Stratigraphy in space and time: A reproducible approach to analysis and visualization

Abstract

Time-elevation plots and chronostratigraphic diagrams are valuable for understanding and analyzing stratigraphy when time-elevation data, or some approximation of them, are available, for example in flume experiments, numerical models, and three-dimensional seismic reflection surveys. We developed a Python module called stratigraph, aimed at the reproducible analysis and visualization of stratigraphy, and we use it here to explore data from forward stratigraphic models of meandering channels, the eXperimental EarthScape (XES) facility XES-02 experiment, and two experiments that were conducted at the Tulane University Sediment Dynamics and Stratigraphy Laboratory. We use these tools to generate and visualize three-dimensional chronostratigraphic diagrams, compute maps of stratigraphic completeness and other stratigraphic attributes, and explore the nature of the erosional surfaces. We show that, using a 3D Wheeler diagram, it is possible to create maps of important stratigraphic attributes, in addition to the conventional thickness maps. There are six fundamental stratigraphic attributes that are direct consequences of a quantitative chronostratigraphic approach, as follows. (1) Sediments that were preserved after deposition have a thickness and (2) a duration; normalized by the total time, this duration of preserved deposition is called stratigraphic completeness. (3) The duration of deposition of sediment that was eroded later (called vacuity); (4) the thickness of these sediments is the eroded thickness. (5) At any given geographic location, erosion occurs some of the time, and the duration of these erosive periods is the fifth quantity. (6) Finally, it is quite common that neither significant deposition nor erosion takes place for some time and the duration of this stasis can be considered at every location. These maps give an overview of where erosion or deposition dominate in a source-to-sink system, and for how long; and they makeit possible to quickly identify sites with both a high degree of stratigraphic completeness and a significant thickness.