Rates of sedimentation, and stratigraphical completeness

Abstract

The most obvious result of sedimentation processes is the change in the thickness of accumulated sediment with time. Whenever the net change over a period of time is positive, a record is left of a sedimentation system's existence, a stratigraphical section. For the stratigrapher, the problem that such a section poses is to determine the detailed correspondence of thickness to time¹: for the sedimentologist, the problem is to infer the nature of the parent sedimentation system, and to estimate its parameters. A simple stochastic model is used here: (1) to illustrate some basic stratigraphical results of clastic sedimentation processes; (2) to offer an explanation for the commonly cited systematic decrease of mean sedimentation rate with increasing time span; and (3) to assess the concept of stratigraphical completeness. (It will be assumed that all post-depositional, non-erosional processes, such as compaction, can be identified, and their effects on stratigraphical thickness allowed for.)