Huge Landslides Reshaped Southwest Utah’s Topography 20-25 Million Years Ago

Attending GSA Connects in San Antonio? Check out this student abstract! 

Smith, A., Rivera, T.A., Biek, R.F., Malone, D.H., Hacker, D.B., Braunagel, M., Griffith, W.A., 2025. Volcanism before the big slide: a study of the volcanic suite preceding the Black Mountains gravity slide, Utah, USA. Geological Society of America Abstracts with Programs. 

A series of volcanic eruptions from 31 to 21 million years ago covered southwest Utah’s landscape in cooled lava flows, ash-flow deposits, and jumbled mudflows, with some of these deposits spanning hundreds of meters in thickness. Decades of field observations have revealed that a massive sheet of these deposits was shifted from their original location. More recent studies have determined three mega-landslide events as the reason for the displacement, known collectively as the Marysvale Gravity Slide Complex (MGSC).

The three landslides are named after the area in which they occurred. The Sevier slide lies to the east near the Sevier Plateau, and the Black Mountain slide lies to the west within the Black Mountains. The Markagunt slide, the largest of the three, lies in between them on the Markagunt Plateau. We investigate these landslides by dating the upper and lower rock units that bound the sliding surface via 40Ar/39Ar dating technique thereby constraining the age that the landslide occurred. Sanidine is collected from the outcropping tuff to be used in the dating analyses. We also perform bulk geochemical analyses to describe the rock units as well as to relate them to the different eruption events.

Investigation of the gravity slides is a collaborative project with the University of Missouri, The Ohio State University, Kent State University, Illinois State University, and Utah Geological Survey. 

This work is supported by National Science Foundation award EAR-2412838.

Researchers

Publications

Manuscripts

1. Malone, D., Stevens, G., Lesmann, S.R., Rivera, T., Biek, R., Braunagel, M., Griffith, W.A., Hacker, D., and Rowley, P., 2025. Claron basin provenance shift from Sevier-Laramide compression to Basin and Range extension—detrital zircon geochronology from the Eocene-Oligocene Brian Head Formation, Utah: Geology of the Intermountain West, v. 12, p. 155–167, https://doi.org/10.31711/giw.v12.pp155-167.

2. Braunagel, M.J., Malone, D.H., Hacker, D.B., Biek, R.F., Rivera, T.A., Loffer, Z., Holliday, M., Griffith, W., 2025. Zircon geochronology records frictional wear during emplacement of the Sevier gravity slide, southwest Utah (USA). Geology, v. 53, p. 415-419, https://doi.org/10.1130/G52838.1.

3. Rivera, T.A., Holliday, M.E., Jicha, B.R., Malone, D.H., Braunagel, M.J., Bonilla Franco, V.A., Biek, R.F., Griffith, W.A., Hacker, D.B., 2025. Emplacement age of the Sevier gravity slide, Utah, USA. Geochronology, v. 7, p. 35-44, https://doi.org/10.5194/gchron-7-35-2025. 

4. Rivera, T.A., Malone, D.H., Biek, R.F., Lesmann, S.R., Stevens, G., Hacker, D.B., Braunagel, M.J., Griffith, W.A., Rowley, P.D., 2025. The growth and collapse of a volcanic field: detrital zircon U-Pb geochronology and provenance of the Oligocene Bear Valley Formation, southwest Utah. The Sedimentary Record, v. 23, https://doi.org/10.2110/001c.138729. 

5. Malone, D.H., Stevens, G., Lesmann, S.R., Rivera, T.A., Biek, R.F., Braunagel, M.J., Griffith, W.A., Hacker, D.B., Rowley, P.D., 2025. Claron Basin Provenance Shift from Sevier Laramide Compression to Basin and Range Extension:  Detrital Zircon Geochronology from the Eocene-Oligocene Brian Head Formation. Geology of the Intermountain West, v. 12, p. 155-167, https://doi.org/10.31711/giw.v12.pp155-167. 

6. Hacker, D.B., Biek, R.F., Rowley, P.D., Malone, D.H., Griffith, W.A., Rivera, T.A., Braunagel, M.J., 2025. Catastrophic Gravity Sliding During Growth of the Cenozoic Marysvale Volcanic Field, Southwest Utah, USA. In “From the Late Mesozoic Forearc to the Quaternary Great Basin” eds. P. Garcia, D. Nelson, D. H. Shimabukuro, J. Wakabayashi. Geological Society of America Field Trip Guide, v. 73, https://doi.org/10.1130/2025.0073.

Abstracts 2025

1. Smith, A., Rivera, T.A., Malone, D., Biek, D., Braunagel, M., Griffith, W.A., Hacker, D., 2025. Geochemistry of pseudotachylytes from the mega-scale Markagunt and Sevier gravity slides (Utah).  Geological Society of America Abstracts with Programs v. 57 no. 5; DOI: 10.1130/abs/2025RM-409615.

2. Stevens, G., Hacker, D., Malone, D.H., Biek, R., Rivera, T.A., Braunagel, M., 2025. Understanding and extending the western boundary of the Cenozoic Marysvale volcanic field, southwest, Utah. Geological Society of America Abstracts with Programs v. 57 no. 5; DOI: 10.1130/abs/2025RM-410077.

Abstracts 2024

1. Smith, A., Rivera, T.A., 2024. Pseudotachylyte of the Marysvale Gravity Slide Complex: geochemical controls on friction melt generation. 7th Annual Student Research Colloquium, Missouri Geological Survey, Rolla, MO. 

Awards

Students 2025

1. Smith, A., GSA Rocky Mountain section travel grant. To offset travel costs to the meeting in Provo, Utah. May 2025