Reconstructing the Quaternary Depositional History Using Geologic Mapping and Three-Dimensional Modeling of the Subsurface Near Fort Morgan, Northeastern Colorado
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- Document: Report (60.0 MB pdf)
- Data Releases:
- USGS data release - Luminescence data for: Reconstructing the Quaternary depositional history using geologic mapping and a 3D model of the subsurface in the vicinity of Fort Morgan, Eastern Colorado
- USGS data release - Digital drillhole lithologic data and a radiocarbon age -- data supporting interpretation of Quaternary depositional history in the vicinity of Fort Morgan, Eastern Colorado
- Download citation as: RIS | Dublin Core
Abstract
Centered on Fort Morgan, Colorado, this study is intended to build from previous work by adding a three-dimensional (3D) view of the subsurface to better understand the depositional history of Quaternary deposits. A 1:100,000 scale geologic map was made by combining previous geologic maps, regional soil maps, and recent field investigations. In addition to the geologic mapping, drill hole lithologic data from water wells and oil and gas exploration were compiled and lithologic units simplified to best represent the stratigraphy of the Quaternary deposits. From these subsurface data, a 3D subsurface model was constructed, trimmed at the surface by a digital elevation model, and a bedrock surface foundation gridded from drill hole data was added. The surface of the 3D model was then compared visually to the surficial geologic map. Cross sections were constructed from the 3D model and compared to site-specific drilling that was done as part of this project. Finally, the model was examined in detail to reconstruct the depositional history of the subsurface alluvial and eolian units. Alluvial and fluvial drainage basins exposed in the subsurface have a greater areal extent than the present-day narrow drainages. Older eolian sand in the subsurface tends to be interbedded with loess indicating coeval deposition. Holocene sand, both eroded from bedrock exposed at the surface north of the study area and reworked from the South Platte River, buries most of the interbedded older sand and loess.
Suggested Citation
Taylor, E.M., Berry, M.E., Mahan, S.A., and Havens, J.C., 2026, Reconstructing the Quaternary depositional history using geologic mapping and three-dimensional modeling of the subsurface near Fort Morgan, northeastern Colorado: U.S. Geological Survey Scientific Investigations Report 2025–5052, 48 p., https://doi.org/10.3133/sir20255052.
ISSN: 2328-0328 (online)
Table of Contents
- Abstract
- Introduction
- Previous Work—Soil and Geologic Mapping
- Methods
- Mapping Quaternary Deposits Based on Natural Resources Conservation Service Maps, Field Investigations, and Previous Mapping
- Fluvial and Alluvial Deposits
- Creating a Three-Dimensional Lithologic Model of the Subsurface and Correlating to the Surficial Geologic Map
- Reconstruction of the Depositional History of Sediments in the Study Area
- Summary
- References Cited
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Reconstructing the Quaternary depositional history using geologic mapping and three-dimensional modeling of the subsurface near Fort Morgan, northeastern Colorado |
| Series title | Scientific Investigations Report |
| Series number | 2025-5052 |
| DOI | 10.3133/sir20255052 |
| Publication Date | February 26, 2026 |
| Year Published | 2026 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston VA |
| Contributing office(s) | Geosciences and Environmental Change Science Center |
| Online Only (Y/N) | Y |