Continental tectonics, landscape evolution, and crustal geodynamics
The interactions between active tectonics, surface processes, and climate
Mountain belt-sedimentary basin coevolution and sedimentary provenance
Supercontinent cycles and Proterozoic Earth
Low-temperature thermochronometry method development and radiation damage effects in minerals
The formation and history of sedimentary basins and assessment of resource potential
My training has been focused on tectonic processes and geomorphology, basin analysis/sedimentology, structural geology, and noble gas geochemistry with particular attention to low-to-medium temperature (U-Th)/He, fission track, and 40Ar/39Ar thermochronology. In my case, these tools are mainly applied to understanding the evolution of mountain landscapes and the processes involved in shaping them, large-scale tectonic problems, and particularly of interest are the thermal histories of slowly-cooled terranes, which are inherently important for understanding deep-time continent evolution.
I am principally interested in understanding the interactions between tectonics, geomorphic processes, and climate. My near-term research interests are centered on four main areas: (1) understanding long-term continental dynamics, with a focus on the poorly-known Proterozoic history of cratons, (2) Neoproterozoic tectonic reorganizations, vertical tectonics, and implications for geochemical cycles and evolution of life, (3) deformation, exhumation histories, and landscape dynamics of central Asia (Mongolia), North America, South Africa, and the Canadian Arctic, and (4) refining analytical methodologies and knowledge of the diffusion/annealing kinetics of the mineral apatite used in low-temperature thermochronometry.
CONTINENTAL TECTONICS & LANDSCAPE EVOLUTION
1. Evolution of the North American craton
In deep time, Earth remains thermochronologically underexplored. The geologic records that we do have could reflect significant preservation bias and for such older terranes we have often framed questions in terms of "events" rather than processes. In this context, thermochronology has great promise for revealing previously unknown aspects of Earth system evolution. The Neoproterozoic Era extending from 1000 to 540 million years ago encompassed a number of significant changes in Earth’s systems, including major diversification and complexification of the biosphere, episodes of nearly planetary-scale glaciation, and breakup of the supercontinent Rodinia. Preliminary data suggest that this time interval also saw a period of surprisingly robust erosional exhumation of several kilometers, in cratonic settings traditionally thought of as stable and quiescent. Such exhumation could be a key link in connecting Earth-system processes, if it were widespread enough in extent, significant enough in magnitude, and had the correct timing. Depending on details of their thermal histories and crustal temperatures, these cratonic rocks then must have experienced ~3-8 km of exhumation, only some of it happening in the Phanerozoic.
This adds to recent thermochronological work that documents significant amounts of exhumation associated with the formation of the extensive Great Unconformity and provide support for significant cratonic epeirogeny that resulted in widespread Neoproterozoic erosional exhumation post-1 Ga, a process that (1) must reflect a linked geodynamic cause, and (2) may be linked to Snowball Earth glaciations, the global carbon cycle, and the rise of biotic complexity.
Earth and Planetary Science Letters preprint: https://doi.org/10.31219/osf.io/4ec26
Precambrian Research preprint: https://eartharxiv.org/45ns9
2. Resolving the Proterozoic thermal history of the Kaapvaal craton through integrated thermochronometry
The primary objective of this project is to assess the stability record of the South African interior. The Kaapvaal craton that makes up the core of South Africa is conventionally viewed as a highly stable feature that has persisted for billions of years spanning the Proterozoic interval between craton consolidation (>2.5 Ga) and much more recent Phanerozoic epeirogenic activity. Yet evidence for craton stability is mostly founded on this Phanerozoic record, and for significant parts of the craton, prior stability has been inferred more from a lack of direct evidence than actual data, forming an observational gap exceeding a billion years or more. Preliminary thermal-history data from across the craton indicate that currently exposed rocks were at temperatures of ~200C at ~1 Ga. This suggests that post-orogenic exhumation was long-delayed, or alternatively, if reheating occurred, rocks currently at the surface might have experienced [burial] temperatures of up to 200C. In either case, these observations lead to a hypothesis that a large portion of the craton underwent significant, widespread exhumation beginning at or after ca. 1 Ga in the Neoproterozoic.
McDannell, K. T., Zeitler, P. K., & Idleman, B. D. (2018). Relict topography within the Hangay Mountains in central Mongolia: Quantifying long-term exhumation and relief change in an old landscape. TECTONICS.
Available from EarthArxiv as a preprint https://dx.doi.org/10.17605/OSF.IO/BPHYS
High-elevation, low relief surfaces are common on continents. These intercontinental plateaus influence river networks, climate, and the migration of plants and animals. How these plateaus form is not clear. We (see link above) are studying the geodynamic processes responsible for surface uplift in the Hangay in central Mongolia to better understand the origin of high topography in continental interiors.
4. Exhumation of western Alaska and implications for Arctic-Alaska tectonics during the late Mesozoic-Cenozoic
PDF here: McDannell et al 2014 G-cubed
The goal of this project was to employ (U-Th)/He thermochronology of apatite to constrain the exhumation history of the Bendeleben pluton, located in the eastern Bendeleben Mountains on the Seward Peninsula of Alaska. It has been previously suggested that the Bendeleben pluton and neotectonic structures associated with extensional deformation in the Bendeleben and Darby Mountains contain a record of the structural and geomorphic evolution of the Seward Peninsula and the Arctic region. This work mainly combined thermochronology, structural analysis, Bouguer gravity modeling, and seismic interpretation to incorporate western Alaska into the regional arctic tectonic framework and characterize the exhumation history since the Cretaceous. The Early Tertiary represents a renewed period of faulting, offshore basin formation, and erosion that occurred throughout the Seward Peninsula, whereas the prior history in the mid-Cretaceous represents a time of crustal thinning that can be observed in previous studies in the Kigluaik Mountains to the west of the study area. This renewed extensional signal can be seen in our apatite (U-Th)/He ages from the Bendeleben Mountains. The Tertiary tectonic regime can be modeled as episodic extension related to block rotations induced by tectonic extrusion in response to Pacific margin convergence and terrane accretion. Extension in the Seward Peninsula also corresponds to normal faulting in the Hope Basin, NW of the Seward Peninsula. We propose that these events are linked and are part of the same system and our results are in good agreement with regional tectonic and geochronologic information. Apatite (U-Th)/He, biotite 40Ar/39Ar thermochronology and thermal history modeling was used to constrain the cooling and exhumation of the central Seward Peninsula. Inverse time-temperature modeling shows that rapid cooling occurred in the mid-Late Cretaceous, after batholith emplacement, and has progressively slowed into recent time. Exhumation of the Bendeleben footwall block is estimated to be approximately 0.2–0.25 mm/yr from the late Cretaceous to Eocene and approximately 0.04–0.06 mm/yr from the Eocene to present.