Karl J Ellefsen
Karl Ellefsen is an Emeritus with the Geology, Geophysics, and Geochemistry Science Center.
Science and Products
Filter Total Items: 64
Manual hierarchical clustering of regional geochemical data using a Bayesian finite mixture model
Interpretation of regional scale, multivariate geochemical data is aided by a statistical technique called “clustering.” We investigate a particular clustering procedure by applying it to geochemical data collected in the State of Colorado, United States of America. The clustering procedure partitions the field samples for the entire survey area into two clusters. The field samples in each cluster
Authors
Karl J. Ellefsen, David Smith
User’s guide for GcClust—An R package for clustering of regional geochemical data
GcClust is a software package developed by the U.S. Geological Survey for statistical clustering of regional geochemical data, and similar data such as regional mineralogical data. Functions within the software package are written in the R statistical programming language. These functions, their documentation, and a copy of the user’s guide are bundled together in R’s unit of sharable code, which
Authors
Karl J. Ellefsen, David B. Smith
First steps of integrated spatial modeling of titanium, zirconium, and rare earth element resources within the Coastal Plain sediments of the southeastern United States
The Coastal Plain of the southeastern United States has extensive, unconsolidated sedimentary deposits that are enriched in heavy minerals containing titanium, zirconium, and rare earth element resources. Areas favorable for exploration and development of these resources are being identified by geochemical data, which are supplemented with geological, geophysical, hydrological, and geographical da
Authors
Karl J. Ellefsen, Bradley S. Van Gosen, David L. Fey, James R. Budahn, Steven M. Smith, Anjana K. Shah
A modified procedure for mixture-model clustering of regional geochemical data
A modified procedure is proposed for mixture-model clustering of regional-scale geochemical data. The key modification is the robust principal component transformation of the isometric log-ratio transforms of the element concentrations. This principal component transformation and the associated dimension reduction are applied before the data are clustered. The principal advantage of this modificat
Authors
Karl J. Ellefsen, David B. Smith, John D. Horton
Using vertical Fourier transforms to invert potential-field data to magnetization or density models in the presence of topography
A physical property inversion approach based on the use of 3D (or 2D) Fourier transforms to calculate the potential-field within a 3D (or 2D) volume from a known physical property distribution within the volume is described. Topographic surfaces and observations at arbitrary locations are easily accommodated. The limitations of the approach and applications to real data are considered.
Authors
Jeffrey Phillips
Geochemical and mineralogical maps for soils of the conterminous United States
The U.S. Geological Survey began sampling in 2007 for a low-density (1 site per 1,600 square kilometers, 4,857 sites) geochemical and mineralogical survey of soils in the conterminous United States as part of the North American Soil Geochemical Landscapes Project. The sampling protocol for the national-scale survey included, at each site, a sample from a depth of 0 to 5 centimeters, a composite of
Authors
David B. Smith, William F. Cannon, Laurel G. Woodruff, Federico Solano, Karl J. Ellefsen
Integrated characterization of the geologic framework of a contaminated site in West Trenton, New Jersey
Fractured sedimentary bedrock and groundwater at the former Naval Air Warfare Center in West Trenton, New Jersey (United States of America) are contaminated with chlorinated solvents. Predicting contaminant migration or removing the contaminants requires an understanding of the geology. Consequently, the geologic framework near the site was characterized with four different methods having differen
Authors
Karl J. Ellefsen, William C. Burton, Pierre J. Lacombe
Geochemical mapping of the Denver, Colorado (USA) urban area: A comparison of studies in 1972 and 2005
No abstract available.
Authors
D. B. Smith, R. G. Garrett, G. Closs, K.J. Ellefsen, J. E. Kilburn, J.D. Horton, S. M. Smith
Development of industrial minerals in Colorado
Technology and engineering have helped make mining safer and cleaner for both humans and the environment. Inevitably, mineral development entails costs as well as benefits. Developing a mine is an environmental, engineering, and planning challenge that must conform to many Federal, State, and local regulations. Community collaboration, creative design, and best management practices of sustainabili
Authors
Belinda F. Arbogast, Daniel H. Knepper, William H. Langer, James A. Cappa, John W. Keller, Beth L. Widmann, Karl J. Ellefsen, Terry L. Klein, Jeffrey E. Lucius, John S. Dersch
Computer programs for forward and inverse modeling of acoustic and electromagnetic data
A suite of computer programs was developed by U.S. Geological Survey personnel for forward and inverse modeling of acoustic and electromagnetic data. This report describes the computer resources that are needed to execute the programs, the installation of the programs, the program designs, some tests of their accuracy, and some suggested improvements.
Authors
Karl J. Ellefsen
Using stable isotopes to understand hydrochemical processes in and around a Prairie Pothole wetland in the Northern Great Plains, USA
Millions of internally drained wetland systems in the Prairie Potholes region of the northern Great Plains (USA and Canada) provide indispensable habitat for waterfowl and a host of other ecosystem services. The hydrochemistry of these systems is complex and a crucial control on wetland function, flora and fauna. Wetland waters can have high concentrations of SO2-4 due to the oxidation of large am
Authors
Christopher T. Mills, Martin B. Goldhaber, Craig A. Stricker, JoAnn M. Holloway, Jean Morrison, Karl J. Ellefsen, Donald O. Rosenberry, Roland S. Thurston
Phase and amplitude inversion of crosswell radar data
Phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2.5D heterogeneous model. The inversion is formulated in the frequency domain using the vector Helmholtz equation. The objective function is minimized using a back-propagation method that is suitable for a 2.5D model and that accounts for the near-, intermediate-, and far-field regions of the an
Authors
Karl J. Ellefsen, Aldo T. Mazzella, Robert Horton, Jason R. McKenna
Science and Products
Filter Total Items: 64
Manual hierarchical clustering of regional geochemical data using a Bayesian finite mixture model
Interpretation of regional scale, multivariate geochemical data is aided by a statistical technique called “clustering.” We investigate a particular clustering procedure by applying it to geochemical data collected in the State of Colorado, United States of America. The clustering procedure partitions the field samples for the entire survey area into two clusters. The field samples in each cluster
Authors
Karl J. Ellefsen, David Smith
User’s guide for GcClust—An R package for clustering of regional geochemical data
GcClust is a software package developed by the U.S. Geological Survey for statistical clustering of regional geochemical data, and similar data such as regional mineralogical data. Functions within the software package are written in the R statistical programming language. These functions, their documentation, and a copy of the user’s guide are bundled together in R’s unit of sharable code, which
Authors
Karl J. Ellefsen, David B. Smith
First steps of integrated spatial modeling of titanium, zirconium, and rare earth element resources within the Coastal Plain sediments of the southeastern United States
The Coastal Plain of the southeastern United States has extensive, unconsolidated sedimentary deposits that are enriched in heavy minerals containing titanium, zirconium, and rare earth element resources. Areas favorable for exploration and development of these resources are being identified by geochemical data, which are supplemented with geological, geophysical, hydrological, and geographical da
Authors
Karl J. Ellefsen, Bradley S. Van Gosen, David L. Fey, James R. Budahn, Steven M. Smith, Anjana K. Shah
A modified procedure for mixture-model clustering of regional geochemical data
A modified procedure is proposed for mixture-model clustering of regional-scale geochemical data. The key modification is the robust principal component transformation of the isometric log-ratio transforms of the element concentrations. This principal component transformation and the associated dimension reduction are applied before the data are clustered. The principal advantage of this modificat
Authors
Karl J. Ellefsen, David B. Smith, John D. Horton
Using vertical Fourier transforms to invert potential-field data to magnetization or density models in the presence of topography
A physical property inversion approach based on the use of 3D (or 2D) Fourier transforms to calculate the potential-field within a 3D (or 2D) volume from a known physical property distribution within the volume is described. Topographic surfaces and observations at arbitrary locations are easily accommodated. The limitations of the approach and applications to real data are considered.
Authors
Jeffrey Phillips
Geochemical and mineralogical maps for soils of the conterminous United States
The U.S. Geological Survey began sampling in 2007 for a low-density (1 site per 1,600 square kilometers, 4,857 sites) geochemical and mineralogical survey of soils in the conterminous United States as part of the North American Soil Geochemical Landscapes Project. The sampling protocol for the national-scale survey included, at each site, a sample from a depth of 0 to 5 centimeters, a composite of
Authors
David B. Smith, William F. Cannon, Laurel G. Woodruff, Federico Solano, Karl J. Ellefsen
Integrated characterization of the geologic framework of a contaminated site in West Trenton, New Jersey
Fractured sedimentary bedrock and groundwater at the former Naval Air Warfare Center in West Trenton, New Jersey (United States of America) are contaminated with chlorinated solvents. Predicting contaminant migration or removing the contaminants requires an understanding of the geology. Consequently, the geologic framework near the site was characterized with four different methods having differen
Authors
Karl J. Ellefsen, William C. Burton, Pierre J. Lacombe
Geochemical mapping of the Denver, Colorado (USA) urban area: A comparison of studies in 1972 and 2005
No abstract available.
Authors
D. B. Smith, R. G. Garrett, G. Closs, K.J. Ellefsen, J. E. Kilburn, J.D. Horton, S. M. Smith
Development of industrial minerals in Colorado
Technology and engineering have helped make mining safer and cleaner for both humans and the environment. Inevitably, mineral development entails costs as well as benefits. Developing a mine is an environmental, engineering, and planning challenge that must conform to many Federal, State, and local regulations. Community collaboration, creative design, and best management practices of sustainabili
Authors
Belinda F. Arbogast, Daniel H. Knepper, William H. Langer, James A. Cappa, John W. Keller, Beth L. Widmann, Karl J. Ellefsen, Terry L. Klein, Jeffrey E. Lucius, John S. Dersch
Computer programs for forward and inverse modeling of acoustic and electromagnetic data
A suite of computer programs was developed by U.S. Geological Survey personnel for forward and inverse modeling of acoustic and electromagnetic data. This report describes the computer resources that are needed to execute the programs, the installation of the programs, the program designs, some tests of their accuracy, and some suggested improvements.
Authors
Karl J. Ellefsen
Using stable isotopes to understand hydrochemical processes in and around a Prairie Pothole wetland in the Northern Great Plains, USA
Millions of internally drained wetland systems in the Prairie Potholes region of the northern Great Plains (USA and Canada) provide indispensable habitat for waterfowl and a host of other ecosystem services. The hydrochemistry of these systems is complex and a crucial control on wetland function, flora and fauna. Wetland waters can have high concentrations of SO2-4 due to the oxidation of large am
Authors
Christopher T. Mills, Martin B. Goldhaber, Craig A. Stricker, JoAnn M. Holloway, Jean Morrison, Karl J. Ellefsen, Donald O. Rosenberry, Roland S. Thurston
Phase and amplitude inversion of crosswell radar data
Phase and amplitude inversion of crosswell radar data estimates the logarithm of complex slowness for a 2.5D heterogeneous model. The inversion is formulated in the frequency domain using the vector Helmholtz equation. The objective function is minimized using a back-propagation method that is suitable for a 2.5D model and that accounts for the near-, intermediate-, and far-field regions of the an
Authors
Karl J. Ellefsen, Aldo T. Mazzella, Robert Horton, Jason R. McKenna