Rise of the Colorado Plateau and Southern Rocky Mountain Region: A Synthesis of Paleoelevation Constraints and a Path Forward Using Temperature-Based Elevation Proxies
Abstract
The surface uplift history of the Colorado Plateau and southern Rocky Mountain region is key to resolving the long-debated evolutionary history of the Colorado River system. However, there remains controversy over the robustness of paleoelevation estimates in the region. We 1) synthesize existing constraints on the region's surface uplift history from sedimentary, stratigraphic, and geomorphic records to highlight research gaps and a path forward to refine paleoelevation estimates, and 2) present preliminary clumped isotope data for comparison with paleobotanical data from Eocene-Oligocene lacustrine deposits with the well-studied Florissant, Creede, and Antero floras in Western Colorado. Some constraints are inarguable, for example: 1) marine deposits dated ~80-70 Ma indicate when the region was last at sea level, 2) barbed tributaries along sections of the Grand Canyon indicate that there was once northeast drainage, and 3) erosional unconformities constrain when uplift began and provide minimum surface elevations. While these provide some limits, other proxy data permit a range of paleoelevation estimates through time. For instance, thermochronometric data used as proxies for river incision and denudation have been argued to permit Grand Canyon incision ages ranging from 70-5 Ma, and the use of the elevation-δ18O carbonate proxy is limited in the region due to the effects of multiple moisture sources with unique δ18O signatures. Surface temperature proxies are independent of these factors, yet paleobotanical proxies yield a range of temperatures based on various empirical relationships resulting in paleoelevation estimates that vary as much as 0.5-4km for a single sample locality. In contrast, the carbonate clumped isotope paleothermometer (Δ47) is thermodynamically based on the temperature dependence of 13C-18O bond ordering within carbonate. To improve and expand the use of temperature-based proxies, we compared clumped isotope and paleobotanical thermometry methods within the same units. Our preliminary Δ47 data tend to agree with the Nearest Living Relative and Digital Leaf Physiognomy methods, and together with existing geologic constraints suggest uplift began prior to the late Eocene in the northeastern Colorado Plateau and southern Rocky mountain region.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMEP026..02H
- Keywords:
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- 9820 Techniques applicable in three or more fields;
- GENERAL OR MISCELLANEOUS;
- 1199 General or miscellaneous;
- GEOCHRONOLOGY;
- 1699 General or miscellaneous;
- GLOBAL CHANGE;
- 8175 Tectonics and landscape evolution;
- TECTONOPHYSICS