Leah Morgan is a Research Geologist with the Geology, Geophysics, and Geochemistry Science Center.
I joined the 40Ar/39Ar geochronology lab at the USGS in Denver, Colorado as a research geologist in 2015. I was previously a Marie Curie postdoctoral fellow at the Scottish Universities Environmental Research Center and at the Vrije Universiteit Amsterdam. I received a PhD from the University of California at Berkeley in 2009, and a BA from Carleton College in 2004. I was born and raised in Vermont.
I have worked on a range of applications and method development issues in 40Ar/39Ar geochronology. Applications have largely focused on questions in paleoanthropology and the geologic timescale. Method development projects include developing metrologically traceable systems for measuring absolute quantities of 40Ar and 40K, and the design of a mobile neutron source for the future in situ deployment of 40Ar/39Ar capabilities on planetary surfaces
USGS Service
- 2020-present, USGS TRIGA Reactor Operating Committee
- 2017-present, USGS Radiation Safety Committee
- 2016-present, USGS Rocky Mountain Science Seminar Series Convener
- 2018-2020 GGGSC Early Career Advisory Team, GGGSC
Professional Experience
2015-present, Research Geologist, U.S. Geological Survey
2014, Visiting Assistant Professor, Geology Department, Carleton College
2011-2014, Marie Curie Postdoctoral Fellow, Scottish Universities Environmental Research Center, University of Glasgow, Scotland
2009-2011, Marie Curie Postdoctoral Fellow, Vrije Universiteit Amsterdam, The Netherlands
Education and Certifications
Ph.D. Earth & Planetary Science, University of California at Berkeley, 2009
B.S. Geology, Carleton College, 2004
Affiliations and Memberships*
2018-present, Affiliate Faculty, Colorado School of Mines, Golden, CO
2021, co-Chair, Gordon Research Conference on Geochronology
2019, vice-Chair, Gordon Research Conference on Geochronology
2018-2019, Chair and Founder, Geochronology Division of the Geological Society of America
2019-present, Advisory Member, Committee for the Stratigraphy and Chronology Commission, International Union for Quaternary Research
2018-present, Steering Committee Member, EarthRates Research Coordination Network
Honors and Awards
2019, USGS Superior Service Award
Science and Products
USGS Geochron: A database of USGS geochronologic data
Argon Geochronology
Geologic Framework of the Intermountain West
Serving the U.S. Geological Survey’s geochronological data
USGS Geochron: A Database of Geochronological and Thermochronological Dates and Data
Argon data for HD-B1 intercalibration
Argon data for Santa Cruz Basin (ver. 1.1, November 2022)
Argon data for Hugub Area, Kesem-Kebena-Dulecha, Ethiopia
Argon data for Klamath Mountains
Argon data for Nepal
Argon data for Amazon Craton
Argon data for Central Andes (Domeyko Range, Chile)
Argon data for Yellow Pine
Argon data for Central Anatolian Ophiolite
Argon data for Southern Patagonian Andes
Argon geochronology data for eastern Bhutan
Geologic map of the Poncha Pass area, Chaffee, Fremont, and Saguache Counties, Colorado
Geologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado
First principles calibration of 40Ar abundances in 40Ar/39Ar mineral neutron fluence monitors: Methodology and preliminary results
Early Neoproterozoic gold deposits of the Alto Guaporé province, southwestern Amazon craton, western Brazil
Late Jurassic-Early Cretaceous orogenic gold mineralization in the Klamath Mountains, California: Constraints from 40Ar/39Ar dating of hydrothermal muscovite
Gondwanic inheritance on the building of the western Central Andes (Domeyko Range, Chile): Structural and thermochronological approach (U-Pb and 40Ar-39Ar)
Constraining central Himalayan (Nepal) fault geometry through integrated thermochronology and thermokinematic modeling
Conditions and timing of high-grade metamorphism and ductile deformation of the southern segment of the Central Anatolian Ophiolite
Interpreting and reporting 40Ar/39Ar geochronologic data
Detrital record of the late Oligocene – Early Miocene mafic volcanic arc in the southern Patagonian Andes (~51 °S) from single-clast geochronology and trace element geochemistry
Multiproxy Cretaceous-Paleogene boundary event stratigraphy: An Umbria-Marche basin-wide perspective
The influence of foreland structures on hinterland cooling: evaluating the drivers of exhumation in the eastern Bhutan Himalaya
Petrology of volcanic rocks associated with silver-gold (Ag-Au) epithermal deposits in the Tonopah, Divide, and Goldfield Mining Districts, Nevada
Petrographic, geochemical, and geochronologic data for cenozoic volcanic rocks of the Tonopah, Divide, and Goldfield Mining Districts, Nevada
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
- Science
USGS Geochron: A database of USGS geochronologic data
Geochronologic data are integral to geologic mapping and are utilized by researchers, stakeholders, and the science-interested public to study the Earth’s lithosphere and landscapes and to manage resources and natural hazards. To address these questions, scientists at the United States Geological Survey (USGS) and State geological surveys have generated a significant amount of geochronologic data...Argon Geochronology
This project supports the USGS argon geochronology laboratory in Denver. The USGS 40Ar/39Ar geochronology laboratory is a state-of-the-art research facility for determining absolute ages of minerals and rocks. The 40Ar/39Ar laboratory contributes critical geochronology to individual USGS research projects and to partners in academia and other Federal agencies. This laboratory develops methodology...Geologic Framework of the Intermountain West
The Geologic Framework of the Intermountain West project was launched with the goal of producing a new digital geologic map database and 3D geologic model of a transect from the Rio Grande rift to the Basin and Range, based on a synthesis of existing geologic maps with new targeted new mapping, subsurface data, and other data sets. This database will integrate disparate map data, resolve...Serving the U.S. Geological Survey’s geochronological data
Geochronological data provide essential information necessary for understanding the timing of geologic processes and events, as well as quantifying rates and timescales key to geologic mapping, mineral and energy resource and hazard assessments. The USGS’s National Geochronological Database (NGDB) contains over 30,000 radiometric ages, but no formal update has occurred in over 20 years. This proj - Data
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USGS Geochron: A Database of Geochronological and Thermochronological Dates and Data
USGS Geochron is a database of geochronological and thermochronological dates and data. The data set contains published ages, dates, analytical information, sample metadata including location, and source citations. The following analytical techniques are represented in the data set: 40Ar/39Ar, K-Ar, U-Th-Pb, Sm-Nd, Rb-Sr, Lu-Hf, fission track, and luminescence. This data set incorporates data prevArgon data for HD-B1 intercalibration
This data release includes 40Ar/39Ar intercalibration data from the U.S. Geological Survey for neutron fluence monitors HD-B1 (Heidelberg biotite) and FCs (Fish Canyon sanidine). Potassium-bearing mineral grains were analyzed by argon geochronology at the U.S. Geological Survey Argon Geochronology Laboratory in Denver, Colorado. These data provide intercalibration information between the two fluenArgon data for Santa Cruz Basin (ver. 1.1, November 2022)
This data release includes 40Ar/39Ar data from the U.S. Geological Survey for samples from the Santa Cruz Basin, Arizona. Mineral samples were collected by Kenzie Turner and William Page from the upper Santa Cruz Basin, Arizona. Potassium-bearing mineral grains were separated from the bulk sample and analyzed by argon geochronology at the U.S. Geological Survey Argon Geochronology Laboratory in DeArgon data for Hugub Area, Kesem-Kebena-Dulecha, Ethiopia
Tephra samples were collected by Leah Morgan (now at the U.S. Geological Survey (USGS)) from the Hugub Area, Kesem-Kebena-Dulecha, Afar, Ethiopia. Sanidine grains were separated from the bulk sample and analyzed by argon geochronology at the Scottish Universities Environmental Research Centre, Scotland. The data indicate that the age of the Hugub Bed, which is rich in archarological artifacts, isArgon data for Klamath Mountains
This dataset accompanies planned publication '40Ar/39Ar geochronology of hydrothermal activity related to orogenic gold mineralization in the Klamath Mountains, California, U.S.A.'. The Ar/Ar data are for samples that record the mineralization of the area. The geochronology provides time constraints for the mineralization studied in the manuscript. Samples were collected from the Klamath MountainsArgon data for Nepal
This dataset accompanies planned publication 'Determining fault geometry through the transport-parallel distribution of thermochronometer cooling ages'. The Ar/Ar data is for samples that record the thermal history of the area. The geochronology provides time constraints for the thermal histories studied in the manuscript. Samples were collected from Nepal, overseen by Nadine McQuarrie (UniversityArgon data for Amazon Craton
This dataset accompanies planned publication 'Genesis of early Neoproterozoic gold deposits, southwestern Amazon Craton, western Brazil'. The Ar/Ar data is for samples that record the mineralization of the area. The geochronology provides time constraints for the mineralization studied in the manuscript. Samples were collected from the Amazon Craton region, and collection was done by Rodrigo PrudeArgon data for Central Andes (Domeyko Range, Chile)
This dataset accompanies planned publication 'Gondwanan inheritance on the building of the western Central Andes (Domeyko Range, Chile): Structural and thermochronological approach (U-Pb and 40Ar-39Ar)'. The Ar/Ar data is for samples that record the sedimentation of the area. The geochronology provides time constraints for the sedimentation studied in the manuscript. Samples were collected from thArgon data for Yellow Pine
This dataset accompanies planned publication 'Timing of Hydrothermal Alteration and Au-Sb-W Mineralization, Stibnite-Yellow Pine District, Idaho'. The Ar/Ar data is for samples that record the mineralization of the area. The geochronology provides time constraints for the mineralization studied in the manuscript. Samples were collected from the Yellow Pine region, and collection was done by numeroArgon data for Central Anatolian Ophiolite
This dataset accompanies planned publication 'Conditions, mechanisms, and timing of high-grade metamorphism and ductile deformation of the southern segment of the Central Anatolian Ophiolite'. The Ar/Ar data are for samples that record the metamorphic deformation of the ophiolite. The geochronology provides time constraints for the deformation studied in the manuscript. Samples were collected fromArgon data for Southern Patagonian Andes
This dataset accompanies planned publication 'Detrital record of the Late Oligocene - Early Miocene mafic volcanic arc in the Southern Patagonian Andes (~51S) from single-clast geochronology and trace element geochemistry'. The Ar/Ar data is for samples that record the detrital sedimentary record of the basin. The geochronology provides time constraints for the sedimentation studied in the manuscrArgon geochronology data for eastern Bhutan
This dataset accompanies publication 'The influence of foreland structures on hinterland cooling: evaluating the drivers of exhumation in the eastern Bhutan Himalaya'. The Ar/Ar data provides time constraints for the cooling of rocks in the study area. - Maps
Geologic map of the Poncha Pass area, Chaffee, Fremont, and Saguache Counties, Colorado
This report presents a 1:24,000-scale geologic map, cross sections, and descriptive and interpretative text for the Poncha Pass area in central Colorado. The map area is irregular in shape, covering all of one 7 ½' quadrangle (Poncha Pass) and parts of five others (Mount Ouray, Maysville, Salida West, Salida East, and Wellsville). The map boundaries were drawn to cover all of the “Poncha mountainGeologic map of the San Antonio Mountain area, northern New Mexico and southern Colorado
The geologic map of the San Antonio Mountain area in northern New Mexico and southern Colorado is located along the west-central part of the San Luis Valley. The San Luis Valley is the geomorphic expression of the San Luis Basin, an extensional basin associated with the northern Rio Grande rift. Deposits within the map area record volcanic, sedimentary, and tectonic processes over the last ~33 mil - Publications
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First principles calibration of 40Ar abundances in 40Ar/39Ar mineral neutron fluence monitors: Methodology and preliminary results
The accuracy and traceability of geochronometers are of vital importance to questions asked by many Earth scientists. The widely applied 40Ar/39Ar geochronometer relies on the co-irradiation of samples with neutron fluence monitors (reference materials) of known ages; the ages and uncertainties of these monitors are critical to our ability to apply this chronometer. Previously, first principles, aEarly Neoproterozoic gold deposits of the Alto Guaporé province, southwestern Amazon craton, western Brazil
The Alto Guaporé gold province, southwestern Amazon craton, contains gold deposits that have been mined since the beginning of the 18th century and these deposits, together, have modern-day, pre-mining gold resources of at least 1.8 Moz. The ore is associated with quartz vein systems along the southeastern part of the Aguapei belt, a ~35-km-wide and ~500-km-long, NNW-trending shear zone formed dueLate Jurassic-Early Cretaceous orogenic gold mineralization in the Klamath Mountains, California: Constraints from 40Ar/39Ar dating of hydrothermal muscovite
The Klamath Mountains gold province is the second most important historical producer in California, having produced more than 7 Moz of gold from both lode and placer sources. Hydrothermal muscovite grains from gold-bearing veins provide the first 40Ar/39Ar age constraints indicative of a protracted period of mineralization in the Klamath Mountains. The data indicate that the window for orogenic goGondwanic inheritance on the building of the western Central Andes (Domeyko Range, Chile): Structural and thermochronological approach (U-Pb and 40Ar-39Ar)
Tectonics inheritance controls the evolution of many orogens. To unravel the role of the Gondwanan heritage (late Paleozoic to Triassic) over the building of the Central Andes in northern Chile (Domeyko Range), we performed detrital U‐Pb zircon and 40Ar/39Ar muscovite geochronology along with structural analyses (kinematics and structural balancing). 40Ar/39Ar dating of detrital muscovite revealsConstraining central Himalayan (Nepal) fault geometry through integrated thermochronology and thermokinematic modeling
Constraining the subsurface structural geometry of the central Himalaya continues to prove difficult, even after the 2015 Gorkha earthquake and the resulting insights into the trajectory of the Main Himalayan thrust (MHT). To this end, we apply a thermokinematic model to evaluate four possible balanced cross section geometries based on three estimates of the MHT in central Nepal. We compare the efConditions and timing of high-grade metamorphism and ductile deformation of the southern segment of the Central Anatolian Ophiolite
Ophiolitic fragments scattered over a wide area of Central Anatolia exhibit varying degrees of metamorphism, from unmetamorphosed to upper amphibolite facies, although geochemical similarities suggest they are all part of the Central Anatolian Ophiolite (CAO). Magmatic crystallization of oceanic crust in the CAO at ~ 91 Ma coincided with high-grade metamorphism of rocks that underlie the southern,Interpreting and reporting 40Ar/39Ar geochronologic data
The 40Ar/39Ar dating method is among the most versatile of geochronometers, having the potential to date a broad variety of K-bearing materials spanning from the time of Earth’s formation into the historical realm. Measurements using modern noble-gas mass spectrometers are now producing 40Ar/39Ar dates with analytical uncertainties of ∼0.1%, thereby providing precise time constraints for a wide raDetrital record of the late Oligocene – Early Miocene mafic volcanic arc in the southern Patagonian Andes (~51 °S) from single-clast geochronology and trace element geochemistry
Retroarc foreland basins are important archives of continental arc magmatism and upper plate deformational processes that control the evolution of continental lithosphere. However, resolving source areas in foreland basin infill dominated from mixed mafic and recycled sediment using conventional methods such as detrital zircon geochronology poses a challenge to thorough analysis due to lower zircoMultiproxy Cretaceous-Paleogene boundary event stratigraphy: An Umbria-Marche basin-wide perspective
The complete and well-studied pelagic carbonate successions from the Umbria-Marche Basin (Italy) permit the study of the event-rich stratigraphical interval around the Cretaceous-Paleogene (K-Pg) boundary (e.g., Deccan volcanism, boundary impact, Paleocene recovery and climate). To test the robustness of various proxy records (bulk carbonate δ13C, δ18O, 87Sr/86Sr and Ca, Fe, Sr and Mn concentratioThe influence of foreland structures on hinterland cooling: evaluating the drivers of exhumation in the eastern Bhutan Himalaya
Understanding, and ideally quantifying, the relative roles of climatic and tectonic processes during orogenic exhumation is critical to resolving the dynamics of mountain building. However, vastly differing opinions regarding proposed drivers often complicate how thermochronometric ages are interpreted, particularly from the hinterland portions of thrust belts. Here we integrate three possible croPetrology of volcanic rocks associated with silver-gold (Ag-Au) epithermal deposits in the Tonopah, Divide, and Goldfield Mining Districts, Nevada
Miocene calc-alkaline volcanic rocks, part of the southern segment of the ancestral Cascades magmatic arc, are spatially, temporally, and likely genetically associated with precious metal epithermal deposits in the Tonopah, Divide, and Goldfield Districts of west-central Nevada. In the Tonopah mining district, volcanic rocks include the Mizpah Trachyte, Fraction Tuff, and Oddie Rhyolite; in the DiPetrographic, geochemical, and geochronologic data for cenozoic volcanic rocks of the Tonopah, Divide, and Goldfield Mining Districts, Nevada
The purpose of this report is to summarize geochemical, petrographic, and geochronologic data for samples, principally those of unmineralized Tertiary volcanic rocks, from the Tonopah, Divide, and Goldfield mining districts of west-central Nevada (fig. 1). Much of the data presented here for the Tonopah and Divide districts are for samples collected by Bonham and Garside (1979) during geologic mapNon-USGS Publications**
Mark, D.F., P.R. Renne, R. Dymock, V.C. Smith, J.I. SImon, L.E. Morgan, R.A. Staff, and B.S. Ellis, 2017. High-precision 40Ar/39Ar dating of pleistocene tuffs and temporal anchoring of the Matuyama-Brunhes boundary. Quaternary Geochronology 39, 1-23, https://doi.org/10.1016/j.quageo.2017.01.002.Morgan, L.E., 2017. 40Ar/39Ar and K-Ar Geochronology, in: A.S. Gilbert (ed.), Encyclopedia of Geoarchaeology. Encyclopedia of Earth Science Series. Springer, Dordrecht, https://doi.org/10.1007/978-1-4020-4409-0.Morgan, L.E., 2015. Noble Gas Mass Spectrometry, in: W.J. Rink, and J.W. Thompson (eds.), Encyclopedia of Scientific Dating Methods. Encyclopedia of Earth Science Series. Springer, Dordrecht, https://doi.org/10.1007/978-94-007-6304-3_118.Sahle, Y., L.E. Morgan, D.R. Braun, W.K. Hutchings, 2014. Chronological and behavioral contexts of the earliest Middle Stone Age in the Gademotta Formation, Main Ethiopian Rift, Quaternary International, v. 331, p. 6-19, https://doi.org/10.1016/j.quaint.2013.03.010.Mark, D.F., M. Petraglia, V.C. Smith, L.E. Morgan, D.N. Barfod, B.S Ellis, N.J. Pearce, J.N. Pal, R. Korisettar, 2014. A high-precision 40Ar/39Ar age for the Young Toba Tuff and dating of ultra- distal tephra: forcing of Quaternary climate and implications for hominin occupation of India, Quaternary Geochronology, v. 21, p. 90-103, https://doi.org/10.1016/j.quageo.2012.12.004.Sahle, Y., W.K. Hutchings, D.R. Braun, J.C. Sealy, L.E. Morgan, A. Negash, B. Atnafu, 2013. Earliest stone-tipped projectiles from the Ethiopian Rift date to >279,000 years ago. PLOS ONE, v. 8, no. 11, e78092, https://doi.org/10.1371/journal.pone.0078092.Morgan, L.E., D.F. Mark, J. Imlach, D.N. Barfod, 2013. FCs-EK: A new sampling of the Fish Canyon tuff 40Ar/39Ar neutron flux monitor, in: Jourdan, F., Mark, D., and Verati, C. (eds.), Advances in 40Ar/39Ar Dating: from Archaeology to Planetary Sciences. Geological Society, London, Special Publications, 378, https://doi.org/10.1144/SP378.21.Renne, P.R., A.L. Deino, F.J. Hilgen, K.F. Kuiper, D.F. Mark, W.S. Mitchell, L.E. Morgan, R. Mundil, J. Smit, 2013. Timescales of critical events around the Cretaceous-Paleogene boundary. Science, v. 339, p. 684-687, https://doi.org/10.1126/science.1230492.Schoene, B., D.J. Condon, L.E. Morgan, N. McLean, 2013. Precision and accuracy in geochronology. Elements Magazine, v.9, no.1, p. 23-28, http://elementsmagazine.org/past-issue-archive/2013-volume-9/#February2013.Renne, P.R., S.R. Mulcahy, W.S. Cassata,, L.E. Morgan, S.P. Kelley, L. Hlusko, J. Njau, 2012. Retention of inherited Ar by alkali feldspar xenocrysts in a magma: Kinetic constraints from Ba zoning profiles. Geochimica et Cosmochimica Acta, v. 93, p. 129-142, https://doi.org/10.1016/j.gca.2012.06.029.Morgan, L.E., P.R. Renne, R. Galotti, G. Kieffer, M. Piperno, J.-P. Raynal, 2012. A chronological framework for a long and persistent archeological record: Melka Kunture, Ethiopia. Journal of Human Evolution, v. 62, no. 1, p. 104-115, https://doi.org/10.1016/j.jhevol.2011.10.007.Frost, S.R., H.L. Schwartz, L. Giemsch, L.E. Morgan, P.R. Renne, M. Wildgoose, C. Saanane, F. Schrenk, K. Harvati, 2012. Refined age estimates and paleoanthropological investigation of the Manyara Beds, Tanzania. Journal of Anthropological Sciences, v. 90, p. 151-161, https://doi.org/10.4436/jass.90001.Schwartz, H., P.R. Renne, L.E. Morgan, M.M. Wildgoose, P.C. Lippert, S.R. Frost, K. Harvati, F. Schrenk, C. Saanane, 2012. Geochronology of the Manyara Beds, northern Tanzania: stratigraphy and new magnetostratigraphy and 40Ar/39Ar ages. Quaternary Geochronology, v. 7, no. 1, p. 48-66, https://doi.org/10.1016/j.quageo.2011.09.002.Morgan, L.E., O. Postma, K.F. Kuiper, D.F. Mark, W. van der Plas, S. Davidson, M. Perkin, I. Villa, J.R. Wijbrans, 2011. A metrological approach to measuring 40Ar* concentrations in K-Ar and 40Ar/39Ar mineral standards, Geochem. Geophys. Geosyst., v. 12, p. A0AA20, https://doi.org/10.1029/2011GC003719.Renne, P.R., A.L. Deino, W.E. Hames, M.T. Heizler, S.R. Hemming, K.V. Hodges, A.A.P. Koppers, D.F. Mark, L.E. Morgan, D. Phillips, B.S. Singer, B.D. Turrin, I.M. Villa, M. Villeneuve and J.R. Wijbrans, 2009. Data reporting norms for 40Ar/39Ar geochronology. Quaternary Geochronology, v. 4, no. 5, p. 346-352, https://doi.org/10.1016/j.quageo.2009.06.005.Renne, P.R., W.S. Cassata, and L.E. Morgan, 2009. The isotopic composition of atmospheric argon and 40Ar/39Ar geochronology: time for a change? Quaternary Geochronology, v. 4, no. 4, p. 288-298, https://doi.org/10.1016/j.quageo.2009.02.015.Renne, P. R., L.E. Morgan, G. WoldeGabriel, W.K. Hart, Y. Haile-Selassie, and T.D. White, 2009. 40Ar/39Ar Ages of the Middle Awash Late Miocene, in: Haile-Selassie, Y., and WoldeGabriel, G. (eds.), Ardipithecus kadabba: Late Miocene evidence from the Middle Awash, Ethiopia. University of California Press, Berkeley, CA.Morgan, L.E., P.R. Renne, R.E. Taylor, and G. WoldeGabriel, 2009. Archaeological age constraints from eruption ages of obsidian: Examples from the Middle Awash, Ethiopia. Quaternary Geochronology, v. 4, p. 193-203, https://doi.org/10.1016/j.quageo.2009.01.001.Morgan, L.E. and P.R. Renne, 2008. Diachronous Dawn of Africa’s Middle Stone Age: New 40Ar/39Ar ages from the Ethiopian Rift. Geology, v. 36, no. 12, p. 967-970, https://doi.org/10.1130/G25213A.1.Gihring, T.M., L.-H. Lin, M. Davidson, T.C. Onstott, L. Morgan, M. Milleson, T.L. Kieft, E. Trimarco, D.L. Balkwill, and M.E. Dollhopf, 2006. The Distribution of Microbial Taxa in the Subsurface Water of the Kalahari Shield, South Africa. Geomicrobiology Journal, v. 23, p. 415-430, https://doi.org/10.1080/01490450600875696.**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
*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