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
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
*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