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Despite years of research on low-angle detachments, much about them remains enigmatic. This thesis addresses some of the uncertainty regarding two particular detachments, the Mormon Peak detachment in Nevada and the Heart Mountain detachment in Wyoming and Montana. Constraints on the geometry and kinematics of emplacement of the Mormon Peak detachment are provided by detailed geologic mapping of the Meadow Valley Mountains, along with an analysis of structural data within the allochthon in the Mormon Mountains. Identifiable structures well suited to constrain the kinematics of the detachment include a newly mapped, Sevier-age monoclinal flexure in the hanging wall of the detachment. This flexure, including the syncline at its base and the anticline at its top, can be readily matched to the base and top of the frontal Sevier thrust ramp, which is exposed in the footwall of the detachment to the east in the Mormon Mountains and Tule Springs Hills. The ~12 km of offset of these structural markers precludes the radial sliding hypothesis for emplacement of the allochthon. The role of fluids in the slip along faults is a widely investigated topic, but the use of carbonate clumped-isotope thermometry to investigate these fluids is new. Faults rocks from within ~1 m of the Mormon Peak detachment, including veins, breccias, gouges, and host rocks, were analyzed for carbon, oxygen, and clumped-isotope measurements. The data indicate that much of the carbonate breccia and gouge material along the detachment is comminuted host rock, as expected. Measurements in vein material indicate that the fluid system is dominated by meteoric water, whose temperature indicates circulation to substantial depths (c. 4 km) in the upper crust near the fault zone. Slip along the subhorizontal Heart Mountain detachment is particularly enigmatic, and many different mechanisms for failure have been proposed, predominantly involving catastrophic failure. Textural evidence of multiple slip events is abundant, and include multiple brecciation events and cross-cutting clastic dikes. Footwall deformation is observed in numerous exposures of the detachment. Stylolitic surfaces and alteration textures within and around “banded grains” previously interpreted to be an indicator of high-temperature fluidization along the fault suggest their formation instead via low-temperature dissolution and alteration processes. There is abundant textural evidence of the significant role of fluids along the detachment via pressure solution. The process of pressure solution creep may be responsible for enabling multiple slip events on the low-angle detachment, via a local rotation of the stress field. Clumped-isotope thermometry of fault rocks associated with the Heart Mountain detachment indicates that despite its location on the flanks of a volcano that was active during slip, the majority of carbonate along the Heart Mountain detachment does not record significant heating above ambient temperatures (c. 40-70°C). Instead, cold meteoric fluids infiltrated the detachment breccia, and carbonate precipitated under ambient temperatures controlled by structural depth. Locally, fault gouge does preserve hot temperatures (>200°C), as is observed in both the Mormon Peak detachment and Heart Mountain detachment areas. Samples with very hot temperatures attributable to frictional shear heating are present but rare. They appear to be best preserved in hanging wall structures related to the detachment, rather than along the main detachment. Evidence is presented for the prevalence of relatively cold, meteoric fluids along both shallow crustal detachments studied, and for protracted histories of slip along both detachments. Frictional heating is evident from both areas, but is a minor component of the preserved fault rock record. Pressure solution is evident, and might play a role in initiating slip on the Heart Mountain fault, and possibly other low-angle detachments., Cite this record as: Swanson, E. M. G. (2015). Geologic Map of Meadow Valley Mountains, Nevada: Supplement 1 from "Structural and Clumped-Isotope Constraints on the Mechanisms of Displacement Along Low-Angle Detachments" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1084 or choose a different citation style. Download Citation , Unique Views: 5 Unique Downloads: 1 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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This thesis describes the active structures of Myanmar and its surrounding regions, and the earthquake geology of the major active structures. Such investigation is needed urgently for this rapidly developing country that has suffered from destructive earthquakes in its long history. To archive a better understanding of the regional active tectonics and the seismic potential in the future, we utilized a global digital elevation model and optical satellite imagery to describe geomorphologic evidence for the principal neotectonic features of the western half of the Southeast Asia mainland. Our investigation shows three distinct active structural systems that accommodate the oblique convergence between the Indian plate and Southeast Asia and the extrusion of Asian territory around the eastern syntaxis of the Himalayan mountain range. Each of these active deformation belts can be further separated into several neotectonic domains, in which structures show distinctive active behaviors from one to another. In order to better understand the behaviors of active structures, we focused on the active characteristics of the right-lateral Sagaing fault and the oblique subducting northern Sunda megathrust in the second part of this thesis. The detailed geomorphic investigations along these two major plate-interface faults revealed the recent slip behavior of these structures, and plausible recurrence intervals of major seismic events. We also documented the ground deformation of the 2011 Tarlay earthquake in remote eastern Myanmar from remote sensing datasets and post-earthquake field investigations. The field observation and the remote sensing measurements of surface ruptures of the Tarlay earthquake are the first study of this kind in the Myanmar region., Cite this record as: Wang, Y. (2013). Neotectonic map of Myanmar (Burma): Supplement 1 from "Earthquake geology of Myanmar" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1067 or choose a different citation style. Download Citation , Unique Views: 11 Unique Downloads: 2 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swing up to 90˚ westward, taking on an east-west trend; 3) western zone rocks are truncated by eastern zone rocks along the proto-Kern Canyon fault, a Late Cretaceous oblique ductile thrust; and 4) fragments of shallow-level eastern SNB affinity rocks overlie deeper-level western zone rocks and subjacent subduction accretion assemblages (Rand, San Emigdio, and Sierra de Salinas schists) along a major Late Cretaceous detachment system. Integration of these observations with new and existing data reveals a temporal relationship between schist unroofing and upper crustal extension and rotation. I present a model whereby Late Cretaceous shallow subduction and subsequent trench-directed channelized extrusion of the schist triggered gravitational collapse of the overlying crustal column. This overarching model is based on several investigations summarized below. Thermobarometry, thermodynamic modelling and garnet diffusion modelling are presented that elucidate the tectonics of subduction and eduction of the San Emigdio Schist. I document an upsection increase in peak temperature (i.e. inverted metamorphism), from 590 to 700 °C, peak pressures ranging from 8.5 to 11.1 kbar, limited partial melting, microstructural evidence for large seismic events, rapid cooling (825–380 °C/Myr) from peak conditions and an “out and back” P–T path. Progressive cooling and tectonic underplating beneath an initially hot upper plate following the onset of shallow subduction provide a working hypothesis explaining high temperatures, inverted metamorphism, partial melting, and the observed P–T trajectory calculated from the San Emigdio body. New geologic mapping and microstructural analysis indicate that the schist was transported to the SSW during structural ascent along a mylonitic contact (the Rand fault and Salinas shear zone) with upper plate assemblages. Crystallographic preferred orientation patterns in deformed quartzites reveal a decreasing simple shear component with increasing structural depth, suggesting a pure shear-dominated westward flow within the subduction channel and localized simple shear along the upper channel boundary. The resulting flow type within the channel is that of general shear extrusion. Structural, thermobarometric, U-Pb geochronologic, and geochemical data from plutonic and metamorphic framework assemblages in the southern SNB also suggest SSW-directed transport of upper plate(s) along a major Late Cretaceous detachment system. The timing and pattern of regional dispersion of crustal fragments in the southern SNB is most consistent with Late Cretaceous collapse above the underplated schist. These observations imply a high degree of coupling between the shallow and deep crust during high magnitude extension. Zircon (U-Th)/He data presented herein reveal a rapid cooling event at 77 ± 5 Ma, probably reflecting the time of large magnitude detachment faulting. A comparison of this dataset with existing apatite (U-Th)/He thermochronometry suggests that the development of modern landscape and arrangement of tectonic elements in southern California was greatly preconditioned by Late Cretaceous tectonics. Finally, detrital and metamorphic zircon of the structurally highest and earliest subducted portions of the San Emigdio Schist constrain the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower plate schist and upper plate batholithic assemblages reveal a δ18O shift of ~ 1.5‰ between igneous (~ 5.5‰) and metamorphic (~ 7‰) domains. These results, taken with previous zircon and whole-rock δ18O measurements, provide evidence for massive devolatilization of the San Emigdio Schist and fluid traversal of upper plate batholithic assemblages, thereby altering the isotopic composition of overlying material. Furthermore, the timing of fluid-rock interaction in the southwestern SNB is coincident with eastward arc migration and an associated pulse of voluminous magmatism. I posit that during flattening of the Farallon slab the schist was rapidly delivered to the magmatic source, where ensuing devolatilization triggered a magmatic flare-up in the southeastern SNB. This short-lived (less than 15 Myr) high-flux event was followed by the termination of arc magmatism as the shallow subduction zone approached thermal equilibrium., Cite this record as: Chapman, A. D. (2012). Geologic map of the San Emigdio Mountains: Supplement 1 from "Late Cretaceous gravitational collapse of the southern Sierra Nevada batholith and adjacent areas above underplated schists, southern California" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1063 or choose a different citation style. Download Citation ,
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The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swing up to 90˚ westward, taking on an east-west trend; 3) western zone rocks are truncated by eastern zone rocks along the proto-Kern Canyon fault, a Late Cretaceous oblique ductile thrust; and 4) fragments of shallow-level eastern SNB affinity rocks overlie deeper-level western zone rocks and subjacent subduction accretion assemblages (Rand, San Emigdio, and Sierra de Salinas schists) along a major Late Cretaceous detachment system. Integration of these observations with new and existing data reveals a temporal relationship between schist unroofing and upper crustal extension and rotation. I present a model whereby Late Cretaceous shallow subduction and subsequent trench-directed channelized extrusion of the schist triggered gravitational collapse of the overlying crustal column. This overarching model is based on several investigations summarized below. Thermobarometry, thermodynamic modelling and garnet diffusion modelling are presented that elucidate the tectonics of subduction and eduction of the San Emigdio Schist. I document an upsection increase in peak temperature (i.e. inverted metamorphism), from 590 to 700 °C, peak pressures ranging from 8.5 to 11.1 kbar, limited partial melting, microstructural evidence for large seismic events, rapid cooling (825–380 °C/Myr) from peak conditions and an “out and back” P–T path. Progressive cooling and tectonic underplating beneath an initially hot upper plate following the onset of shallow subduction provide a working hypothesis explaining high temperatures, inverted metamorphism, partial melting, and the observed P–T trajectory calculated from the San Emigdio body. New geologic mapping and microstructural analysis indicate that the schist was transported to the SSW during structural ascent along a mylonitic contact (the Rand fault and Salinas shear zone) with upper plate assemblages. Crystallographic preferred orientation patterns in deformed quartzites reveal a decreasing simple shear component with increasing structural depth, suggesting a pure shear-dominated westward flow within the subduction channel and localized simple shear along the upper channel boundary. The resulting flow type within the channel is that of general shear extrusion. Structural, thermobarometric, U-Pb geochronologic, and geochemical data from plutonic and metamorphic framework assemblages in the southern SNB also suggest SSW-directed transport of upper plate(s) along a major Late Cretaceous detachment system. The timing and pattern of regional dispersion of crustal fragments in the southern SNB is most consistent with Late Cretaceous collapse above the underplated schist. These observations imply a high degree of coupling between the shallow and deep crust during high magnitude extension. Zircon (U-Th)/He data presented herein reveal a rapid cooling event at 77 ± 5 Ma, probably reflecting the time of large magnitude detachment faulting. A comparison of this dataset with existing apatite (U-Th)/He thermochronometry suggests that the development of modern landscape and arrangement of tectonic elements in southern California was greatly preconditioned by Late Cretaceous tectonics. Finally, detrital and metamorphic zircon of the structurally highest and earliest subducted portions of the San Emigdio Schist constrain the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower plate schist and upper plate batholithic assemblages reveal a δ18O shift of ~ 1.5‰ between igneous (~ 5.5‰) and metamorphic (~ 7‰) domains. These results, taken with previous zircon and whole-rock δ18O measurements, provide evidence for massive devolatilization of the San Emigdio Schist and fluid traversal of upper plate batholithic assemblages, thereby altering the isotopic composition of overlying material. Furthermore, the timing of fluid-rock interaction in the southwestern SNB is coincident with eastward arc migration and an associated pulse of voluminous magmatism. I posit that during flattening of the Farallon slab the schist was rapidly delivered to the magmatic source, where ensuing devolatilization triggered a magmatic flare-up in the southeastern SNB. This short-lived (less than 15 Myr) high-flux event was followed by the termination of arc magmatism as the shallow subduction zone approached thermal equilibrium., Cite this record as: Chapman, A. D. (2012). Color contour map showing regional variations in compiled U-Pb zircon ages from plutonic rocks of the SNB, Salinian block, and Mojave Desert draped over a DEM: Supplement 2 from "Late Cretaceous gravitational collapse of the southern Sierra Nevada batholith and adjacent areas above underplated schists, southern California" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1064 or choose a different citation style. Download Citation , Unique Views: 4 Unique Downloads: 0 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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The greater Sierra Nevada batholith (SNB) is an ~ 600 km long NNW-trending composite arc assemblage consisting of a myriad of plutons exhibiting a distinct transverse zonation in structural, petrologic, geochronologic, and isotopic patterns. However, south of 35.5 °N: 1) the depth of exposure increases markedly; 2) primary zonation patterns swing up to 90˚ westward, taking on an east-west trend; 3) western zone rocks are truncated by eastern zone rocks along the proto-Kern Canyon fault, a Late Cretaceous oblique ductile thrust; and 4) fragments of shallow-level eastern SNB affinity rocks overlie deeper-level western zone rocks and subjacent subduction accretion assemblages (Rand, San Emigdio, and Sierra de Salinas schists) along a major Late Cretaceous detachment system. Integration of these observations with new and existing data reveals a temporal relationship between schist unroofing and upper crustal extension and rotation. I present a model whereby Late Cretaceous shallow subduction and subsequent trench-directed channelized extrusion of the schist triggered gravitational collapse of the overlying crustal column. This overarching model is based on several investigations summarized below. Thermobarometry, thermodynamic modelling and garnet diffusion modelling are presented that elucidate the tectonics of subduction and eduction of the San Emigdio Schist. I document an upsection increase in peak temperature (i.e. inverted metamorphism), from 590 to 700 °C, peak pressures ranging from 8.5 to 11.1 kbar, limited partial melting, microstructural evidence for large seismic events, rapid cooling (825–380 °C/Myr) from peak conditions and an “out and back” P–T path. Progressive cooling and tectonic underplating beneath an initially hot upper plate following the onset of shallow subduction provide a working hypothesis explaining high temperatures, inverted metamorphism, partial melting, and the observed P–T trajectory calculated from the San Emigdio body. New geologic mapping and microstructural analysis indicate that the schist was transported to the SSW during structural ascent along a mylonitic contact (the Rand fault and Salinas shear zone) with upper plate assemblages. Crystallographic preferred orientation patterns in deformed quartzites reveal a decreasing simple shear component with increasing structural depth, suggesting a pure shear-dominated westward flow within the subduction channel and localized simple shear along the upper channel boundary. The resulting flow type within the channel is that of general shear extrusion. Structural, thermobarometric, U-Pb geochronologic, and geochemical data from plutonic and metamorphic framework assemblages in the southern SNB also suggest SSW-directed transport of upper plate(s) along a major Late Cretaceous detachment system. The timing and pattern of regional dispersion of crustal fragments in the southern SNB is most consistent with Late Cretaceous collapse above the underplated schist. These observations imply a high degree of coupling between the shallow and deep crust during high magnitude extension. Zircon (U-Th)/He data presented herein reveal a rapid cooling event at 77 ± 5 Ma, probably reflecting the time of large magnitude detachment faulting. A comparison of this dataset with existing apatite (U-Th)/He thermochronometry suggests that the development of modern landscape and arrangement of tectonic elements in southern California was greatly preconditioned by Late Cretaceous tectonics. Finally, detrital and metamorphic zircon of the structurally highest and earliest subducted portions of the San Emigdio Schist constrain the depositional age to between ca. 102 and 98 Ma. Zircon oxygen isotope data from both lower plate schist and upper plate batholithic assemblages reveal a δ18O shift of ~ 1.5‰ between igneous (~ 5.5‰) and metamorphic (~ 7‰) domains. These results, taken with previous zircon and whole-rock δ18O measurements, provide evidence for massive devolatilization of the San Emigdio Schist and fluid traversal of upper plate batholithic assemblages, thereby altering the isotopic composition of overlying material. Furthermore, the timing of fluid-rock interaction in the southwestern SNB is coincident with eastward arc migration and an associated pulse of voluminous magmatism. I posit that during flattening of the Farallon slab the schist was rapidly delivered to the magmatic source, where ensuing devolatilization triggered a magmatic flare-up in the southeastern SNB. This short-lived (less than 15 Myr) high-flux event was followed by the termination of arc magmatism as the shallow subduction zone approached thermal equilibrium., Cite this record as: Chapman, A. D. (2012). Color contour map showing regional variations in compiled Sr i ratios from plutonic rocks of the SNB, Salinian block, and Mojave Desert draped over a DEM: Supplement 3 from "Late Cretaceous gravitational collapse of the southern Sierra Nevada batholith and adjacent areas above underplated schists, southern California" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1065 or choose a different citation style. Download Citation , Unique Views: 3 Unique Downloads: 1 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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Results from field mapping and analyses of structural and petrochemical data from the southern Sierra Nevada batholith are presented to offer insight into the development of a major intra-arc fault system. The Kern Canyon fault system comprises an early ductile shear zone overprinted in its northern and central segments by a younger, recently active brittle fault. The divergence of these two faults at their middle latitudes poses a complex puzzle with regard to the physical and temporal evolution of deformation in the southern Sierra. Faulting began with ductile thrusting (the Proto-Kern Canyon fault zone) during emplacement of granitic plutons in the central to eastern part of the batholith at ca. 95 Ma. Early thrusting resulted in mismatched levels of pluton emplacement depths across the fault, truncation of significant regional geochemical markers in the batholith, and exhumation of the deepest level of the batholith in its southernmost region. Early ductile thrusting gave way to dextral strike-slip shearing by ca. 90 Ma. The youngest plutons in the batholith, emplaced along the fault between 90 and 80 Ma, are north-south elongate and reflect the dextral transpressional setting into which they were emplaced and deformed. Metamorphic country rocks were also highly sheared along the fault, and paleostress estimates from these deformed rocks suggest stresses along the middle segment of the Proto-Kern Canyon fault were 20–40 MPa, while strain rates were as high as 10-12 s-1 (comparable with other ductile faults). Strain studies and aspect ratios of igneous and metamorphic rocks strung out along the shear zone suggest ductile dextral displacement was 5–15 km. While ductile shearing ceased in the southern part of the batholith by ca. 85 Ma, it continued along the middle and northern segments of the Proto-Kern Canyon fault until ca. 80 Ma, when brittle deformation took over. This chronology suggests that the modern Kern Canyon fault, which shows ample evidence of activity into at least Quaternary time, initiated as a brittle structure in the southwestern part of the batholith, perhaps as early as 85 Ma, and shunted into the ductile shear zone at its middle latitudes ca. 5 Myrs later., Cite this record as: Nadin, E. S. (2007). Geologic map of metamorphic pendant rocks and their bounding igneous intrusions, Walker Basin to Durrwood Creek, Kern County, Sierra Nevada, CA: Supplement 1 from "Structure and history of the Kern Canyon fault system, southern Sierra Nevada, California" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1045 or choose a different citation style. Download Citation , Unique Views: 11 Unique Downloads: 1 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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Visible, near infrared, short-wave infrared, and thermal infrared multi-channel remote sensing data, MODIS-ASTER (MASTER), are used to extract geologic information from two volcanic regions in Baja California, Mexico: Tres Virgenes-La Reforma Volcanic Region and the volcanic island of Isla San Luis. The visible and near infrared and short-wave infrared data were atmospherically corrected and classified. The resulting classification roughly delineates surfaces that vary in their secondary minerals. Attempts to identify these minerals using ENVI's Spectral Analyst(TM) were moderately successful. The analysis of the thermal infrared data utilizes the shift to longer wavelengths in the Reststrahlen band as the mineralogy changes from felsic to mafic to translate the data into values of weight percent SiO2. The results indicate that the general approach tends to underestimate the weight percent SiO2 in the image. This discrepancy is removed with a "site calibration," which provides good results in the calculated weight percent SiO2, with errors of a few percent. However, errors become larger with rugged topography or low solar angle at the time of image acquisition. Analysis of bathymetric data around Isla San Luis, and consideration of the island's alignment with the Ballenas transform fault zone to the south and volcanic seamounts nearby, suggest Isla San Luis is potentially volcanically active and could be the product of a "leaky" transform fault. The results from the image analysis in the Tres Virgenes-La Reforma Volcanic Region show the La Reforma and El Aguajito volcanic centers to be bimodal in composition and verify the most recent volcanism in the Tres Virgenes region to be basaltic-andesite. The results of fieldwork and image analysis indicate that the volcanic products of the central dome of La Reforma are likely a sequence of welded ash flow tuffs and lavas of varied composition, evidence of its origin as a caldera., Cite this record as: Dmochowski, J. E. (2005). Twenty-eight images of MASTER VNIR-SWIR data from the Tres Virgenes-La Reforma region, Baja California, Mexico: Supplement 1 from "Application of MODIS-ASTER (Master) simulator data to geological mapping of young volcanic regions in Baja California, Mexico" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1051 or choose a different citation style. Download Citation , Unique Views: 2 Unique Downloads: 1 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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Visible, near infrared, short-wave infrared, and thermal infrared multi-channel remote sensing data, MODIS-ASTER (MASTER), are used to extract geologic information from two volcanic regions in Baja California, Mexico: Tres Virgenes-La Reforma Volcanic Region and the volcanic island of Isla San Luis. The visible and near infrared and short-wave infrared data were atmospherically corrected and classified. The resulting classification roughly delineates surfaces that vary in their secondary minerals. Attempts to identify these minerals using ENVI's Spectral Analyst(TM) were moderately successful. The analysis of the thermal infrared data utilizes the shift to longer wavelengths in the Reststrahlen band as the mineralogy changes from felsic to mafic to translate the data into values of weight percent SiO2. The results indicate that the general approach tends to underestimate the weight percent SiO2 in the image. This discrepancy is removed with a "site calibration," which provides good results in the calculated weight percent SiO2, with errors of a few percent. However, errors become larger with rugged topography or low solar angle at the time of image acquisition. Analysis of bathymetric data around Isla San Luis, and consideration of the island's alignment with the Ballenas transform fault zone to the south and volcanic seamounts nearby, suggest Isla San Luis is potentially volcanically active and could be the product of a "leaky" transform fault. The results from the image analysis in the Tres Virgenes-La Reforma Volcanic Region show the La Reforma and El Aguajito volcanic centers to be bimodal in composition and verify the most recent volcanism in the Tres Virgenes region to be basaltic-andesite. The results of fieldwork and image analysis indicate that the volcanic products of the central dome of La Reforma are likely a sequence of welded ash flow tuffs and lavas of varied composition, evidence of its origin as a caldera., Cite this record as: Dmochowski, J. E. (2005). Twenty-eight images of MASTER TIR data from the Tres Virgenes-La Reforma region, Baja California, Mexico: Supplement 2 from "Application of MODIS-ASTER (Master) simulator data to geological mapping of young volcanic regions in Baja California, Mexico" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1052 or choose a different citation style. Download Citation , Unique Views: 4 Unique Downloads: 0 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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Under the Sumatran plate boundary the Australian-Indian plate is subducting at about 60 mm/yr in the direction N110E. The oblique convergence is partitioned into trench-parallel slip?accommodated largely by the Sumatran fault zone and trench-perpendicular slip?accommodated by the subduction zone. Our detailed map of the Sumatran fault zone (SFZ) shows that the Sumatran fault is highly segmented. The influence of these fault segmentations on historical seismic source dimensions suggests that the dimensions of future events will also be influenced by fault geometry. The largest geomorphic offsets along the Sumatran fault zone are about 20 km, and may represent the total offset across the fault. The shape and location of the Sumatran fault and the active volcanic arc are highly correlated with the shape and character of the underlying subducting oceanic lithosphere. We utilize coral microatolls in west Sumatra to document evidence for deformation of the underlying subduction interface. Microatolls are very sensitive to fluctuations in sea level, and thus act as natural tide gauges. They record not only the magnitude of vertical deformation associated with earthquakes (paleoseismic data), but also continuously track long-term aseismic deformation that occurs during intervals between earthquakes (paleogeodetic data). Numerous microatolls from the region around the equator record a simple pattern of tilt away from the trench axis in 1935 related to an Mw7.7 earthquake. About 115 km from the trench axis, uplift was nil. Nearer to the trench, uplift progressively increased trench-ward to at least 90 cm. Farther than 115 km from the trench, submergence of up to 35 cm occurred. We model these paleogeodetic data by a 2.3 m slip event on the interface between 88 and 125 km from the trench axis. A large aseismic event or ?silent earthquake? in 1962 is among the most interesting phenomena discovered in the coral record, and is the second largest short-lived event recorded throughout the equatorial region. Furthermore, paleogeodetic data reveal that the interseismic deformation rates have varied both temporally and spatially., Cite this record as: Natawidjaja, D. H. (2003). The Sumatran Fault System, Indonesia: Supplement 1 from "Neotectonics of the Sumatran fault and paleogeodesy of the Sumatran subduction zone" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.1074 or choose a different citation style. Download Citation , Unique Views: 15 Unique Downloads: 0 between August 31, 2018 and December 02, 2019 More info on how stats are collected ,
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Geologic mapping provides structural and stratigraphic observations which lead to new insights into the magnitude, timing, and rate of Cenozoic extensional tectonism in the Death Valley region of the Basin and Range province in the western United States. Detailed mapping of the Grapevine Mountains, in northeastern Death Valley, yields new information on the structural evolution of the Titus Canyon anticline, a west-vergent fold of the Cordilleran thrust belt. The Grapevine Mountains contain the longest exposure of west-vergent folding in the Death Valley region, and detailed mapping supports previous interpretation of this structure as a piece of a single, laterally continuous fold, whose extensionally dismembered fragments form a key marker in reconstructions of Basin and Range extension. Such an interpretation suggests >100 km of west-north-west translation of the Grapevine Mountains away from the Sheep Range in late Cenozoic time. Correlation and re-interpretation of Cenozoic sedimentary and volcanic strata between the Sheep Range and the Grapevine Mountains indicate that this extension occurred on two separate extensional systems, the Sheep Range detachment system, and the Northeastern Death Valley detachment system. The former was active from 16-14 Ma, while the latter was active from 12.5-8 Ma. In contrast, stratigraphic and sedimentological data from the Eagle Mountain Formation suggests that, although extension across the central Death Valley region accommodated a similar magnitude of extension as the northern Death Valley region, ~100 km, extension across this region occurred post-11 Ma, and largely between 8-6 Ma. New geodetic and paleoseismic data are also presented from the eastern Basin and Range. These data indicate that slow (~4 mm/yr), long term (100s ka) strain accumulation is accommodated, geologically, by short (1000s yr) periods of fast (>1cm/yr) strain release, suggesting that the appearance of diffuse deformation across the eastern Basin and Range is likely due to time-averaging of many temporally discrete high-strain release earthquake clusters. These observations together suggest that the diffuse nature of intra-continental extension in the Basin and Range province may be the result of the summation of many spatially and temporally distinct extensional events, which, when active, progress at very high rates, Cite this record as: Niemi, N. A. (2002). Geologic Map of the Central Grapevine Mountains: Supplement 1 from "Extensional tectonics in the Basin and Range province and the geology of the Grapevine Mountains, Death Valley region, California and Nevada" (Thesis) (Version 1.0). CaltechDATA. https://doi.org/10.22002/d1.841 or choose a different citation style. Download Citation , Unique Views: 16 Unique Downloads: 3 between February 13, 2018 and December 02, 2019 More info on how stats are collected ,
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