Student Research
Over the course of my 20-year career at Puget Sound I supervised 55 undergraduate thesis projects, most involving either the petrology and geochronology of igneous rocks in Washington or the chemistry of water and/or sediment from local lakes. Mentoring these projects was the most rewarding aspect of teaching and many of my thesis students have gone on to pursue graduate study. Listed below in reverse chronological order are titles and brief summaries of these projects, accompanied in most cases to links to published abstracts.
Emily Wright (Class of 2022). "Investigating Arsenic Mineralogy is Historic Mine Waste from the Idaho-Maryland Mine, Grass Valley, California". Emily used a variety of microbeam techniques (mainly SEM-EDS and Raman) to determine where As is hosted in waste from a former gold mine. This work was part of a larger USGS project that seeks to understand the relationships between As bioavailability and the phases - both primary and secondary - that contain the As.
Click here to read Emily's 2021 GSA Abstract
Pauline Peterson (Class of 2022). "Petrology and Tectonic Setting of the Silver Pass Volcanics, Central Cascades, Washington". Pauline worked on the Eocene Silver Pass Volcanics, located near Snoqualmie Pass in the central Washington Cascades. She confirmed the existence of two distinct magma series and that these lavas formed in response to breakoff of the subducting Farallon slab.
Click here to read Pauline's 2021 GSA Abstract
Audrey White (Class of 2022). Audrey studied a diverse group of volcanic units that span >40 Ma of activity on the eastern flank of the Cascades in central Washington, including the Wenatchee Pinnacles, Peoh Point, Old Gib, and Burch Mountain. She obtained the first U-Pb zircon ages for several of these units and her Sr-Nd analyses of Burch Mountain revealed these adakites to be the most isotopically depleted rocks in the Cascades.
Click here to read Audrey's 2021 GSA abstract
Colin Glaze (Class of 2022). “Identifying the Effects of Alum Treatment on Water and Sediment Chemistry of Two Lakes in Pierce County, Washington”. Colin collected and studied sediment cores from two local lakes – Waughop and Wapato - that have been treated with alum (aluminum sulfate) as a means of sequestering phosphorus. He is looking in particular at the fate and impacts of the sulfur, which gets in the sediment gets reduced to hydrogen sulfide and is then toxic at high levels to rooted aquatic plants.
Nancy Hollis (Class of 2021). “Exploring Possible Strategies for Hazardous Algal Bloom Mitigation In Spanaway Lake, Tacoma, Washington”. Nan set up macrocosm experiments to assess the effectiveness of zero valent iron as a means of removing phosphorus from groundwater that enters Spanaway Lake from vents, and subsequently contributes to toxic algal blooms.
Lexus Sullivan (Class of 2021). “Chasing the Mystery of the Cascades: A Geochemical Analysis of the Earliest Arc Rocks in Central Oregon”. Lexus investigated the petrology of several units in the Willamette Valley that include the earliest known Cascade arc rocks in Oregon. She merged her data with several published compilations totaling >10,000 whole rock analyses in order to make the first attempt to see whether: (1) the compositions of Cascade arc magmas have evolved over the past 45 Ma, and (2) whether chemical variations along the length of the arc have varied over time.
Click here to read Lexus' 2021 GSA abstract
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Clara Phipps (Class of 2020). “Petrology of the Eocene Goble Volcanics, Southwest Washington: A Record of the Transition from Oceanic to Cascade Arc Magmatism”. The Goble Volcanics lie west of the main Cascade arc but east of the oceanic basalts of the Coast Range. Clara found that this formation consists of two suites of lavas: an earlier group of high alumina olivine tholeiites and a later group of basalt-to-dacites with arc affinities. The Goble may thus record the transition from oceanic to arc magmatism and may contain the earliest rocks associated with the modern Cascade arc.
Click here to read Clara’s 2019 AGU abstract
Robyn Organ (Class of 2020). “Petrology Diversity Among Early Cascade Arc Lavas in SW Washington”. Robyn studied a several small-volume, early Cascade arc units, all located west of the modern arc, and identified a suite of Mg-rich alkaline basalts (among them the Pe Ell volcanics) that erupted in the forearc region, probably in response to passage of a slab window.
Click here to read Robyn’s 2019 AGU abstract
Louisa Cryan (Class of 2020). “The Northcraft, Tukwila, and Rattlesnake Mountain Formations: Petrology of the Earliest Cascade Volcanic Units in Washington and their Implications for the Evolution of the Cascade Arc”. Louisa analyzed the elemental and Sr-Nd isotopic geochemistry of three early Cascade arc units to investigate the long-term evolution of the arc. She found that the earlier units are “drier” and have less of a subduction signature, and concluded that the mantle wedge has become progressively more-enriched by slab-derived melts/fluids over the past ~45 Ma.
Click here to read Louisa’s 2019 AGU abstract
Jack Lindauer (Class of 2019). “Identifying Nutrient Sources Responsible for Hazardous Algal Blooms in Spanaway Lake, Pierce County, Washington”. By monitoring water column chemistry, deploying sediment traps, and measuring the flux of nutrients from the sediment, Jack established that the main source of phosphorus that causes algal blooms at Spanaway Lake is groundwater springs. This contradicts the findings of an earlier study by a consulting firm, and has led to a reassessment of the best options for mitigating the blooms.
Click here to read an article about Jack's research
Miriam Cohen (Class of 2019). “Mineralogy and Bulk Composition of Lunar Mare Basalt Northwest Africa 12008”. Miriam studied the mineral and whole rock chemistry of a basaltic meteorite from the lunar maria, one of only twelve such meteorites known. Her meteorite is similar to some collected in Antarctica, but more Fe-rich than mare basalts collected during the Apollo missons.
Click here to read Miriam's LPSC abstract
Gloria Ferguson (Class of 2019). “Petrology of the Naches Formation, Central Washington Cascades: A Record of Eocene Tectonic Transition”. Gloria expanded on previous studies of this widespread formation, confirming through U-Pb zircon dating that it includes rocks as young as 43 Ma. Her new dates, combined with recognition that some Naches rocks have subduction traits, suggests that this formation in part represents some of the earliest products of the modern Cascade arc.
Click here to read Gloria’s 2018 AGU abstract
Zoe Running (Class of 2019). “Petrology and Geochronology of the Oso Volcanics, Northern Cascades, Washington: Transitioning Tectonism during the Eocene”. The Oso Volcanics were previously thought to be part of the Cascade arc, but Zoe established through U-Pb zircon dating and whole rock chemical analysis that these rocks belong to an earlier magmatic episode (~51-49 Ma) associated with breakoff of the Farallon slab.
Click here to read Zoe’s 2018 AGU abstract
Tommy Kimler (Class of 2018). “Petrology and Tectonic Implications of the Eocene Naches Formation, Central Cascades, Washington”. Tommy mapped, analyzed, and U-Pb dated samples from this volcanic unit and found that it spans a broader age range (50 - 44 Ma) than previously recognized. It appears to include older rocks related to breakoff of the Farallon slab as well as younger rocks associated with initiation of the Cascade arc.
Click here to read Tommy’s 2017 GSA abstract
Jack Randall (Class of 2018). “Petrology and Tectonic Implications of the Basalt of Frost Mountain, Central Cascades, Washington”. Jack studied this bimodal volcanic unit, using whole rock chemistry, Sr-Nd isotopic analyses, and U-Pb zircon dating. His data support a model in which rupture of the Farallon slab led to upwelling of asthenospheric mantle and production of OIB-like basalts, which subsequently drove crustal melting to produce small volume rhyolitic tuffs.
Click here to read Jack’s 2017 GSA abstract.
Cameron Wallenbrock (Class of 2018). “Petrology, Geochronology, and Tectonic Setting of the Taneum Formation, Central Cascades, Washington”. Cam studied a ~52 Ma volcanic formation that consists of basalt, andesite, and more felsic rocks (including adakites). Based on mapping, geochemistry, Sr-Nd isotopic analysis, and zircon U-Pb dating adakites, he concluded that the Taneum resulted from melting at the edges of a rupture in the Farallon slab.
Click here to read Cam’s 2017 GSA abstract
Mitchell Dodo (Class of 2017). “Comparison of Chemical Composition of Surficial Sediment in Tacoma Area Lakes”. Mitchell used a “clamshell” to collect surface sediment samples from nine lakes in the Tacoma area. He found that sediment chemistry varies significantly from lake to lake, and that much of the variation can be explained by mixing of a terrigenous component (glacial silts and clays that wash into the lakes) with organic matter (produced in the water column). He also found significant lake-to-lake differences in Cu/Pb that suggest these metals have been redistributed in the sediment after deposition. Mitchell now works as a consulting geologist in Seattle.
Click here to read Mitchell’s Washington Hydrogeology Symposium abstract (p. 92)
Angelica Calderon (Class of 2017). “Controls on the Distribution of ASARCO Heavy Metals in Tacoma-Area Lakes”. Angie chemically analyzed and Pb-210 dated a core from Lake Kilarney (King County, WA) and compared the record of Cu-Pb pollution there with other nearby lakes. She also measured metal concentrations in soil samples collected from the edges of these lakes to assess whether erosion is continuing to deliver metals to these water bodies. Her data indicate that present day runoff is not a significant source of heavy metal contamination, but that metals may migrate upward through the sediment column and become enriched near the surface.
Click here to read Angie’s Washington Hydrogeology Symposium abstract (p. 97)
Jon Golla (Class of 2017). “Geochemistry and Origin of Hot Spring Waters of the Olympic Peninsula and Cascade Range, Washington”. Jon compared the chemical and O-H isotopic compositions of hot spring waters from two geologically distinct regions of Washington. He identified chemical differences in water from the two areas (attributed in part to a magmatic component in the Cascades) and also used mineral-water equilibria calculations to determine subsurface reservoir temperatures. John earned his M.S. in Geology at the University of New Mexico and is now working on his PhD at the University of Illinois.
Click here to read Jon’s Washington Hydrogeology Symposium abstract (p. 95)
Andrew Oberhelman (Class of 2017). “Comparison of the Chemical and Isotopic Composition of Groundwater and Surface Water in the South Sound Region, Washington”. Andrew measured the chemical and O-H isotopic compositions of over 50 groundwater, surface water, and precipitation samples in order to understand the process(es) responsible to systematic variations in the composition of local lake waters. He was able to demonstrate that many lakes in the Tacoma area can be modeled as mixtures in varying proportions of groundwater and dilute component that is either rain or surface runoff. Andrew is currently in a PhD program at the University of Florida.
Click here to read Andrew’s Washington Hydrogeology Symposium abstract (p. 81)
Sean Tanner (Class of 2016). “Between the Crescent and the Arc: Petrology of Early-to-Middle Eocene Igneous Units in Western Washington”. Sean examined a series of Eocene volcanic units in western Washington that formed prior to establishment of the Cascade arc. The goal was to better understand the tectonic changes that occurred following the accretion of Siletzia. The rock units Sean studied are diverse – some display arc signatures and are interpreted as early stages of Cascade magmatism whereas others display oceanic affinities and may record detachment of the Farallon slab.
Click here to read Sean's 2016 GSA Abstract
Sean Maher (Class of 2016). “Tracking the Growth of a Trachyte Lava Done on Akaroa Volcano, New Zealand with Structural Observations, Geochemistry, and Crystal Size Distributions”. Sean combined field, chemical and petrographic data to demonstrate that this dome was emplaced as a series of four lobes, distinguished by textural and (subtle) chemical differences. Using CSD measurements he was able to document increasing crystallinity of the successive domes, which was also evident in their emplacement structures. Sean earned his M.S. at the University of Bristol and currently pursuing a PhD at UC Santa Barbara, focusing on volcano seismology and infrasound.
Click here to read Sean's 2016 GSA Abstract
Liam Caulfield (Class of 2015). “Geochemistry and Geochronology of Eocene Plutons in Northeastern Washington: A Test of Farallon Slab Rollback as a Cause of the Challis Event”. Liam analyzed and U-Pb dated (by LA-ICP-MS at the University of Arizona) a dozen Eocene plutons from eastern Washington, looking for temporal – spatial patterns in magmatism that could help shed light on the cause of the Challis Event. His data reveal a younger-to-the-southwest pattern between 52 – 46 Ma, which is consistent with rollback of the Farallon slab.
Click here to read Liam's 2015 AGU Abstract
Peter Davidson (Class of 2015). “Petrology of Dikes in the Lake Chelan Region, Washington: Tectonic Setting and Implications for the Challis Event”. Peter studied dikes in north central Washington, utilizing whole rock chemistry, Sr-Nd isotopic analysis, and zircon U-Pb dating (by LA-ICP-MS at the University of Arizona). His data reveal two suites of dikes that overlap in isotopic composition, an adakite suite attributed to melting of eclogitic lower crust and a B-A-D-R suite attributed to melting of similar arc crust but at shallower depths. Peter is now in a PhD program in geology at Oregon State.
Click here to read Peter's 2015 AGU Abstract
Kaitlyn Ruthenberg (Class of 2015). “Delineating Terrane Boundaries in Northeastern Washington Using Isotopic and Geochemical Analysis of Cretaceous Plutons”. Katie sampled Cretaceous plutons from north central Washington, dated them by U-Pb (at the University of Arizona LaserChron Center), and analyzed their chemical and Sr-Nd isotopic compositions. Her data reveal discontinuities in Nd model ages that we interpret as terrane boundaries. Katie now works as a lake water quality analyst for Snohomish County (WA).
Click here to read Katie's 2015 AGU Abstract
Elizabeth Roepke (Class of 2014). “A Geochemical Study of the Teanaway Basalt Formation and its Relationship to the Teanaway Dike Swarm”. Liz measured chemical and Sr-Nd isotopic compositions of Teanaway lavas and concluded that these rocks formed in a slab window setting where asthenospheric melts interacted with continental crust.
Click here to read Liz's 2013 AGU Abstract
Halle Peterson (Class of 2014). “Investigation of Phosphorus Loading and Cycling at Waughop Lake (Pierce County): The Most Toxic Lake in Western Washington”. Halle investigated sources of phosphorus that contribute to toxic algal blooms at Waughop Lake. Combining data from: (1) a 60 cm sediment core, (2) sediment traps, and (3) monitoring of temperature and chemistry through the water column, she was able to show that the main source of the P entering the lake is the sediment on the bottom. Advective transport of P-rich pore water is probably the main process of P delivery. Halle now works for Kiewit Engineering in Seattle.
Click here to read Halle's Hydro Symposium Abstract (on p. 66)
Peter Siegenthaler (Class of 2014). “Distribution and Mobility of Heavy Metals in Lacustrine Sediments, American Lake, Pierce County, WA”. Peter analyzed a sediment core from American Lake that contains a record of heavy metal deposition from the ASARCO smelter. His data indicate maximum metal deposition rates occurred in the 1980’s – after the smelter had closed – and thus imply that the metals have migrated upward in the sediment column. Peter now works for the National Oceanic and Atmospheric Administration (NOAA).
Drew Ivener (Class of 2014). “Petrology and Eruptive Styles of the Teanaway Basalt, Central Washington: Uplift and Bimodal Volcanism in a Subsiding Eocene Basin”. Drew analyzed the elemental and Sr-Nd isotopic compositions of this bimodal (basaltic andesite and rhyolite) formation. He concluded that these lavas are the extrusive equivalents of the underlying Teanaway dikes and that fractional crystallization can account for variation among the mafic rocks but cannot produce the rhyolites. Drew went on to earn a master’s degree in education at the University of Colorado.
Click here to read Drew's 2013 AGU Abstract
Lisa Kant (Class of 2013). “The Eocene Basalt of Summit Creek, Central Cascades, Washington: Magmatism Associated with Farallon Slab Breakoff”. Lisa used elemental and Sr-Nd isotope geochemistry to show that these basalts, which occur in a 1500 m section south of Mt. Rainier, share the same source as the Crescent Basalts on the Olympic Peninsula. Eruption of these oceanic basalts may be a response to breakoff of the Farallon slab following the accretion of Siletzia. Lisa is currently working on her PhD in igneous petrology/geochemistry at the University of Wyoming.
Click here to read Lisa's 2012 AGU Abstract
Elli McKinley (Class of 2013). “Environmental History of a ~13,000 year Sediment Core Record from the Most Contaminated Lake in Western Washington: Waughop Lake, Pierce County”. Elli analyzed a 6.5 meter core that spans ~14,000 years of lake history. Within the upper ~100 cm of the core, dated by 210-Pb, she found evidence of dramatic increases in sedimentation rate and nutrient loading (both caused by dumping of agricultural wastes) and in heavy metal contents (caused by ASARCO smelter fallout). Elli is currently working at a ski resort in Colorado.
Click here to read Elli's Hydrogeology Symposium Abstract
Sam Berkelhammer (Class of 2013). “Petrology of Mafic Bodies Associated with the Eocene “A-Type” Golden Horn Batholith, North Cascades, Washington”. Sam worked on mafic rocks - mostly dikes – in order to characterize mantle inputs during generation of the Golden Horn batholith. He distinguished two suites of adakites as well as “typical” arc basalts and concluded that crustal melting was facilitated by mantle upwelling through a rupture in the slab. Sam went on to earn an M.S. in igneous petrology at Kansas State University.
Click here to read Sam's 2012 AGU Abstract
Monica Hanson (Class of 2012). “Geochemistry of the Mt. Persis Volcanics and Evidence for Spatial and Temporal Changes in Cascade Arc Magmatism”. Monica analyzed samples of the Eocene Mt. Persis volcanics and also compiled a dataset of >1600 chemical analyses of Cascade arc rocks from 34 magmatic centers. She identified spatial and temporal chemical changes that are attributed to changes in slab dip and along-arc source differences. Monica now works as a GIS analyst.
Click here to read Monica's GSA Abstract
Gita Datt (Class of 2012). “Paleolimnology of Lake Louise, Washington: A Geochemical Investigation of Paleoenvironments and Anthropogenic Changes Recorded in Lake Sediments”. Gita collected and analyzed a 6.5 m sediment core that spans ~14,000 years of history. The core includes an ash layer from the Crater Lake eruption as well as the more recent record of ASARCO smelter metal fallout. Gita currently works as a geological consultant in San Francisco.
Evan Eckles (Class of 2012). “Mafic Rocks of the Golden Horn Batholith, North Cascades, WA: Implications for Eocene Slab Window Tectonics”. Evan studied mafic rocks associated with the Golden Horn batholith as a means of characterizing mantle inputs during batholith formation. After graduating from Puget Sound Evan earned an M.S. in Applied Geosciences from the University of Washington; he now works for an environmental consulting firm.
A.J. Clifford (Class of 2012). “Petrographic and Geochemical Study of the Formation of an Anorthosite Layer in the Cutthroat Peak Diorite, North Cascades, Washington”. The Cutthroat Peak Diorite, a mafic pluton within the Golden Horn Batholith, contains a ~2m thick anorthosite layer. Based on mineral chemistry, petrography, and melt density calculations, A.J. concluded that this layer formed by plagioclase flotation. The dip of the layer - ~55° NE - may record regional tilting.
Paul Woodward (Class of 2011). “Geochemical Study of a Sediment Core from Gravelly Lake, WA: A 1000-Year Environmental History”. Paul analyzed a sediment core from Gravelly Lake, measuring elemental abundances and biogenic silica. He documented abrupt increases in nutrient levels (P, N) and biogenic silica that occurred ~1840, coincident with the nearby establishment of Fort Nisqually.
Click here to read Paul's Hydrogeology Symposium Abstract
Sam Blakely (Class of 2010). “A Comparison of Eocene and Cretaceous Plutons, Boundary County, Idaho: Petrology and Tectonic Implications”. Sam studied several plutons in the Selkirk Mountains of Norhern Idaho, including the zoned Trapper Peak stock (Eocene) and three adjacent Cretaceous granitoids. Zoning at Trapper Peak was found to be the result of in situ crystallization at shallow depth; the Cretaceous plutons were emplaced at mid-crustal depth, which implies there was significant uplift between the two plutonic events. Sam currently works as for a mineral exploration company in Spokane.
Click here to read Sam's NWSA Abstract
Micah Gregory-Lederer (Class of 2010). “Petrology of the Jordan Lakes Pluton: An Investigation of Separate Source Versus Structural Tilt Hypotheses in the North Cascades”. Micah studied a small Cretaceous pluton in the North Cascades to understand why different parts of the intrusion are texturally distinct. He found that there were no significant differences in composition or emplacement depth, but that eastern part of the pluton was more deformed by nearby faulting. Micah currently works as a geological consultant in Bellingham.
Click here to read Micah's NWSA Abstract
Duncan Knudsen (Class of 2010). “Comparison of Cretaceous vs. Eocene Granitoid Intrusions in NE Washington: Petrology and Al-in-Hornblende Barometry”. Duncan compared four adjacent plutons in north central Washington to see whether there were chemical or depth-of-emplacement differences between Cretaceous vs. Eocene magmatism. Plutons from both time periods display similar arc traits but hornblende barometry suggests the late Cretaceous pluton was emplaced at greater depth than the earlier or later plutons. Duncan currently works as a geological consultant in the Bay Area.
Click here to read Duncan's 2010 GSA Abstract
Christine Chan (Class of 2010). “Petrology of the Grays River Volcanics, Southwest Washington: Plume-Influenced Slab Window Magmatism in the Cascadia Forearc”. Christine studied the Gray’s River Volcanics, a package of late Eocene basalts in Southwest Washington. She showed that these lavas, based on their chemical and isotopic traits and age, probably represent slab window magmatism that was influenced by a mantle plume source. After graduating from Puget Sound Christine earned her M.S. in igneous petrology at Oregon State. She is now pursuing a PhD in geochronology at the University of Kansas.
Click here to read Christine's 2009 GSA Abstract
Sarah Glancy (Class of 2009). "Geochemically Anomalous Igneous Rocks of the Olympic Peninsula: Implications for Eocene Tectonics" Sarah studied the petrology of a suite of "chemically anomalous" volcanic rocks collected from various sites on the Olympic Peninsula. These rocks include hornblende-bearing basaltic andesites, hornblende dacites, and tuffs. In addition to characterizing and dating these rocks, she evaluated the hypothesis that some or all of them could be related to passage of one or more slab windows beneath western Washington during the Eocene. Sarah earned a M.S. in igneous petrology from the University of Hawaii in 2014 and now teaching geology in Honolulu.
Click here to read Sarah's 2009 GSA Abstract
Ben Shapiro (Class of 2009). "Unique Geochemistry of Gravelly Lake, Tacoma, WA: Evidence for a Deep Groundwater Component" Ben studied the water chemistry of Gravelly Lake (Pierce County, WA), which is chemically different (higher in pH and most cations) from other lakes in the vicinity (all of which are kettle lakes). He showed that the anomalous chemistry of this lake is a result of being fed by springs that probably originate from a deeper aquifer than those feeding the other lakes. After graduating from UPS Ben earned his M.S. in biogeochemistry at the University of Oregon.
Click here to read Ben's 2009 GSA Abstract
Matthew Loewen (Class of 2008). Matt's project focused on the petrology and geochemistry of Eocene ("Challis event") plutonic and volcanic rocks in Eastern Washington. Using a combination of trace element and Sr-Nd isotopic data he was able to show that these rocks formed by melting of thickened crust and then ascended rapidly. These results are consistent with the hypothesis that Challis magmatism was related to passage of the Kula-Farallon slab window. Matt's Nd isotopic data also reveal the existence in eastern Washington of at least three distinct lower crustal domains. Matt received his PhD in igneous petrology from Oregon State University in 2013 and is now a volcanologist at the USGS Alaska Volcano Observatory.
Click here to read Matt's 2007 AGU Abstract
Christian Manthei (Class of 2006). "Behavior of Heavy Metals in Marine and Lacustrine Sediment Cores, South Puget Sound, Washington" Christian studied the distribution of heavy metals in sediment cores collected from Tacoma-area lakes and from Commencement Bay to see what factors influence the behavior of lead, copper, and other pollutants after they are deposited. His results suggest that redox-driven dissolution and reprecipitation processes can lead to enrichment of metals in the upper sediment layers of lakes, but that the process is less important in marine environments. Christian subsequently earned his M.S. in igneous petrology / isotope geochemistry from the University of Arizona and a second M.S. from MIT. He is currently a wine importer in London.
Click here to read Christian's 2006 GSA Abstract
Rachel Peters (Class of 2006). "Petrology of the Teanaway Dike Swarm, Central Cascades, Washington" Rachel's research focused on the geochemistry of the Teanaway dikes, a swarm of Eocene basaltic-andesite dikes that intrude sedimentary rocks of the Swauk Formation in Central Washington. She demonstrated the Teanaway rocks are chemically distinct from the younger and more voluminous Columbia River Basalts, and that the Teanaway magmas came from a heterogeneous mantle source.
Click here to read Rachel's 2006 GSA Abstract
Kevin Stein (Class of 2006). "Petrology and Origin of Crustal Xenoliths from Tumalo Cinder Cone, Central Oregon Cascades" Kevin worked on a suite of granitic xenoliths collected from the Tumalo Cinder Cone, a small volcano located west of Bend, OR. The goal of his work is to establish the age and composition of the crust under this region of the Oregon Cascades. Based on age dating and geochemistry, Kevin found that the xenoliths are derived from a young (<1 Ma) pluton that is geochemically distinct from any of the felsic volcanic rocks in the region. After graduating from Puget Sound Kevin earned his MD/PhD from Washington University in St. Louis.
Click here to read Kevin's 2006 GSA Abstract
Joe Gustafson (Class of 2005). "Petrology in the Western Oregon Cascades: A Study of Four Miocene Plutons". Joe studied the petrology of four plutons in the Oregon Cascades, including the Nimrod granite, which is the only "true granite" in that portion of the Cascades. He showed that this granite probably formed by fractional crystallization of a dioritic magma, accompanied by late-stage potassium addition. Another outcome of his study was the discovery that the compositions of Cascade magmas (in particular their Ca/Na ratios) have changed systematically over the past 35 Ma. We think this effect records the gradual thickening of the crust beneath the Cascades. Joe earned his M.S. in hydrology at the University of Arizona and now works in the oil industry in Montana.
Click here to read Joe's 2004 GSA Abstract
Melissa Wolfe (Class of 2005). "Petrology and Geochronology of Felsic Volcanic Rocks on the Olympic Peninsula: Implications for Eocene Tectonics". Melissa worked on felsic volcanic rocks from four localities on the Olympic Peninsula. The rocks at three of these sites are adakites and probably formed in response to subduction of the Kula-Farallon Ridge during the Eocene. Melissa dated two of these adakite deposits and based on these ages was able to constrain the timing and location of ridge subduction. Her adakite data show that the rocks fall into two groups which differ in Ca/Na ratio, an effect that we think may reflect spilitization of the slab. Melissa subsequently earned her M.S. in Geology at the University of Kansas.
Click here to read Melissa's 2004 GSA Abstract
Peter Bell (Class of 2004). Peter worked with the USGS on a study of slag-contaminated sediment from Lake Roosevelt, the water body behind Grand Coulee Dam. He worked out a procedure for separating slag grains from the rest of the sediment and then used a sequential extraction procedure and SEM imaging to determine where various elements were hosted in the sediments. He showed that some elements (e.g., Cd) are primarily present on grain surfaces while others are still contained in slag grains (and thus presumably less bioavailable). Peter now works for an environmental consulting firm in Minnesota.
Click here to read Peter's 2003 GSA Abstract
Cara Ponzini (Class of 2004). "Petrology of the Index Batholith, North Cascades, Washington". Cara's project focused on the petrology of the Index batholith, but also included the first regional comparison of chemical data from Cascade arc batholiths. She identified a difference in the composition of Cascade arc rocks - both plutonic and volcanic - in northern Washington versus those to the south. We think this difference may reflect a change in the composition of the crust that occurs around the latitude of Highway 2. Cara earned her law degree from Lewis and Clark and is a lawyer in Bend, OR.
Click here to read Cara's 2003 GSA Abstract
Erika von Schneidemesser (Class of 2004). Erika developed a procedure for extracting and analyzing organic compounds in a sediment core collected in the Thea Foss, Tacoma. She identified phthalates at all depths within the ~60 cm long core, which suggests that these synthetic organic compounds (which may be carcinogenic) can persist in sediment for many decades. Erika subsequently earned her PhD in atmospheric chemistry from the University of Wisconsin – Madison and is now a research scientist at the Institute for Advanced Sustainability Studies in Potsdam, Germany.
Kristin Hill (Class of 2003). "Petrology of Mafic Plutons Associated with the Snoqualmie Batholith, North Cascades, Washington". Kris studied the petrology of four small gabbro and diorite bodies that are associated with the Oligocene Snoqualmie batholith. All four bodies have geochemical traits indicative of an arc setting, but only one is demonstrably related to the Snoqualmie batholith (based on field evidence). After graduation Kris went to graduate school at Western Washington University where she conducted gravity surveys at Mt. Baker and received her M.S. in 2007.
Click here to read Kris's 2003 GSA Abstract
Pete Doumit (Class of 2002). "Stratigraphy of the Type Section of the Bumping River Tuff, Mt. Rainier National Park, WA". Pete studied the stratigraphy and geochemistry of a 1250 foot section through the type locality of the Bumping River Tuff, which erupted about 24 Ma forming the Mt. Aix caldera. After UPS he earned his M.S. in Geology from University of Northern Colorado; he now works as a geologist in Utah.
Kerry Schmidtbauer (Class of 2002). "Petrology and Mode of Emplacement of Andesite Bodies Near Enumclaw, WA: Magmatism West of the Main Cascade Arc". Kerry worked on two andesite plugs that form isolated "hills" in the Puyallup River Valley near Enumclaw, WA. Her main goal, aside from describing their petrology, was to determine their mode of emplacement, specifically whether they were volcanic necks or erosional remnants of one of more sills. Based on chemical differences and crystal size distribution, Kerry determined that the two bodies were separate intrusions and probably represent volcanic necks. Kerry received her PhD in geology at University of Nevada-Reno.