Quantifying the morphologies and hydrodynamics of paleorivers in four dimensions: Cretaceous Western Interior Basin, Utah, USA
Abstract
Quantitative reconstruction of paleohydrologic parameters from fluvial stratigraphy is challenging, but in principle offers sophisticated insights into the response of ancient landscapes to tectonic and climatic drivers. Here we use detailed field data and a suite of quantitative approaches to derive a four-dimensional (space/time) reconstruction of paleohydrology for Late Cretaceous paleorivers that drained to the Western Interior Seaway of North America. Our field data span five parallel fluvial systems, two of which include up-system to down-system transects, across seven stratigraphic intervals through Blackhawk Formation, Castlegate Sandstone and Price River Formation deposition, now exposed in central Utah. These data include grain-size (>200 counts) and cross-set measurements (n = ~2000). We use these data to quantitatively reconstruct fluvial morphologies, including their flow depths, paleoslopes, paleorelief, and planform stability, as well as various hydrodynamic properties, including flow velocity, discharge, and sediment transport modes.
From our results, we identify spatiotemporal changes in regional paleohydraulics, especially in response to long-period tectonic and climatic drivers. We reconstruct and quantify an increase in paleoslope at the Blackhawk-Castlegate transition; here, paleorelief in the alluvial domain increases from 10s of metres to c. 100 m. Despite this increase, fluvial morphologies and dynamics are overall similar in space and time — in detail we reconstruct no change in unit discharges at the Blackhawk-Castlegate transition, which raises questions about the implications of uncertainty in paleochannel widths on interpretation. Moreover, our reconstructions enable us to probe the efficacy of quantitative tools in a region where qualitative facies interpretations of paleohydraulics are well documented, and highlight crucial knowledge gaps for the advancement and application of these tools in the geologic past.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMEP011..08L
- Keywords:
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- 3344 Paleoclimatology;
- ATMOSPHERIC PROCESSES;
- 1825 Geomorphology: fluvial;
- HYDROLOGY;
- 1862 Sediment transport;
- HYDROLOGY;
- 1873 Uncertainty assessment;
- HYDROLOGY