Harrison Gray, Ph.D
Earth's surface is shaped by the transfer of sediment across time and space. As we live on the Earth's surface, understanding this transport of sediment is key to the well-being of our species. I work on solving problems asscociated with landscapes and sediment transport using the tools of computer landscape evolution modeling and the trapped-charge phenomena known as luminescence.
Biography
Ph.D Geomorphology, University of Colorado - Boulder, 2018
M.S. Geology, Univeristy of Cincinnati, 2013
B.S. Earth Sciences, University of California - Santa Cruz, 2010
Google Scholar: https://scholar.google.com/citations?user=bicRRxgAAAAJ&hl
Science and Products
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
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<1 km south of the boundary...
Bennett, Scott E. K.; Duross, Christopher; Gold, Ryan D.; Briggs, Richard W.; Personius, Stephen; Reitman, Nadine G.; Devore, Joshua; Hiscock, Adam; Mahan, Shannon A.; Gray, Harrison J.; Gunnarson, Sydney; Stephenson, William J.; Pettinger, Elizabeth; Odum, Jackson K. Examining 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...
Gray, Harrison J.; Mahan, Shannon A.; Springer, Kathleen B.; Pigati, Jeffrey S. Application 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...
Gray, Harrison J.; Tucker, Gregory E.; Mahan, Shannon A. Dating 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...
Foster, Melissa A.; Anderson, Robert S.; Gray, Harrison J.; Mahan, Shannon A. On 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...
Gray, Harrison J.; Tucker, Gregory E.; Mahan, Shannon A.; McGuire, Chris; Rhodes, Edward J. User guide for luminescence sampling in archaeological and geological contexts
Luminescence dating provides a direct age estimate of the time of last exposure of quartz or feldspar minerals to light or heat and has been successfully applied to deposits, rock surfaces, and fired materials in a number of archaeological and geological settings. Sampling strategies are diverse and can be customized depending on local...
Nelson, Michelle S.; Gray, Harrison J.; Johnson, Jack A.; Rittenour, Tammy M.; Feathers, James K.; Mahan, Shannon Variables and potential models for the bleaching of luminescence signals in fluvial environments
Luminescence dating of fluvial sediments rests on the assumption that sufficient sunlight is available to remove a previously obtained signal in a process deemed bleaching. However, luminescence signals obtained from sediment in the active channels of rivers often contain residual signals. This paper explores and attempts to build theoretical...
Gray, Harrison J.; Mahan, Shannon Guide to luminescence dating techniques and their application for paleoseismic research
Over the past 25 years, luminescence dating has become a key tool for dating sediments of interest in paleoseismic research. The data obtained from luminescence dating has been used to determine timing of fault displacement, calculate slip rates, and estimate earthquake recurrence intervals. The flexibility of luminescence is a key complement to...
Lund, William R.; Gray, Harrison J.; Mahan, Shannon A.; Rittenour, Tammy M.; Nelson, Michelle Summa Quaternary landscape development, alluvial fan chronology and erosion of the Mecca Hills at the southern end of the San Andreas Fault zone
Quantitative geomorphic analysis combined with cosmogenic nuclide 10Be-based geochronology and denudation rates have been used to further the understanding of the Quaternary landscape development of the Mecca Hills, a zone of transpressional uplift along the southern end of the San Andreas Fault, in southern California. The similar timing of...
Gray, Harrison J.; Owen, Lewis A.; Dietsch, Craig; Beck, Richard A.; Caffee, Marc A.; Finkelman, Robert B.; Mahan, Shannon A high-elevation, multi-proxy biotic and environmental record of MIS 6-4 from the Ziegler Reservoir fossil site, Snowmass Village, Colorado, USA
In North America, terrestrial records of biodiversity and climate change that span Marine Oxygen Isotope Stage (MIS) 5 are rare. Where found, they provide insight into how the coupling of the ocean–atmosphere system is manifested in biotic and environmental records and how the biosphere responds to climate change. In 2010–2011,...
Miller, Ian M.; Pigati, Jeffrey S.; Anderson, R. Scott; Johnson, Kirk R.; Mahan, Shannon; Ager, Thomas A.; Baker, Richard G.; Blaauw, Maarten; Bright, Jordon; Brown, Peter M.; Bryant, Bruce; Calamari, Zachary T.; Carrara, Paul E.; Michael D., Cherney; Demboski, John R.; Elias, Scott A.; Fisher, Daniel C.; Gray, Harrison J.; Haskett, Danielle R.; Honke, Jeffrey S.; Jackson, Stephen T.; Jiménez-Moreno, Gonzalo; Kline, Douglas; Leonard, Eric M.; Lifton, Nathaniel A.; Lucking, Carol; McDonald, H. Gregory; Miller, Dane M.; Muhs, Daniel R.; Nash, Stephen E.; Newton, Cody; Paces, James B.; Petrie, Lesley; Plummer, Mitchell A.; Porinchu, David F.; Rountrey, Adam N.; Scott, Eric; Sertich, Joseph J. W.; Sharpe, Saxon E.; Skipp, Gary L.; Strickland, Laura E.; Stucky, Richard K.; Thompson, Robert S.; Wilson, Jim A geochronologic framework for the Ziegler Reservoir fossil site, Snowmass Village, Colorado
The Ziegler Reservoir fossil site near Snowmass Village, Colorado, provides a unique opportunity to reconstruct high-altitude paleoenvironmental conditions in the Rocky Mountains during the last interglacial period. We used four different techniques to establish a chronological framework for the site. Radiocarbon dating of lake organics, bone...
Mahan, Shannon; Gray, Harrison J.; Pigati, Jeffrey S.; Wilson, Jim; Lifton, Nathaniel A.; Paces, James B.; Blaauw, Maarten