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
A paleoseismic transect across the northwestern Basin and Range Province, northwestern Nevada and northeastern California, USA
Quaternary displacement rates on the Meeman‐Shelby fault and Joiner ridge horst, eastern Arkansas: Results from coring Mississippi River alluvium
The Carolina Sandhills: Quaternary eolian sand sheets and dunes along the updip margin of the Atlantic Coastal Plain province, southeastern United States
Active faulting on the Wallula fault zone within the Olympic-Wallowa lineament, Washington State, USA
Latest Pleistocene and Holocene glacial events in the Colonia valley, Northern Patagonia Icefield, southern Chile
Episodic bedrock erosion by gully-head migration, Colorado High Plains, USA
Quaternary alluvial fans of Ciudad Juárez, Chihuahua, northern México: OSL ages and implications for climatic history of the region
Active tectonics within the NW and SE extensions of the Pambak-Sevan-Syunik fault: Implications for the present geodynamics of Armenia
Identification and dating of indigenous water storage reservoirs along the Rio San José at Laguna Pueblo, western New Mexico, USA
Earthquake geology of the Bulnay Fault (Mongolia)
Construction ages of the Upton Stone Chamber: Preliminary findings and suggestions for future luminescence research
Lithostratigraphic, borehole-geophysical, hydrogeologic, and hydrochemical data from the East Bay Plain, Alameda County, California
Science and Products
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A paleoseismic transect across the northwestern Basin and Range Province, northwestern Nevada and northeastern California, USA
We use new and existing data to compile a record of ∼18 latest Quaternary large-magnitude surface-rupturing earthquakes on 7 fault zones in the northwestern Basin and Range Province of northwestern Nevada and northeastern California. The most recent earthquake on all faults postdates the ca. 18–15 ka last glacial highstand of pluvial Lake Lahontan and other pluvial lakes in the region. These lacusAuthorsStephen Personius, Richard W. Briggs, J. Zebulon Maharrey, Stephen J. Angster, Shannon A. MahanQuaternary displacement rates on the Meeman‐Shelby fault and Joiner ridge horst, eastern Arkansas: Results from coring Mississippi River alluvium
This research used coring and optically stimulated luminescence (OSL) dating of displaced, deeply buried Quaternary alluvium to determine vertical displacement rates for the Meeman‐Shelby fault and the Joiner ridge horst, two structures in northeastern Arkansas that have no modern seismicity associated with them. We drilled continuous cores of the entire alluvial section in the hanging wall of eacAuthorsAlex Ward, Ronald C. Counts, Roy Van Arsdale, Daniel Larsen, Shannon A. MahanThe Carolina Sandhills: Quaternary eolian sand sheets and dunes along the updip margin of the Atlantic Coastal Plain province, southeastern United States
The Carolina Sandhills is a physiographic region of the Atlantic Coastal Plain province in the southeastern United States. In Chesterfield County (South Carolina), the surficial sand of this region is the Pinehurst Formation, which is interpreted as eolian sand derived from the underlying Cretaceous Middendorf Formation. This sand has yielded three clusters of optically stimulated luminescence ageAuthorsChristopher S. Swezey, Bradley A. Fitzwater, G. Richard Whittecar, Shannon A. Mahan, Christopher P. Garrity, Wilma B. Alemán‑González, Kerby M. DobbsActive faulting on the Wallula fault zone within the Olympic-Wallowa lineament, Washington State, USA
The Wallula fault zone is an integral feature of the Olympic-Wallowa lineament, an ∼500-km-long topographic lineament oblique to the Cascadia plate boundary, extending from Vancouver Island, British Columbia, to Walla Walla, Washington. The structure and past earthquake activity of the Wallula fault zone are important because of nearby infrastructure, and also because the fault zone defines part oAuthorsBrian L. Sherrod, Richard J. Blakely, John P. Lasher, Andrew P. Lamb, Shannon A. Mahan, Franklin F. Foit, Elizabeth BarnettLatest Pleistocene and Holocene glacial events in the Colonia valley, Northern Patagonia Icefield, southern Chile
The Northern Patagonia Icefield (NPI) is the primary glaciated terrain worldwide at its latitude (46.5–47.5°S), and constraining its glacial history provides unique information for reconstructing Southern Hemisphere paleoclimate. The Colonia Glacier is the largest outlet glacier draining the eastern NPI. Ages were determined using dendrochronology, lichenometry, radiocarbon, cosmogenic 10Be and opAuthorsDavid A. Nimick, Daniel Mcgrath, Shannon A. Mahan, Beverly A. Friesen, Jonathan LeidichEpisodic bedrock erosion by gully-head migration, Colorado High Plains, USA
This study explores the frequency of bedrock exposure in a soil-mantled low-relief (i.e. non-mountainous) landscape. In the High Plains of eastern Colorado, gully headcuts are among the few erosional features that will incise through the soil mantle to expose bedrock. We measured the last time of bedrock exposure using optically stimulated luminescence dating of alluvial sediment overlying bedrockAuthorsFrancis K. Rengers, G.E. Tucker, Shannon MahanQuaternary alluvial fans of Ciudad Juárez, Chihuahua, northern México: OSL ages and implications for climatic history of the region
Alluvial fans formed from sediments derived from erosion of the Juárez Mountains in northernmost México have a significant flood impact on the Ciudad Juárez, which is built on the fan system. The northern part of Ciudad Juárez is the most active; further south, older parts of the fan, upon which the rest of the city is built, were largely eroded by natural processes prior to human habitation and sAuthorsDavid Zúñiga de León, Stephen Kershaw, Shannon A. MahanActive tectonics within the NW and SE extensions of the Pambak-Sevan-Syunik fault: Implications for the present geodynamics of Armenia
This study analyzes the active tectonics within the northwestern and southeastern extensions of the Pambak-Sevan-Syunik fault (PSSF), a major right-lateral strike-slip fault cutting through Armenia. Quantifying the deformations in terms of geometry, kinematics, slip rates and earthquake activity, using cosmogenic 3He, OSL/IRSL and radiocarbon dating techniques, reveal different behaviors between tAuthorsJeff Ritz, A. Avagyan, M. Mkrtchyan, H. Nazari, P. H. Blard, A. Karakhanian, H. Philip, Sanda Balescu, Shannon A. Mahan, Sebastien Huot, P. Münch, M. LamotheIdentification and dating of indigenous water storage reservoirs along the Rio San José at Laguna Pueblo, western New Mexico, USA
An investigation into indigenous water storage on the Rio San José in western New Mexico was conducted in support of efforts by the Pueblo of Laguna to adjudicate their water rights. Here we focus on stratigraphy and geochronology of two Native American-constructed reservoirs. One reservoir located near the community of Casa Blanca was formed by a ∼600 m (2000 feet) long stone masonry dam that impAuthorsGary Huckleberry, T.J. Ferguson, Tammy M. Rittenour, Chris Banet, Shannon A. MahanEarthquake geology of the Bulnay Fault (Mongolia)
The Bulnay earthquake of July 23, 1905 (Mw 8.3-8.5), in north-central Mongolia, is one of the world's largest recorded intracontinental earthquakes and one of four great earthquakes that occurred in the region during the 20th century. The 375-km-long surface rupture of the left-lateral, strike-slip, N095°E trending Bulnay Fault associated with this earthquake is remarkable for its pronounced expreAuthorsMagali Rizza, Jean-Franciois Ritz, Carol S. Prentice, Ricardo Vassallo, Regis Braucher, Christophe Larroque, A. Arzhannikova, S. Arzhanikov, Shannon A. Mahan, M. Massault, J-L. Michelot, M. TodbilegConstruction ages of the Upton Stone Chamber: Preliminary findings and suggestions for future luminescence research
The Upton Chamber in Massachusetts, an earth-covered stone structure 3.4 meters (m) in diameter, with a corbelled stone dome, and a 4.3 m long entrance passageway, is studied with the aim of determining whether optically stimulated luminescence (OSL) dating methods can be used to establish the approximate construction date of the entranceway. Three samples, taken from soil behind the lowest stonesAuthorsShannon A. Mahan, Frederick Martin, Cathy TaylorLithostratigraphic, borehole-geophysical, hydrogeologic, and hydrochemical data from the East Bay Plain, Alameda County, California
The U.S. Geological Survey, in cooperation with the East Bay Municipal Utility District, carried out an investigation of aquifer-system deformation associated with groundwater-level changes at the Bayside Groundwater Project near the modern San Francisco Bay shore in San Lorenzo, California. As a part of the Bayside Groundwater Project, East Bay Municipal Utility District proposed an aquifer storaAuthorsMichelle Sneed, Patricia v.P. Orlando, James W. Borchers, Rhett R. Everett, Michael Solt, Mary McGann, Heather Lowers, Shannon 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