Exploring Initial and Preserved Depositional Shapes from Experimental Strata

John Martin¹ and Chris Paola^2
1 St. Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN
² University of Minnesota, Minneapolis, MN

We report on a physical experiment conducted at St. Anthony Falls Laboratory intended to examine the effects of slow, rapid, and superposed base-level cycles on experimental stratigraphy given a foretilted subsidence profile and constant water and sediment supply. During the experiment 101 scans were taken of the entire experimental surface that yields a highly resolved record of erosion and deposition. In this unique research environment, we are able to quantitatively describe the shape of initial and preserved deposition, and to graphically evaluate the accumulated effect of erosion in modifying the initial depositional package to its final preserved shape in the stratigraphic record.

A heuristic measure of the depositional center of mass is defined here as the centroid, which provides a natural reference point for calculating planview depositional dispersion and the depositional moment of inertia in three dimensions. Initial experimental results show that, given the subsidence profile and base-level curve, there is a clear association between 1) the shape of the initial depositional package and 2) the degree of erosional modification that deforms the initial body during its transition from the near-surface to the preserved record. This link is rooted in the streamwise position of the initial centroid and its topographic elevation.

We show that volumetric preservation potential of deposition is maximized during base-level minimums, and accordingly there is a strong positive correlation coefficient between the initial and final depositional shape. Conversely, poor to negative shape correlations exist at base-level maximums prior to relatively rapid falls.