Spring 2007 Thesis Defenses

Provenance of quartzite clasts from the Upper Cretaceous Cabrillo Formation, San Diego County, California
John Abeid
B.S. Geological Sciences
Advisor Dr. Dave Kimbrough

ABSTRACT
Sub-rounded to well rounded, equant, dominantly cobble sized quartzite clasts are found throughout the Campanian-Maastrichtian Cabrillo Formation. The origins of these “exotic” clasts have been proposed by previous workers to have been derived from the Peninsular Ranges, but an actual bedrock source has never been matched. Determining the provenance of these quartzite clasts has implications for paleogeographic reconstructions of the Peninsular Ranges magmatic arc in Cretaceous time. Population clast counts in the Cabrillo Formation coastal section north of False Point, Tourmaline Beach, shows that a dark gray sedimentary quartzite is the dominant type of quartzite in the section. Detrital zircon U-Pb age distributions from two of the dark gray Cabrillo quartzite clasts are dominated by ~1800 and 2700 Ma peaks that match the Peace River Arch (PRA) signature defined by Ordovician miogeoclinal strata of the western North American Cordillera. Scanning electron microscopy work has showed zircon separates from this type of quartzite to be very well rounded, consistent with a supermature sandstone origin and characteristic of miogeoclinal environments. The PRA signature is present in Peninsular Ranges prebatholithic strata in San Felipe area of northern Baja California and represents a potential source for the Cabrillo Formation quartzite clasts. A metamorphic quartzite-type in the Cabrillo Formation resembles the Ken Quartzite found in the northern Peninsular Ranges in the San Jacinto Mountains.



Cenozoic changes in the South Atlantic Carbonate Compensation Depth: Constraints from Ocean Drilling Site 1262 (Walvis Ridge), part I
Diego Almanza
B.S. Geological Sciences
Advisor Dr. Stephen Schellenberg

ABSTRACT




Utilizing Remote Sensing to Estimate Seismic Hazards within the Panama Region
Andy Arifandy
B.S. Geological Sciences
Advisor Dr. Rob Mellors

ABSTRACT
Previous studies and research indicates that the Panama Canal Zone may be subject to large earthquakes, yet little is known about the hazard. Large earthquakes occurring near the Canal Zone could lead to catastrophic damages and long-term shutdown of the canal. This would have world-wide economic impact. Using remote sensing data, earthquake hazards are estimated within the Panama Canal Zone by generating earthquake strong motion modeling. Possible fault lineaments are mapped using a satellite radar image and the effects of strong earthquakes are modeled using strong-motion software. The results are then mapped using Google Earth and the structures of the area are identified. The technique is also tested and applied on Jogjakarta, an area that has suffered a large earthquake on May 2006. The findings and techniques are also compared to similar researches.



Cenozoic changes in the South Atlantic Carbonate Compensation Depth: Constraints from Ocean Drilling Site 1262 (Walvis Ridge), part II
Tina Baynes
B.S. Geological Sciences
Advisor Dr. Stephen Schellenberg

ABSTRACT




Evaluating the robustness of Mytilus californianus skeletal chemistry as an paleoenvironmental archive: Effects of microenvironment and ontogeny
Heather Ford
M.S. Geological Sciences
Advisor Dr. Stephen Schellenberg

ABSTRACT




Hydrogeology of Lee Valley, Jamul, CA.
Jeremy Jensen
B.S. Geological Sciences
Advisor Dr. Kathy Thorbjarnarson

ABSTRACT




Geochemical, petrological, and grain size analysis of the Santa Margarita River sand bar deposits
Brandon Koons
B.S. Geological Sciences
Advisor Dr. Gary Girty

ABSTRACT
The composition of sediment sampled from sand bar deposits along the Santa Margarita River in Temecula, CA is the result of mixing detritus derived from granite, tonalite, and diorite rocks exposed along the canyon. The angularity and poor sorting of the riverine sediments indicate minimal transportation distances. Their modal mineralogy is consistent with a plagioclase arkose composition. In addition, they lack a significant lithic rock fragment population, and, as a result, they plot in the basement uplift field on the standard provenance discrimination diagram. Chemical data are consistent with petrological data, and imply that the riverine sands are mixtures of plutonic rock debris shed from various drainages feeding the Santa Margarita River. Hence, data presented here suggest that the production of soil and saprolite kept up with erosion and delivery of debris to the riverine system.



Mineralogical and textural changes accommodating the production of saprolite from a dioritic corestone in a Mediterranean climate, Peninsular Ranges, southern California
Chris Martinez
B.S. Geological Sciences
Advisor Dr. Gary Girty

ABSTRACT
A detailed petrological and chemical study of a single exposure of corestone surrounded by saprolite was conducted at Santa Margarita Ecological Reserve, Temecula, California. An ~1 m traverse extending from the center of the corestone outward and through ~0.5 m of saprolite resulted in five samples of corestone, two from an ~5 cm centimeter thick transition zone, and five from saprolite. All samples where thin sectioned and analyzed for major, minor, and trace elements. Thin section analysis showed that the conversion of quartz diorite corestone to saprolite primarily involved the progressive alteration of biotite to clay. XRD studies by Ms. S. Johnson suggest that in the most extensively altered saprolitic samples biotite is converted to a mixed layer expandable clay. Alteration appears to have been generated by fluid migration along the {001} cleavage plane, and around the fringes of individual biotite crystals. In contrast to biotite, plagioclase was altered to a much lesser degree while quartz and amphibole appear to have been unaffected. The average Chemical Index of Alteration (CIA) for corestone is 59.9 ± 0.1 (95% confidence interval) and for saprolite is 60.9 ± 0.3. On an A-CN-K diagram, movement away from the K apex toward the A-CN join supports thin section observations, as biotite is the only potassium bearing mineral in the quartz diorite. The transport function, τ, suggests that the masses of Si, Al, Fe, Ca, Na, Mg, and Mn relative to the framework element, Ti, changed little from corestone to saprolite. However, the masses of K, Rb, and Ba are significantly depleted within the saprolite where K is reduced in mass by up to 50%. The function T was used to assess changes in bulk mass. It showed a slight increase of ~3% near the corestone-saprolite boundary but then increased to ~14% increase within the transition zone. However, T then dropped back to 0±~2% within the saprolite. Volume strain (ε) was estimated for 4 samples of saprolite. The two samples that were closest to the transition zone yielded values around ~50% while the two near the end of the sampling traverse produced values between ~35% and ~40%. The four samples for which volume strains were evaluated yielded porosity values around ~28% - ~38%. Data summarized above suggest that in the relatively dry Mediterranean climate at Santa Margarita Ecological Reserve conversion of dioritic corestone to saprolite is primarily controlled by the removal of K+ from biotite. This process is accompanied by a concomitant volume expansion as biotite is converted to mixed layer expandable clay. Such conversions stress adjacent grain boundaries weakening and fracturing them, and thus promote further fluid infiltration that over time leads to the conversion of corestone to saprolite.



Magmatism & tectonics associated with the initiation of the Late Cretaceous-early Tertiary Laramide orogeny
Rob Moniz
M.S. Geological Sciences
Advisor Dr. Dave Kimbrough

ABSTRACT
There are numerous models explaining the widely debated Laramide low-angle subduction event that occurred on the western edge of North America from ~80-40 Ma. The shallowing of the subduction slab, or more likely a section of the slab, created a compressional regime that was expressed well inboard of the trench. Geologic evidence of this contraction has been documented from Canada down into Sonora, Mexico and includes the under-thrusting of the amphibolite facies Rand-Orocopia-Pelona schists to the uplifting of the continental interior. Despite the abundant geologic data for this time, the processes that caused the shallowing as well as the extent of shallowing are still unknown.
Using zircon U/Pb geochronology a new suite of latest Cretaceous (i.e., 86-70 Ma) early Laramide granitic intrusives has been found in the eastern-most Peninsular Ranges batholith. Previously, igneous rocks of this age were thought to only have been emplaced further to the east in mainland Mexico and eastern California and beyond. This suite is sparsely exposed for at least 300 km along strike and comprises >200 km2 in surface outcrop exposure mainly in the Santa Rosas in California and the Sierra Cucapas through the Sierra San Felipe in northern Baja California, Mexico. It intruded into La Posta-type plutonic rocks that comprise the main phase (100-90 Ma) of the eastern batholith. This suite records the tectonics and magmatism associated with a major transition in Cordilleran geology. The eastern Peninsular Ranges batholith has been described as a “migrating” arc representing the initial stage of inboard migration of Laramide Cordilleran magmatism. The identification of a temporal gap coupled with the absence of a spatial gap however suggests that following the voluminous La Posta magmatic flare-up at 100-90 Ma, magmatism stalled but continued intermittently until ~70 Ma in the eastern Peninsular Ranges batholith before inboard migration was initiated.
Major and minor elemental geochemistry from 54 samples indicates that the majority of granitics in the eastern Peninsular Ranges are, as previously documented, part of the La Posta suite. However, many of these bodies do not follow the typical documented deep crustal root signature of the La Posta suite as defined by high Sr/Y ratios. The few Laramide aged samples found overlap almost completely with the La Posta suite of this study, making characterization difficult.
To further characterize the suite, whole rock rare earth elemental geochemistry will be used. This will help determine if they share a deeper La Posta characteristic or are more closely related to the shallow formed and emplaced eastern Laramide units. The presence or absence of a mantle signature may also help reveal the extent of the shallow slab under this region during magma formation.The absence of a spatial gap between the Peninsular Ranges batholith and this new suite makes it a unique area to study and decipher the initiation and transition into Laramide low-angle subduction.



Geochemistry and Petrogenesis of the Jacumba Volcanics, California
Maureen Moses
B.S. Geological Sciences
Advisor Dr. Vic Camp

ABSTRACT
The Jacumba Volcanics are 18.7 +/- 1.3myo and the lie less than a kilometer north of the U.S.-Mexican Border in California. They are aphanitic and typically phyric, with micro-phenocrysts of plagioclase in most lavas. Olivine and clinopyroxene are common in some mafic flows, and clinopyroxene and basaltic hornblende are generally present in the intermediate rock types. The stratigraphy has been subdivided upward by Minch and Abbott (1959) into lower basalts, andesite, and upper basalts, together with a few felsic plugs scattered throughout the Jacumba region. The upper and lower flows show a distinct platy weathering pattern. Their normalized whole-rock chemistries of all rock types range from basaltic andesites to rhyolites, and they fall along a linear calc-alkaline trend of Fe-depletion. Incompatible elements should typically lie along similar trends of crystal fractionation and partial melting. However, the Jacumba volcanics fall instead into four separate groups on such incompatible-element plots indicating that they are unrelated to a common magmatic parent source or process. Although Nb typically behaves as an incompatible element in the partial melting of peridotite and in the subsequent fractionational crystallization of basalt, there appears to be a distinct Nb-depletion in these rocks when plotted against other incompatible elements. This could be a function of the crystallization of a Nb-bearing mineral phase such as an opaque mineral or perhaps hornblende. There is some ambiguity in the tectonic association of the Jacumba volcanics, in that they may be related to Basin and Range extension or to the early opening of the proto-Gulf of Californial. The calc-alkaline trend of these rocks is typical of a subduction-related process, but their age postdates the subduction of the Farallon Plate. The Jacumba volcanics appear to have been generated decompressional melting associated with extension and their chemistry reflects a metasomatized source affected by the prior subduction of the Farallon Plate.



The Death and Rebirth of Kilauea’s Magma Chamber 2.8 - 1.1 kyr Before Present Inferred from the Major- and Trace-Element Chemistry of the Uwekahuna Ash
Kyle Welchans
B.S. Geological Sciences
Advisor Dr. Aaron Pietruszka

ABSTRACT
The Uwekahuna Ash was deposited at Kilauea Volcano (Hawaii) ~2.8 – 1.1 kyr before present. The deposit from this explosive eruption covers an area of 420 km2. The Uwekahuna Ash records a series of phreatic and phreatomagmatic eruptions associated with a collapse of Kilauea’s summit which produced an ancient caldera. The summit collapse may have been triggered by the draining of Kilauea’s magma chamber through a submarine eruption along one of Kilauea’s rift zones. Four glass samples from the Uwekahuna ash were analyzed for major- and trace-element abundances using electron microprobe and laser ablation inductively coupled plasma mass spectrometry. Major-element variation diagrams show unusually high abundances of K2O and TiO2 (for a given MgO) for one of the four samples. This sample also shows higher than normal ratios of highly to moderately incompatible trace-elements (e.g. La/Yb vs. Nb/Y). Crystal fractionation cannot explain the unusual chemistry of this sample. Ratios of highly incompatible trace elements (e.g. Nb/Th vs Ba/U) are all similar, suggesting all four samples were derived from a mantle source typical for Kilauea lavas. Instead, the enriched glass sample must be a product of an unusually low degree of melting. I speculate that the unusual chemistry of this sample is an indirect result of the “death” of Kilauea’s magma chamber during the caldera collapse. In this case, lack of the magma chamber would have allowed the low degree melt to be transmitted to the surface. Subsequently, the refilling and “rebirth” of the magma chamber would have helped to mix any heterogeneous melts to generate more typical glass compositions.



Testing the use of GPR to detect clandestine graves in a San Diego soil
Luke Zimmerman
B.S. Geological Sciences
Advisor Dr. Rob Mellors

ABSTRACT
The purpose of the experiment is to consider the usefulness of GPR in forensic investigations of clandestine graves in the San Diego region. Ground Penetrating Radar (GPR) is a common tool used to view objects within the subsurface.The penetration and resolution of a GPR unit can vary with frequency used and soil type. A 6.58 kg turkey and 4.54 kg ham were buried at a depths to bottom of .75 meters and 1.25 meters respectively. There is also a 1m diameter aqueduct pipe that traverses the site at approximately two meters deep. The soil type at location of survey was a poorly graded clayey silty sand common of the San Diego area. The 100MHz antenna revealed no significant data. The 500MHz antenna revealed the shallower ham and the aqueduct. The turkey was not obvious, but may become more apparent with further filtering.

A Trip to Death Valley for SDSU Geologists

A trip to Death Valley for SDSU geologists
Group encounters sandstorm while studying outdoors
By: Maureen Moses, Contributor
Issue date: 4/26/07 Section: Science & Technology

Death Valley National Park is mostly known as a foreboding landscape that brought some of the gold-seeking 49ers to their graves. To the untrained eye, the intense heat and desolate surroundings play into the valley's infamous reputation, but to geologists, the valley is more than a death trap. It's science outside the confinement of the lab.Death Valley's geological history has many chapters that span billions of years. Even the most well-written textbooks can fail to capture the scope of what occurs there. The best lesson is one that's experiential.Two weekends ago, the San Diego State department of geological sciences hosted a camping trip to Death Valley where students, alumni and faculty braved adverse weather conditions to study the valley's geology. The trip was planned to overlap with the four-month-long pupfish mating season, but what was supposed to be the highlight became secondary. On the last day, after a hike at the famous Dante's View, the caravan of vehicles made an unexpected turn back to camp and back into the eye of the storm.The hot wind picked up the sand and dust, bending the tents in its path. Everybody helped to temporarily break down the camp, removing poles from the tents to prevent them from breaking and weighing down light objects.Wind is one of many active processes that shape the desert, and it speeds up in the heated terrain. As sand grains are blown in the wind, the dunes migrate and travel across the landscape. If the wind changes direction, the sand grains will follow a new path. The sandstorm was still in full force as the group pulled up to the sand dunes. Some geologists, with T-shirts wrapped around their heads to protect them from the flying grains of sand, went out across the dune fields to climb the highest dune. The grains of the sand slamming into your skin and getting caught in your teeth were an unavoidable consequence of being there.While there could have been complaints, the students were instead excited. This was an adventure. Teaching that the dunes form by wind is one thing, but experiencing it is something else. So much of what occurs on a field trip like this is social. Students get the chance to meet other enthusiastic students in their major. Professors can teach in the field, utilizing actual rock formations, which are usually presented as abstract hypothetical concepts."You can apply all of the discussions we have in class in the real world, and you can really see them put the pieces together," natural disasters professor Damon DeYoung said.Working on virtually a one-to-one student-to-teacher ratio, DeYoung had a huge educational influence working with freshman Alex Greene, who's currently enrolled in a geology lab."Hiking down Golden Canyon with Damon, and we were talking about the (sediment) layers up-close and picking it apart," Greene said. "He explained every little thing."When Greene returned to the class the following week he felt like he had a better understanding of the science than some of his peers."They know it because they study it, I know it because I got to climb on top of it and feel it." Greene said. Greene's lab-tech assistant, graduate student Melanie Biggs, noted the immense value this will have for his future education as a scientist."I know I probably gave him a hard time in the field, asking questions and quizzing him, but in the end it will help him to remember it," Biggs said.From Dante's View, a ridge that overlooks the valley, it was impossible to ignore the striking beauty of Death Valley. The fresh air and erratic weather greatly contrasted the climate-controlled labs. It's hard to forget a lesson learned in a place such as Death Valley."We don't just go out there to measure; we go out there to stand in awe and wonder," Biggs said.

Media Credit: Maureen Moses, Contributor
SDSU students hike the Golden Canyon Trail in Death Valley. Two weekends ago, the students went to see the pupfish mating season at Lake Manly but were pleasantly surprised when a sandstorm hit the valley

Trip Photo Slide Show

Other Department Field Trips - Photogallery

SDSC CiChannel - Interviews Kim Bak Olsen

Enabling Science Interviews

Ground Motion Research - Kim Olsen discusses how he uses SDSC Compute power to conduct his ground motion research

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SEMINAR - Judith Chester

The macroscopic behavior of earthquake rupture depends, in part, on processes operating at the mesoscopic and microscopic scales both along rupture surfaces and in the bordering damaged rocks. Earthquake rupture propagation is strongly influenced by the balance of energy radiated as seismic waves and that associated with the breakdown in strength at the rupture tip. Creation of new fracture surfaces and frictional slip both on and off the rupture surface contribute to the breakdown energy. In spite of recent success in quantifying fracture and friction in fault zones, efforts to understand slip processes and quantify the energy budget during seismic rupture are hindered by uncertainty in the characteristics and origin of various types of damage. We are using field and laboratory data from exhumed and drilled faults, and from faults produced in the laboratory, to place constraints on the processes of dynamic weakening and the energy balance for rupture propagation. Structural observations of the Punchbowl fault, a large-displacement exhumed fault, document extreme localization of slip consistent with weakening by frictional heating. The data suggest that the creation of fracture surfaces may only account for a small fraction of the total energy budget ( < 1%), whereas the energy associated with activation of frictional slip on secondary faults away from the master fault surface is significant (3 to 10% of the total energy for a strong and weak fault model, respectively). An outstanding question is how the energy dissipated by fracture surface creation throughout the fault zone and by frictional slip off the fault surface is spatially and temporally distributed over the earthquake cycle. In particular, it is important to determine whether slip on subsidiary faults in the damage zone occurs in response to the dynamic stress concentration associated with the rupture tip, or is a result of a wear process during subsequent coseismic sliding on the main fault surface and fault creep (e.g., by sub-critical cracking) during interseismic periods. Field observations of fracture fabrics in the damage zone support the assumption that some damage is associated with dynamic rupture-tip stresses, particularly in the region near the fault surface. If a large fraction of off-fault frictional dissipation occurs during breakdown in the tip region of the earthquake rupture, then the energy available for rupture propagation and seismic radiation is diminished. Dissipation of energy by frictional slip away from the rupture surface may reduce or delay the onset of weakening processes, such as thermal fluid pressurization, at the rupture surface. Furthermore, if the damage zone of an earthquake rupture surface is characterized by significant lateral variations in fracture density, one might expect significant variations in rupture characteristics and radiation efficiency.

Judith's seminar title: "Geologic constraints on mechanisms of energy dissipation during earthquakes"; Wednesday the 24th of April 2007

SEMINAR - Rob Mellors

ABSTRACT

We examine the potential triggering relationship between large earthquakes and methane mud volcano eruptions. Our dataset consist of a 191-year catalog (1810 to 2001) of eruptions from 77 volcanoes in Azerbaijan, Central Asia, supplemented with reports from mud volcano eruptions in Japan, Romania, Pakistan and the Andaman Islands. We compare the occurrence of historical regional earthquakes (M > 5) with the occurrence of Azerbaijan mud volcano eruptions and find the number of same-day earthquake/eruption pairs is significantly higher than expected if the eruptions and earthquakes are independent Poisson processes. The temporal correlation between earthquakes and eruptions is most pronounced for nearby earthquakes (within ~100 km) that produce seismic intensities of Mercalli 6 or greater at the location of the mud volcano. This assumed magnitude/distance relationship for triggering observed in the Azerbaijan data is consistent with documented earthquake induced mud volcano eruptions elsewhere. We also find a weak correlation that heightened numbers of mud volcano eruptions occur within 1 year after large earthquakes. The distribution of yearly eruptions roughly approximates a Poisson process, although the repose times somewhat favor a nonhomogenous failure rate, which implies that the volcanoes require some time after eruption to recharge. The volcanic triggering likely results from some aspect of the seismic wave’s passage, but the precise mechanism remains unclear.


Rob's seminar title: "Mud volcanoes and earthquakes: was the Lusi mud volcano due to drilling or an earthquake?"; Wednesday the 18th of April 2007

Largest TeraGrid Allocation Ever!

The Southern California Earthquake Center (SCEC), received the largest NSF compute allocation ever! --a whopping 15 million CPU hours on TeraGrid resources. The TeraGrid is the largest cyberinfrastructure facility available for nonclassified use in the US. The TeraGrid is a centerpiece of the efforts of the US National Science Foundation (NSF) to enable new, 21st century science innovations. The TeraGrid provides a network of supercomputers with well over 100 teraflops of computing power, and data storage facilities to store more than 15 petabytes of data, high-resolution visualization environments, and toolkits for grid computing, all connected through a very high-capacity network. The SCEC community will use this large allocation to support simulations of the realistic models required to predict the impacts of massive earthquakes. The SCEC simulations not only are compute-intensive, but data-intensive, and the SCEC community currently stores more than 150 Terabytes (150 X 10^12 bytes) of data at SDSC. A portion of this resource will be used by department researchers Kim Bak Olsen and Steve Day to model earthquake strong ground motion and wave propagation.

The New 2007 AGS T-Shirt!

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San Diego State University's AGS (Associated Geology Students) has released it new 2007 AGS T-Shirt.

An order form is available on the AGS Website. You have a choice of black or tan shirts in small, medium, large, or extra large. Cost $15.00, Shirts should be in stock by the end of the month.


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AGS ORDER FORM

2007 AAPG Outstanding Student Chapter Award

The SDSU AAPG (American Association of Petroleum Geologists) Student Chapter was awarded the 2007 Outstanding Student Chapter Award. This award is in recognition of the active participation in the AAPG Student Chapter Program, utilization of chapter benefits and attention to communication requirements. The Student Chapter Program of AAPG is made up of collegiate groups of geoscience students and one of the world's foremost co-educational programs within the geoscience sector with over 145 chapters. It provides students the opportunity to develop leadership skills and serves as a focal point for developing a feeling of professionalism through meeting industry representatives.

April Crossword Puzzle - Volcanology

Java Interactive Puzzle

Printable Puzzle (pdf)