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Laramide Tectonics

figure
Mesozoic strata near Gallup tilted to high angle during Laramide tectonism. Site accessed with permission from the Navajo Nation.
(click for a larger version)
2021 Jacob Thacker
figure
Small crystals of the mineral apatite from the southeast Zuni Mountains. These grains were used for thermochronologic analysis and record cooling through ~90–40 °C approximately 59 million years ago.
(click for a larger version)
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Minor (small) strike slip faults near Gallup. Measurements of orientation and slip direction from minor faults can be used to reconstruct local and regional shortening directions.
(click for a larger version)
Jacob Thacker

The Laramide orogeny was a mountain building event that affected the US western interior during the Late Cretaceous to Paleogene (approximately 90–45 million years ago). Many of the iconic mountains and major oil and gas producing intermontane basins of the Rocky Mountains and Colorado Plateau, such as the Wind River range in Wyoming and the San Juan Basin here in New Mexico, formed during this time as Earth’s crust was compressed. The Laramide orogeny remains a major point of controversy, as it is difficult to explain how tectonism proceeded so far into the North American plate. Similar features in the Sierras Pampeanas in Argentina are forming above a zone of shallow-angle subduction, suggesting a similar process may have occurred beneath western North America during the Late Cretaceous. However, the larger width and along-strike extent of the Laramide belt remains difficult to explain.

Active New Mexico Bureau of Geology mapping and research focuses on studying Laramide features in the state. New Mexico was a key location for establishing modern thinking on Laramide tectonism (e.g., Coney and Reynolds, 1977), and provides important information for reconciling regional observations. Work is centered on geologic mapping, and utilizes structural geology (faults and folds), low-temperature thermochronology (timing of cooling), and minor basin analysis (sedimentology and stratigraphy) to better understand the spatial configuration, style, and timing of Laramide tectonism. Such information provides important constraints to deduce what tectonic processes were at play, and can help inform our understanding of enigmatic tectonic events around the world and through geologic time. In New Mexico, the work has important implications for the state’s natural resources, such as oil and gas and metals, as well as groundwater.

Study Areas to Date

  • Zuni Mountains, west-central NM
  • Greater Gallup area, west-central NM
  • Eastern San Juan Basin, northwest to north-central NM
  • Sangre de Cristo Mountains, north-central NM
  • South-central NM

For more information, contact:

References

Related Papers

  1. Thacker, Jacob O., Karlstrom, K.E., Kelley, S.A., Kendall, J.J., Crow, R.S., in review, Late Cretaceous time-transgressive onset of Laramide arch exhumation and basin subsidence across northern Arizona–New Mexico.
  2. Hobbs, K.M., and Fawcett, P.J., 2021, A physical and chemical sedimentary record of Laramide tectonic shifts in the Cretaceous-Paleogene San Juan Basin, New Mexico, USA: Geosphere, v. 17, no. 3, p. 854–875, https://doi.org/10.1130/GES02324.1
  3. Thacker, Jacob O., Kelley, S.A., Karlstrom, K.E., 2021, Late Cretaceous–Recent low-temperature cooling history and tectonic analysis of the Zuni Mountains, west-central New Mexico: Tectonics, v. 40, https://doi.org/10.1029/2020TC006643.
  4. Thacker, Jacob O., 2020, Horizontal shortening of the Laramide Zuni arch, west-central New Mexico: A preliminary study: New Mexico Geological Society Special Publication 14, p. 167–175.

Related Geologic Maps

  1. Thacker, Jacob O., in progress, Geologic Map of the 7.5-Minute Bread Springs Quadrangle, McKinley County, New Mexico, New Mexico Bureau of Geology, scale 1:24,000.
  2. Seager, W.R., Thacker, Jacob O., Kelley, S.A., in prep., Geologic Map of the 7.5-Minute Selden Canyon Quadrangle, Doña Ana County, New Mexico, New Mexico Bureau of Geology, scale 1:24,000.

Conference Presentations

  1. Hobbs, K., Thacker, Jacob O., 2021, Syn-seismic deposition or syndepositional seismicity: Paleoseismites record 10 m.y. of early Paleogene Laramide seismicity in San Juan Basin, north-central New Mexico: GSA Abstracts with Programs, v. 53, n. 6, https://doi.org/10.1130/abs/2021AM-370112.
  2. Thacker, Jacob O., 2021, Laramide shortening and exhumation of the Zuni Mountains, west-central New Mexico: GSA Abstracts with Programs, v. 53, n. 4, https://doi.org/10.1130/abs/2021CD-363058.

Press

  1. Bureau News: Zuni Mountains Tell a Story of Complex Uplift

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