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Slow Earthquakes in Continental Strike-slip Faults
The discovery of slow earthquakes (slow slip ± tremor) along the central San Andreas fault using geophysics indicates our current models of the earthquake cycle do not account for energy released during these largely aseismic events. Establishing an understanding of the geological structures and mechanisms that accommodate seismic and aseismic slip modes is critical for evaluating the seismic potential of active faults and their associated hazards. This research investigates the structures and deformation mechanisms that accommodate strain within the slow earthquake source region using excellent exposures of a fossil brittle-ductile transition zone along the Norumbega fault system, Maine, USA – an ancient analogue to the San Andreas fault.
Project funded by NSF EAR Postdoctoral Fellowship Grant
Diagram showing the relationships between geological and geophysical obsertations of slip modes along continental transform faults.
Pseudotachylyte - earthquake-generated melt - within an ultramylonitic shear zone.
Petrochronology of Fluid-Mediated Strain Localization
Strain localization is a fundamental characteristic of the progressive evolution of plate boundary fault zones and thus fundamentally governs crustal and lithospheric deformation. Dynamic recrystallization and fluid-rock interaction are the principal mechanical and chemical processes, respectively, that influence fabric development and promote weakening during strain localization. These processes have an imprint on accessory phases in terms of their textures, microstructures, chemical composition and isotopic ages, which can be leveraged to reveal the timing and conditions of progressive strain localization. We are investigating the evolution of zircon, apatite and titanite textures, trace element chemistry and U-Pb ages during progressive strain localization within the Early Devonian Lincoln Syenite pluton, Maine, USA.
Manuscript in review at EPSL (as of January 2026)
Backscattered electron image of a syn-kinematic titanite sigma clast.
Directly Dating Ductile Deformation
The timing of crustal deformation is primarily determined through geochronology of deformed, cross-cutting or overlying rock units, however such constraints are relative and do not directly date deformation. During ductile deformation, chronometrically important accessory phase minerals (i.e., apatite and titanite) may experience crystal plastic strain, which may generate fast diffusion pathways for radiogenic Pb to escape the crystal lattice. This process effectively resets the U-Pb clock at the timing of deformation. I am exploring the occurrence of this phenomena and its applicability to directly date ductile deformation using an integrated microstructural (EBSD) and petrochronological approach (LA-ICP-MS U-Pb + TE).
BSE image of deformed apatite grain within recrystallized pseudotachylyte.
EBSD Mis2Mean map showing dislocation microstructure within apatite.
Mechanisms of Shallow Granulite Facies Metamorphism
Granulite facies metamorphism is an important driver of crustal differentiation and continental stabilization. Shallow granulite facies metamorphism requires exceptionally high heat flow due to a high mantle heat flux, magmatic heating, and/or radiogenic heating. The tectonic setting and driver of Paleoproterozoic granulite facies metamorphism within the Mojave Province -- a classic granulite facies terrane, which hosts the world class Mountain Pass REE deposit -- is poorly constrained. We are applying detailed geological mapping and geochronology to unravel the complex structural and metamorphic history of granulite facies rocks exposed in the McCullough Mountains, southern Nevada, USA.
Peritectic garnet in leucosome within metasedimentary gneiss, McCullough Mountains, Nevada, USA.
Deformation-Metamorphism Feedbacks during Orogenic Collapse
Orogenic collapse is a fundamental part of the orogenic cycle, and contributes to the thermal and mechanical structure of the lithosphere, and the differentiation of continental crust. I have worked to elucidate the evolution from orogenic construction to collapse in the US Cordillera through integration of geological mapping, macro- and microstructural analysis, and petrochonology. Through this detailed analysis I have found metamorphism exerted a first-order control on the development of mid-crustal shear zones during the Eocene-Oligocene ignimbrite flare-up. These mid-crustal fabrics were captured by normal faults during widespread Middle Miocene Basin and Range extension leading to exhumation of deep crustal rocks in the metamorphic core complexes.
Collecting samples within the anatectic core of the Ruby Mountains-East Humboldt Range metamorphic core complex, Nevada, USA.
How is Strain Partitioned during Subduction Initiation?
Subduction is a fundamental plate tectonic process and knowledge of how new subductions zones initiate is critical for understanding the onset of plate tectonics on Earth. My work in the Late Paleozoic thrust belt of Eastern California showed how progressive strain partitioning along an oceanic-continental plate boundary transform system accommodated convergence during incipient subduction initiation.
Geological map of the Hanging Rock Canyon 1:24,000-scale quadrangle, Death Valley National Park, California, USA.
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