Transient electromagnetic soundings in the San Luis Valley, Colorado, near the Great Sand Dunes National Park and Preserve and the Alamosa National Wildlife Refuge (field seasons 2007, 2009, and 2011)
Links
- Document: Report (3.92 MB pdf)
- Data Release: USGS data release - Transient Electromagnetic Sounding Data Collected in the San Luis Valley, Colorado near the Great Sand Dunes National Park and Preserve and the Alamosa National Wildlife Refuge (Field Seasons 2007, 2009, and 2011)
- Download citation as: RIS | Dublin Core
Abstract
Transient electromagnetic (TEM) soundings were made in the San Luis Valley, Colorado, to map the location of a blue clay unit as well as to investigate the presence of suspected faults. A total of 147 soundings were made near and in Great Sand Dunes National Park and Preserve, and an additional 6 soundings were made near Hansen Bluff on the eastern edge of the Alamosa National Wildlife Refuge. The blue clay is a significant hydrologic feature in the area that separates an unconfined surface aquifer from a deeper confined aquifer. Knowledge of its location is important to regional hydrological models. Previous analysis of well logs has shown that the blue clay has a resistivity of 10 ohm-meters or less, which is in contrast to the higher resistivity of sand, gravel, and other clay units found in the area, making it a very good target for TEM soundings. The top of the blue clay was found to have considerable relief, suggesting the possibility of deformation of the clay during or after deposition. Because of rift activity, deformation is to be expected. Of the TEM profiles made across faults identified by aeromagnetic data, some showed resistivity variations and (or) subsurface elevation relief of resistivity units, suggestive of faulting. Such patterns were not associated with all suspected faults. The Hansen Bluff profile showed variations in resistivity and depth to conductor that coincide with a scarp between the highlands to the east and the floodplain of the Rio Grande to the west.
Suggested Citation
Fitterman, D.V., 2017, Transient electromagnetic soundings in the San Luis Valley, Colorado, near the Great Sand Dunes National Park and Preserve and the Alamosa National Wildlife Refuge (field seasons 2007, 2009, and 2011): U.S. Geological Survey Data Series 1043, 39 p., https://doi.org/10.3133/ds1043.
ISSN: 2327-638X (online)
Study Area
Table of Contents
- Abstract
- Introduction
- History of Field Effort
- Sounding Locations and Elevations
- Description of Transient Electromagnetic Sounding
- Data Quality and Averaging Procedure
- Inversion of Transient Electromagnetic Measurements
- Description of Results
- Conclusions
- Acknowledgments
- References Cited
- Appendix 1. Description of Transient Electromagnetic (TEM) Data Processing
- Appendix 2. Description of Transient Electromagnetic (TEM) Data Files
- Appendix 3. Voltage Units and Apparent Resistivity
- Appendix 4. Description of Transient Electromagnetic (TEM) Sounding Report Files and Plots
| Publication type | Report |
|---|---|
| Publication Subtype | USGS Numbered Series |
| Title | Transient electromagnetic soundings in the San Luis Valley, Colorado, near the Great Sand Dunes National Park and Preserve and the Alamosa National Wildlife Refuge (field seasons 2007, 2009, and 2011) |
| Series title | Data Series |
| Series number | 1043 |
| DOI | 10.3133/ds1043 |
| Year Published | 2017 |
| Language | English |
| Publisher | U.S. Geological Survey |
| Publisher location | Reston, VA |
| Contributing office(s) | Crustal Geophysics and Geochemistry Science Center |
| Description | Report: vii; 52 p. |
| First page | 1 |
| Last page | 39 |
| Country | United States |
| State | Colorado |
| Other Geospatial | San Luis Valley |
| Online Only (Y/N) | Y |
| Google Analytic Metrics | Metrics page |