CSDMS 2015 annual meeting poster DanielOHara

Presentation provided during CSDMS annual meeting 2015

Landscape Evolution in Response to Laccolith Inflation: Insights from Numerical Modeling with Application to the Colorado Plateau

Daniel O'Hara, University of Oregon, Oregon, United States. dohara@uoregon.edu
Leif Karlstrom, University of Oregon, Oregon, United States.
Benjamin Black, University of California, Berkeley California, United States.
Kendra Murray, University of Arizona, Arizona, United States.


Laccoliths are shallow plutonic structures that uplift and deform overlying horizontal and near-horizontal strata, proposed to develop through short (possibly < 100 yr) episodic magmatic events. Numerous laccoliths ranging in age ~25-35 Ma occur around the rim of the Colorado Plateau. These structures provide a natural laboratory for studying localized dynamic topography that occurs on a smaller scale than typical drainage basin size. The coupling between initial river drainage geometry, laccolith emplacement rate and intrusion size on drainage development is poorly understood. Our research aims to understand the effect of an uplifting laccolith on pre-existing, steady-state topography, both to constrain magmatic rates of processes and also the geometry of the paleo landscape.

Using a bedrock landscape evolution model, we vary initial drainage geometries, laccolith shapes and sizes, and laccolith emplacement timescales to study drainage response to topography. We analyze the underlying equations that govern bedrock landscape evolution, as well as characteristics of the resulting river networks such as drainage area, drainage divides, and channel orientations and longitudinal profiles. These are used to develop metrics that characterize the drainage disruption caused by the laccolith, the effect of initial drainage geometry on laccolith erosion, and the timescales of inflation and landscape erosional response. We then apply our results to the Colorado Plateau, in particular, Mt. Hillers (Henry Mountains, UT) and Navajo Mountain (UT) to understand their emplacement rate, landscape response to inflation, and paleo drainage networks.

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