Controls on fault damage zone width, structure, and symmetry in the Bandelier Tuff, New Mexico

2010 ◽  
Vol 32 (6) ◽  
pp. 766-780 ◽  
Author(s):  
Paul R. Riley ◽  
Laurel B. Goodwin ◽  
Claudia J. Lewis
1972 ◽  
Vol 2 (4) ◽  
pp. 554-578 ◽  
Author(s):  
Glen A. Izett ◽  
Ray E. Wilcox ◽  
Glenn A. Borchardt

A rhyolitic volcanic ash bed about 0.3 m thick is exposed in a roadcut along Texas Highway 193 near Mount Blanco in the upper part of a sequence of Pleistocene sedimentary deposits at the type locality of the Blanco Formation, about 59 km northeast of Lubbock, Texas. This ash, here named informally the Guaje ash bed, has chemical and petrographic characteristics closely resembling those of the rhyolitic air-fall tephra (Guaje Pumice Bed) that directly underlies ash flows of Pleistocene age in the Jemez Mountains of northern New Mexico. The Guaje Pumice Bed and the ash flows belong to the Otowi Member of the Bandelier Tuff. Properties common to the Guaje ash bed and the Guaje Pumice Bed include: refractive index of glass, 1.497–1.498; microphenocrysts of quartz, sanidine (Or42–44), ferrohedenbergite (Fe51Ca42Mg7), chevkinite, allanite, zircon, and magnetite. Chemical composition of the glass of the Guaje ash bed matches that of the Guaje Pumice Bed for all major elements except K and Na and for trace elements determined by standard chemical analyses, atomic absorption, and neutron activation. Paleomagnetic measurements indicate that the ash has reverse depositional remanent magnetization. Glass shards of the ash have a fission-track age of about 1.4 ± 0.2 m. y. Sanidine from the Guaje Pumice Bed and its genetically related ash-flow sheet in the Jemez Mountains was K-Ar dated at about 1.4 m. y. by R. R. Doell and his colleagues in 1968. Correlation of the Guaje ash bed with the radiometrically dated Guaje Pumice Bed establishes a minimum age of about 1.4 m. y. for the Blanco Formation.


2012 ◽  
Vol 35 ◽  
pp. 64-77 ◽  
Author(s):  
Hideo Takagi ◽  
Kazuhiro Takahashi ◽  
Koji Shimada ◽  
Kosuke Tsutsui ◽  
Reiko Miura ◽  
...  

2001 ◽  
Vol 34 (4) ◽  
pp. 1643
Author(s):  
A. Kostakioti ◽  
P. Xypolias ◽  
S. Kokkalas ◽  
T. Doutsos

In this study, we present structural, fracture orientation and fracture density (FD) data in order toquantify the deformation pattern of a damage zone that form around the slip plane of a large scalethrust fault which is located on the Ionian zone (External Hellenides) in northwestern Greece. Structuralanalysis showed at least two major deformation stages as indicated by the presence of refolding,backthrusting and break-back faulting. The fracture orientation analysis revealed three mainfracture systems, a dominant conjugate fracture system which is perpendicular to the transport direction(NW-to NNW trending sets), a conjugate fracture system trending parallel to the transport direction(ENE-trending conjugate sets) and a third diagonal conjugate fracture system (WNW andNNE trending sets). Resulting fracture density-distance diagrams display a decrease of total fracturedensity away from the studied fault, which is largely heterogeneous and irregular on both footwalland hanging wall. The conjugate fracture system trending perpendicular to the transport directionhas the dominant contribution to the accumulation of total fracture density. Based on theseresults we suggest that the observed heterogeneous and irregular distribution of fracture densityfashioned during the second deformation stage and is attributed to the formation of backthrusts andbreak-back thrust faults.


2021 ◽  
Vol 84 (1) ◽  
Author(s):  
Megan A. Saalfeld ◽  
M. L. Myers ◽  
R. deGraffenried ◽  
T. Shea ◽  
C. M. Waelkens

Geophysics ◽  
1997 ◽  
Vol 62 (2) ◽  
pp. 451-465 ◽  
Author(s):  
Philip E. Wannamaker

An extensive tensor controlled‐source audiomagnetotelluric (CSAMT) survey has been carried out over the Sulphur Springs geothermal area, Valles Caldera, New Mexico. Forty‐five sites were acquired using two crossed transmitter bipoles placed approximately 13 km south of the center of the survey. The soundings in the Sulphur Springs area were arranged in four profiles to cross major structural features. To curtail spatial aliasing, the electric bipoles along each profile were deployed contiguously. The frequency range of acquisition was 4096 Hz down to 1 Hz for the central line, but only down to 4 Hz for most sites of the other lines. CSAMT and magnetotelluric (MT) data taken outside Valles Caldera were constrained by drill logs and imply resistive Bandelier Tuff, underlain by conductive Paleozoic sediments, and further underlain by resistive, primarily Precambrian crystalline rocks. Model cross‐sections within the caldera were derived using 2-D parameterized inversion constrained by drilling, with layered‐earth inversion for starting models. Southeast of the Sulphur Creek fault, the upper 200 m of the section are of relatively low resistivity and correspond to unconsolidated land‐slide and debris flows. The Bandelier Tuff below exhibits higher but variable resistivities because of alteration controlled by local faulting. Beneath the Bandelier Tuff, the Paleozoic sedimentary layer is only moderately less resistive than it is outside the caldera, with the lowest values occuring northwest of Sulphur Creek. Its low resistivity per se does not necessarily represent a hydrothermal aquifer. The Sulphur Creek fault appears to be a locus of substantial change in structural relief; up‐throw of stratigraphy and basement to its west appears to be about 400–500 m. A major normal fault down to the southeast is located under the topographic expression of Freelove Canyon, which is up to 1 km farther southeast than suggested by previous geologic sections. High resistivities possibly corresponding to a vapor zone in the upper 500 m near VC-2B and VC-2A are not consistent with the CSAMT data.


Author(s):  
L.M. Houser ◽  
A.K. Ault ◽  
D.L. Newell ◽  
J.P. Evans ◽  
F‐A. Shen ◽  
...  

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