Publications
Publications from the staff of the Geology, Minerals, Energy, and Geophysics Science Center
Filter Total Items: 2354
Benthic foraminiferal biotic events related to the Paleocene–Eocene Thermal Maximum along the California Margin
The faunal expression of the Paleocene-Eocene Thermal Maximum (PETM) is well documented in deep-sea sediments. However, few studies have examined continental margin sections, especially active margins. The Moreno and Lodo formations, Central California, were deposited along the eastern margin of a north-south trending forearc basin on the convergent margin of California during the Cretaceous throu
Authors
Kristin McDougall-Reid, Cedric M John
Petrology of volcanic rocks associated with silver-gold (Ag-Au) epithermal deposits in the Tonopah, Divide, and Goldfield Mining Districts, Nevada
Miocene calc-alkaline volcanic rocks, part of the southern segment of the ancestral Cascades magmatic arc, are spatially, temporally, and likely genetically associated with precious metal epithermal deposits in the Tonopah, Divide, and Goldfield Districts of west-central Nevada. In the Tonopah mining district, volcanic rocks include the Mizpah Trachyte, Fraction Tuff, and Oddie Rhyolite; in the Di
Authors
Edward A. du Bray, David John, Joseph Colgan, Peter G. Vikre, Michael A. Cosca, Leah E. Morgan
Variability in shelf sedimentation in response to fluvial sediment supply and coastal erosion over the past 1,000 years in Monterey Bay, CA, United States
Continental shelf environments are uniquely situated to capture some of the most dynamic processes on Earth including climatic variability and anthropogenic modifications to coastal systems. Understanding how these processes have affected sediment delivery and accumulation on the shelf in the past may provide insight into potential changes in the future. To address this, we investigated shelf sedi
Authors
Joseph Carlin, Jason A. Addison, Amy Wagner, Valerie Evelyn Schwartz, Jamie Hayward, Victoria Severin
Relaxation response of critically stressed macroscale surficial rock sheets
Rock environments both underground and on Earth’s surface show indications of energetic macroscale fracture. In tunnels and excavations, these manifest as rockbursts—energetic explosions of rock that can damage engineering projects, and may pose ongoing financial and safety risk as rock stresses adjust during post-failure relaxation. In natural settings at the surface, evidence for rockbursts exis
Authors
Brian D. Collins, Greg M. Stock, Martha-Cary Eppes
Fault initiation in serpentinite
Serpentinite fault rheology is fundamental to tectonic and earthquake processes, yet links between deformation textures and strength evolution during fault initiation are poorly constrained. Here I present field and petrographic microstructural observations of unsheared and sheared serpentinite that demonstrate a progression of fault development. I compliment observations with a clast size distrib
Authors
Benjamin Melosh
Strike-slip fault interactions at Ivanpah Valley, California and Nevada
Ivanpah Valley is flanked by high mountain ranges, and represents one of the most imposing valleys of the eastern Mojave Desert. Its sinuous shape implies a complex origin as does the fact that it is not bordered by prominent range-front normal faults like valleys of the Basin and Range Province. In Addition, its deepest sedimentary basin is restricted to a small part of the valley near Nipton tha
Authors
David M. Miller, Victoria E. Langenheim, Kevin Denton, David A. Ponce
Distributed fault slip in the eastern California shear zone: Adding pieces to the puzzle near Barstow, California
We investigate the dextral Lockhart and Mt. General faults, which are among four active structures in the northwestern portion of the eastern California shear zone (ECSZ). Early mapping depicts the Lockhart and Mt. General faults as discontinuous fault traces that continue northwest of the Lenwood Fault. Recent work indicates that the Lenwood Fault slips at ~0.2-1.0 mm/yr over the past ~8 ka and 0
Authors
Elizabeth K. Haddon, David M. Miller, Victoria Langenheim, Shannon A. Mahan
Geology and paleontology of the late Miocene Wilson Grove Formation at Bloomfield Quarry, Sonoma County, California
An extensive fauna of at least 77 taxa is reported from the basal Wilson Grove Formation in a small quarry just north of the town of Bloomfield, Sonoma County, California. The fauna represents intertidal to shallow subtidal water depths and water temperatures interpreted from the fauna, consistent with the latitude of the fossil locality (37° north) during the late Miocene. The fauna from Bloomfie
Authors
Charles L. Powell, Robert W. Boessenecker, N. Adam Smith, Robert J. Fleck, Sandra J. Carlson, James R. Allen, Douglas J. Long, Andrei M. Sarna-Wojcicki, Raj B. Guruswami-Naidu
Pleistocene hydrothermal activity on Brokeoff volcano and in the Maidu volcanic center, Lassen Peak area, northeast California: Evolution of magmatic-hydrothermal systems on stratovolcanoes
Partially eroded stratovolcanoes worldwide, notably Mounts Rainier and Adams in the Cascades and several volcanoes in Japan, record episodic periods of eruption and geothermal activity that produce zones of hydrothermal alteration. The partly eroded core of late Pleistocene Brokeoff volcano on the south side of Lassen Peak exposes the upper 1 km of multiple ancient (ca. 410–300 ka) magmatic-hydrot
Authors
David John, Robert G. Lee, George N. Breit, John H. Dilles, Andrew T. Calvert, L. J. Patrick Muffler, Michael A. Clynne
Comment on “Particle fluxes in groundwater change subsurface rock chemistry over geologic time”
Over the last decade, studies at the Shale Hills Critical Zone Observatory (Shale Hills) have greatly expanded knowledge of weathering in previously understudied, shale-mantled terrains, as well as Earth's Critical Zone as a whole. Among the many discoveries made was the importance of redistribution and losses of micron-sized particles during development of shale-derived soils. A geochemical finge
Authors
Carleton R. Bern, Tiffany Yesavage
Rate of magma supply beneath Mammoth Mountain, California based on helium isotopes and CO2 emissions
Mammoth Mountain, California, has exhibited unrest over the past ~30 years, characterized by seismicity over a broad range of depths, elevated 3He/4He ratios in fumarolic gas, and large-scale diffuse CO2 emissions. This activity has been attributed to magmatic intrusion, but minimal ground deformation and the presence of a shallow crustal gas reservoir beneath Mammoth Mountain pose a challenge for
Authors
Jennifer L. Lewicki, William C. Evans, Emily Montgomery-Brown, Margaret T. Mangan, John King, Andrew Hunt
U-Pb geochronology of tin deposits associated with the Cornubian Batholith of southwest England: Direct dating of cassiterite by in situ LA-ICPMS
The Cornwall and Devon vein- and greisen-type copper and tin deposits of southwest England are spatially and genetically related to shallow-seated granitic intrusions. These late Variscan intrusions, collectively known as the Cornubian Batholith, extend over 200 km and form a continuous granitic spine from the Isles of Scilly Granite in the west to the Dartmoor Granite in the east. The granitic pl
Authors
Richard J. Moscati, Leonid A. Neymark