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Research
 My research focuses on the
kinematic evolution of mountain belts.
My interests range from evaluating the sequential accumulation of
strain in folds and faults that form a wide (350-350 km), high elevation plateau
to the kinematics and dynamics of diffuse continental extension. Research projects start with
structurally based field studies, typically through the creation of new
geologic maps at previously unpublished scales or resolutions. Projects also
typically involve the creation and sequential restoration of cross sections
to evaluate viable kinematic deformation histories. Current projects I am working on in conjunction with
colleagues and students are: 1) tectonic reconstructions of the North
America-Pacific plate boundary over the last 36 Myr, 2) the interaction
between erosion and deformation in fold-thrust belts in Bolivia and Ecuador
3) the fundamental controls on the width of mountain belts, specifically
looking at the northern edge of the Andean Plateau in Peru, Kinematics of the
Himalayan Orogen in Bhutan, and 5) evolution of arc-continent collision in
time and space in East Timor.
Past projects I have worked on
include the kinematics of the Arabia/Eurasia collision zone, evaluating both
the development of the Zagros fold-thrust belt as well as the causes of plate
motion before and after collision.
I have also studied the kinematic evolution of the Andean fold-thrust
belt in Bolivia and its relationship to the Andean Plateau.
Tectonic reconstructions of
the North America-Pacific plate boundary:
 Precise displacement fields of continental deformation are
becoming increasingly more common and exact through the advent and expansion
of global positioning systems (GPS).
However, displacement histories over much longer scales (105-107)
are required for addressing questions of how the lithosphere responds to
major changes in plate geometry and kinematics. For many regions on earth the detailed geologic history
necessary for long-term displacement fields is just not available. However, in western North America
more is known about timing, amount, and spatial variations of deformation
than any other comparable region. By using an Arc GIS (global information
systems) database of timing, magnitude and direction of deformation, we can
sequentially restore deformation through western North America with time
creating a series of palinspastic maps from 36 million years ago to present.
The data from these maps can be displayed in a variety of ways that highlight
not only the areas where the reconstructions are accurate, but more
importantly where the reconstructions are inaccurate (implying where more
field-based data are needed).
The maps can also be displayed as a movie that illustrates how
extension varies with time and as velocity fields over 2-5-10 m.y. increments
that can be compared to the modern GPS strain field. The first version of these
reconstructions was published in Geospheres, 2005. The power of these sequential
reconstructions come from 1) highlighting areas that are not strain
compatible and require additional research on the timing, magnitude and style
of deformation, and 2) The
palinspastic reconstructions allow us to restore other data sets of interest,
such as the volcanic eruptive centers through the Basin and Range.
Download
the movie here
Interaction between erosion and deformation in
fold-thrust belts:
 Quantifying
the interactions of lithology, tectonics and climate on multi-scale
morphologies of mountain ranges is at the forefront of current geological
research. One of the central
facets to this research is the magnitude of control climate and the
associated erosion has on the formation and development of orogens. Active research in Bolivia
(collaborative research with Dr.
Todd Ehlers and graduate student Jason Barnes at
University of Michigan) use low-temperature thermochronometry,
field-constrained structural analysis, and numerical models to delineate the
kinematic evolution of the fold-thrust belts, and the impact of erosional
variations on their formation.
In Bolivia we have obtained cooling ages and structural data that has
been combined in a preliminary kinematic model of how the fold thrust belt
has developed through time. An animation illustrating these kinematics is available at: http://geoweb.princeton.edu/people/mcquarrie/Bolivia_AGU-self_contained.mov The animation and associated
balanced cross section is based on new mapping across the Andean plateau from
the volcanic arc to the undeformed foreland. The restored cross section was
imported into 2-D MOVE (a cross section restoration program) and the displacement along folds and faults was
forward modeled providing a quantitative description of the kinematics
(displacement, velocity, velocity change) of fold-thrust belt deformation.
The simulated velocity field will be the input into 2D and 3D thermo-mechanical
models that link uplift and erosion to an evolving thermal field. This thermal history is used to calculate and
predict apatite fission track and apatite and zircon (U-Th)/He sample ages.
Controls on orogen width:
 The Andes mountains extend
over 8000 km along the western side of the South American continent. Significant along strike changes in
morphology, structure and zonal climate regimes make the South American Andes
an ideal location to look at the multiple factors that could potentially
control the width of orogens.
Interesting, the widest portion of the Andes, between 12° and 27° S,
is also some of the driest suggesting the lack of erosion is an important
factor in broad (350-550 km) high (4-5 km) plateaus. One of the most abrupt along strike
changes in morphology of the Andes is along the northern edge of the Andean
plateau in Peru. Here a wide
zone (~350 km) of high topography with minimal vertical relief transitions
abruptly into a significantly narrower (150 km) mountain range with a narrow
drainage divide. This west
stepping, right angle bend in topography is also seen in the map pattern of
lower Paleozoic rocks.
Quantifying the changes in topography, structure and stratigraphy
provides a unique opportunity to evaluate the factors that govern the width
of orogens. To address these questions we (graduate student Nicole Gotberg
and myself) have mapped two transects through the Peruvian Andes. The northern transect was through the narrow
portion of the mountain range (see above picture) and the southern transect
was across wide, northern border of the Andean plateau. Nicole is digitally
combining her mapping with Peruvian geologic maps to create new geologic maps
that can be used as the bases for balanced cross sections across each region.
Kinematics of the Himalayan
Orogen in Bhutan:
 The Tibetan-Himalayan orogenic system is the archetype of
continent-continent collision, and tectonic models born in the Himalaya are
invoked to explain orogenesis all around the world. Yet, encompassing a region greater than 2.5x106
km2, and only accessible to geologic field research in the last
20-30 years, the Tibetan-Himalayan orogen may be one of the more incompletely
mapped and thus least understood orogens. The Bhutan Himalaya has
traditionally been an area of limited access. However, through formal
collaborations with the Department of Geology and Mines of the Kingdom of
Bhutan, specifically with the help of Tobgay Tobgay,
a geologist in the Department of Geology and Mines who is pursuing his Ph.D.
at Princeton University, we have the opportunity to map lesser known regions
of the country. To determine the first order framework of the eastern
Himalaya in Bhutan, and to constrain the kinematic history of deformation we
plan on: 1) mapping the frontal, unexplored portion of the Bhutan Himalayas;
2) integrating new mapping with existing maps of the hinterland regions; 3)
creating balanced crustal-scale structural cross-sections along two
transects; and 4) restoring these sections sequentially using new 40Ar/39Ar
ages to elucidate regional cooling patterns and ages of synkinematic mineral
growth to date fault motion.
Graduate students Tobgay Tobgay
and Sean Long
are compiling preliminary and existing mapping, determining U-Pb ages and eNd concentrations in our
initial rock samples and analyzing white mica in fault rocks to ascertain 40Ar/39Ar
ages of synkinematic minerals.
Elevation versus
Deformation:
 Traditionally the topographic
history of mountain ranges has been thought to mimic the deformational
history. Thus as compressive
forces shorten and thicken the continental crust, the buoyancy forces
associated with a thicker lighter crust raises the surface elevation of
mountain ranges. Recent
analytical advances that capitalize on systematic changes in the ratios of
stable isotopes with elevation, particularly the ratio of O18/O16,
suggest that the deformation history of a mountain range may be decoupled in
time from the elevation history.
We have two projects determining the deformation and elevation history
of the Andes in Bolivia and Ecuador.
In these regions much of the deformation occurred between 40-30 Mya
implying long-lived elevations, however youthful topography and low temperature
thermochronometers suggest young (10-5 Ma) uplift and exhumation. This
discrepancy needs to be reconciled or understood. Postdoctoral researcher Andrew Leier is
combining sedimentology, U-Pb ages of detrital zircons and O18/O16
isotope ratios to compare the timing of isotopic changes in areas of unknown
elevation (the Bolivian Altiplano today) to timing of isotopic changes in
areas of known elevation (the Amazon Basin). Graduate Student Sarah Johnston
is combining detailed structural mapping of the Ecuadorian Andes with cooling
ages from multiple thermochronometers to document the history of deformation (when
faults moved) and exhumation (when minerals cooled) and to model the
elevation history of the mountain range through time.
4-D Evolution of
arc-continent collision in East Timor:
The island of Timor in
southeast Asia formed and is actively growing by the processes of island arc
collision with a continental margin.
Collision of the Indonesian volcanic islands (the Banda arc) with the
Australian continental margin caused the growth and emergence of  Timor, Rote, Savu and Sumba
islands in the Banda forearc. In the mountainous region of East Timor,
maximum elevations reach ~ 3000 m.
Preserved in these mountains are: 1) Flights of coral terraces that record the emergence of the
islands by marking an elevation that once was at sea level, 2, Young, marine sedimentary rocks record the progressive
shoaling of ocean water depths. 3) Deformed rocks sufficiently exposed to
reveal their deformation history and 4) Rocks which can provide cooling ages
of apatite grains which indicate the window of time these rocks were cooled
through uplift and erosion.
These factors allow is to quantify both rates of crustal shortening as
well as potentially determine rates of surface uplift in East Timor. The
collision history of the Banda arc is also significant because the obliquity
of the collision provides a unique insight into the temporal evolution of the
orogen through trading space for time along strike. The westward propagation
of the orogen (110 km/m.y.) provides a way to simultaneously observe this
active arc-continent collision at various stages of development.
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