Influence of Water and Sediment Supply on the Completeness of the Stratigraphic Record and the Construction of Stratigraphic Surfaces in Alluvial Fans and Deltas
Straub, Kyle M.; Esposito, Christopher
Stratigraphy contains the most complete record of information necessary to quantitatively reconstruct paleolandscape dynamics for the majority of Earth history, but this record contains significant gaps over a range of time and space scales. These gaps result from stasis on geomorphic surfaces and erosional events that remove previously deposited sediment. Building on earlier statistical studies, we examine stratigraphic completeness in three controlled laboratory experiments where topography of aggrading deltas were monitored at high temporal and spatial resolution. The three experiments cover unique combinations in the absolute magnitudes of sediment and water discharge in addition to generation of accommodation space through base-level rise. This analysis centers on the influence of three time scales: 1) the time at which a record is discretized (t), 2) the time necessary to build a deposit with mean thickness equivalent to the maximum roughness on a surface (Tc), and 3) the time necessary for channelized flow to migrate over all locations in a basin (Tch). We find that stratigraphic completeness increases as a function of t/Tc but decreases as a function of Tc/Tch, over the parameter space covered in the experiments. We also examine how absolute curvature changes as a function of measurement window for geomorphic and stratigraphic surfaces and how to relate them to each other. We find that high curvature features on deltaic geomorphic surfaces (i.e. channels) are preferentially transferred to the stratigraphic record and that their stratal boundaries are crafted during erosional events. In addition, the width of the geomorphic channels can be estimated from the stratigraphy by identifying a scale break in the plot of mean absolute slope of stratigraphic surfaces vs. measurement window.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013