Shannon Mahan
My work focuses on the geochronology and associated dosimetry of luminescence dating, with the goal of understanding when, how, and the rates at which mineral grains acquire (and lose!) their luminescence signal.
I graduated from Adams State University (Colorado) with a B.S. in Geology in 1987 and was immediately hired into the USGS in April 1987. For those of you that are counting, this makes me the end of the “baby boomers” and working well into my third decade with the USGS. My career has been as varied as my interests, as I have worked in radiogenic isotopes, hydrology, stable isotopes, gamma spectrometry, and luminescence. I have been the USGS Luminescence Geochronology Lab Director since 1997 and routinely work on 20 to 30 projects during a year throughout the USGS mission areas.
Over the past 40 years, luminescence dating has become a key tool for dating sediments of interest in geologic, paleontologic, and archeologic research and this is my obvious scientific interest. Luminescence is also used to date paleoseismology sites, fluvial terraces (including paleoflood deposits), eolian deposits, and is increasingly used to calibrate wildfire temperatures, sediment transport processes, and thermochronology. The flexibility of luminescence is a key complement to other chronometers such as radiocarbon or cosmogenic nuclides. Like all geochronologic techniques, context is necessary for interpreting and calculating luminescence results and this can be achieved by supplying our lab with associated trench logs, photos, and stratigraphic locations of sample sites if you choose to work with us (Taken from Gray et al, 2015 paper Guide to Luminescence Dating Techniques and their Application for Paleoseismic Research; Mahan and DeWitt, 2019, Principles and history of Luminescence Dating Chapter 1 in Handbook of Luminescence Dating AND Mahan et al, 2022 guide for interpretating and reporting luminescence dating results).
The USGS Luminescence Geochronology Lab is composed of myself, Harrison Gray, and Emma Krolczyk. We are an integral part of multi-disciplinary, multi-agency, and multi-institutional projects that provide chronologic control for Quaternary field studies in the continental United States. The growth of the laboratory is due to the science that our partnership can generate with many other science agencies, both Federal, state, and academic. Additional publications and projects can be viewed from USGS Luminescence Dating Laboratory and on Research Gate.
Professional Experience
2023 - present: Acting Deputy Center Director
2021 - present: TRIGA Reactor System Administrator and Science Advisor
2008 - present: Research Geologist
1987 - 2008: Geologist
Education and Certifications
1986: B.S., Geology, Adams State College
Affiliations and Memberships*
Geological Society of America
Friends of the Pleistocene
INQUA
Science and Products
Four major Holocene earthquakes on the Reelfoot fault recorded by sackungen in the New Madrid seismic zone, USA
The Las Vegas Formation
Paleoseismic results from the Alpine site, Wasatch fault zone: Timing and displacement data for six holocene earthquakes at the Salt Lake City–Provo segment boundary
Examining the relationship between portable luminescence reader measurements and depositional ages of paleowetland sediments, Las Vegas Valley, Nevada
Holocene fault reactivation in the eastern Cascades, Washington
Application of a luminescence‐based sediment transport model
Combining conflicting Bayesian models to develop paleoseismic records—An example from the Wasatch Fault Zone, Utah
Late Quaternary loess and soils on uplands in the Canyonlands and Mesa Verde areas, Utah and Colorado
Can thermoluminescence be used to determine soil heating from a wildfire?
Holocene surface-faulting earthquakes at the Spring Lake and North Creek Sites on the Wasatch Fault Zone: Evidence for complex rupture of the Nephi Segment
On extracting sediment transport information from measurements of luminescence in river sediment
Dating of river terraces along Lefthand Creek, western High Plains, Colorado, reveals punctuated incision
Science and Products
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Filter Total Items: 136
Four major Holocene earthquakes on the Reelfoot fault recorded by sackungen in the New Madrid seismic zone, USA
Three sequences of well-documented, major ~M7+ earthquakes (1811-1812 CE, ~1450 CE, and ~900 CE) in the New Madrid seismic zone, USA, contribute significantly to seismic hazard in the region. However, it is unknown whether thisAuthorsRyan D. Gold, Christopher DuRoss, Jaime E. Delano, Randall W. Jibson, Richard W. Briggs, Shannon A. Mahan, Robert Williams, D. Reide CorbettThe Las Vegas Formation
The Las Vegas Formation was established in 1965 to designate the distinctive light-colored, fine-grained, fossil-bearing sedimentary deposits exposed in and around the Las Vegas Valley, Nevada. In a coeval designation, the sediments were subdivided into informal units with stratigraphic and chronologic frameworks that have persisted in the literature. Use of the Las Vegas Formation name over the pAuthorsKathleen B. Springer, Jeffrey S. Pigati, Craig R. Manker, Shannon A. MahanPaleoseismic results from the Alpine site, Wasatch fault zone: Timing and displacement data for six holocene earthquakes at the Salt Lake City–Provo segment boundary
To improve the characterization of Holocene earthquakes on the Wasatch fault zone (WFZ), we conducted light detection and ranging (lidar)‐based neotectonic mapping and excavated a paleoseismic trench across an 8‐m‐high fault scarp near Alpine, Utah, located <1 km<1 km south of the boundary between the Salt Lake City and Provo segments (SLCS and PS). We document evidence for six paleoearthquakesAuthorsScott E. K. Bennett, Christopher DuRoss, Ryan D. Gold, Richard W. Briggs, Stephen Personius, Nadine G. Reitman, Joshua Devore, Adam Hiscock, Shannon A. Mahan, Harrison J. Gray, Sydney Gunnarson, William J. Stephenson, Elizabeth Pettinger, Jackson K. OdumExamining the relationship between portable luminescence reader measurements and depositional ages of paleowetland sediments, Las Vegas Valley, Nevada
Portable luminescence readers are exciting new tools that have the potential to rapidly determine the age structure of late Quaternary stratigraphic columns. This is important because high-resolution age profiling can reveal details about the temporal dynamics of climate cause and ecosystem effect, often while researchers are still in the field. In this paper, we compare new portable luminescenceAuthorsHarrison J. Gray, Shannon A. Mahan, Kathleen B. Springer, Jeffrey S. PigatiHolocene fault reactivation in the eastern Cascades, Washington
Significant uncertainty remains concerning how and where crustal shortening occurs throughout the eastern Cascade Range in Washington State. Using light detection and ranging (lidar) imagery, we identified an ∼5‐km‐long lineament in Swakane canyon near Wenatchee, roughly coincident with a strand of the Entiat fault. Topographic profiles across the lineament reveal a southwest‐side‐up break in slopAuthorsBenjamin L. Carlson, Elizabeth R. Schermer, Colin B. Amos, William J. Stephenson, Brian L. Sherrod, Shannon A. MahanApplication of a luminescence‐based sediment transport model
Quantifying the transport history of sand is a challenging but important goal in geomorphology. In this paper, we take a simple idea that luminescence is bleached during transport and regenerates during storage, and use this as a basis to re‐envision luminescence as a sediment tracer. We apply a mathematical model describing luminescence through an idealized channel and reservoir system and then cAuthorsHarrison J. Gray, Gregory E. Tucker, Shannon A. MahanCombining conflicting Bayesian models to develop paleoseismic records—An example from the Wasatch Fault Zone, Utah
Bayesian statistical analyses of paleoseismic data result in the probabilistic determination of earthquake times using geochronological data evaluated in the context of a stratigraphic model. However, a fundamental problem in paleoseismology is how to use the Bayesian approach to model sparse and/or conflicting geochronological datasets, such as those derived from sites exhibiting episodic sedimenAuthorsChristopher DuRoss, Scott E. K. Bennett, Richard W. Briggs, Stephen Personius, Ryan D. Gold, Nadine G. Reitman, Adam I. Hiscock, Shannon A. MahanLate Quaternary loess and soils on uplands in the Canyonlands and Mesa Verde areas, Utah and Colorado
Thin loess deposits on the uplands of the southeastern Colorado Plateau have previously not been well studied. We sampled deposits and soils from trenches on Hatch Point (HP) mesa near Canyonlands National Park, Utah, and from two outcrops in Mesa Verde National Park, Colorado. At HP, the oldest buried unit yielded 2 optically stimulated luminescence (OSL) ages of 10,370 and 7555 yr; the middle unAuthorsMarith C. Reheis, Harland L. Goldstein, Richard L. Reynolds, Steven L. Forman, Shannon A. Mahan, Paul E. CarraraCan thermoluminescence be used to determine soil heating from a wildfire?
The Silverado wildfire occurred from September 12 to 20, 2014, burning 960 acres in Orange County, California. Soil samples from within the burn area were obtained and the thermoluminescence (TL) properties of those samples were compared against a control sample to understand wildfire heating. We performed a series of experiments investigating the degree to which the control differed from the wildAuthorsFrancis K. Rengers, Vasilis Pagonis, Shannon A. MahanHolocene surface-faulting earthquakes at the Spring Lake and North Creek Sites on the Wasatch Fault Zone: Evidence for complex rupture of the Nephi Segment
The Nephi segment of the Wasatch fault zone (WFZ) comprises two fault strands, the northern and southern strands, which have evidence of recurrent late Holocene surface-faulting earthquakes. We excavated paleoseismic trenches across these strands to refine and expand their Holocene earthquake chronologies; improve estimates of earthquake recurrence, displacement, and fault slip rate; and assess whAuthorsChristopher DuRoss, Michael D. Hylland, Adam Hiscock, Stephen Personius, Richard W. Briggs, Ryan D. Gold, Gregg Beukelman, Geg N McDonald, Ben Erickson, Adam McKean, Steve Angster, Roselyn King, Anthony J. Crone, Shannon A. MahanOn extracting sediment transport information from measurements of luminescence in river sediment
Accurately quantifying sediment transport rates in rivers remains an important goal for geomorphologists, hydraulic engineers, and environmental scientists. However, current techniques for measuring long-time scale (102–106 years) transport rates are laborious, and formulae to predict transport are notoriously inaccurate. Here we attempt to estimate sediment transport rates by using luminescence,AuthorsHarrison J. Gray, Gregory E. Tucker, Shannon A. Mahan, Chris McGuire, Edward J. RhodesDating of river terraces along Lefthand Creek, western High Plains, Colorado, reveals punctuated incision
The response of erosional landscapes to Quaternary climate oscillations is recorded in fluvial terraces whose quantitative interpretation requires numerical ages. We investigate gravel-capped strath terraces along the western edge of Colorado's High Plains to constrain the incision history of this shale-dominated landscape. We use ¹⁰Be and ²⁶Al cosmogenic radionuclides (CRNs), optically stimulatedAuthorsMelissa A. Foster, Robert S. Anderson, Harrison J. Gray, Shannon A. Mahan
*Disclaimer: Listing outside positions with professional scientific organizations on this Staff Profile are for informational purposes only and do not constitute an endorsement of those professional scientific organizations or their activities by the USGS, Department of the Interior, or U.S. Government