Rs. Keir et Rl. Michel, INTERFACE DISSOLUTION CONTROL OF THE C-14 PROFILE IN MARINE SEDIMENT, Geochimica et cosmochimica acta, 57(15), 1993, pp. 3563-3573
The process of carbonate dissolution at the sediment-water interface h
as two possible end-member boundary conditions. Either the carbonate p
articles dissolve mostly before they are incorporated into the sedimen
t by bioturbation (interface dissolution), or the vertical mixing is r
apid relative to their extermination rate (homogeneous dissolution). I
n this study, a detailed radiocarbon profile was determined in deep eq
uatorial Pacific sediment that receives a high rate of carbonate suppl
y. In addition, a box model of sediment mixing was used to simulate ra
diocarbon, carbonate content, and excess thorium profiles that result
from either boundary process following a dissolution increase. Results
from homogeneous dissolution imply a strong, very recent erosional ev
ent, while interface dissolution suggests that moderately increased di
ssolution began about 10,000 years ago. In order to achieve the observ
ed mixed layer radio-carbon age, increased homogeneous dissolution wou
ld concentrate a greater amount of clay and Th-230 than is observed, w
hile for interface dissolution the predicted concentrations are too sm
all. These results together with small discontinuities beneath the mix
ed layer in Th-230 profiles suggest a two-stage increase in interface
dissolution in the deep Pacific, the first occurring near the beginnin
g of the Holocene and the second more recently, roughly 5000 years ago
.