Research Themes
My general geoscience research theme has been to better understand the evolution of the Earth’s lithosphere and the processes that influence it. These can be tectonic, magmatic and climatic, and my goal has been to unravel how these interact. I have done this through a combination of geologic mapping, potential field geophysics, geochemistry and geochronology. I strongly believe that scientific questions can be best answered by using multiple interlocking data sets.
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Geologic evolution of the Panama arc and formation of the Isthmus
The Panama arc first formed approximately 73 million years ago on the trailing edge of the Caribbean plate. It has been influenced by subduction zone magmatism, arc collision and a myriad of tectonic complications. Ultimately, the collision between the Panama block and South America led to the formation of the Isthmus of Panama. This event has been one of the most geologically significant of the Cenozoic, and has wide reaching implications for ocean circulation, the distribution of both marine and terrestrial species and potentially the Earth’s climate.
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Geologic evolution of southern Alaska: Arcs, triple Junctions and accretionSouthern Alaska is a fantastic natural laboratory for understanding subduction zone processes. These range from arc magmatism, to the influence of triple junctions, and accretionary tectonics. I have worked mostly on Kodiak Island, but also some in interior Alaska just south of Denali.
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The physical and chemical behavior of magmatic systems
I have worked primarily on understanding the dynamics of silicic magmatic systems. This has been accomplished using diverse data sets and techniques, including: 1) high resolution mapping of granitoids to better determine magma emplacement and ascent mechanisms, 2) U-Pb geochronology to determine the rate and time scales of individual magmatic pulses, 3) gravity data collection and modeling to determine the 3-D geometry of intrusive bodies, and 4) major, trace and isotopic geochemistry and modeling to determine the petrologic origin of granitic plutons.
Gravity constraints on faults, sedimentary basins and magmatic structures
I have used gravity measurements and modeling to examine the geometry of faults, sedimentary basins and magmatic structures. These projects have ranged from: 1) Using multiple high resolution transects to analyze the Palos Verdes and San Andreas faults in California, 2) Examining the structure of sedimentary basin such as the Raton basin in southern Colorado, the Canal basin in Panama and the Sibundoy basin in Colombia, and 3) Determining the subsurface geometry of the El Valle Volcano in Panama.
Taconic arc evolution in the southern AppalachiansIn the southern Appalachians, the nature of the Taconic orogeny is not clear. However, in the northern Appalachians it has been characterized as an arc collision event. The Dadeville complex of the Alabama Inner Piedmont comprises the most likely Taconic arc assemblage in the southern Appalachians. It contains mafic/ultramafic intrusions (pyroxenites), batholith-scale granitic bodies, and volcanic sequences with a combined tectonostratigraphic thickness of ≈15 km. My co-workers and I are using a combination of geologic mapping, Nd and Hf isotopes, potential field geophysics, igneous geochemistry and U-Pb zircon dating to better understand its evolution and determine how it fits into Appalachian geodynamics and Laurentian crustal evolution.
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