Sediment accumulation rates and vertical mixing of deep-sea sediments derived from C-14 and Pb-210 in the southern Gulf of Mexico

摘要

Here we present new results on the sedimentation rates and vertical mixing in the deep-water region (966-3741 m) of the southern Gulf of Mexico, from a collection of 42 cores retrieved from the continental slopes and the abyssal plain. These cores were dated with the aid of accelerator mass spectrometry (AMS) C-14 determinations on planktic foraminifera. We applied the Modified Mixing Box Model (MMBM) to evaluate the mean sedimentation rates (S-m), to estimate the age of surface sediments (T-0) that result from mixing processes. Sm range between 5 and 9 cm kyr(-1) in cores from the abyssal plain and the continental slopes, highest rates are consistently observed in specific locations on the slopes (17-24 cm kyr(-1)). T-0 values range between 1000 and 2000 years, in cores from the abyssal plain and the continental slope sites, most probably as a result from the relatively low sedimentation rates and consequent mixing of older sediments. However, some cores from the continental slopes show consistently higher sedimentation rates, and T-0 values that are close to zero age. Here we further show Pb-210 profiles from 15 cores to evaluate the non-homogeneous mixing processes in surface sediments (0-10 cm). Biodiffusion coefficients (D-b) derived from the solution of advection-diffusion model range between 14 and 51 cm(2) kyr(-1) on the abyssal plain and between 42 and 158 cm(2) kyr(-1) on the continental slopes.