A framework to quantify paleogeomorphologic responses to ancient climate change
Abstract
River forms are dynamic, expressing a variety of environmental parameters such as changes in climate conditions, land cover, and precipitation. The current form of a river represents a signature of the integrative effects of historical events and environmental signals. For instance, an increase in precipitation due to climate change can be translated into an increase in river discharge as well as suspended sediment load. Investigating an ancient fluvial system can reveal the response of that system and their basins to dramatic episodes of paleoclimatic change. Currently, there is no quantitative estimate of how these paleohydrologic changes manifest in ancient rivers. This research describes a framework for modeling fluvial geomorphic change across a major paleoclimate transition; the White River Group (WRG) exposed in Nebraska and South Dakota was deposited during the greenhouse to icehouse transition that occurred during the Late Eocene and Early Oligocene in North America approximately 34 million years ago. Measurements from WRG strata, including grain size distribution and the presence of the bedforms, were used to create an estimate of channel geometry and paleoflow characteristics. Based on field observations, the geometry of the ancient river was constructed from the geometry of a modern river that approximates paleoclimate conditions of the WRG. The mean annual peak flood can be constructed from the current river hydrograph, coupled with the paleoclimatology of the study area. A hydraulic-geomorphologic model was used to simulate the flow conditions and sediment transport in the domain. Finally, the geomorphologic changes predicted by the model, including the aggradation, degradation, and changes in the form of the river are compared and verified against field data. Ultimately, this work leverages knowledge of ancient river systems to illustrate how rivers respond to environmental change.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMEP011..06S
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY;
- 1873 Uncertainty assessment;
- HYDROLOGY