Robert J Fleck (Former Employee)
Science and Products
Filter Total Items: 43
Rapid middle Miocene extension and unroofing of the southern Ruby Mountains, Nevada Rapid middle Miocene extension and unroofing of the southern Ruby Mountains, Nevada
Paleozoic rocks in the northern Ruby Mountains were metamorphosed during Mesozoic crustal shortening and Cenozoic magmatism, but equivalent strata in the southern Ruby Mountains were never buried deeper than stratigraphic depths prior to exhumation in the footwall of a west dipping brittle normal fault. In the southern Ruby Mountains, Miocene sedimentary rocks in the hanging wall of this...
Authors
Joseph P. Colgan, Keith A. Howard, Robert J. Fleck, Joseph L. Wooden
The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: Tectonically anomalous forearc volcanism in an urban setting The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: Tectonically anomalous forearc volcanism in an urban setting
More than 80 small volcanoes are scattered throughout the Portland-Vancouver metropolitan area of northwestern Oregon and southwestern Washington. These volcanoes constitute the Boring Volcanic Field, which is centered in the Neogene Portland Basin and merges to the east with coeval volcanic centers of the High Cascade volcanic arc. Although the character of volcanic activity is typical...
Authors
Russell C. Evarts, Richard M. Conrey, Robert J. Fleck, Jonathan T. Hagstrum
Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California
The right lateral San Gabriel Fault Zone in southern California extends from the northwestern corner of the Ridge Basin southeastward to the eastern end of the San Gabriel Mountains. It bifurcates to the southeast in the northwestern San Gabriel Mountains. The northern and older branch curves eastward in the range interior. The southern younger branch, the Vasquez Creek Fault, curves...
Authors
Larry A. Beyer, Thane H. McCulloh, Rodger E. Denison, Ronald W. Morin, Roy J. Enrico, John A. Barron, Robert J. Fleck
Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada
Because major mineral deposits in north-central Nevada predate significant Basin and Range extension, a detailed understanding of the timing and kinematics of extensional faulting is necessary to place these deposits in their original structural context. The complexity of pre-Cenozoic deformation in northern Nevada makes restoring Basin and Range faulting difficult without locating well...
Authors
Joseph P. Colgan, David A. John, Christopher D. Henry, Robert J. Fleck
The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present
We report the results of recent geologic mapping and radiometric dating that add considerable detail to our understanding of the eruptive history of Mount St. Helens before its latest, or Spirit Lake, stage. New data and reevaluation of earlier work indicate at least two eruptive periods during the earliest, or Ape Canyon, stage, possibly separated by a long hiatus: one about 300-250 ka...
Authors
Michael A. Clynne, Andrew T. Calvert, Edward W. Wolfe, Russell C. Evarts, Robert J. Fleck, Marvin A. Lanphere
Age, stratigraphy, and correlations of the late Neogene Purisima Formation, central California coast ranges Age, stratigraphy, and correlations of the late Neogene Purisima Formation, central California coast ranges
The Purisima Formation is an important upper Miocene and Pliocene stratigraphic unit in central California, cropping out from the coast at Point Reyes north of San Francisco to more extensive exposures in the Santa Cruz Mountains to the south. The fine-grained rocks in the lower parts of the Purisima Formation record a latest Miocene transgressive event, whereas the middle and upper...
Authors
Charles L. Powell, John A. Barron, Andrei M. Sarna-Wojcicki, Joseph C. Clark, Frank A. Perry, Earl E. Brabb, Robert J. Fleck
Tephra layers of Blind Spring Valley and related upper Pliocene and Pleistocene tephra layers, California, Nevada, and Utah: Isotopic ages, correlation, and magnetostratigraphy Tephra layers of Blind Spring Valley and related upper Pliocene and Pleistocene tephra layers, California, Nevada, and Utah: Isotopic ages, correlation, and magnetostratigraphy
Numerical ages have been determined for a stratigraphic sequence of silicic tephra layers exposed at the Cowan Pumice Mine in Blind Spring Valley, near Benton Hot Springs, east-central California, as well as at Chalk Cliffs, north of Bishop, Calif. The tephra layers at these sites were deposited after eruptions from nearby sources, most of them from near Glass Mountain, and some from...
Authors
Andrei M. Sarna-Wojcicki, Marith C. Reheis, Malcolm S. Pringle, Robert J. Fleck, Doug Burbank, Charles E. Meyer, Janet L. Slate, Elmira Wan, James R. Budahn, Bennie Troxel, James P. Walker
Location, Age, and Tectonic Significance of the Western Idaho Suture Zone (WISZ) Location, Age, and Tectonic Significance of the Western Idaho Suture Zone (WISZ)
The Western Idaho Suture Zone (WISZ) represents the boundary between crust overlying Proterozoic North American lithosphere and Late Paleozoic and Mesozoic intraoceanic crust accreted during Cretaceous time. Highly deformed plutons constituted of both arc and sialic components intrude the WISZ and in places are thrust over the accreted terranes. Pronounced variations in Sr, Nd, and O...
Authors
Robert J. Fleck, Robert E. Criss
Ad Duwayhi, Saudi Arabia: Geology and geochronology of a neoproterozoic intrusion-related gold system in the Arabian shield Ad Duwayhi, Saudi Arabia: Geology and geochronology of a neoproterozoic intrusion-related gold system in the Arabian shield
The Ad Duwayhi gold deposit, located in the east-central part of the Arabian shield, is the newest gold discovery in Saudi Arabia. Exploration to date has identified a gold resource of greater than 1 million ounces (oz) with significant potential for expansion. Gold mineralization was closely associated, in time and space, with emplacement of a late- to postorogenic, intracrustal...
Authors
Jeff Doebrich, S.G. Zahony, J.D. Leavitt, J.S. Portacio, A.A. Siddiqui, Joseph L. Wooden, Robert Fleck, Holly J. Stein
Age and tectonic significance of volcanic rocks in the northern Los Angeles Basin, California Age and tectonic significance of volcanic rocks in the northern Los Angeles Basin, California
Volcanic rocks, mostly basalts and some andesites, are interbedded with middle Miocene strata and are overlain by younger rocks throughout the greater part of the Los Angeles Basin, California. Roughly correlative flows, previously dated radiometrically (or paleontologically) at about 16.4 to 10.7 Ma, crop out in five separate regions around the basin perimeter. Los Angeles Basin...
Authors
Thane H. McCulloh, Robert J. Fleck, Rodger E. Denison, Larry A. Beyer, Richard G. Stanley
Origin, extent, and thickness of quaternary geologic units in the Willamette Valley, Oregon Origin, extent, and thickness of quaternary geologic units in the Willamette Valley, Oregon
Stratigraphic and chronologic information collected for Quaternary deposits in the Willamette Valley, Oregon, provides a revised stratigraphic framework that serves as a basis for a 1:250,000-scale map, as well as for thickness estimates of widespread Quaternary geologic units. We have mapped 11 separate Quaternary units that are differentiated on the basis of stratigraphic, topographic...
Authors
Jim E. O'Connor, Andrei M. Sarna-Wojcicki, Karl C. Wozniak, Danial J. Polette, Robert J. Fleck
Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California
This digital geologic map of the Nevada Test Site (NTS) and vicinity, as well as its accompanying digital geophysical maps, are compiled at 1:100,000 scale. The map compilation presents new polygon (geologic map unit contacts), line (fault, fold axis, metamorphic isograd, dike, and caldera wall) and point (structural attitude) vector data for the NTS and vicinity, Nye, Lincoln, and Clark...
Authors
Janet L. Slate, Margaret E. Berry, Peter D. Rowley, Christopher J. Fridrich, Karen S. Morgan, Jeremiah B. Workman, Owen D. Young, Gary L. Dixon, Van S. Williams, Edwin H. McKee, David A. Ponce, Thomas G. Hildenbrand, W. C. Swadley, Scott C. Lundstrom, E. Bartlett Ekren, Richard G. Warren, J. C. Cole, Robert J. Fleck, Marvin A. Lanphere, David A. Sawyer, Scott A. Minor, Daniel J. Grunwald, Randell J. Laczniak, Christopher M. Menges, James C. Yount, Angela S. Jayko
Science and Products
Filter Total Items: 43
Rapid middle Miocene extension and unroofing of the southern Ruby Mountains, Nevada Rapid middle Miocene extension and unroofing of the southern Ruby Mountains, Nevada
Paleozoic rocks in the northern Ruby Mountains were metamorphosed during Mesozoic crustal shortening and Cenozoic magmatism, but equivalent strata in the southern Ruby Mountains were never buried deeper than stratigraphic depths prior to exhumation in the footwall of a west dipping brittle normal fault. In the southern Ruby Mountains, Miocene sedimentary rocks in the hanging wall of this...
Authors
Joseph P. Colgan, Keith A. Howard, Robert J. Fleck, Joseph L. Wooden
The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: Tectonically anomalous forearc volcanism in an urban setting The Boring Volcanic Field of the Portland-Vancouver area, Oregon and Washington: Tectonically anomalous forearc volcanism in an urban setting
More than 80 small volcanoes are scattered throughout the Portland-Vancouver metropolitan area of northwestern Oregon and southwestern Washington. These volcanoes constitute the Boring Volcanic Field, which is centered in the Neogene Portland Basin and merges to the east with coeval volcanic centers of the High Cascade volcanic arc. Although the character of volcanic activity is typical...
Authors
Russell C. Evarts, Richard M. Conrey, Robert J. Fleck, Jonathan T. Hagstrum
Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California Post-Miocene Right Separation on the San Gabriel and Vasquez Creek Faults, with Supporting Chronostratigraphy, Western San Gabriel Mountains, California
The right lateral San Gabriel Fault Zone in southern California extends from the northwestern corner of the Ridge Basin southeastward to the eastern end of the San Gabriel Mountains. It bifurcates to the southeast in the northwestern San Gabriel Mountains. The northern and older branch curves eastward in the range interior. The southern younger branch, the Vasquez Creek Fault, curves...
Authors
Larry A. Beyer, Thane H. McCulloh, Rodger E. Denison, Ronald W. Morin, Roy J. Enrico, John A. Barron, Robert J. Fleck
Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada Large-magnitude Miocene extension of the Eocene Caetano caldera, Shoshone and Toiyabe Ranges, Nevada
Because major mineral deposits in north-central Nevada predate significant Basin and Range extension, a detailed understanding of the timing and kinematics of extensional faulting is necessary to place these deposits in their original structural context. The complexity of pre-Cenozoic deformation in northern Nevada makes restoring Basin and Range faulting difficult without locating well...
Authors
Joseph P. Colgan, David A. John, Christopher D. Henry, Robert J. Fleck
The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present The Pleistocene eruptive history of Mount St. Helens, Washington, from 300,000 to 12,800 years before present
We report the results of recent geologic mapping and radiometric dating that add considerable detail to our understanding of the eruptive history of Mount St. Helens before its latest, or Spirit Lake, stage. New data and reevaluation of earlier work indicate at least two eruptive periods during the earliest, or Ape Canyon, stage, possibly separated by a long hiatus: one about 300-250 ka...
Authors
Michael A. Clynne, Andrew T. Calvert, Edward W. Wolfe, Russell C. Evarts, Robert J. Fleck, Marvin A. Lanphere
Age, stratigraphy, and correlations of the late Neogene Purisima Formation, central California coast ranges Age, stratigraphy, and correlations of the late Neogene Purisima Formation, central California coast ranges
The Purisima Formation is an important upper Miocene and Pliocene stratigraphic unit in central California, cropping out from the coast at Point Reyes north of San Francisco to more extensive exposures in the Santa Cruz Mountains to the south. The fine-grained rocks in the lower parts of the Purisima Formation record a latest Miocene transgressive event, whereas the middle and upper...
Authors
Charles L. Powell, John A. Barron, Andrei M. Sarna-Wojcicki, Joseph C. Clark, Frank A. Perry, Earl E. Brabb, Robert J. Fleck
Tephra layers of Blind Spring Valley and related upper Pliocene and Pleistocene tephra layers, California, Nevada, and Utah: Isotopic ages, correlation, and magnetostratigraphy Tephra layers of Blind Spring Valley and related upper Pliocene and Pleistocene tephra layers, California, Nevada, and Utah: Isotopic ages, correlation, and magnetostratigraphy
Numerical ages have been determined for a stratigraphic sequence of silicic tephra layers exposed at the Cowan Pumice Mine in Blind Spring Valley, near Benton Hot Springs, east-central California, as well as at Chalk Cliffs, north of Bishop, Calif. The tephra layers at these sites were deposited after eruptions from nearby sources, most of them from near Glass Mountain, and some from...
Authors
Andrei M. Sarna-Wojcicki, Marith C. Reheis, Malcolm S. Pringle, Robert J. Fleck, Doug Burbank, Charles E. Meyer, Janet L. Slate, Elmira Wan, James R. Budahn, Bennie Troxel, James P. Walker
Location, Age, and Tectonic Significance of the Western Idaho Suture Zone (WISZ) Location, Age, and Tectonic Significance of the Western Idaho Suture Zone (WISZ)
The Western Idaho Suture Zone (WISZ) represents the boundary between crust overlying Proterozoic North American lithosphere and Late Paleozoic and Mesozoic intraoceanic crust accreted during Cretaceous time. Highly deformed plutons constituted of both arc and sialic components intrude the WISZ and in places are thrust over the accreted terranes. Pronounced variations in Sr, Nd, and O...
Authors
Robert J. Fleck, Robert E. Criss
Ad Duwayhi, Saudi Arabia: Geology and geochronology of a neoproterozoic intrusion-related gold system in the Arabian shield Ad Duwayhi, Saudi Arabia: Geology and geochronology of a neoproterozoic intrusion-related gold system in the Arabian shield
The Ad Duwayhi gold deposit, located in the east-central part of the Arabian shield, is the newest gold discovery in Saudi Arabia. Exploration to date has identified a gold resource of greater than 1 million ounces (oz) with significant potential for expansion. Gold mineralization was closely associated, in time and space, with emplacement of a late- to postorogenic, intracrustal...
Authors
Jeff Doebrich, S.G. Zahony, J.D. Leavitt, J.S. Portacio, A.A. Siddiqui, Joseph L. Wooden, Robert Fleck, Holly J. Stein
Age and tectonic significance of volcanic rocks in the northern Los Angeles Basin, California Age and tectonic significance of volcanic rocks in the northern Los Angeles Basin, California
Volcanic rocks, mostly basalts and some andesites, are interbedded with middle Miocene strata and are overlain by younger rocks throughout the greater part of the Los Angeles Basin, California. Roughly correlative flows, previously dated radiometrically (or paleontologically) at about 16.4 to 10.7 Ma, crop out in five separate regions around the basin perimeter. Los Angeles Basin...
Authors
Thane H. McCulloh, Robert J. Fleck, Rodger E. Denison, Larry A. Beyer, Richard G. Stanley
Origin, extent, and thickness of quaternary geologic units in the Willamette Valley, Oregon Origin, extent, and thickness of quaternary geologic units in the Willamette Valley, Oregon
Stratigraphic and chronologic information collected for Quaternary deposits in the Willamette Valley, Oregon, provides a revised stratigraphic framework that serves as a basis for a 1:250,000-scale map, as well as for thickness estimates of widespread Quaternary geologic units. We have mapped 11 separate Quaternary units that are differentiated on the basis of stratigraphic, topographic...
Authors
Jim E. O'Connor, Andrei M. Sarna-Wojcicki, Karl C. Wozniak, Danial J. Polette, Robert J. Fleck
Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California Digital Geologic Map of the Nevada Test Site and Vicinity, Nye, Lincoln, and Clark Counties, Nevada, and Inyo County, California
This digital geologic map of the Nevada Test Site (NTS) and vicinity, as well as its accompanying digital geophysical maps, are compiled at 1:100,000 scale. The map compilation presents new polygon (geologic map unit contacts), line (fault, fold axis, metamorphic isograd, dike, and caldera wall) and point (structural attitude) vector data for the NTS and vicinity, Nye, Lincoln, and Clark...
Authors
Janet L. Slate, Margaret E. Berry, Peter D. Rowley, Christopher J. Fridrich, Karen S. Morgan, Jeremiah B. Workman, Owen D. Young, Gary L. Dixon, Van S. Williams, Edwin H. McKee, David A. Ponce, Thomas G. Hildenbrand, W. C. Swadley, Scott C. Lundstrom, E. Bartlett Ekren, Richard G. Warren, J. C. Cole, Robert J. Fleck, Marvin A. Lanphere, David A. Sawyer, Scott A. Minor, Daniel J. Grunwald, Randell J. Laczniak, Christopher M. Menges, James C. Yount, Angela S. Jayko
*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