CAREER: Quantifying tectonic and biologic controls on erosion using detrital thermochronology

Erosion is an important process that removes Earth materials from a source area then transports and deposits them somewhere else. Understanding the timing, rate, and magnitude of erosion is fundamental to the work of nearly all fields of geosciences and is critical to predict and identify water, hydrocarbon, and mineral resources. It has been particularly difficult for geologists to quantify the effect that vegetation has on erosion because in modern landscapes vegetation is ubiquitous and difficult to prescribe for a controlled study especially at a regional or continental scale.

This study will address this question using data from sedimentary rocks deposited in the Midwest United States throughout different stages of land plant evolution including before plants evolved, and during different stages of plant evolution including the developments of roots and expansion of seeded plants. These rocks serve as a natural experiment for studying how erosion efficiency changed at the continental scale in response to land plant evolution.

The PI will trace minerals eroded from different landscapes and measure the cooling history of these minerals, which is a proxy for erosion that exposes rocks once buried at warm temperatures deep in the Earth to surface temperatures. This work contributes to important societal outcomes including developing new quantifications of Earth processes that can be used to predict and locate Earth resources.

It also cultivates a pipeline for recruiting and training Geoscientists in the Midwest including 1) support of MS student training providing students with practical skills working in core that prepares them to enter the regional workforce, and 2) development of a one-week Earth Science curriculum for high school teachers linking Indiana subsurface geology to active research in this project as well as regional resources, infrastructure, and careers.

Although it is widely recognized that plant macroevolution modified the composition and character of sedimentary rocks through weathering, this project will provide one of the first efforts to systematically quantify volumetric changes in rock denudation across landscapes and vegetated environments. This project defines an integrated research and education project centered on the inherently “hidden” geology of the North American craton (Midwest USA) interrogating how vegetation modifies erosion in tectonic and cratonic landscapes.

Does vegetation increase, decrease, or not affect erosion in tectonically active and cratonic landscapes? This project leverages the detrital record preserved in Cambrian – Pennsylvanian core samples from the cratonic Michigan Basin. This study will double-date zircon and apatite from clastic units indexed by stage of plant macroevolution (first vascular plants, emergence of large roots, evolution and expansion of seeded plants).

U-Pb dating will establish single grain provenance identifying grains from the tectonically stable craton or the tectonically active Appalachian orogen. Low-temperature thermochronology will be used to measure changes in rock exhumation and erosion from grains derived from cratonic and active orogen sources across stages of plant macroevolution. Combined, these contributions contextualize the relative contributions of vegetation and tectonic landscape (cratonic vs. orogenic) on erosion providing measurements of erosion rates and magnitudes that will be used to frame future studies of erosion and reframe or even revisit decades of past work that was unable to extract the relative contributions of vegetation and tectonics on erosion.

These results have the potential to revolutionize geoscientists’ ability to predict and reconstruct erosion patterns and magnitudes, calculate sediment flux in modern and ancient environments, and understand erosional systems in extraterrestrial (unvegetated) landscapes like Mars.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.