On the Connections Between Surficial Processes and Stratigraphy in River Deltas

TL;DR

This study uses a numerical model to link surface deltaic processes with the stratigraphic record, highlighting the role of backwater effects and channel residence times in shaping subsurface features.

Contribution

It introduces a novel cellular model including backwater effects to analyze the connection between delta surface processes and stratigraphy.

Findings

Channel deposit patterns vary spatially with avulsion statistics.

Channel residence times follow a power law distribution with a cutoff.

Residence time distributions are approximately lognormal.

Abstract

We explore connections between surficial deltaic processes (e.g. avulsion, deposition) and the stratigraphic record using a simple numerical model of delta-plain evolution, with the aim of constraining these connections and thus improving prediction of subsurface features. The model represents channel dynamics using a simple but flexible cellular approach, and is unique in that it explicitly includes backwater effects that are known to be important in low-gradient channel networks. The patterns of channel deposits in the stratigraphic record vary spatially due to variation in avulsion statistics with radial distance from the delta's source of water and sediment. We introduce channel residence time as an important statistical measure of the surface channel kinematics. The model suggests that the mean channel residence time anywhere within the delta is nicely described by a power law distribution showing a cutoff that depends on radial distance. Thicknesses of channel deposits are not uniquely determined by the residence time of channelization. The channel residence time distributions at given radial distances from the source are found to be approximately lognormally distributed, a finding consistent with the scale-dependent radial structure of channel deposits in the stratigraphic record.