Tectonics and Structure Commons^™

Long Dormancy, Low Slip Rate, And Similar Slip‐Per‐Event For The Emerson Fault, Eastern California Shear Zone, Charles M. Rubin, Kerry Sieh

All Faculty Scholarship for the College of the Sciences

Excavations in a playa along the 1992 rupture of the Emerson fault reveal evidence of two paleoseismic events, with only one large prehistoric rupture in the past 15 millennia. Accelerator mass spectrometer radiocarbon ages of charcoal from playa sediments and from fault‐scarp colluvium directly beneath the playa beds indicate that the last large prehistoric slip event occurred about 9000 ka. Trench‐wall exposures revealed clear evidence of at least one pre‐9 ka rupture at the playa site. The event horizon of this earthquake is between two pedogenic carbonate layers that have radiocarbon ages of 14.8 ka and 24.1 ka, implying that …

Microanalytical Investigations Of Gold-Bearing Rocks From The An Najadi Region In Saudi Arabia, Nazrul I. Khandaker, M. Ahmed, M. M. Hariri, M. A. Garwan, K. R. Khan, M. M. Al-Ohali

Publications and Research

The Proton Induced X-ray Emission technique with a scanning microbeam (micro-PIXE) and Scanning Electron Microscopy (SEM) were employed to study gold-bearing rocks from the An Najadi and adjacent regions situated within the exposed northeastern part of the Arabian Shield. These microanalytical investigations, together with routine petrological and ore microscopic studies, demonstrated the presence of important partitioning of major minerals and trace elements in several samples. These measurements also revealed microstructural features including brecciation within quartz grains and metal concentrations within these fracture-controlled micro-conduits. Results showed promise in terms of using distinctive geochemical signatures for ore body recognition. Of particular interest …

Grand Tour-Part 2: Petrogenesis And Thermal Evolution Of Deep Continental-Crust: The Record From The East Humboldt Range, Nevada, Allen J. Mcgrew, Mark T. Peters

Geology Faculty Publications

The northern part of the East Humboldt Range, Nevada, provides a rare opportunity to explore the petrogenetic environment of deep levels in the middle crust during both large-scale Mesozoic contraction and Cenozoic regional extension. On this segment of the field trip, we will explore evidence bearing on the character of the metamorphic and magmatic history of this terrane, and attempt to link these constraints to the rheology and tectonic evolution of the middle crust during the Mesozoic and Cenozoic.

The Grand Tour Of The Ruby-East Humboldt Metamorphic Core Complex, Northeastern Nevada: Part 1-Introduction & Road Log, Arthur W. Snoke, Keith A. Howard, Allen J. Mcgrew, Bradford R. Burton, Calvin G. Barnes, Mark T. Peters, James E. Wright

Geology Faculty Publications

The purpose of this geological excursion is to provide an overview of the multiphase developmental history of the Ruby Mountains and East Humboldt Range, northeastern Nevada. Although these mountain ranges are commonly cited as a classic example of a Cordilleran metamorphic core complex developed through large-magnitude, mid-Tertiary crustal extension, a preceding polyphase Mesozoic contractional history is also well preserved in the ranges. An early phase of this history involved Late Jurassic two-mica granitic magmatism, high-temperature but relatively low-pressure metamorphism, and polyphase deformation in the central Ruby Mountains. In the northern Ruby Mountains and East Humboldt Range, a Late Cretaceous history …

Paleoseismicity Of The North Branch Of The Newport-Inglewood Fault Zone In Huntington Beach, California, From Cone Penetrometer Test Data, Lisa B. Grant, John T. Waggoner, Thomas K. Rockwell, Carmen Von Stein

Biology, Chemistry, and Environmental Sciences Faculty Articles and Research

Application of cone penetrometer testing (CPT) is a promising method for studying subsurface fault zones in stratified, unconsolidated sediment where trenching is not feasible. Analysis of data from 72 CPTs, spaced 7.5 to 30.0 m apart, and 9 borings indicates that the North Branch fault, the active strand of the Newport-Inglewood fault zone (NIFZ) in Huntington Beach, has generated at least three and most likely five recognizable surface ruptures in the past 11.7 +/- 0.7 ka. Additional smaller earthquakes similar to the M-w 6.4 1933. Long Beach earthquake may also have occurred but would not be recognizable with this method. …

Prolonged History Of Silicic Peralkaline Volcanism In The Eastern Pacific Ocean, Wendy A. Bohrson, Mary R. Reid, Anita L. Grunder, Matthew Heizler, T. Mark Harrison, Jeffrey Lee

All Faculty Scholarship for the College of the Sciences

Socorro Island, Mexico, is an alkaline and peralkaline volcanic island located in the eastern Pacific Ocean on a mid-ocean ridge spreading center that was abandoned at ∼3.5 Ma. Silicic peralkaline rocks comprise up to 80% of the surface of the island, rendering Socorro virtually unique in the Pacific Ocean. Precise, replicate ⁴⁰Ar/³⁹Ar ages of 21 peralkaline trachytes and rhyolites reveal a history of episodic volcanic activity from ∼540 to 370 ka that may have culminated with caldera formation; repose periods between these episodes may have had maximum duration of ∼30 kyr. After up to 200 kyr of …

Study Of Volcanic Sediments By Microbeam-Pixe Technique, Nazrul I. Khandaker, M. Ahmed, M. A. Garwan

Publications and Research

Single mineral grains in a suite of Cretaceous (85–90 Ma) volcanic sedimentary rocks were analyzed using the microbeam-PIXE technique to understand fundamental geological processes responsible for micro-scale variation in elemental composition across mineral zones, twinning, cleavage planes, fractures and grain boundaries. Distributions of major and trace elements show distinct geochemical features indicative of a specific geological setting and a subsequent diagenetic process in these volcanic sediments. Examples of mineral zoning, microstructures of variable chemistry and post-depositional fluid flow are discussed using the data on feldspar group of minerals.

Constraints On Present-Day Basin And Range Deformation From Space Geodesy, Jeffrey Lee, Timothy H. Dixon, Stefano Robaudo, Marith C. Reheis

All Faculty Scholarship for the College of the Sciences

We use new space geodetic data from very long baseline interferometry and satellite laser ranging combined with other geodetic and geologic data to study contemporary deformation in the Basin and Range province of the western United States. Northwest motion of the central Sierra Nevada block relative to stable North America, a measure of integrated Basin and Range deformation, is 12.1±1.2 mm/yr oriented N38°W±5° (one standard error), in agreement with previous geological estimates within uncertainties. This velocity reflects both east-west extension concentrated in the eastern Basin and Range and north-northwest directed right lateral shear concentrated in the western Basin and Range. …

Book Review: Quaternary Geology And Geomorphology Of South America By C. Clapperton, William J. Wayne

Department of Earth and Atmospheric Sciences: Faculty Publications

Dr. Clapperton is to be commended for having taken on the monumental task of a review of the present state of knowledge of the Quaternary of the entire continent of South America. Quaternary Geology and Geomorphology of South America is a massive, interestingly written, but expensive volume that covers exactly what its title suggests. In spite of the paucity of information on many aspects of the Quaternary geology of this continent, which extends from north of the equator nearly to the Antarctic, the author has succeeded in reviewing and synthesizing most of the material that does exist. To do so …

Rapid Uplift And Rotation Of Mylonitic Rocks From Beneath A Detachment Fault: Insights From Potassium Feldspar 40ar/39ar Thermochronology, Northern Snake Range, Nevada, Jeffrey Lee

All Faculty Scholarship for the College of the Sciences

The thermal histories of mylonitic rocks from the footwall of the northern Snake Range decollement (NSRD), Nevada, were calculated using multiple diffusion domain analyses of potassium feldspar Arrhenius data and ⁴⁰Ar/³⁹Ar age spectra in order to characterize the cooling (exhumation) history of these mylonitic rocks and thereby constrain the origin and movement history of the NSRD. The calculated thermal histories, along with reported apatite fission track ages, indicate the three following episodes of rapid cooling (10–55°C/m.y.) related to extensional denudation: (1) middle Eocene (48–41 Ma), (2) late Oligocene (30–26 Ma), and (3) early Miocene (20–16 Ma). The …

Do Microplates In Subduction Zones Leave A Geological Record?, Jeffrey Lee, Joann M. Stock

All Faculty Scholarship for the College of the Sciences

Active microplate boundaries in ocean-continent subduction zones may induce deformation of the overlying plate and spatial or geochemical variations in the volcanic arc. We discuss two modern cases. The first is the South Gorda-Juan de Fuca plate boundary in the Cascadia subduction zone, where there is little or no effect on the overriding plate and the oceanic plate takes up much of the deformation. The second case is the Cocos-Rivera plate boundary in the Middle America trench, where the overlying Colima graben contains substantial deformation in a zone extending from the trench to the volcanic arc and the sub-duction-related volcanism …

The Origin And Evolution Of The Southern Snake Range Decollement, East Central Nevada, Allen J. Mcgrew

Geology Faculty Publications

Regional and local stratigraphic, metamorphic, and structural constraints permit reconstruction of the southern Snake Range extensional deformational system in east central Nevada. The dominant structure of the range, the southern Snake Range décollement (SSRD), operated during Oligocene and Miocene extensional deformation to exhume a footwall of multiply deformed metasedimentary and plutonic rocks. Intrusion of three plutons (∼160 Ma, 79.1 ± 0.5 Ma, and 36 ± 1 Ma, respectively) and development of two cleavages preceded the onset of extensional deformation. Plastic deformation of lower plate metasedimentary rocks accompanied the early phases of regional extension and produced bedding-parallel grain shape foliations and …

Plate Tectonics, Space, Geologic Time, And The Great Plains: A Primer For Non-Geologists, Robert F. Diffendal Jr.

School of Natural Resources: Faculty Publications

For most Americans, "The Great Plains" evokes images of grasslands, dust storms, prairie fires, Native Americans on horseback, cowboys and wheat lands, and perhaps flat valleys crossed by braided rivers carrying a heavy load of sand and gravel, extremes of weather, and a climate typified by an alternation of droughts and wetter periods. Geologists picture such general images, too, but they also see radical changes in the landscape over periods expressed in millions rather than hundreds of years. Geologically speaking, human activities on the Great Plains are too recent to have much of a place in the broad geologic history …

Loma Prieta's Call To Action, Seismic Safety Commission

California Agencies

No abstract provided.

Ua66/8/2 Earthquake Risk Assessment For Warren County, Kentucky, Wku Center For Local Government, Nicholas Crawford, Thomas Tweddell, Shaun Winter, Peter Erlenbach, Amy Huot, Grant Whittle

WKU Archives Records

Earthquake risk assessment report for Bowling Green and Warren County, Kentucky. Include illustrations and maps.

Central Utah Regional Seismotectonic Study, U.S. Deparment Of The Interior, Bureau Of Reclamation

Elusive Documents

This report presents the results of a Bureau of Reclamation seismotectonic

evaluation for dams in the Wasatch Mountains in north-central Utah. The

major objectives of this study were to identify potential earthquake sources

in the region and to estimate MCEs (maximum credible earthquakes) for these

sources. The conclusions presented in this report are based on geologic

mapping, trenching, study of aerial photography, mapping and correlation of

Quaternary deposits, soil profile descriptions and sampling, and analysis of

historic seismicity. The Regional Study area includes an area on the eastern

margin of the Basin and Range province that extends east from the …

Geologic And Tectonic Setting Of The Mark Area, R. S. Detrick, P. J. Fox, N. Schulz, R. Pockalny, L. Kong, Larry A. Mayer, W.B. F. Ryan

Affiliate Scholarship

No abstract provided.

Paleomagnetic Results From Luzon And The Central Philippines, Robert Mccabe, Eichi Kikawa, Jay T. Cole, Ariel J. Malicse, Paul E. Baldauf, Jun Yumul, Jose Almasco

Marine & Environmental Sciences Faculty Articles

Samples were collected from 86 paleomagnetic sites from the islands of Luzon, Marinduque, Mindoro, Panay, Negros, Cebu, and Mindanao in the Philippine Arc. The sampling sites range in age from Pleistocene to Jurassic. Characteristic directions of magnetization of the samples were determined by the use of vector plots. Curie temperature determinations, thin section studies, and hysteresis studies showed that remanence of these samples is carried by fine-grained (pseudo-single domain) magnetite. Positive fold tests from Miocene data from Panay, Jurassic data from Mindoro, and Cretaceous data from Cebu suggest that the magnetization of these regions was acquired prior to folding. Rotations …

Fault Movements And Tectonics Of Eastern Iran: Boundaries Of The Lut Plate, Ali A. Nowroozi, A. Mohajer-Ashjai

OES Faculty Publications

Summary. From 1977 March 21 to 1981 July 28, about 15 earthquakes with M_s ≥6.0 and many earthquakes with M_s≥4.5 have occurred in Iran. The upsurge of seismic activity started following the Khorqu earthquake of 1977 March 21, M,=7.0, south-east of the Fars folded series of Zagros. This shock had a thrust focal mechanism solution indicating the general northward movement of the Arabian plate with respect to the Iranian landmass. It was followed by six major damaging earthquakes in eastern Iran. The earthquakes are associated with extensive faulting which surrounds the Lut plate. (1) The Zarand earthquake …

Chemical Trends In The Ice Springs Basalt, Black Rock Desert, Utah, W. C. Lynch, W. P. Nash

All U.S. Government Documents (Utah Regional Depository)

The Holocene Ice Springs volcanic field of west-central Utah consists of 0.53 km3 of tholeitic basalts erupted as a sequence of nested cinder cones and associated lava flows. Whole rock x-ray fluorescence and atomic absorption analysis of ninety-six samples of known relative age document statistically significant inter- and intra- eruption chemical variations. Elemental trends include increases in Ti, Fe, Ca, P, and Sr and decreases in Si, K, Rb, Ni, Cr, and Zr with decreasing age. Microprobe analyses of microphenocrysts of olivine, plagioclase, and Fe-Ti oxides and of groundmass olivine, plagioclase, and clinopyroxene indicate limited chemical variation between mineral assemblages …

Study Of Earthquake Recurrence Intervals On The Wasatch Fault, Utah: Little Cottonwood Canyon Site, F. H. Swan, Iii, Kathryn L. Hanson, David P. Schwartz, Peter L. Knuepfer, U.S. Geological Survey

All U.S. Government Documents (Utah Regional Depository)

Detailed geologic mapping, topographic profiling, and trenching are being conducted at selected sites along the Wasatch fault zone to measure the cumulative fault displacements in Quaternary strata of various ages and to obtain data regarding the amount of displacement per surface faulting event and the number and recurrence of faulting events that produced the cumulative displacement. These data are used to estimate the frequency of occurrence and magnitude of earthquakes associated with surface faulting along individual segments of the Wasatch fault zone. Investigations have been completed at three sites, the Kaysville, Hobble Creek, and Little Cottonwood Canyon sites. The results …

La Deriva De Los Continentes, Aldemaro Romero Jr.

Publications and Research

No abstract provided.

Stratigraphy And Structure Of The Goajira Peninsula, Northwestern Venezuela And Northeastern Colombia, John F. Rollins

Papers from the University Studies series (University of Nebraska)

The Goajira Peninsula forms the northernmost extension of continental South America (see Fig. 1). Its lobate outer portion, the area of this geologic study, is a mountainous region about 75 kilometers wide at its widest part and juts 150 kilometers northeastward into the Caribbean Sea. Although only about 110 kilometers north of the city of Maracaibo, Venezuela, the Peninsula is isolated and little known. Only a narrow coastal strip lies in Venezuela; the remainder is in Colombia; but the Peninsula is largely a desert wasteland not extensively entered by people other than its own sparse Indian population. Its remoteness has …

Shelf Observations - Hydrography Cruise Of August 21-26, 1962, Maynard M. Nichols, Robert C. Barnes

Reports

No abstract provided.

Ua94/6/2/14 Physiography Notebook, Annie Reis

Student/Alumni Personal Papers

Physiography notebook kept by student Annie Reis in 1910. Notebook includes notes and drawings related to physical geography such as solar systems, rivers, faults, weather and glaciers.