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Nadine McQuarrie - 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projects start with structurally based field studies, typically through the creation of new geologic maps at previously unpublished scales or resolutions.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   3) the geodynamics of high topography in Bolivia and Peru, 4) kinematic evolution of the Himalayan Orogen in Bhutan, and 5) evolution of arc-continent collision in time and space in East Timor and 6) the sequential development of the central Appalachian fold-thrust belt, Pennsylvania.

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 field research on the timing, magnitude and style of deformation, 2) restoring other data sets of interest, such as the volcanic eruptive centers through the Basin and Range (see animation), or geophysical data collected though the NSF Earthscope initiative, and 3) comparing robust features of the reconstruction velocity field with the latest GPS velocity field such as the counterclockwise rotation of the Sierra Nevada Mountains, California.

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 Dr. Jason Barnes) 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 here. 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. Between northern and southern Bolivia there is a pronounced switch in hemisphere–scale Hadley precipitation regimes dividing the Andes into wet (15°–16°S) and dry (21°S) regions. In these regions, tectonics, basin geometry, and style of deformation are similar, allowing us to use variations in the width of the orogen (or changes in percent shortening) to evaluate whether the changes in width and morphology are climate driven. Comparing percent shortening and exhumation along 2 cross sections, north and south of 17.5°S, We determined that percent shortening is the same north and south during early (45-20 Ma) deformation, indicating changes in precipitation had very little effect on the width of the orogen. However, the later (~15 Ma to present) deformation is narrower in the north than the south suggesting a coupling between climate and tectonics that began between ca. 19 and 8 Ma, and continues to 0 Ma, (McQuarrie et al., 2008, Geology).

The geodynamics of high topography:

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. CAUGHT: Central Andean Uplift the Geodynamics of High Topography is a multi-institutional, NSF-funded, Continental Dynamics project designed to document the deformation, elevation and erosional history of the central Andes mountains in South America, specifically to evaluate whether the rise of the Andean plateau was (1) slow-and-steady, commensurate with crustal shortening, or (2) rapid, associated with removal of dense lower lithosphere following significant crustal shortening.  The CAUGHT team combines geophysics, structural geology, sedimentology, stable isotope geochemistry, thermochronology, and climate modeling to study interactions between climate, erosion, deformation, surface uplift, lithospheric removal.  Preliminary work with Andrew Leier found that early (27 Ma) changes in O18/O16 isotope ratios were just as significant as later (8 Ma) changes that have been used to infer an ~3 km rapid change in elevation. Taken together, the data may infer 2 periods of uplift possibly via mantle delamination, albeit each of a smaller magnitude than originally proposed.  Our work on the age of deformation requires that most of the shortening and thickening of the crust predated either of these potential changes in elevation.  What is unclear is the magnitude of uplift associated with each shift in O18/O16 isotope ratios and whether the final pulse of uplift (at ~8 Ma) was followed by rapid propagation of the frontal Subandean zone.  Our contribution to the project at Princeton is determining the age, geometry and rate of Subandean shortening as well as understanding the 3D geometry of shortening in a curved orogen.

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 are: 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 5 transects; and 4) restoring these sections sequentially using a suite of thermochronologic ages (apatite fission track, zircon U-Th/He, 40Ar/39Ar to completely describe cooling patterns from high to low temperature)  as well as the ages of synkinematic mineral growth to date fault motion. These data will allow us to determine rate and the tempo of shortening in the Bhutan Himalayas and allow us to compare that to modern rates of shortening in the region, paleoseismicity and long-term rates of shortening across the entire Himalayan front. Graduate students Tobgay Tobgay and Sean Long have complete over 5 months of field work in Bhutan and are continually updating our understanding of the architecture of the orogen.

Australia down under: 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.  Arc-continent collision marks the ultimate demise of an intra-oceanic subduction zone and is a common phenomenon during ocean closure. In this project we propose to test whether arc-continent collision events modify overall convergence rates, with the island of Timor as test-case.  We plan on doing this through integrating balanced of structural cross-sections, paleomagnetism, thermochronometry, and thermal modeling to find the best fit between the predicted and measured cooling ages. These datasets will ideally document the timing of collision, magnitude of shortening, tempo of shortening and potentially provide estimates of the long-term convergence rate through paleomagnetism. By determining the timing of collision and magnitude of shortening we can place limits on the magnitude of continental subduction, evolution of island arc collision and both style and magnitude of subsequent exhumation.