Open AccessComment on “Do geochemical estimates of sediment focusing pass the sediment test in the equatorial Pacific?” by M. Lyle et al.
Author(s) -
Francois Roger,
Frank Martin,
Rutgers van der Loeff Michiel,
Bacon Michael P.,
Geibert Walter,
Kienast Stephanie,
Anderson Robert F.,
Bradtmiller Louisa,
Chase Zanna,
Henderson Gideon,
Marcantonio Franco,
Allen Susan E.
Publication year - 2007
Publication title -
paleoceanography
Language(s) - English
Resource type - Journals
eISSN - 1944-9186
pISSN - 0883-8305
DOI - 10.1029/2005pa001235
Subject(s) - geology , sediment , oceanography , pacific ocean , geochemistry , geomorphology
Accurately estimating the vertical flux of material\udreaching the seafloor from the overlying surface waters is\udessential for the paleoceanographic reconstruction of a wide\udvariety of oceanic processes. Two approaches are currently\udbeing used. One consists of estimating mass accumulation\udrates (MAR) between dated horizons as the product of linear\udsedimentation rates, sediment dry bulk densities, and concentrations.\udOne pitfall with this approach is that sediments\udcan be redistributed on the seafloor by bottom currents, and\udtheir accumulation may not necessarily reflect the true\udvertical rain rate originating from the overlying water\udcolumn. To address this problem, the method of ²³⁰Th\udnormalization was developed [Bacon, 1984]. This method\udis based on the assumption that the rapid scavenging of\ud²³⁰Th produced in the water column by decay of dissolved\uduranium results in its flux to the seafloor always being close\udto its known rate of production. To the extent that this\udassumption is correct, scavenged ²³⁰Th can be used as a\udreference to estimate the settling flux of other sedimentary\udconstituents and to correct for sediment redistribution on the\udseafloor [Henderson and Anderson, 2003; Francois et al.,\ud2004]