Agassiz Visiting Lecturer 2017

We have the pleasure of welcoming Professor Sean Willett as our Agassiz Visiting Lecturer the week of April 3, 2017. Every year the graduate student community has the opportunity to invite a visiting scholar to be the Agassiz Visiting Lecturer to join the department for an extended stay to give a colloquium, lead seminars and workshops, and meet with the members of the department. 

Below is the schedule for his talks and workshop. 

EPS Agassiz Colloquium: The Dynamics and Patterns of River Channel Networks
Monday, April 3, 12:00-1:00. Lunch provided.
Location: Haller Hall, Geological Museum 102, 24 Oxford Street

The planform geometry of river channel networks has long been regarded as a potential tool for inferring tectonic deformation, uplift history, or the signature of climate change. However, in practice, simple interpretation or models have produced ambiguous results. Some studies demonstrate that rivers are passive markers for strain, but other studies have demonstrated universal scaling relationships for geometric characteristics of drainage patterns, implying that channel dynamics respond to counter tectonic and climatic forcing in order to maintain a uniform geometry. In this talk, I explore some of the consequences of geometric scaling parameters and demonstrate how these can be used to assess the stability and transience of planform channel patterns at a continental scale. I show two examples, the first from central Europe, where the remnants of the Tethys Ocean are drained by the Danube river in an inherently unstable configuration. The second example is from the US midcontinent, where the Rocky Mountain foreland basin has experienced multiple cycles of sedimentation and erosion. Each cycle has reorganized the drainage pattern; in the modern High Plains we observe the transition from the depositional megafans of the Ogallala group to a younger erosional river network producing a landscape characterized by high plateaus, eroding bluffs and badlands. [Background reading]

Seminar: Taiwan, A Natural Laboratory for the Study of Coupled Tectonics, Climate and Erosion
Tuesday, April 4, 10:00-11:30. Breakfast provided.
Location: Hoffman Faculty Lounge, 4th floor, 20 Oxford Street

A summary of historic and recent work on the tectonics, erosion, and landscape evolution of this classic arc-continent collision will be presented. Extensive thermochronometry studies give a detailed picture of the collision-related exhumation rates and patterns and to this we can now add cosmogenic isotope studies of the Holocene erosion rates in order to test models of steady or transient exhumation.

Workshop: Global Chi Mapping of River Networks
Wednesday, April 5, 10:00-12:00. Breakfast provided.
Location: Hoffman Faculty Lounge, 4th floor, 20 Oxford Street

Presentation of methodology for calculating and interpreting the chi structure (Willett et al., Science, 2014) of river networks in order to interpret patterns and dynamics of reorganization in response to tectonic forcing.  Examples will be shown, but suggestions will be taken from the participants as to other regions of interest.  Sean can take suggestions by email and produce maps prior to the workshop, or give instruction to participants as to how to do this. We can then make an interpretation together in the workshop.

Seminar: Forearc Basins – evaluating the interplay between critical wedge deformation and sedimentation
Friday, April 7, 12:00-1:00. Lunch provided.
Location: Geological Museum Room 204, 24 Oxford Street

Forearc basins develop on nearly every active margin and are linked to the tectonic deformation of the margin, but otherwise have no general genetic mechanism. Numerical and analytical models of accretionary wedge deformation can be used to demonstrate how deformation is affected by sedimentation and how feedback between gravitational stresses and deformation can help explain the diversity of forearc basin styles, sizes, and stratigraphic architectures. I summarize past and recent work with examples from around the world.