Floyd Gray
Floyd Gray is a Scientist Emeritus with the USGS Geology, Minerals, Energy, and Geophysics Science Center in Tucson, AZ. Floyd's work with the USGS has included regional geologic studies, metallogenic studies, mineral-resource assessments, and mineral-environmental studies.
As a mineral resource specialist in the MRP, he studies the genesis and geologic setting of early magmatic and hydrothermal ore deposits and conducts assessments for undiscovered mineral resources in the Southwestern US, northern Mexico, Central America and the Caribbean basin. He is the project chief of the USGS Puerto Rico, U.S. Virgin Islands and Adjacent Areas of the Greater Antilles Quantitative Mineral Resource Assessment project. His recent research efforts have been in the area of flood hazard early warning systems, hydrogeologic framework studies, aqueous and environmental geochemistry, soil geochemistry, and limnology focusing on mineral-related environmental/ecological vulnerabilities resulting from dispersal of metal contaminants from abandoned and newly developing mine lands. Part of the long-term focus has been to understand the physical and biogeochemical processes that control the distribution, transport, and fate of trace elements in aquatic systems.
Education and Certifications
M.S. Geology, University of Massachusetts, Amherst, 1982
B.A. Earth Science, Anthropology, University of California, Santa Cruz, 1976
Honors and Awards
Inaugural Rufus D. Catchings Diversity Award, 2021
Science and Products
Maps showing aeromagnetic data and interpretation for the Kalmiopsis Wilderness, southwestern Oregon
Geologic map of the Wild Rogue Wilderness, Coos, Curry, and Douglas counties, Oregon
Mineral resource potential map of the Kalmiopsis Wilderness, southwestern Oregon
Reconnaissance geologic map of the Selma Quadrangle, Josephine County, Oregon
Geologic map of the Kalmiopsis Wilderness Area, Oregon
Nickel-cobalt laterites: a deposit model
The Borderlands and climate change: Chapter 10 in United States-Mexican Borderlands: Facing tomorrow's challenges through USGS science
Socio-environmental health analysis in Nogales, Sonora, Mexico
Introduction to pathways of metal transfer from mineralized sources to biorecptors
Global mineral resource assessment: porphyry copper assessment of Mexico: Chapter A in Global mineral resource assessment
Nogales flood detention study
The Border Environmental Health Initiative: Investigating the transboundary Santa Cruz watershed
Porphyry copper deposit model
A high-resolution land-use map; Nogales, Sonora, Mexico
Stratigraphy and Mesozoic–Cenozoic tectonic history of northern Sierra Los Ajos and adjacent areas, Sonora, Mexico
Developing an ecosystem services online decision support tool to assess the impacts of climate change and urban growth in the Santa Cruz watershed: Where we live, work, and play
Understanding Metal Pathways in Mineralized Ecosystems
Science and Products
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Maps showing aeromagnetic data and interpretation for the Kalmiopsis Wilderness, southwestern Oregon
The distinctive magnetic properties of the major rock types in the Kalmiopsis Wilderness of southwestern Oregon facilitate interpretation of aeromagenetic data. The region is composed of tectonic slices of magnetic ultramafic, gabboric, and other ophiolitic rocks faulted against the realitively nonmagnetic Dothan Formation, the equivalent of the Franciscan Complex of Western California. The sharpGeologic map of the Wild Rogue Wilderness, Coos, Curry, and Douglas counties, Oregon
No abstract available.Mineral resource potential map of the Kalmiopsis Wilderness, southwestern Oregon
Under the provisions of the Wilderness Act (Public Law 88-577, September 3, 1964) and the Joint conference Report on Senate Bill 4, 88th Congress, the U.S. Geological Survey and the U.S. Bureau of Mines have been conducting mineral surveys of wilderness and primitive areas. Areas officially designated as "wilderness," wild," or "canoe" when the act was passed were incorporated into the National WiReconnaissance geologic map of the Selma Quadrangle, Josephine County, Oregon
No abstract available.Geologic map of the Kalmiopsis Wilderness Area, Oregon
No abstract available. - Publications
Filter Total Items: 58
Nickel-cobalt laterites: a deposit model
Nickel-cobalt (Ni-Co) laterite deposits are supergene enrichments of Ni±Co that form from intense chemical and mechanical weathering of ultramafic parent rocks. These regolith deposits typically form within 26 degrees of the equator, although there are a few exceptions. They form in active continental margins and stable cratonic settings. It takes as little as one million years for a laterite profAuthorsErin E. Marsh, Eric D. Anderson, Floyd GrayThe Borderlands and climate change: Chapter 10 in United States-Mexican Borderlands: Facing tomorrow's challenges through USGS science
The prediction of global climate change in response to both natural forces and human activity is one of the defining issues of our times. The unprecedented observational capacity of modern earth-orbiting satellites coupled with the development of robust computational representations (models) of the Earth’s weather and climate systems afford us the opportunity to observe and investigate how these sAuthorsJoan Fitzpatrick, Floyd Gray, Russell Dubiel, Jeff Langman, J. Bruce Moring, Laura M. Norman, William R. Page, Jean W. ParcherSocio-environmental health analysis in Nogales, Sonora, Mexico
In Nogales, Sonora, Mexico, some neighborhoods, or colonias, have intermittent delivery of water through pipes from the city of Nogales’s municipal water-delivery system while other areas lack piped water and rely on water delivered by truck or pipas. This research examined how lifestyles, water quality, and potential disease response, such as diarrhea, differs seasonally from a colonia with accesAuthorsLaura M. Norman, Felipe Caldeira, James Callegary, Floyd Gray, Mary Kay O’ Rourke, Veronica Meranza, Saskia Van RijnIntroduction to pathways of metal transfer from mineralized sources to biorecptors
Since 1995, the Mineral Resources Program of the U.S. Geological Survey has funded a number of studies in the western United States that address environmental issues associated with mineral deposits.AuthorsRoger P. Ashley, Elizabeth A. Bailey, Laurie S. Balistrieri, Andrea L. Foster, Larry P. Gough, Floyd Gray, Randolph A. Koski, James J. Rytuba, Robert R. Seal, Kathleen S. Smith, Lisa L. Stillings, Richard B. WantyGlobal mineral resource assessment: porphyry copper assessment of Mexico: Chapter A in Global mineral resource assessment
Mineral resource assessments provide a synthesis of available information about distributions of mineral deposits in the Earth’s crust. A probabilistic mineral resource assessment of undiscovered resources in porphyry copper deposits in Mexico was done as part of a global mineral resource assessment. The purpose of the study was to (1) delineate permissive areas (tracts) for undiscovered porphyryAuthorsJane M. Hammarstrom, Gilpin R. Robinson, Steve Ludington, Floyd Gray, Benjamin J. Drenth, Francisco Cendejas-Cruz, Enrique Espinosa, Efrén Pérez-Segura, Martín Valencia-Moreno, José Luis Rodríguez-Castañeda, Rigobert Vásquez-Mendoza, Lukas ZürcherNogales flood detention study
Flooding in Ambos Nogales often exceeds the capacity of the channel and adjacent land areas, endangering many people. The Nogales Wash is being studied to prevent future flood disasters and detention features are being installed in tributaries of the wash. This paper describes the application of the KINEROS2 model and efforts to understand the capacity of these detention features under various floAuthorsLaura M. Norman, Lainie Levick, D. Phillip Guertin, James Callegary, Jesus Quintanar Guadarrama, Claudia Zulema Gil Anaya, Andrea Prichard, Floyd Gray, Edgar Castellanos, Edgar Tepezano, Hans Huth, Prescott Vandervoet, Saul Rodriguez, Jose Nunez, Donald Atwood, Gilberto Patricio Olivero Granillo, Francisco Octavio Gastellum CeballosThe Border Environmental Health Initiative: Investigating the transboundary Santa Cruz watershed
In 2004 the U.S. Geological Survey (USGS) launched the Border Environmental Health Initiative (BEHI), a major project encompassing the entire U.S.-Mexico border region. In 2009, a study of the Santa Cruz River Watershed (SCW), located in the border region of Arizona and Sonora, Mexico, was initiated as part of the BEHI. In this borderland region of the desert Southwest, human health and the ecosysAuthorsLaura M. Norman, James Callegary, Charles van Riper, Floyd GrayPorphyry copper deposit model
This report contains a revised descriptive model of porphyry copper deposits (PCDs), the world's largest source (about 60 percent) and resource (about 65 percent) of copper and a major source of molybdenum, gold and silver. Despite relatively low grades (average 0.44 percent copper in 2008), PCDs have significant economic and societal impacts due to their large size (commonly hundreds of millionsAuthorsRobert A. Ayuso, Mark D. Barton, Richard J. Blakely, Robert J. Bodnar, John H. Dilles, Floyd Gray, Fred T. Graybeal, John L. Mars, Darcy McPhee, Robert R. Seal, Ryan D. Taylor, Peter G. VikreA high-resolution land-use map; Nogales, Sonora, Mexico
The cities of Nogales, Sonora, and Nogales, Arizona, are located in the Ambos Nogales Watershed, a topographically irregular bowl-shaped area with a northward gradient. Throughout history, residents in both cities have been affected by flooding. Currently, the primary method for regulating this runoff is to build a series of detention basins in Nogales, Sonora. Additionally, the municipality alsoAuthorsLaura M. Norman, Miguel L. Villarreal, Cynthia S.A. Wallace, Claudia Z. Gil Anaya, Israel Diaz Arcos, Floyd GrayStratigraphy and Mesozoic–Cenozoic tectonic history of northern Sierra Los Ajos and adjacent areas, Sonora, Mexico
Geologic mapping in the northern Sierra Los Ajos reveals new stratigraphic and structural data relevant to deciphering the Mesozoic–Cenozoic tectonic evolution of the range. The northern Sierra Los Ajos is cored by Proterozoic, Cambrian, Devonian, Mississippian, and Pennsylvanian strata, equivalent respectively to the Pinal Schist, Bolsa Quartzite and Abrigo Limestone, Martin Formation, EscabrosaAuthorsWilliam R. Page, Floyd Gray, Alexander Iriondo, Daniel P. Miggins, Robert B. Blodgett, Florian Maldonado, Robert J. MillerDeveloping an ecosystem services online decision support tool to assess the impacts of climate change and urban growth in the Santa Cruz watershed: Where we live, work, and play
Using respective strengths of the biological, physical, and social sciences, we are developing an online decision support tool, the Santa Cruz Watershed Ecosystem Portfolio Model (SCWEPM), to help promote the use of information relevant to water allocation and land management in a binational watershed along the U.S.-Mexico border. The SCWEPM will include an ES valuation system within a suite of liAuthorsLaura M. Norman, Nita Tallent-Halsell, William Labiosa, Matt Weber, Amy McCoy, Katie Hirschboeck, James B. Callegary, Charles van Riper, Floyd GrayUnderstanding Metal Pathways in Mineralized Ecosystems
Successful management of ecosystems containing historical mine wastes requires understanding of processes that are responsible for the distribution, concentration, and bioavailability of potentially toxic elements. U.S. Geological Survey (USGS) scientists recently completed several investigations at historical mine sites in the western United States. These investigations have improved our understaAuthorsLaurie S. Balistrieri, Andrea L. Foster, Larry P. Gough, Floyd Gray, James J. Rytuba, Lisa L. Stillings