Relationship
of ostracode abundance and taphonomy to environmental variables on the
Luiche Delta Platform, Lake Tanganyika, East Africa
Jana M. Van Alstine1, Andrew
S. Cohen1 and Kiram E. Lezzar2
1Department of Geosciences, University of Arizona, Tucson, 85721, AZ
2Department of Geology, Syracuse University
Email: janava@geo.arizona.edu
Tanganikan subfossil ostracodes
from Lake Tanganyika accumulated over the past 50 years in surficial
sediment were analyzed in order to examine relationships between taphonomic,
subfossil abundance, and environmental variables, and identify variables
of taphonomic potential value for paleoclimate reserach. Samples were
taken from five northeast-southwest transects, shallow to deep profiles,across
the Luiche Delta Platform in the Kigoma region of Lake Tanganyika, Tanzania.
Ostracode valves were examined for redox staining, breakage, and abundance,
and compared against depth, geography, proximity to river mouth, and
total organic carbon. Strong relationships were shown to exist between
the taphonomic and environmental variables with this study, revealing
a complex system of associations on the delta platform. In particular,
a strong correlation between vavle breakage and water depth was shown
by this research. The exponential regression produced by this relationship
makes it possible to generate a paleo-lake level curve for Lake Tanganyika
using core samples taken in 1999 with the Nyanza Project.
Soil characterization at the World's Fair mine site,
Patagonia mountains, Santa Cruz County, SE Arizona: Implications for
baseline metal transport during storm runoff events
Kelly L Ashton1 and Oscar
A. Duarte2
1College of Agriculture and Life Sciences, University of Arizona, Tucson,
Arizona 85721
2US Geological Survey, ENRB, Tucson, Arizona 85719
Email: kashton@usgs.gov
The World's Fair Mine, located
in the Patagonia Mountains, SE Arizona, produced just over $1,000,000
in ore by the early turn of the century (1915). The reported workings
yielded silver, gold, lead, and copper ores in the form of lead-silver
sulfides, tetrahedrite, along with minor chalcocite and silver-bearing
stibnite. The target mineralizing system occurs as N. - S. trending
quartz-barite veins hosted in a body of Cretaceous-age quartz diorite
and rhyolite. The altered area ranges from 15-35 ft wide and is closely
associated with a rhyolite dike that crosscuts the diorite. The vein
is exposed for approximately 1000 ft down the dip slope; 600 ft of the
vein has been excavated during the development of the mine. Currently,
the mine site is abandoned and is part of a cluster of deposits found
in the upper portions of Alum Gulch. The World's Fair Mine site has
been identified as a contributor to the degraded condition of the Alum
Gulch Watershed. The objective of this study was to characterize the
soils and exposed waste rock material in the vicinity of the mine site
with respect to their pH, mineralogy, acid generating potential, and
trace element content and evaluate their impact on storm runoff in the
watershed.
A portion of the area is
underlain by a thin, rocky soil horizon representing undisturbed soils
developed over country rock (diorite) and mineralized but heavily oxidized
vein and selvage zones (altered rhyolite and quartz vein); segments
of the lower slopes hosting the mineralized veins are marked by adits,
shafts, and dissected waste-rock piles. Several traverses were selected
to cross the country rock, undisturbed oxidized vein segment, and the
disturbed waste rock piles. Composite samples were obtained at approximately
10 ft intervals across structure. Preliminary analysis of soils show
that: 1) pH of soils overlying diorite country rock, altered diorite/rhyolite
vein and selvage showed slightly acidic values (~6- 5.5). The soil pH
of waste rock was considerably lower at around 3.6; 2) selected metals
(Zn, Pb, Ag, Cu, Fe, Al, Cd) and trace element concentrations were highly
variable in soils overlying oxidized vein material and waste rock but
generally elevated. Oxidized vein material anomalous values were comparable
to waste rock samples. Both sample sources were an order of magnitude
greater than the soils overlying unmineralized country rock; 3) acid
generation potential was negligible (neutral) in the soils of country
rock and oxidized vein material, however, high acid generating potential
was noted in waste rock samples.
Although further testing
is warranted, preliminary data suggest that surface exposures of weathered
mineralized soils and rock materials may contain elevated metal concentration
similar to waste rock, however neutral to near-neutral pH conditions
in intermittent waters in contact with the site preclude metals release
and transport. This stands in contrast to the acidification of waters
in contact with pyrite-bearing waste rock and accompanying dissolution
of resident metal species.
Experimentally derived constraints on calcareous lacustrine
fossil preservation following the Chicxulub acid trauma
J.V. Bailey1, A.S. Cohen1
and D.A. Kring2
1Department of Geosciences, University of Arizona, Tucson, AZ 85721-0077
2Department of Planetary Sciences, Lunar and Planetary Laboratory, University
of Arizona ,Tucson, AZ 85721
Email: jbailey@jupiter.lpl.arizona.edu
The end-Cretaceous Chicxulub
impact event, which occurred on a shallow marine shelf, produced an
estimated 10 to 1000 GT of sulfur oxides, which were injected into the
stratosphere as part of a globally-distributed vapor-rich plume. These
sulphate aerosols eventually settled to the troposphere from which they
promptly fell as acid rain. Whereas the deep ocean probably had a buffering
capacity able to withstand the most extreme estimates of impact-generated
acid rain fallout, the acid's effect on shallow water systems such as
lakes, rivers, and shallow epicontinental seas, is far less certain.
Some workers have suggested acid rain as a possible K/T extinction mechanism.
Potentially, such an influx of acid could also affect fossil preservation
by dissolution of calcareous remains at the surface and by the removal
of buried remains via the leaching action of acidic groundwater.
We investigated the effects
of hypothetical acid traumas on the preservation of buried lacustrine
microfossils through a series of dissolution experiments. Because factors
such as lake size, catchment area, precipitation, local humic acid production,
and natural buffering capacity strongly influence a lake's resistance
to acidification, the effect of the Chicxulub acid trauma on any particular
Cretaceous paleolake would be influenced by the lake's initial conditions
and the magnitude and duration of the acid input. Our experimental setup
and conditions were designed to test the preservation potential of sediments
from a variety of shallow water environments, which were subjected to
a range of acidification conditions. Plastic tanks, filled with lake
mud and ~12L of water, served as proxies for the sediment-water interface
of several hypothetical acidified paleolakes. Modern ostracod carapaces
were added to the sediment at depths of 1 cm, 5 cm, and 10 cm. In order
to simulate a range of initial lake alkalinity and bedrock buffering
conditions, the inorganic carbon content of the sediment (1, 10, and
20% CaCO3) was varied. Differing sulfuric acid treatments (pH 1.9, 3
and 4) were used in combination with each buffering treatment, with
daily water changes to maintain acidity conditions. Four cores were
taken from each tank 3, 12, 42, and 150 days after the initial acidification.
Post-treatment ostracod abundances were determined by light microscopy
and taphonomic condition of the valves was determined using electron
microscopy. Carapace recovery was measured as a function of time, burial
depth, inorganic carbon of the sediment, and pH of the water. Presence
of carapaces showed a strong positive correlation with the amount of
inorganic carbon in the tank's sediments. Of 108 total recovered core
sections, 31 contained no carapaces. Of the 31 core sections with no
carapace recovery, 26 were from tanks with the lowest (1% CaCO3) buffering
capacity. Carapace recovery also showed a weak negative correlation
with increasing time, lower pH, and shallowing depth. These data suggest
that buffering capacity, rather than pH, time, and burial depth, is
the primary mitigating factor in microfossil preservation. Buffering
capacity may also have determined the survival of organisms with calcareous
or Ca-phosphate skeletons in lakes and other shallow water settings
at the K/T boundary. Because buffering capacity is governed by the mineralogical
composition of the bedrock, we predict that survival of lacustrine organisms
and preservation of calcareous lacustrine fossils would have been much
higher in lakes with calcareous catchments, versus poor preservation
in lakes underlain by black shales or granitic rocks.
Our results suggest that
the biostratigraphy of fossils studied from K/T boundary shallow water
sediments should be viewed within the context of local fossil preservation
conditions, including the paleowatershed's bedrock composition. Furthermore,
the survivability of shallow-water taxa, may be intimately related to
the paleogeology and buffering capacity of their local habitat.
Debris aprons and channels in the Reull Vallis region
of Mars
Daniel C. Berman1,2, William
K. Hartmann2 and David A. Crown2,
1Department of Geosciences, University of Arizona, Tucson, AZ 85721
2Planetary Science Institute, 620 N. 6th Ave., Tucson, AZ 85705
Email: bermandc@geo.arizona.edu.
The highlands to the east
of the Hellas impact basin in the southern hemisphere of Mars contain
a variety of complex, interacting geologic structures. The older highland
terrain is intermixed with younger, smoother plains; it is dotted with
mountains, volcanoes, massifs with debris aprons, and is intersected
by several outflow channels. This work includes a comprehensive survey
of images from the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)
of the Reull Vallis region. Through crater counts and stratigraphic
analyses, the precise interactions of these various terrains is studied.
It is clear that the same processes affect these terrains and their
histories are inter-related. By studying not only the youngest surface
features, but the geologic history of the entire region, we can gain
a better understanding of the continuing activity in the area. Water
plays a primary role in the geologic history of this region [1]. Aside
from the outflow channels, water has also influenced the evolution of
the volcanoes and the debris flows. We hope to gain a better understanding
of the sources of the water, as well as any present content, through
this study.
Using the Hartmann crater
counting methodology [4], we have obtaines crater population data for
many MOC images. Counting craters on MOC images tends to give small
statistics. To make these data more robust, we count multiple images
over similar terrains. The counts on each image are then plotted together
to see how well they match up. In most cases, they overlap very clearly.
In that case, the counts are then summed together, giving counts of
a larger, but not necessarily contiguous area. This region contains
four major outflow channels: Reull Vallis, Harmakhis Vallis, Dao Vallis,
and Niger Vallis. Studies of the latter two are underway. Reull Vallis
extends for ~1500 km through terrains of varied ages and morphologies,
and there is evidence for multiple flow events. The floor of the channel
contains infill deposits with pits and lineations that parallel its
walls, suggesting possible ice flow activity. Crater counts show an
age of the floor material on the order of 100 My, which is also very
close to the age we found for the surrounding plains. The debris aprons,
previously mapped by Crown [3] are clearly very young features. MOC
imagery shows few unmodified craters on the debris flows. Distinct,
overlapping flows are also evident, which indicates multiple, discontinuous
movements down the slopes. The crater counts of the debris aprons show
a distinct pattern that differs from almost any other region we have
analyzed; the pronounced flattening of the curve at smaller diameters
suggests either multiple episodes of flow, with different crater populations
on neighboring flows, or even continuous mass movement down the slope.
The geologic history of
this region is highly complex, with clear interactions between the various
landforms. By using crater counting techniques, we can gain a better
understanding of these processes.
References: [1] Mest S.
C. and Crown D. A. (2001) Icarus, 153, 89-110. [2] Crown D. A. et al.
(1992) Icarus, 100, 1-25. [3] Crown D. A. et al. (2002) LPSC XXXIII,
Abstract #1642. [4] Hartmann W. K. and Neukum G. (2001) Space Sci. Rev.,
96, 165-194.
Whispers from the Proterozoic Ruin Granite: Possible
down-dip extensions of previously mapped Laramide reverse faults into
crystalline rocks in the Tortilla Mountains, Arizona
Deb Bryan
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Email: debbryan@geo.arizona.edu
Proterozoic Ruin Granite
is exposed in the Tortilla Mountains, 120 km north of Tucson, Arizona.
The Tortilla Mountains have a complex history of multiple episodes of
Proterozoic intrusion, Laramide magmatism, Proterozoic and Laramide
hydrothermal alteration and Tertiary normal faulting with associated
tilting which is still not fully understood. In the study area, the
Proterozoic Ruin Granite (1.4 Ga), previously mapped as a single unit
exhibits several textural phases and is intruded by sheets of Proterozoic
diabase (1.1 Ga) and late-Laramide rhyodacite dikes. Current mapping
as an Independent Study with the Center for Mineral Resources and with
the EDMAP program has provided new information. Evidence from the attitude
of Tertiary sedimentary rocks on the eastern side of the mountain range
suggests that the entire range is tilted on its side, top to the east.
Recent mapping of Tertiary sedimentary rocks and bedrock exposures indicates
that the 90° of net rotation was produced by many episodes of normal
faulting and associated tilting. (GeoDaze 2003 abstract by Dave Maher
et al) Moreover, new mapping suggests that the range also may have been
affected by early Laramide-age reverse faulting, prior to emplacement
of the Teacup Pluton (new U-Pb date of 73 Ma) and its associated rhyodacite
dikes. (GeoDaze 2003 abstract by Gibbons et al,) The inferred reverse
faults place Ruin Granite directly on Ruin Granite and display local
ductile fabrics. These reverse faults appear to cut off sheets of Proterozoic
diabase, which are then shown repeated across the map area before being
transected by the late-Laramide rhyodacite dikes. The hypothesis of
Laramide reverse faults in crystalline basement is supported by the
occurrence of inferred Laramide-age reverse faults involving Proterozoic
and Paleozoic sedimentary strata structurally up section to the east.
In addition to the above-mentioned ductile deformation and hydrothermal
alteration, the Ruin Granite also occurs as brecciated masses lying
against unaltered undeformed Ruin Granite. The brecciated rocks of uncertain
origin contain very angular clasts, seemingly formed by some form of
brittle deformation. Further examination of brecciated Ruin Granite
may shed new light on the structural history of the area.
Geophysical and GIS investigation of Black Mesa Basin,
northeastern Arizona: Implications to Natural Resource Management
Robert R. Casavant1, Justin
Manuel1,*, Mark Gettings2 and Shanda Wagner1
* presenter
1Department of Mining and Geological Engineering, University Of Arizona,
Tucson, AZ
2U.S. Geological Survey, Tucson, AZ
Email: jmanuel@email.arizona.edu
The Black Mesa Basin, in
northeastern Arizona, occupies most of the southwestern portion of the
Colorado Plateau and encompasses a majority of the Navajo and Hopi Reservations.
Previous field studies and laboratory models infer the presence of a
coarse network of regional, deep-seated northeast- and northwest-trending
fracture zones beneath the exposed Mesozoic rocks. Determination of
fracture zones was based largely on morphological discontinuities, alignments
of exposed Laramide-age fold structures and Cenozoic volcanic centers.
Our recent geological and
geophysical analysis validates this, however, we interpret the fracture
zones to represent deep-seated basement fault zones. Image processing
of residual aeromagnetic and isostatic gravity maps reveal discontinuous,
regionally linear, anomalously steep gradient lineaments trending northeast,
northwest and north. These lineaments support a basement fault interpretation
and are exhibited by the well documented Mesa Butte and Bright Angel
fault zones. These faults zones, which are more numerous than previously
documented, define blocks of variable dimensions in a dense mosaic arrangement.
Some zones have undergone periodic reactivation, whereas, others exhibit
en echelon patterns suggesting wrench faulting.
A GIS analysis integrating
basement fault fabrics with surface drainage patterns, groundwater movement
and the structural and stratigraphic architecture of Mesozoic and Paleozoic
formations reveals that deep faulting plays a profound role in the continuing
geologic and hydrologic evolution of the region. Integrating deep structure
into future geologic and hydrologic models could improve the characterization
and management of natural resources on the Navajo and Hopi Nations.
Eastern
Whetstone mountains fault model investigation
Scott Geauner1, Ross Waldrip2
and Robert R. Casavant1
1Department of Mining and Geological Engineering, University of Arizona,
Tucson, AZ
2Department of Geosciences, University of Arizona, Tucson, AZ
Email: sgeauner@email.arizona.edu
Kartchner Caverns State
Park, located in the Whetstone Mountains 13 km south of Benson, is an
isolated block of Paleozoic limestone, referred to as the "Kartchner
block". The enigmatic block is downthrown to the east juxtaposing
the Mississippian Escabrosa Limestone against Precambrian alaskite.
Substantially more faulted than previously mapped, our recent studies
also reveal the presence of oblique normal faulting and shearing, which
appear to characterize major faults that cross the block. These faults
and shear characteristics can be located on the surface and within the
caverns. Their origin may relate to Cenozoic-age seismic events that
resulted in transtensional deformation throughout the southeastern Arizona
and the Northern Sonora region. Fault gouge, anatomizing patterns, oblique
normal rake, and fault intensity provide evidence of shearing across
the block suggesting a new model that incorporates a minor strike-slip
component.
Testing for this model will include a detailed characterization of footwall
deformation immediately to the west and northwest of the block and along
the eastern flank of the Whetstone Mountains. Fault mapping will be
integrated with regional and local gravity and aeromagnetic analyses.
Aerial photograph interpretations and fluvial geomorphic indices will
be used to guide the field mapping of exposed and buried faults. The
additional surface mapping will help to a better reconcile regional
structural trends and contribute to an improved understanding of the
tectonic processes that shaped the Basin and Range Province of southeast
Arizona.
Multiple episodes of magmatism and metasomatism in
the Tortilla Mountains revealed by Tertiary crustal extension, Southeast
Arizona.
Stacie Gibbins, Julie Hamblock,
Eric Jensen, Chao Li and Dave Maher
In the Tortilla Mountains
of southeast Arizona, Tertiary extensional faults have tilted crustal
blocks on the order of 90¼ to the east. In the vicinity of Grayback
Mountain (northern Tortilla Mountains) this tilting has exposed a portion
of the crust to paleo-depths on the order of 10km. This has presented
an extraordinary opportunity to study, in map view, a cross section
through several magmatic-hydrothermal systems from shallow to deep levels.
Important igneous lithologies exposed in the Grayback area include (1)
1.4Ga Ruin Granite, (2) 1.1Ga diabase sills, (3) 73 Ma Teacup Pluton
and related rhyodacite porphyry dikes, and (4) younger Laramide (?)
hornblende andesite dikes. Field mapping, complemented by select lab
work, reveals a complex history of multiple intrusive phases and related
hydrothermal alteration associated with both the Ruin and Teacup magmatic
events.
Detailed mapping of the fault block has identified multiple igneous
phases and their time-space distribution in the Ruin Granite and Teacup
Pluton. The Ruin Granite is comprised of: (1) a megacrystic K-feldspar
granite, (2) an equigranular granite, (3) a porphyritic granite (a finer-grained
version of the megacrystic granite(?)), and (4) an aplitic granite.
The Teacup Pluton is comprised of: (1) a bio-hbl granodiorite, (2) a
bio(( hbl) granodiorite, (3) a musc-bio granodiorite, (4) a bio-hbl
monzodiorite, (5) a garnet-musc granite with abundant aplites and pegmatites,
(6) rhyodacite porphyry dikes.
We were able to differentiate
and map hydrothermal events related to Proterozoic magmatism from those
related to Laramide magmatism. Alteration associated with the hydrothermal
system(s) of the Ruin Granite includes veins of: (1) qtz + tourmaline(±
Kspar ± musc), (2) qtz + Kspar, (3) specular hematite + (Mn-rich)
calcite(cc) + montmorillonite, and (4) late calcite. These veins are
truncated by the Teacup bio-hbl granodiorite. Alteration associated
with the Teacup pluton includes: (1) High-temperature K-silicate alteration
(Kspar-bio-qtz) observed near the cupola of the pluton (now exposed
to the east due to rotation), (2) sericitic (qtz-ser-py) alteration
lateral to the K-silicate alteration (north and south) and in the direction
of paleo-up (farther east), (3) low-temperature, epidote-rich alteration
outward from the cupola (north and south), and, related to subsequent
phases of the Teacup pluton intruded at deeper levels (farther west),
(4) renewed K-silicate alteration (Kspar-qtz) and (5) sheeted greisen
veins (qtz-course musc-py).
Zircons from two phases
of the Teacup pluton (the oldest and one of the youngest intrusions,
based on cross-cutting relationships) were dated using the laser ablation
ICP-MS technique at the University of Arizona. The older, abio-hbl granodiorite,
yielded a date of 73.8 ± 3.1 Ma and the younger, a musc-bio granodiorite
yielded a date of 72.7 ± XXXXXXXXXX Ma. This places the timing
of crystallization of the Teacup Pluton 10Ma earlier than previously
reported K-Ar ages.
The occurrence of multiple
intrusions and hydrothermal systems during the Laramide reveals a complexity
that has not previously been recognized or associated with Laramide
magmatism. New mapping of intrusive phases and related alteration can
be used to reconstruct the complex structural history in the region.
Yields a better understanding porphyry related hydrothermal systems
(can make excellent observations at various levels in the crust)
(see also abstract by Maher,
et. al., this volume)
This work was completed
during the Spring of 2002 as part of an EDMAP-supported (USGS educational
mapping program) course at the University of Arizona. Mark Barton, George
Gehrels, David Johnson, and Eric Seedorff also contributed to the mapping,
geochronologic, and other aspects of this study.
Use of seismic attributes in gas hydrate reservoir
interpretation, North Slope, Alaska
Casey Hagbo and Roy Johnson
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Email: chagbo@geo.arizona.edu
Gas clathrates, commonly
known as methane or gas hydrates, are an ice like crystalline solid
composed of water and natural gas, primarily methane. Gas hydrates occur
in the shallow subsurface where both water and gas are present within
low temperature and moderate pressure regimes. The shallow subsurface
geology of the North Slope is structurally dominated by a broad antiform,
known as the Barrow Arch, and is riddled with a myriad of high angle
normal faults trending roughly north south and east west. In addition
to the complex structure, the hydrate bearing units are predominantly
fluvial and northward prograding deltaic strata. The complexity of the
local geology coupled with the lack of a consistent amplitude anomaly
associated with hydrate occurrences make simple horizon interpretation
of hydrates difficult to impossible. In order to gain a better understanding
of the hydrate distribution as well as a clearer picture of the local
geology, seismic attributes are being used in conjunction with traditional
horizon to well tie interpretation techniques. Several of the attributes,
based in the Hilbert Transform, can yield information about the physical
properties of the hydrate bearing units. For example hydrate layers
may have an anomalous frequency response based on their relatively high
acoustic velocity. Delineation of high angle faults and possible channel
deposits are aided by the use of calculated coherency and edge detection
volumes. Coherency and edge detection volumes are essentially a measure
of trace to trace similarity, so discontinuities in the seismic data
are brought into tighter focus. The use of these attributes as well
as others yields a clearer picture of hydrate distribution as well as
a more accurate structural model. This poster was prepared with the
support of the U.S. Department of Energy under Award No. DE-FC26-01NT41332.
However, any opinions, findings, conclusions, or recommendations expressed
herein are those of the author(s) and do not necessarily reflect the
views of the DOE.
Digital Earth natural disaster readiness activity
Nievita B. Hartness1, Martin
J. Seneca2, Katie L. Nealeigh3, S. Raj Chaudhury4, Waldo J. Rodriguez5,
Barbara J. Cooper-Pabis6 and Kerry Lee6
1Department of Geosciences, University of Arizona, Tucson, AZ
2Department of Mathematics, Northeastern Illinois University
3Department of English, Wright State University
4Department of Physics, Norfolk State University
5Department of Atmospheric Sciences, Norfolk State University
6BEST Lab, Norfolk State University
Email: nhartnes@geo.arizona.edu
We have developed an interactive
learning module, designed for the non-science major college student,
which involves analysis of the effects of the 1997-1998 El Niño
Southern Oscillation anomaly on natural disasters in the United States.
Case studies are presented on flood, fire and drought. Our methods involved
data mining information available on government, educational and public
information websites and the creation of qualitative and quantitative
exercises. The module will be tested with the target student population
during the Spring of 2003.
Holocene fault activity beneath the Great Salt Lake
Andrew M. Hennes and Roy
A. Johnson
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Email: ahennes@geo.arizona.edu
Fault scarps along the Wasatch
Front evidence seismically active normal faults that accommodate east-west
extension along the eastern margin of the Basin and Range province.
These well-defined normal faults accommodate large offsets that juxtapose
Precambrian rocks of the Wasatch Range against thick syntectonic Tertiary
strata in the Salt Lake Basin. Mohapatra and Johnson (1998) identified
a system of similar listric normal faults with large offsets in seismic
reflection data from beneath the Great Salt Lake. Offsets near the surface
on these listric faults are evident in several seismic profiles from
the Great Salt Lake and suggest displacement has continued through at
least the Tertiary. Some of these young faults may in fact have movement
recent enough to breach the surface and produce a scarp even in the
relatively rapid sedimentation of this sub-aqueous environment. Fathometer-recorded
water depths collected during this dense seismic program in the Great
Salt Lake allow a unique opportunity to construct a detailed bathymetric
map of the Great Salt Lake. Geostatistical analysis of the water depth
reveals the expected relatively smooth overall bathymetric surface of
the floor of the Great Salt Lake except for several abrupt changes in
the bathymetry. A plot of the gradient magnitude, or rate of change
of the bathymetry, indicates several linear features with steep surfaces
much like fault scarps that trend along the regional fault fabric. These
anomalous surface gradients correlate well with seismically defined
normal faults that run along the western margin of Promontory Point
and Antelope Island, as well as along the northern side of Carrington
Island, suggesting that these faults do breach the surface. Development
of a fault scarp in a flat, shallow, internally drained basin indicates
very recent fault activity along large faults beneath the Great Salt
Lake.
Middle-Cambrian faunas of the Weeks formation, west-central
Utah
Hector R. Hinojosa
University of Utah, Salt Lake City; Summer Research Opportunity Program
2001
Email: pachuco411@hotmail.com
The North Canyon Quarry
of the Weeks Formation crops out in the House Range of Utah. It is a
sequence of an inner belt of marine sandstone and shale, an intermediate
belt of carbonate rocks, and an outer belt of mud and breccias with
exceptionally well-preserved polymeroid trilobites, in its uppermost
section. The trilobites date from the upper-middle to the lower-upper
Cambrian, and are important to stratigraphic zonation in western North
America because amplify the understanding of geologic processes in west-central
Utah. Modocia (Walcott) from the upper part of the Weeks formation allows
correlation with the upper Cambrian Kulyumbe stage, in Igar region of
northwestern Siberia. L. laevigata, from the lower part of the formation
correlates with strata in: 1) the uppermost Bolaspidella zone and much
of the Cedaria Zone in North America; 2) the L. laevigata zone of North
Greenland, which ranges throughout Formation T2 of the Tausens Iskappe
Group; 3) the Westergard's Solenopleura brachymetopa zone in Sweden,
and the upper subzone with his zone of L. laevigata; 4) the lowest observed
occurrence in the Huaquio Formation, Hunan China, and 5) Antarctica,
Argentina, Australia, Canada, Kazakhstan, Siberia.
Construction of the upper Sabino Canyon dam
Dave Hohman
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Email: hohman@email.arizona.edu
In the 1930's a large dam
was to be constructed in Upper Sabino Canyon. The road that is there
now was built for the construction crews to build the dam. This dam
would create a large lake for boating, swimming and other recreation.
Funding issues led to the cancellation of the project.
Using digital elevation
models (DEM's) of Sabino Canyon and its surrounding area, along with
computer mapping programs, my project digitally finishes the construction
of the dam. I explore what the landscape of the area would be like today
with a lake and also take a look at the potential future consequences
of drastically changing the river profile.
The poster will give a history
of the dam project, show the canyon as it is today, show the canyon
as it would be today with a lake, and show what could happen in the
future to the river profile and how that would affect Tucson.
Plutons on end: A new look at the Proterozoic Ruin
Granite, Tortilla mountains, Arizona
Steven Hubbs
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Email: shubbs@geo.arizona.edu
In the northern Tortilla
Mountains (~100 km north of Tucson) the middle Proterozoic Ruin Granite
(1.440 ± 0.020 Ga U-Pb; Silver et al., 1981) has been previously
mapped as a single block of unfaulted, undifferentiated quartz monzonite.
Faults systems that offset overlying strata are usually not indentified
in these Proterozoic plutonic units because of the difficulty in recognizing
structural offset in what was regarded as a relatively homogenous plutonic
body. New field mapping has identified in detail multiple textural units
within the Ruin Granite and numerous types of superimposed hydrothermal
alteration, the latter related to both Ruin-age and Laramide alteration.
Laramide alteration is interpreted to be associated with the nearby
Teacup Granodiorite intrusion, recently dated at ~73 Ma (U-Pb; G. Gehrels
et al., unpublished data), and is part of a system that includes the
Kelvin and Riverside porphyry copper prospects.
Currently recognized textural
phases of the Proterozoic Ruin Granite include: (1) Megacrystic granite
(K-feldspar megacrysts locally >4 cm), (2) Porphyritic granite (quartz
phenocrysts, locally with strongly lineated qtz), (3) Pegmatitic granite
(quartz-K-feldspar ± tourmaline), (4) Aplitic granite (aplitic
groundmass of quartz-K-feldspar), and (5) Equigranular-seriate granite
(variably biotite-bearing). The superimposed alteration includes veins
of quartz + K-feldspar + tourmaline of probably Proterozoic age and
multiple zones of sericitic, biotitic, and chloritic alteration of probably
Laramide age. The Ruin Granite in the study area is anything but homogenous.
Nearby Tertiary strata exhibit
locally extreme tilting, with some beds rotated to ~90°. Indeed,
the northern Tortilla Mountains provide a rare opportunity to view a
pluton on its side, where paleodepth can be viewed to several kilometers
in well-exposed terrain. Evidence for extensive Tertiary normal faulting
within the Ruin Granite includes: (1) The presence of heavily gouged
zones of varying thickness and (2) the juxtaposition of contrasting
igneous phases and Laramide alteration styles. Field evidence indicates
faults in widely varying orientations, suggesting multiple generations
of crosscutting normal faults. The structural story of the study area
is of special interest in light of the copper resources of the area,
which includes the nearby Ray Cu-porphyry deposit. Recognition and mapping
of Tertiary faulting in the plutonic parts of the Proterozoic section
is essential to regional reconstruction.
Obstacles preventing K-12 science teachers from implementing
GLOBE in their classrooms
Kathy Likos and Michelle
Hall-Wallace
Department of Geosciences, University of Arizona, Tucson, AZ 85721
Email: klikos@geo.arizona.edu
GLOBE (Global Learning and
Observations Benefiting the Environment) is an international environmental
and science education program that involves K-12 students in collecting
and interpreting environmental data from their local area. Students
use universal protocols (that have been developed by GLOBE primary investigators/scientists)
to collect data in four major areas: soil, water, land cover, and atmosphere.
The data can then be entered into a database that is accessible to students
and researchers worldwide via the Internet. The goals of the program
are to enhance the environmental awareness of individuals throughout
the world, contribute to scientific understanding of the Earth, and
help all students reach a higher level of achievement in science and
mathematics. Teachers who choose to implement the GLOBE program in their
classrooms are required to attend a 20-30 hour training session to learn
about the program, the data collection protocols, and content knowledge
on each of the investigation areas. Approximately 30-40 teachers are
trained per year throughout southeastern Arizona. However, after earning
certification in GLOBE, few teachers implement any part of the program
in their classrooms. Discussion forums and surveys are being conducted
to investigate what obstacles prevent such a large percentage of GLOBE
certified teachers from implementing the program. We suspect that common
obstacles include lack of funds for specified equipment, challenges
integrating GLOBE program goals with the curriculum, and lack of initiative
to start the program due to the overwhelming amount of material covered
in the training sessions. Surveys to determine whether and how the GLOBE
program affects teachers' perspectives of the nature of science will
be developed as well. Lessons learned from evaluating the GLOBE program
will be used to adapt the program to better meet the needs of K-12 teachers
and to increase the program implementation in K-12 science classrooms.
Synextensional sediments record progressive faulting
and tilting in the Tortilla Mountains, AZ
David Maher1, Aaron Martin2,
Deb Bryan1, David Mauel3 and Steven Hubbs1
1 Center for Mineral Resources,
Department of Geosciences, University of Arizona, Tucson, AZ 85721
2 Department of Geosciences, University of Arizona, Tucson, AZ 85721
3 Department of Geological Sciences/MSC 3AB, New Mexico State University,
P.O. Box 30001, Las Cruces, NM 88003
Email: geodave@mindspring.com
Tertiary terrestrial sediments
were deposited in normal fault-controlled basins in the Tortilla Mountains
west of Ray, AZ from about 25 Ma to about 18 Ma. These deposits are
classic growth strata, with interfingered debris flow, fluvial, lacustrine,
and landslide megabreccia deposits exhibiting progressively shallower
dips in younger sediments as down-to-the-west faulting and rotation
of crustal blocks occurred. The sediments were deposited disconformably
on the bedrock, and locally the oldest beds are tilted more than 90°
from paleo-horizontal. The sediments are composed of variably mixed
older rocks, including altered and mineralized rocks related to various
hydrothermal systems. The study area is in the vicinity of several hydrothermal
systems, including the Teacup (Kelvin) and the Ray porphyry copper systems.
The Ray system is the largest known with approximately 6.5 million metric
tonnes of total contained copper.
A measured section about
1900 meters thick, in conjunction with reconnaissance mapping of sedimentary
successions in the Tortilla Mountains, provide insights into the tectonic
environment at the time of deposition, source areas for sediment, and
depth of erosion of those source areas.
From 100 to 420 meters above the base of the section, about ten large-scale
landslide megabreccia deposits occur. These moderately to locally very
thick (over 100 meters) oligomictic sediments are brecciated, but still
exhibit original stratigraphic features at a larger scale, suggesting
large-scale mass movement. Each megabreccia lithosome is monolithologic,
and the individual bedrock unit that was the source can usually be identified.
The landslide blocks dip about 60° to 50°. We suggest, therefore,
that the source area for the landslides was the hangingwall, which had
been tilted about 30° to 40° at the time the landslides occurred.
At this degree of tilt, bedrock stratigraphic horizons would become
unstable slip planes.
The monolithologic megabreccias
separate the basin fill into two genetically different successions.
Sediments within and beneath the megabreccias are composed entirely
of sedimentary-lithic clasts derived from Paleozoic and Proterozoic
strata widely exposed in southern Arizona. Cobble to boulder conglomerates
beneath the megabreccias were deposited in braided streams with dominant
paleoflow to the southeast. All units above the megabreccias are dominated
by volcanic-lithics, with very minor input from Paleozoic and Proterozoic
sources. Gravelly braided stream deposits with paleoflow to the northeast
are interbedded with debris flow deposits in the interval 420 to 940
meters. Above 940 meters, the debris flows become tuffaceous, and several
ash fall tuffs are present. Interfingering of braided stream and debris
flow facies suggests deposition on alluvial fans. Paleoflow direction
turns to the northwest in the upper part of the section.
Reconstruction of a cross
section (Seedorff, 2002) utilizing local and regional bedrock contact
relationships shows several sets of cross cutting faults and progressive
tilting during extension. The pattern of dip changes within the measured
section suggests that the process of tilting (resulting in the deposition
of growth strata) was episodic, separated by periods of relative "tectonic
quiescence". These periods of development of growth strata may
correlate to the generation and movement of new faults.
A new look at middle Tertiary dismemberment and rotation of Laramide
porphyry systems in southern Arizona
David Maher, Eric Seedorff
and Mark Barton
Center for Mineral Resources, Department of Geosciences, University
of Arizona, Tucson, AZ 85721
Email: geodave@mindspring.com
In southern Arizona, crustal
extension has dismembered, displaced, and rotated numerous porphyry
copper and associated igneous systems. From Globe-Miami to San Manuel,
re-evaluation of well-mapped quadrangles and new observations permit
an improved assessment of middle Tertiary crustal extension and its
profound impact on the distribution of igneous-related Laramide copper
mineralization. This provides an improved framework for exploration
for hidden mineral deposits and development of accurate deposit models.
The Globe-Miami and San
Manuel to Kelvin areas apparently lie within individual tilt domains
where on the order of 100% extension occurred on multiple generations
of faults that collectively cut and rotate paleo-up from <10 to >90°.
Regional tilt domains overlap in the area near Ray, Arizona. Here, multiple
generations of faults with opposing displacement directions result in
a number of smaller fault blocks that underwent a more complex tilt
history. The present orientation of individual blocks is the sum of
the tilts of the overlapping fault events (see also abstracts by Gibbins,
et al. and Maher, et. al., this volume).
Models of hydrothermal alteration
in porphyry systems were strongly influenced by exploration-driven work
in this region in the 1950s and 1960s when dismemberment of porphyry
systems by normal faults was first recognized. Evolving understanding
of regional-scale, post-mineral structure remains critical to reconstruction
of both hydrothermal and related igneous systems. Key issues in this
ongoing study include determination of paleo-up, identification of all
deposit fragments (including eroded portions), and clarifying what constitutes
variation in mineralogical zoning patterns versus structural juxtaposition
of different portions of hydrothermal systems. Tertiary extension was
also important to the supergene history through rapid exhumation of
deposits and modification of groundwater flow patterns.
Numerous complex geologic
contact relationships are seen in map view as approximate paleo-cross
sections and establish the structural pierce points in the faulted blocks
that have been displaced more or less laterally relative to the present
day surface. The structural pierce points observed in the study in southern
Arizona allow the reconstruction of numerous fault blocks that contain
mineral deposits, and highlight areas that may contain faulted segments
of known deposits.
Given that many of the mineral
deposits in southern Arizona are fault-bounded, exploration for deposits
in this terrain has long utilized structural interpretations. A revised
interpretation of regional extension opens windows for finding hidden
deposits or displaced fragments of known deposits. Application of regional
structural understanding to the deposit scale also has substantial economic
implications from feasability through production. For example, understanding
faults within deposits is key to generating accurate reserve calculations,
mine planning, and anticipating dilution effects and predicting ore-waste
boundaries for ore control.
Regional characterization of the Cretaceous Nanushuk
group: Preliminary assessment for CBM potential in northern Alaska
Keith Mitchell, Robert R.
Casavant and Justin Manuel
Department of Mining and Geological Engineering, University of Arizona,
Tucson, AZ
Email: keithm@email.arizona.edu
This NSF undergraduate research
experience (REU) will initiate a preliminary regional geological characterization
of the Cretaceous-age (Brookian) Nanushuk Group in Arctic Alaska. The
goals of the study include investigating the role of structure on the
distribution, storage potential and effective diffusivity of CBM (coalbed
methane) resources across the NPRA (National Petroleum Reserve of Alaska)
using 3D interpretation workstation in the newly developed Subsurface
Characterization and Imaging Lab (SCIL) in MGE. We are proposing that
regional syndepositional faulting, related to tectonism and kilometer-scale
denudation across the Arctic Alaska Terrane, could be related to the
quality and distribution of gas-rich coal seams. We hypothesize that
North Slope coal deposits may be more abundant and fractured, thicker
and thermally matured as a result of sediment accommodation and hanging
wall deformation associated with basement faulting and renewed thrusting
events.
The coal-bearing Nanushuk
Group is a sequence of fluvial-deltaic to shallow marine deposits that
has been studied extensively for its oil and gas potential. The studies
include characterizations by the U. S. Geological Survey (USGS), Alaska
Division of Geological and Geophysical Surveys (ADGGS) and a number
of exploration petroleum companies. The overall sequence consists of
interfingering parasquences of interbedded conglomerate, sandstone,
siltstone, shale and coal. Two- and three-dimensional reflection seismic
data reveal that the sequence thins to the north and east, transitioning
basinward into marine shales. In some locations, it is indistinguishable
from the clastic-rich shale-rich topsets of shale-dominated clinoforms
in the underlying Torok Formation. Surface and subsurface studies of
the petroliferous and coal-bearing Nanushuk Group continue to underpin
reassessments of energy resources throughout the vast NPRA. Current
petroleum exploration activities within the eastern portion of the NPRA
have included the Nanushuk clastics as one of several target horizons.
Our preliminary study will
reassess regional variations in gross thickness of Nanushuk and relate
it to the distribution and quality of coal deposits. Published two-dimensional
reflection seismic will be used to construct gross isopachs and structural
maps of the unit. Outcrop and well log data will serve as control points
for verifying formation thickness and variations in coal thickness and
quality. Results of this study will be interrogated in light of Cretaceous-
and Tertiary-age basement fault reactivation as indicated by stratigraphic
data and apatite fission track studies. Coal thickness, thermal maturation
and fracturing will be key factors in the anticipated exploration and
reservoir engineering of CBM resources throughout northern Alaska.
Bacterial adhesion in the subsurface environment:
Investigating the role of extracelluar polysaccharides
Sanjai J. Parikh, Anselm
Omoike and Jon Chorover
Department of Soil, Water, and Environmental Science, College of Agriculture,University
of Arizona, Tucson, AZ
Email: sjparikh@ag.arizona.edu
Molecular-level interactions
of bacterial adhesion to surfaces have not been adequately explained.
Understanding the surface chemical reactions of bacterial adhesion is
required to manipulate and control the adhesion process. Bacteria adhering
to natural surfaces can both be beneficial and detrimental. In aquatic
environments bacterial adhesion can be utilized to improve water quality.
These reactions are controlled by surface chemical reactions between
the exterior of bacteria cells, the physical characteristics of the
surface, and solution chemistry. The exterior surfaces of bacterial
cells comprise extracellular polymeric substances (EPS) and lipopolysaccharides
(LPS) (gram negative bacteria only) that likely are crucial in the adhesion
process. Studies investigating the role of both EPS and LPS in the initial
moments of adhesion increase understanding of, and the ability to predict
microbial binding. This in turn helps predict the fate and transport
of bacteria cells and environmental contaminants. In situ experiments
monitor the adhesion and growth of bacteria on a Ge crystal using attenuated
total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy.
Use of Attenuated Total
Reflectance/Fourier Transform Infrared Spectroscopy allows for non-destructive,
real time, in situ observation of bacterial adhesion. Using this technique
to study the adhesion of Pseudomonas aeruginosa, wild type (PAO1) and
alginate (negatively charged extracellular polymeric substance) over-producer
(PDO300), we have observed that the presence of excess alginate reduces
initial adhesion. Proteinaceous materials (1550 cm-1 and 1650 cm-1)
are important fingerprint regions in monitoring the adhesion of this
bacteria. A general trend of increased intensities for PAO1 is observed,
particularly for the amide I (1650 cm-1) and amide II (1550 cm-1) regions
of the spectra. PDO300 intensities do not increase significantly, consistent
with less adhesion. For PAO1, increased cell density is well correlated
with increased IR absorbance of bacterial surface functional groups.
The over production of alginate by PDO300 likely reduces the initial
attachment of P. aeruginosa to the Ge substratum. We believe that positively-charged
regions (proteins) control the initial adhesion of P. aeruginosa to
the Ge crystal. To compliment this research batch experiments will be
conducted to investigate the kinetics and effect of solution chemistry
on adhesion of LPS with environmentally relevant surfaces.
Evidence for Himalayan Paleozoic deformation through
magmatic intrusion analysis
Guy Pinhassi, George E.
Gehrels, Bishal N. Upreti and T.P. Ojha
Department of Geosciences, University of Arizona, Tucson, 85721, AZ
Email: guyp@swfo.arizona.edu
Cross-cutting relationships
among hosting neoproterozoic schists and granitic dikes, provides new
age constraints and important information on the importance of early
Paleozoic deformation in the Himalayan orogenic belt. In the Kathmandu
nappe, Bhimphedi Group schists are intruded by 2 phases of granitic
dikes. Older dikes that have a foliation are 486- 476 ± 18 Ma
in age, whereas a non-foliated, cross-cutting dike is 472 ± 12
Ma in age (ages from U-Pb in zircon). These dikes may indicate the cessation
of early Paleozoic deformation in the crystalline nappes of the Himalayan
orogenic belt.
Chronology and sedimentology of major lake-level
fluctuations on the Southern Bolivian Altiplano
Christa Placzek1, Jonathan
Patchett1, Jay Quade1 and Julio Betancourt2
1Department of Geosciences, The University of Arizona, Tucson, Arizona
85721
2U.S. Geological Survey, 1675 West Anklam Road, Tucson, Arizona, 85745
Email: cplaczek@geo.arizona.edu
A key controversy in South
American paleoclimatogy centers around conflicting lake histories based
on shoreline and downcore evidence from the Bolivian Altiplano. The
Altiplano depression, spanning 14 to 22°S (~3800 meters asl), is
defined by three large lake basins, Lake Titicaca to the north, Lake
Poopo in the center and the salt pans of Coipasa and Uyuni to the south.
These basins have coalesced into one megalake >90 m deep and ~50,000
km2 at least twice in the Quaternary, but the exact timing is disputed.
At stake in these megalake chronologies is the influence of global temperature
and the long-term history of the South American Summer Monsoon (SASM),
which could be sensitive to variations in seasonal insolation over precessional
time scales and changes in tropical and meridional SST gradients. Radiocarbon
dates from calcareous crusts and mollusks in both cores and shoreline
deposits in the Uyuni-Coipasa Basins suggest that Paleolake Tauca persisted
between 19 and 12 ka, with a highstand at ~16 ka. In contrast, a radiocarbon
chronology from total organic carbon suggests that Paleolake Tauca persisted
between 26.1 and 14.9 ka, centered on a peak in summer solar insolation
(~21 ka). This latter chronology argues for direct forcing of the SASM
by summer insolation over the Altiplano, the former calls for other
forcing such as changing SST gradients. The timing of an older Paleolake,
called Minchin, could help discriminate between competing hypotheses.
Paleolake Minchin was originally dated between 26 and 30 C14 ka based
on shoreline deposits but evidence from two recent cores in Uyuni-Coipasa
suggests that Minchin happened before 34 C14 ka.
We propose a chronology
for Altiplano megalakes based on U/Th chronology, radiocarbon dating,
and shoreline stratigraphy. This approach allows direct establishment
of lake level and replication of dates using more than one method. Lacustrine
units are manifested as diatomite, tufa, and gastropod-rich sediments.
We infer that only two megalake events occurred in the last 130 ka,
separated by a well-developed and persistent paleosol. The youngest
lake phase dates between 17-12.1 ka, with a maximum lake level at ~15.5
ka; the U/Th and 14C ages are remarkably consistent. U/Th dates from
the oldest lacustrine unit fall between 122 and 94 ka. Radiocarbon dates
from this unit, however, are as young as 30 C14 ka. The sensitivity
of infinite radiocarbon samples to in situ contamination call into question
the reliability of previous C14 dates for the Minchin Phase. Our chronology
suggests that climatic explanations be reexamined for megalake expansion
on the Bolivian Altiplano. For example, during periods of cold global
temperature (20-80 ka), thermal forcing of the SASM is probably insufficient
to sustain summer rains over the southern Altiplano. On the other hand,
higher lake evaporation and evapotranspiration rates, and more persistent
drought associated with higher ENSO frequencies, may also prevent lake
expansion during interglacials. Hypothetically, megalake expansion should
happen during periods of moderate global temperature, cool enough to
diminish lake evaporation and reduce evapotranspiration at higher elevations,
but warm enough to still drive large-scale monsoonal circulation and
summer precipitation over the Altiplano.
Seismic analysis of the space shuttle Columbia disaster
Marie D. Renwald, Tammy
K. Baldwin and Terry C. Wallace
Southern Arizona Seismic Observatory, University of Arizona, Tucson,
AZ 85721
Email: mrenwald@geo.arizona.edu
On February 1, 2003, the
Space Shuttle Columbia and crew were lost during reentry 16 minutes
before landing at Cape Canaveral, Florida. Columbia was at an altitude
of 200,000 feet over north-central Texas, traveling at 12,500 mph when
mission control lost contact and tracking data. Debris from the shuttle
was scattered over thousands of square miles of Texas and Louisiana.
Investigative efforts are focused on understanding how Columbia broke
apart.
Seismic data provides a
means of investigating this tragedy. Both sonic booms and atmospheric
explosions can be recorded on land-based seismometers. Using NASA's
projected flight path for the Columbia, we were able to identify seismic
networks and stations that recorded useful data. Comparing data from
this Columbia mission to previous shuttle missions allows us to constrain
the specific sequence of events during and after Columbia's disintegration.
For example, station LTL in Louisiana recorded a sonic boom during reentry
of the Columbia shuttle after a mission to service the Hubble Space
Telescope in March 2002. This is seen as a high frequency pulse (one
to two seconds long) in the seismic record. During reentry of Columbia
on February 1, 2003, LTL did not record a sonic boom, but rather, an
explosion. The event is approximately 100 seconds long and contains
both high and low frequency signal.
The signals can be used
to locate the explosion if the velocity of sound is known for the atmosphere.
Since the Columbia disaster took place at an altitude greater than 200,000
feet, the model is quite complex because of cold and warm regions. By
considering an atmospheric velocity model with data from stations near
the shuttle's flight path, we determined the location of the shuttle
explosion and correlated arrivals on the seismic records with the sequence
of events that led to the shuttle's disintegration.
Engaging and educating via the Web: Designing a national
scale outreach effort
Marie D. Renwald1, 2, Bryan
D. Hance1, Michelle K. Hall-Wallace2
1The IRIS Consortium
2Southern Arizona Seismic Observatory, University of Arizona, Tucson,
AZ 85721
Email: mrenwald@geo.arizona.edu
EarthScope is a proposed
decade-long, continental scale experiment to understand the structure,
formation, and evolution of the North American continent. Data collected
from this experiment and the subsequent insights derived from this data
will be of inherent interest to scientists, educators, and the general
public. For the past year, we have been developing a web-based interface
to engage and educate a broad audience with the scientific contributions
made by the EarthScope experiment. The result, http://www.earthscope-eon.org,
features a suite of tools and interfaces which include the Discovery
Map, a dynamic map that highlights ten areas of North America each week
which are geologically unique or interesting; the Data section which
currently allows users to view real-time seismic and GPS data, and in
the future it will allow users access to other geologic data collected
from the experiment; and the Research section which allows participating
scientists and educators a seamless method of sharing general information
and results about individual projects via customized database queries
and dynamically generated web pages.
Designing a website which
targets a range of users requires a working knowledge of both website
programming and design. Issues considered when building the site included
designing a logical navigational structure; accounting for browser differences,
both in terms of site look and functionality; utilizing current website
development tools, such as PHP, MySQL, and RDF feeds, as well as existing
geoscience applications like Antelope, an environmental monitoring software
package; site maintenance automation; database development; and accessibility
for users with a range of internet skills and physical limitations.
By accounting for each of these items, we have built a dynamic interface
which can be utilized by anyone interested in the EarthScope experiment.
Additionally, we feel these efforts can also serve as a model for research
groups, both large and small, wishing to make an effective presence
on the internet.
What happens to soil when it rains?: Investigations
and implications of soil development across a rainfall gradient in Hawaii
Aaron Thompson and Jon Chorover
Dept. of Soil, Water and Environmental Science, University of Arizona
Email: athompson@ag.arizona.edu
At a macro level, you get
mud, right? But chemically, the soil changes from a oxygen rich, environment
to an oxygen deprived environment as water fills the pore spaces in
the soil. This can dissolve Fe and other metals adhered to the iron,
greatly influencing the surface properties of soil minerals. Does the
amount of rainfall change the influence rock-derived constituents have
on an ecosystem? How important are Fe-oxides in regulating nutrient
and pollutant cycles? These basic questions impact a myriad of human
interactions with our earth's upper crust. Everything we eat comes from
and eventually ends up back in the soil. The location of farm fields,
the productivity of forests, and the positioning of waste disposal systems
all hinge on the type and nutrient status of our soils.
We are using the natural
age and climate gradients in the Hawaiian Islands to answer these important
questions. From previous aspects of this research, it is clear that
a "sweet-spot" in productivity exists in middle-aged soils
(~150 ky) and that climate alters this "sweet-spot" towards
greater rainfall at younger soils and towards lower rainfall in older
soils. Soil iron content is a critical parameter delineating productivity.
This current work focuses on the changing role iron plays in ecosystem
biogeochemistry as rainfall increases (2.2 to 4.2 meters of mean annual
precipitation (MAP)). All sites are on forest soils with similar vegetation,
developed from a 400,000-year-old Kula volcanic flow on the island of
Maui, HI. At sites with higher rainfall, oxygen concentrations are diminished
and previously solid iron dissolves in the rainwater through the process
of chemical reduction. At intermediate rainfall sites, this dissolved
iron can re-precipitate and form very small (nanoscale) particles. The
newly formed particles have very high surface area and are important
sorbents for nutrients (e.g., phosphate), pollutants (e.g., heavy metals)
and natural organic matter (NOM). This process of reduction (dissolution)
and oxidation (precipitation) can be referred to as iron redox-cycling
{Fe(III) ßà Fe(II)}. Our preliminary results indicate that
fluctuations between reduced and oxidized iron increases the fraction
of soil iron available for nutrient and pollutant sorption ("active
fraction"). This may indicate that in the "sweet spot"
is in part maintained by recycling of iron within the soil profile.
If this is indeed the observed result, the implications of this research
extend beyond ecosystem and soil biogeochemistry and could offer a method
for improving land-based waste disposal systems. The capacity of soil
based wastewater disposal systems (such as leach-fields), might be improved
by subjecting the soil to several redox fluctuations to increase the
"active fraction" of soil iron for attenuating and remediating
the waste.
Near-surface seismic imaging across the Pitaycachi Fault,
northeastern Sonora, Mexico
Frank H. Wagner, III (Trey)
and Roy A. Johnson
Department of Geosciences, University of Arizona, Tucson, 85721, AZ
Email: fwagner@geo.arizona.edu
The Pitaycachi normal fault
of northeastern Sonora, Mexico is the source of the 3 May 1887 Bavispe
earthquake (Mw ~7.4). This fault bounds the eastern margin of the San
Bernardino Valley, extending roughly north-south for over 100 km with
fault-scarp exposures from the 1887 earthquake of up to 4 meters. In
the fall of 2001, a near-surface seismic survey across this fault was
undertaken to attempt to image shallow structures associated with the
fault in order to better constrain recent fault activity. Ray-trace
modeling and tomographic inversion of first arrivals show that unconsolidated
sediments in the footwall are thin (~1 meter) and overlie more consolidated
course alluvial-fan sediments. Unconsolidated sediments near the surface
in the hanging wall are greater than 8 meters thick and show significant
lateral and vertical velocity variations. Total throw on the fault is
estimated at over 4000 meters since fault initiation at about 23 Ma,
giving a total slip rate of 0.17 mm/yr. Although previous estimates
of Quaternary slip rates on this fault are believed to be significantly
less, fault activity remains vigorous. The nature of the faulting in
the San Bernardino Valley is similar to Quaternary fault scarps flanking
numerous basins in southern Arizona, and provides evidence of continued
extensional deformation in the southern Basin and Range Province.
Preliminary kinematic study of the "Kartchner
block", southeastern Arizona
Shanda Wagner1, Robert R.
Casavant 1, Rickard Toomey, III2 and Ginger Nolan2
1Department of Mining and Geological Engineering, University of Arizona,
Tucson, AZ
2Kartchner Caverns State Park
A group of structurally
isolated hills, composed of mostly Paleozoic limestone formations, resides
along the eastern flank of the Whetstone Mountains in southeastern Arizona.
The newly-developed 550 acre Kartchner Caverns State Park (KCSP) encompasses
several of these hills. The hills comprise a fault-bounded block that
is sometimes referred to as the "Kartchner block". Recent
mapping and field investigations indicate that the fault density across
the block is greater than previously interpreted and that fault kinematics
are more complex.
Guided by detailed aerial
photo interpretation, field mapping and a re-examination of fault surfaces
above and below ground were completed. Our preliminary findings indicate
that an undetermined amount of oblique-slip was an important component
of the predominate normal faulting that deformed the block. A pervasive
oblique component had not been previously documented across the block,
except for two faults splays within the caverns. This component is characterized
by the prevalence of brecciated and Fe-rich fault zones, anastomozing
distribution of some major faults, en echelon arrangement and/or lateral
offset of joints and veins, tiled and folded calcite-rich veins, drag
folding, and oblique orientations of fault grooves and slickenlines.
How this oblique component
relates to the structural evolution of the block and cavern formation
is the focus of on-going study. Future results may contribute to an
improved understanding of the geologic, geomorphic and hydrologic evolution
of the adjacent San Pedro Valley. The research may also prove useful
to future cavern management and planning.
Martian dust devil tracks in Argyre Planitia and
Hellas Basin
P. L. Whelley, M. R. Balme
and R. Greeley
Department of Geological Sciences, Arizona State University, Tempe,
AZ, 85287
Email: pwhelley@asu.edu.
Dust devils on Mars are
important mechanisms for delivery of dust into the Martian atmosphere.
Suspended dust in the Martian atmosphere is estimated to be ~1-2mm in
diameter [1,2,3]. Calculations of dust fall-out rate [4,5] imply an
ongoing supply of this fine dust to the atmosphere. Wind tunnel experiments
[6,7], however, suggest that entrainment of fine dust into the atmosphere
requires boundary layer wind speeds exceeding those measured on Mars.
Recent experiments using a laboratory scale vortex generator at low-pressure
[8,9] show that vortex action (i.e. a dust devil) is more efficient
for lifting fine dust than boundary layer winds. Coupled with the many
observations of dust devils on Mars [10], these experiments suggest
that dust devils are an important contributor to the global dust budget.
Characterizing the temporal and spatial distribution of dust devil activity
on Mars is essential for gaining an understanding of the Martian surface
processes. Several studies have attempted to determine the frequency
of active dust devils using Wide Angle [11] and Narrow Angle (NA) [12]
MOC images but they only sample a small fraction of dust devil activity.
The transient nature of dust devils, the limited spatial coverage of
the high resolution images required to resolve them, and restricted
viewing times of the Mars Orbiter Camera (MOC) makes their detection
serendipitous. However, the passage of dust devils over the surface
is inferred to leave surface tracks that remains visible for months
longer than the lifetime of the dust devil that produced it. Here we
investigate the distribution of dust devil tracks in Argyre Planitia
(20o to 50oW; 60o to 30oS) and the Hellas Basin (250o to 320oW; 60o
to 15oS).
The study areas were chosen
because they a) display a variety of geomorphic units, b) cover a range
of elevations, c) are at similar latitudes for seasonal comparisons,
and d) contain images with visible tracks. We searched all MOC NA images
with resolution 7m/pixel or better from the CAL to E12 phases (March
1999 to February 2002) of the Mars Global Surveyor mission for dust
devil tracks. We counted the number of tracks in each image and then
normalized by the surface area of the NA strip to determine the density
of tracks per square km. In total, we searched 637 images in Argyre
and 2037 in Hellas. Results and conclusions: Laboratory experiments
[9] suggest that small changes in surface pressure (as would occur between
regions of different elevation) might influence the efficiency of dust
devil particle entrainment. Hellas shows greater dust devil track abundance
at lower elevations, except for the lowest topographic regions. In Argyre
most tracks are found around 0km elevation and no clear conclusion on
the influence of elevation on track formation can be drawn. In contrast,
the occurrence of dust devil tracks strongly correlate with Martian
season, and is strongest in spring/summer when insolation is at its
peak. From the seasonal differences in dust devil track density we infer
that: "summer" dust devil activity starts earlier and continues
longer in Argyre; almost all dust devil activity appears to cease in
mid fall in Argyre whereas in Hellas, dust devil tracks are still visible
until the onset of winter. These occurrences suggest that dust devil
tracks form preferentially in Argyre but are covered/erased more quickly
than in Hellas. This change could reflect differences in availability
of fine materials for dust devils to pick up (and later to cover their
tracks) or differences in seasonal weather patterns between the two
study areas. In both basins the areas with the highest dust devil track
density are found in areas with high TES (Thermal Emissions Spectrometer)
albedo. As albedo is commonly correlated with dust abundance this suggests
that the areas with the most dust have a higher density of dust devil
tracks.
References: [1] Pollack
J.B. et al. (1979) JGR 84, 2929-2945. [2] Smith P.H. et al. (1997) Science,
278, 1758-1765. [3] Snook K.J. (2002) LPS XXIII, Abstract #1600. [4]
Kahn R.A. (1992) in 'Mars' edited by Kieffer, H.H. et al. [5] Smith
P.H. and Lemmon M.T. (1998) JGR 104, 8975-8985. [6] Greeley R. et al.
(1981) Geol. Soc. Amer., Special Paper 186, 101-121. [7] Iversen J.D.
and White B. (1982) Sedimentology, 29, 111-119. [8] Balme M.R. et al
(2002) EOS Trans. 83 (47) Fall Meet. Suppl., P41A-0334. [9] Greeley
R. et al. (2002) JGR in press. [10] Edgett K.S. and Malin M.C. (2000)
LPS XXXI, Abstract #1073. [11] Biener K.K. et al., (2002) LPS XXXIII,
Abstract #1048. [12] Fisher J. et al. (2002) EOS Trans. 83 (47) Fall
Meet. Suppl., P41A-0332.