Student Research
We encourage our geology
majors to conduct field- and/or lab-based research as part of their
undergraduate experience. This work
commonly culminates in a thesis project, normally conducted over the summer and
followed by a presentation at a professional conference. Listed below are titles, brief summaries, and
links to abstracts of 52 student research projects I have supervised since
2002. Most of these projects involve the
petrology and geochronology of igneous rocks, or the geochemistry of lake
sediment, lake water, and/or groundwater.
Colin
Glaze (Class of 2021). “Identifying the Effects of Alum Treatment on Water and
Sediment Chemistry of Two Lakes in Pierce County, Washington”. Colin is collecting and studying
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 of the
sulfur and its impact on pore water chemistry.
Nancy
Hollis (Class of 2021). “Exploring
Possible Strategies for Hazardous Algal Bloom Mitigation In
Spanaway Lake, Tacoma, Washington”.
Nan is setting 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 is investigating the petrology and
geochronology of the earliest known Cascade arc rocks in Oregon, with the goals
of better understanding: (1) how the compositions of Cascade arc magmas have evolved
over the past ~40 Ma and (2) where the earliest activity related to the modern
occurred.
.
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.
Click here
to read Clara’s 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 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 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 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 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 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 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 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 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 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. He is now teaching outdoor
education for the National Park Service.
Click here
to read Liam's 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 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 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 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 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 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 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 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 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 GSA Abstract
Sarah Glancy (Class of
2009). 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 GSA Abstract
Ben Shapiro (Class of
2009). 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 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 AGU Abstract
Christian Manthei (Class of 2006). 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 GSA Abstract
Rachel Peters (Class of 2006). 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 GSA Abstract
Kevin Stein (Class of 2006). 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 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 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 earned her M.S. in Geology at the University of Kansas.
Click here to read Melissa's 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 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 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 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 is currently pursuing her PhD in geology at University of Nevada-Reno and teaching at a community college.
Click here to read Kerry's GSA abstract.