Preservation potential of sedimentary event layers

Preservation potential of sedimentary event layers (e.g., ash layers or tempestites) is a function of net sedimentation rate and biogenous mixing rate. Previous studies that have used an inverse Peclet number to scale the problem in terms of advection or diffusion are in error due to the improper inclusion of the surface mixed layer thickness as the sole length scale. Herein, focus is on time scales. If the transit time (i.e., time required to advect the signal through the biologically active zone) is less than the dissipation time (i.e., time required to destroy the signal), then some fraction of the original signal is preserved. A simple quantitative model, based on the diffusion analogy of sediment mixing, estimates the actual percentage of preserved signal under various combinations of sedimentation rate, mixing rate, and event layer thickness.