022 Marine Geology and Geophysics: Marine sediments: processes and transport; 4255 Oceanography: General: Numerical modeling (0545, 0560); 4804 Oceanography: Biological and Chemical: Benthic processes, benthos (0408); 4806 Oceanography: Biological and Chemical: Carbon cycling (0428).

Read Full Article (file size: 365654 bytes)    Cited by

Citation: Meile, C., and P. Van Cappellen (2005), Particle age distributions and O2 exposure times: Timescales in bioturbated sediments, Global Biogeochem. Cycles, 19, GB3013, doi:10.1029/2004GB002371.