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Department of Geology
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Department of Geology, University of Maryland
Spring 2012 Seminar Series
2:00pm - 3:00pm
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Andy Nyblade
Upper mantle velocity structure beneath eastern and southern Africa: Implications for the origin of Cenozoic rifting, volcanism and plateau uplift February 3, 2012
Tom Watters
Special Location: 0200 Symons Hall The Tectonics of Mercury: New Views from MESSENGER in Orbit February 10, 2012
Nancy Grimm
March 2, 2012
Peter Heaney
Bacterial Respiration of Mn Oxides: A Real-time X-ray Diffraction Study March 9, 2012
Bill White
Re-examining Earth's composition: Implications for planet formation and mantle structure and dynamics March 30, 2012
Ben Gill
Special Location: 0200 Symons Hall The role of ocean chemistry in exceptional fossil preservation during the Cambrian April 6, 2012
Sue Smrekar
Hotspot volcanism on Venus and implications for the interior, surface and atmosphere Abstract: Venus Colloquium Series
Venus is the planet most like Earth in terms of size and bulk composition. Yet the surface temperature is 735°K, thanks in large part to the runaway greenhouse. How did Venus evolve so differently from Earth, and just how Earth-like is it today? The volcanic history of Venus provides insight into both its interior and its atmospheric processes. A discovery of geologically recent volcanism is based on thermal emissivity data at 1 micron for of the southern hemisphere of Venus from the VIRTIS spectrometer on Venus Express. Several volcanic locations previously identified as hotspots (areas where upwelling mantle plumes create volcanism) contain high emissivity anomalies. The 1 micron spectral region is dominated by the FeO absorption band, indicating relatively unweathered basalts. We model whole mantle convection to predict the estimated number of active mantle plumes (~10). Predicting few plumes constrains the mantle Rayleigh number to be high and amounts of internal heating to be low. The predictions also have implications for atmospheric water, volcanic resurfacing, and possibly dynamo history.
April 13, 2012
Christine Siddoway
Change from wrench to transtension along the Cretaceous Gondwana margin, recorded in isotopic characteristics of zircon in syntectonic anatectic granites in West Antarctica Abstract: The Fosdick Mountains in West Antarctica offer superb 3-D exposures of a migmatite-granite complex formed within a wrench setting during dextral oblique convergence along the East Gondwana margin. Cretaceous granites that are a product of crustal melting yield SHRIMP U-Pb zircon ages of circa 140 to 96 Ma. The granites occupy a variety of structural sites, and their relationships to host fabrics indicate emplacement during wrench to transtension in the deformation. The evolution of strain in the Fosdick range is consistent with that recorded by brittle upper crustal structures, including dike arrays, in the broader region, and with the regional plate tectonic evolution of West Antarctica and then-contiguous greater New Zealand (Zealandia). Mid-crustal complexes were rapidly exhumed and cooled at rates as high as 75°C/m.y. according to available thermochronology, leading to extraordinary preservation of primary structural and petrological relationships. Following an overview of Gondwana margin tectonic evolution, this talk will examine the U-Pb geochronology, oxygen and Lu–Hf isotope characteristics of granites that occupy structural sites in the Fosdick migmatite-granite complex, leading to the hypothesis that there are distinguishable differences in source characteristics for granites emplaced during sequential stages of mid-crustal deformation. The trend during lithospheric thinning is toward a less-evolved, mantle-like source with juvenile εHf(t) and δ18O. If substantiated in Antarctica, the finding has consequences for Late Cretaceous breakup in the Pacific sector of Gondwana and for the paleogeographic reconstructions of Antarctica being used for modeling of Tertiary greenhouse-icehouse climate transitions.
April 20, 2012
Saswata Hier-Majumder
Melt detection, retention, and distribution in the deep Earth May 11, 2012
Kristine Larson
GPS - A New Tool for Water Cycle Studies Abstract: GPS receivers are most typically installed by geoscientists/geodesists to
measure mm-changes in position of GPS stations over time periods of days
to years. The resulting station velocities derived from these data
provide important constraints on how faults and tectonic plates interact. GPS data are also increasingly being used to study earthquake ruptures and volcanic eruptions. In all of these GPS studies, positions are to some
extent contaminated by the effects of surface reflections. My group has
developed methods to measure these surface reflections so that you can
use GPS receivers to measure snow depth, vegetation growth, and soil moisture.
These data are of particular interest to climate scientists because
they sample a larger spatial region than other ground sensors and can be used to validate satellite sensors that only measure very large spatial regions.
The coordinator for the Colloquium Series is Dr. Laurent Montesi. You can contact him at montesi AT umd.edu |
