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
Data release for luminescence: Edwards Air Force Base (CA) and CA Water Science Center report including luminescence data and ages
Bringing the South Dakota southern Black Hills Mammoth Site formation and fossil discovery to light: a chronological reassignment using Luminescence Dating
Geologic setting and geomorphic history of the La Botica area, south-central Colorado
Optically Stimulated Luminescence (OSL) data and ages for selected Native American Sacred Ceremonial Stone Landscape features--Final Project Report Submitted to the Narragansett Tribal Historic Preservation Trust
DATA RELEASE Part 2: Optical luminescence dating of Bradley Lake, Oregon, tsunami deposits, analytical data for: A maximum rupture model for the central and southern Cascadia subduction zone-reassessing ages for coastal evidence of megathrust earthquakes
Data release for application of a luminescence-based sediment transport model
OSL methods and field and laboratory data for Mesa Verde soils to support journal article
Silverado California Thermoluminescence Data
Synthesis of geochronologic research on Late Pliocene to Holocene emergent shorelines in the lower Savannah River area of southeastern Georgia, USA
River terrace evidence of tectonic processes in the eastern North American plate interior, South Anna River, Virginia
Holocene paleoseismology of the Steamboat Mountain Site: Evidence for full‐Llngth rupture of the Teton Fault, Wyoming
Depth-dependent soil mixing persists across climate zones
Neotectonic and paleoseismic analysis of the northwest extent of Holocene surface deformation along the Meers Fault, Oklahoma
Holocene earthquake history and slip rate of the southern Teton fault, Wyoming, USA
Pleistocene lakes and paleohydrologic environments of the Tecopa basin, California: Constraints on the drainage integration of the Amargosa River
Holocene rupture history of the central Teton fault at Leigh Lake; Grand Teton National Park, Wyoming
Quaternary displacement on the Joiner Ridge Fault, eastern Arkansas
Luminescence as a sediment tracer and provenance tool
Principles and history of luminescence dating
Distributed fault slip in the eastern California shear zone: Adding pieces to the puzzle near Barstow, California
Science and Products
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Data release for luminescence: Edwards Air Force Base (CA) and CA Water Science Center report including luminescence data and ages
The following report summarizes the dating results from Aeolian deposits within and around Edwards Air Force Base in California. Within this report, we detail the methodology used by the USGS Luminescence Geochronology Laboratory to obtain ages including sample preparation methods, luminescence measurement, equivalent dose determination, and dating related calculations. We recommend that this repoBringing the South Dakota southern Black Hills Mammoth Site formation and fossil discovery to light: a chronological reassignment using Luminescence Dating
The Mammoth Springs (MS) fossil site at Hot Springs, South Dakota, provides a unique opportunity to reconstruct paleoenvironmental conditions. We used luminescence dating on fine sand sized potassium feldspars to establish a chronological framework for the site. In addition, we dated a late Pleistocene paludal proxy site using luminescence and incorporated those results with previous radiocarbon dGeologic setting and geomorphic history of the La Botica area, south-central Colorado
La Botica is positioned on a topographic bench sharply inset into the gentle eastern slope of the high San Juan Mountains and perched ~70-80 meters above La Jara Creek (fig. 1), a tributary to the Rio Grande. Quaternary surface processes have modified the Tertiary bedrock deposits that underlie La Botica to shape the physical environment. Bedrock deposits consist of Oligocene to Pliocene volcanicOptically Stimulated Luminescence (OSL) data and ages for selected Native American Sacred Ceremonial Stone Landscape features--Final Project Report Submitted to the Narragansett Tribal Historic Preservation Trust
Stone rows, enclosures, structures and chambers can be found in the landscapes of Massachusetts and Rhode Island. Structures similar to those shown in the cover photo are documented elsewhere. The age, cultural affiliation, and purpose of these stone structures--which are found in a variety of forms, such as piles arranged in spatial configurations across landscapes, shapes suggesting animal effigDATA RELEASE Part 2: Optical luminescence dating of Bradley Lake, Oregon, tsunami deposits, analytical data for: A maximum rupture model for the central and southern Cascadia subduction zone-reassessing ages for coastal evidence of megathrust earthquakes
The following report summarizes the dating results from Bradley Lake, Oregon. Within this report, we detail the methodology used by the USGS Luminescence Geochronology Laboratory to obtain ages including sample preparation methods, luminescence measurement, equivalent dose determination, and datingrelated calculations. We recommend that this report be included as the supplementary material for anyData release for application of a luminescence-based sediment transport model
This data release contains luminescence data from the manuscript "Application of a luminescence-based sediment transport model" by Gray et al. It contains data from the luminescence measurements and experiments in the paper.OSL methods and field and laboratory data for Mesa Verde soils to support journal article
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 mesa near Canyonlands National Park, Utah, and from two outcrops in Mesa Verde National Park, Colorado. At Hatch Point, the oldest buried unit yielded two OSL ages of 10,370 and 7,555 yr; the middle unit yielded 10 OSL ages from 6Silverado California Thermoluminescence Data
This dataset represents thermoluminescence (TL) data that was obtained after a series of experiments to investigate how TL techniques can indicate the depth of soil heating. This project was attempted to ultimately predict changes in erosion properties in burned areas subject to debris flow hazards. The soil samples were obtained from an area burned by the Silverado wildfire (September 12 to 20, 2 - Maps
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- Publications
Filter Total Items: 136
Synthesis of geochronologic research on Late Pliocene to Holocene emergent shorelines in the lower Savannah River area of southeastern Georgia, USA
Emergent late Pliocene and Pleistocene shoreline deposits, morphologically identifiable Pleistocene shoreline units, and seaward-facing scarps characterize the easternmost Atlantic Coastal Plain (ACP) of the United States of America. In some areas of the ACP, these deposits, units, and scarps have been studied in detail. Within these areas, temporal and spatial data are sufficient for time-depositAuthorsHelaine W. Markewich, Milan J. Pavich, Shannon A. Mahan, Paul R. Bierman, Wilma B. Alemán‑González, Arthur P. SchultzRiver terrace evidence of tectonic processes in the eastern North American plate interior, South Anna River, Virginia
We show that long-recognized seismicity in the central Virginia seismic zone of the eastern North American intraplate setting arises primarily from tectonic processes predicted by new, fully coupled plate tectonic geodynamic models. The study leverages much new geophysical and geologic data following the 2011 Mineral, Virginia, earthquake that ruptured a steeply dipping, northwest-verging reverseAuthorsFrank J. Pazzaglia, Helen F. Malenda, Matthew L. McGavick, Cody Raup, Mark W. Carter, Claudio Berti, Shannon A. Mahan, Michelle S. Nelson, Tammy M. Rittenour, Ron Counts, Jane K Willenbring, Dru Germanoski, Stephen C. Peters, William D. HoltHolocene paleoseismology of the Steamboat Mountain Site: Evidence for full‐Llngth rupture of the Teton Fault, Wyoming
The 72‐km‐long Teton fault in northwestern Wyoming is an ideal candidate for reconstructing the lateral extent of surface‐rupturing earthquakes and testing models of normal‐fault segmentation. To explore the history of earthquakes on the northern Teton fault, we hand‐excavated two trenches at the Steamboat Mountain site, where the east‐dipping Teton fault has vertically displaced west‐sloping alluAuthorsChristopher DuRoss, Mark S. Zellman, Glenn D. Thackray, Richard W. Briggs, Ryan D. Gold, Shannon A. MahanDepth-dependent soil mixing persists across climate zones
Soil mixing over long (>102 y) timescales enhances nutrient fluxes that support soil ecology, contributes to dispersion of sediment and contaminated material, and modulates fluxes of carbon through Earth’s largest terrestrial carbon reservoir. Despite its foundational importance, we lack robust understanding of the rates and patterns of soil mixing, largely due to a lack of long-timescale data. HeAuthorsHarrison J. Gray, Amanda Keen-Zebert, David Furbish, Gregory E. Tucker, Shannon A. MahanNeotectonic and paleoseismic analysis of the northwest extent of Holocene surface deformation along the Meers Fault, Oklahoma
TheMeers fault (Oklahoma) is one of fewseismogenic structures with evidence for Holocene surface rupture in the stable continental region of North America. The 37-kilometer-long southeast section of the full 54-kilometer-long Meers fault is interpreted to be Holocene active. The 17-kilometer-long northwest section is considered Quaternary active, but not Holocene active.We reevaluate surface expreAuthorsKristofer T. Hornsby, Ashley R. Streig, S. Bennett, Jefferson C. Chang, Shannon A. MahanHolocene earthquake history and slip rate of the southern Teton fault, Wyoming, USA
The 72-km-long Teton normal fault bounds the eastern base of the Teton Range in northwestern Wyoming, USA. Although geomorphic surfaces along the fault record latest Pleistocene to Holocene fault movement, the postglacial earthquake history of the fault has remained enigmatic. We excavated a paleoseismic trench at the Buffalo Bowl site along the southernmost part of the fault to determine its HoloAuthorsChristopher DuRoss, Ryan D. Gold, Richard W. Briggs, Jaime E. Delano, Dean A. Ostenaa, Mark Zellman, Nicole Cholewinski, Seth Wittke, Shannon A. MahanPleistocene lakes and paleohydrologic environments of the Tecopa basin, California: Constraints on the drainage integration of the Amargosa River
The Tecopa basin in eastern California was a terminal basin that episodically held lakes during most of the Quaternary until the basin and its modern stream, the Amargosa River, became tributary to Death Valley. Although long studied for its sedimentology, diagenesis, and paleomagnetism, the basin’s lacustrine and paleoclimate history has not been well understood, and conflicting interpretations eAuthorsMarith C. Reheis, John Caskey, Jordon Bright, James B. Paces, Shannon A. Mahan, Elmira WanHolocene rupture history of the central Teton fault at Leigh Lake; Grand Teton National Park, Wyoming
Prominent scarps on Pinedale glacial surfaces along the eastern base of the Teton Range confirm latest Pleistocene to Holocene surface‐faulting earthquakes on the Teton fault, but the timing of these events is only broadly constrained by a single previous paleoseismic study. We excavated two trenches at the Leigh Lake site near the center of the Teton fault to address open questions about earthquaAuthorsMark Zellman, Christopher DuRoss, Glenn R. Thackray, Stephen Personius, Nadine G. Reitman, Shannon A. Mahan, Cooper BrossyQuaternary displacement on the Joiner Ridge Fault, eastern Arkansas
The New Madrid seismic zone of the central United States is an intraplate seismic zone with blind structures that are not seismically active but may pose seismic hazards. The Joiner Ridge fault is the 35 km long east-bounding fault of the Joiner Ridge blind horst located in eastern Arkansas approximately 50 km northwest of Memphis, Tennessee. Shallow S-wave (SH-mode) seismic reflection profiles, cAuthorsAudrey C. Price, Edward W Woolery, Ron Counts, Roy Van Arsdale, Daniel Larsen, Shannon A. Mahan, Glynn BeckLuminescence as a sediment tracer and provenance tool
Luminescence holds unique potential as a sediment tracer and provenance method. The tracer application of luminescence has key advantages including ease of measurement, relatively low cost, and applicability to geologically ubiquitous quartz and feldspar sand and silt. These advantages can help answer fundamental questions about geomorphology, sediment transport, sediment production, and the tectoAuthorsHarrison J. Gray, Mayank Jain, Andre Sawakuchi, Shannon A. Mahan, Gregory E. TuckerPrinciples and history of luminescence dating
No abstract available.AuthorsShannon A. Mahan, Regina DeWittDistributed fault slip in the eastern California shear zone: Adding pieces to the puzzle near Barstow, California
We investigate the dextral Lockhart and Mt. General faults, which are among four active structures in the northwestern portion of the eastern California shear zone (ECSZ). Early mapping depicts the Lockhart and Mt. General faults as discontinuous fault traces that continue northwest of the Lenwood Fault. Recent work indicates that the Lenwood Fault slips at ~0.2-1.0 mm/yr over the past ~8 ka and 0AuthorsElizabeth K. Haddon, David M. Miller, Victoria Langenheim, 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