TIR spectroscopy of shocked Deccan basalt: Implications for Mars and Martian meteorites
Shawn Wright Institute of Meteoritics Department of Earth and Planetary Sciences University of New Mexico May 6th, 2009
Hundreds of thousands of impact craters dominate the surfaces of the Moon, Mercury, and Mars. There exists much geomorphic and spectral evidence for basalt on those surfaces, so basaltic target rocks are most likely common. However, little work has been done on the thermal infrared (TIR) spectroscopy of shocked basalt metamorphosed by meteorite impact. This will have a direct application to the large amount of TIR data currently being returned from Mars orbiters and Rovers. The relationship between these TIR data collected remotely and laboratory data of samples is of much interest given that our only samples of Mars are shocked basalts. Results of research involving field work and samples from Lonar Crater, India, the only known terrestrial impact site emplaced in basalt, are described. The Deccan “Traps” flood basalts have been labeled as an excellent compositional and spectral analog for plagioclase-rich basalt on Mars identified from various orbiter and Rover instruments. Petrography provides details on the approximate range of shock pressure each class of shocked basalt has been subjected to, and field work has yielded an “ejecta stratigraphy” that displays where each class of shocked basalt is located. A comparison of the TIR spectroscopy of the unshocked Deccan basalt to its shocked equivalent aids in quantifying the changes due to shock. An application of this research has provided constraints on possible source craters/regions of certain shergottite meteorites, the shocked basalts from Mars.
Imaging Fault Damage Zones with Seismic and Geodetic Data
Elizabeth Cochran Department of Earth Sciences University of California, Riverside
During earthquakes slip is often localized on preexisting faults, but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics. Growing evidence suggests that the crust along active faults suffers anomalous strain and damage during large quakes. Data collected along several faults including the Hector Mine rupture, San Andreas Fault at Parkfield, and the Calico Fault show damage zones extending from 100 m to 1 km around the active slip plane. Recent seismic and geodetic data from the Calico fault in the eastern California shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli. Using seismic travel times, trapped waves, and interferometric Synthetic Aperture Radar observations, we document seismic velocities reduced by 40 - 50% and shear moduli reduced by 65% compared to wallrock in a 1.5-km-wide zone along the Calico fault. Observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures, but can sustain further damage in successive events These findings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces, and throughout much of the seismogenic zone, a result with implications for the portion of energy expended during rupture to drive cracking and yielding of rock and development of fault systems.
From a very young age I began to develop a fascination with earth science. In particular, I was intrigued by natural disasters. As I grew older my fascination continued to grow, and after taking a geology class in high school I decided that I would pursue a career studying volcanoes. After graduating high school, I received a B.A. in geology from Humboldt State University, and the following year I came to San Diego State University to work with Dr. Aaron Pietruszka. I have been very lucky throughout my student career and have been able to study various aspects of igneous petrology/volcanology, from experimental petrology and isotope geochemistry to mapping a variety of volcanic terrains. While studying at SDSU, I have had the fortunate opportunity to present my data at multiple scientific conferences, including an oral presentation at the 2008 IAVCEI in Reykjavik, Iceland. I will be graduating this spring (2009) with an M.S. in Geological Sciences, and will be starting my Ph.D. next year at Oregon State University.
Thesis The Recent Prehistoric Geochemical Evolution of Summit Lavas From Kilauea Volcano, Hawaii
In the most general sense, I use isotope ratios along with major and trace element abundances to investigate changes in the composition of what is melting beneath Kilauea Volcano, and how these changes relate to eruption rates in the recent prehistoric times. Research Interests Volcanology, caldera complexes, hydrovolcanic features, isotope geochemistry, general geochemistry, mantle plumes, ignimbrites, and pretty much everything else associated with explosive volcanic eruptions.
Education
Ph.D. Geosciences (starting Fall 2009) Oregon State University, Corvallis, Oregon
M.S. Geological Sciences (2009) San Diego State University, San Diego, California
B.A. Geology (2007) Humboldt State University, Arcata, California
Imaging Fault Damage Zones with Seismic and Geodetic Data
Elizabeth Cochran Department of Earth Sciences University of California, Riverside April 29th, 2009
During earthquakes slip is often localized on preexisting faults, but it is not well understood how the structure of crustal faults may contribute to slip localization and energetics. Growing evidence suggests that the crust along active faults suffers anomalous strain and damage during large quakes. Data collected along several faults including the Hector Mine rupture, San Andreas Fault at Parkfield, and the Calico Fault show damage zones extending from 100 m to 1 km around the active slip plane. Recent seismic and geodetic data from the Calico fault in the eastern California shear zone reveal a wide zone of reduced seismic velocities and effective elastic moduli. Using seismic travel times, trapped waves, and interferometric Synthetic Aperture Radar observations, we document seismic velocities reduced by 40 - 50% and shear moduli reduced by 65% compared to wallrock in a 1.5-km-wide zone along the Calico fault. Observed velocity reductions likely represent the cumulative mechanical damage from past earthquake ruptures, but can sustain further damage in successive events These findings indicate that faults can affect rock properties at substantial distances from primary fault slip surfaces, and throughout much of the seismogenic zone, a result with implications for the portion of energy expended during rupture to drive cracking and yielding of rock and development of fault systems.
Not-So-Simple Cinder Cone Plumbing Systems: Examples From the Sierra Nevada
Brandon Browne Department of Geological Sciences California State University Fullerton
Cinder cones situated in continental monogenetic volcanic fields are generally thought to erupt single magma batches over short periods of time. However, field mapping efforts combined with petrologic, geochemical, and thermobarometric analysis of erupted products from two unrelated volcanic fields in California (Red Cones, 5 km SW of Mammoth Mountain; and Golden Trout, 5 km SW of Mt Whitney) indicate pronounced differences in the eruption volumes and Pressure-Temperature crystallization histories of erupted basalts despite overall similarities in magma source. These findings suggest that magma plumbing systems and the mechanisms for magma supply at cinder cones are actually quite complex, and therefore require us to modify our perspectives on how they from as well as the types of geophysical signals they potentially yield before, during, and after eruptions.
The Cretaceous-Paleogene ("KT") Boundary In Belize and Alabama
David T. King, Jr. Department of Geology and Geography Auburn University, Alabama
Belize - At Albion Island in northern Belize, Cretaceous-Paleogene (KT) boundary deposits, also known as the Albion formation, rest upon karsted and fractured Maastrichtian dolostones. These deposits consist of a basal impactoclastic clay layer (~ 1 to 2-m thick) and an upper carbonate-rich, coarse impactoclastic breccia layer (up to 15-m thick). The focus of this paper is the upper layer, the Albion impactoclastic breccia. The Albion impactoclastic breccia shows several important sedimentary structures, including development of discrete sedimentation units (2 to 7-m thick), which are strata that have been enhanced by horizontal shearing, and other sedimentary structures such as normal and reverse size grading, clast imbrication, flow lamination, and isolated and linked aggregates of clasts (i.e., clast clustering). Most carbonate clasts within the coarse impactoclastic unit show a broad range of angularities and shapes, with the most common being subangular and compact-bladed to compact-elongated, respectively. Surface texture analysis of carbonate clasts shows several types of surface markings, which display a gross sequential order (i.e., facets, polish, striations, cryptographic markings, bruises and pits, and chips). In-situ, apparent-diameter measurements of the carbonate clasts, which ranged in size from 10 to 300 mm (or -3.3 to -8.2 Ø);, resulted in cumulative grain-size (Ø) frequency curves with similar shapes through the interval –3.3 Ø and –6.25 Ø (i.e., 10 to 76 mm). Matrix, the total area comprised of less-than-10 mm (< -3.3 Ø) particles, ranged from approximately 71 to 82 percent. Modified moment measures of these curves show these breccias are “extremely poorly sorted.” The matrix content increase upward through the entire coarse impactoclastic layer, but is slightly lower near its top. The Albion impactoclastic breccia has sedimentary structures and sedimentologic characteristics suggesting its mode of emplacement during the impact aftermath was similar to that of a very large volcanic debris avalanche. Sedimentation units show evidence of early turbulent flow and a more conspicuous later stage of laminar flow with shearing accompanying emplacement of most breccia sedimentation units. Clasts within these debris flows are not locally derived for the most part. We speculate that each sedimentation unit at Albion may represent a separate emplacement event during the process of ejecta curtain collapse, perhaps owing to variations in atmospheric interaction with the debris. Alabama - At Shell Creek stratigraphic section, Wilcox County, Alabama, a < 1 m-thick, Cretaceous-Paleogene boundary sand body crops out over an area of ~ 200 m2. This sand body consists of (1) a basal impact spherule-bearing, coarse to medium sand and (2) an overlying fine sand with hummocky-type cross-lamination. This K-T boundary sand body probably represents post-impact, shelf sedimentation events involving (1) gravity-driven resedimentation of reworked impact spherule-bearing sands and (2) energetic wave reworking of the impart spherule-bearing, gravity-driven deposits or other subsequently deposited sands. Most impact spherules from Shell Creek are spherically shaped grains (~ 1 mm in diameter) that are now hollow, or were hollow prior to secondary calcite filling. Most impact spherules from Shell Creek consist of an outer shell, which is composed of smectitic clays, and an inner region of open space or sparry calcite. Most of these impact spherules still retain features like vesicles that attest to their former molten condition. This stratigraphic section is remarkable in that it represents the most easterly U.S. Gulf Coastal Plain occurrence of abundant impact spherules in a Cretaceous-Tertiary (K-T) boundary sand body.
Not-So-Simple Cinder Cone Plumbing Systems: Examples From the Sierra Nevada
Brandon Browne Department of Geological Sciences California State University Fullerton April 22nd, 2009
Cinder cones situated in continental monogenetic volcanic fields are generally thought to erupt single magma batches over short periods of time. However, field mapping efforts combined with petrologic, geochemical, and thermobarometric analysis of erupted products from two unrelated volcanic fields in California (Red Cones, 5 km SW of Mammoth Mountain; and Golden Trout, 5 km SW of Mt Whitney) indicate pronounced differences in the eruption volumes and Pressure-Temperature crystallization histories of erupted basalts despite overall similarities in magma source. These findings suggest that magma plumbing systems and the mechanisms for magma supply at cinder cones are actually quite complex, and therefore require us to modify our perspectives on how they from as well as the types of geophysical signals they potentially yield before, during, and after eruptions.
Post-rifting deformation in Afar, Ethiopia, following the 2005 intrusion event
Jill Pearse Scripps Institution of Oceanography University of California, San Diego April 15th, 2009
The 300-km wide Afar depression is located at the junction between the Red Sea, Gulf of Aden and East African rifts. In September and October of 2005, a series of large earthquakes and a volcanic eruption signaled the intrusion of a dike along the Dabbahu magmatic segment (in the Red Sea arm) of the Afar rift. Results of elastic modeling constrained by InSAR (Wright et al 2006) data suggest that the 60-km long segment opened by up to 8 m, between depths of 2-9 km. Relaxation of stresses in the crust below the brittle-ductile transition following the intrusion event should create geodetically observable surface deformation, however this signal can be obscured by continuing active intrusions. Using 3-D finite element models, we predict the surface deformation following the 2005 Dabbahu event for a range of crustal and mantle rheologies. We compare our model results to InSAR data spanning the 3 years since the intrusion to quantify the post-rifting deformation and place constraints on the rheology below the brittle-ductile transition in Afar.
The SDSU team wins, for the second years in a row, the Pacific Section AAPG’s Imperial Barrel Award Program (IBA). Accolades include a prize of $1500 and a chance to compete in the IBA finals. Finals are June 5th and 6th in Denver Colorado against national and international competition.
Team members are: John Abeid, Leslie Clayton, Byrant Fulk, Christopher Kohel, and Peter Winther.
The Department of Geological Sciences has been awarded seven licenses for the Midland Valley software 3DMove. 3DMove is the world’s leading 3D software tool for structural restoration, validation and analysis. 3dMove uses the principles of structural geology to help build models where little data exists, and to use the geological evolution of the model to define parameters for further analysis.
The unique advantage of 3DMove, when compared with other model building software, is that it takes into account geological time. Build valid models and analyse your ideas about how the structure developed through geological time with present day & past time steps providing both qualitative & quantitative analysis.The unique advantage of 3DMove, when compared with other model building software, is that it takes into account geological time. Build valid models and analyse your ideas about how the structure developed through geological time with present day & past time steps providing both qualitative & quantitative analysis.
One of the many ways this software will be used is teach students techniques to create more accurate models, reducing risk and improve productivity of gas and oil exploration/production.
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TIR spectroscopy of shocked Deccan basalt: Implications for Mars and Martian meteorites
