Lag-time thermochronology as a possible proxy for changes in erosion rates over the Paleocene-Eocene Thermal Maximum, Tremp-Graus Basin, Spain

The global climate is rapidly warming as a function of elevated green-house gas emissions. Earth’s climate has fluctuated between periods of warming and cooling across it’s ~4.5-billion-year history. One prominent period of past global warming that is similar to what we are observing today is the Paleocene-Eocene Thermal Maximum (PETM, ~56 million years ago) – where Earth’s climate warmed, and then cooled rapidly over a ~200,000-year interval.

The PETM is an excellent archive of how the Earth-system can reduce excess carbon dioxide from the atmosphere through feedbacks with the landscape. The most prominent Earth-system way to remove atmospheric carbon dioxide is through carbon dioxide-enriched rain causing weathering and erosion of magnesium and calcium bearing rocks, which form carbonate minerals and can be stored in sedimentary rocks.

However, our understanding of how efficient this process is to remove carbon dioxide is limited by how difficult it is to assess erosion across these specific paleoclimate excursions. This project applies thermochronology (radiometric dating of minerals which record timing of erosion) to a PETM archive in the Tremp-Graus basin in Spain in order to quantify shift in erosion across a prominent period of global warming.

Results from this study will provide quantifiable estimates on how Earth’s landscapes react to global warming, and how these changes cycle carbon dioxide out of the atmosphere. This project will develop an interactive Earth-sciences outreach activity, designed for home-schooled students in the state of Oklahoma with a focus on Earth’s climate.

Increased silicate weathering and erosion during periods of global warming is an important mechanism of CO2 drawdown, which is required for long-term climate stability. However, quantitative estimates on magnitude and duration of climate-enhanced erosion remain challenging. In the project, the researchers will test if lag-time thermochronology (apatite fission-track and U-Pb dating) is able to resolve shifts in erosion during abrupt paleo-global warming.

The project will apply this proxy to the Tremp Graus Paleocene Eocene Thermal Maximum section in northern Spain in order to resolve erosion rates pre-, syn-, and post-PETM carbon isotope excursion. Lag-time thermochronology will be integrated with detrital zircon U-Pb to track provenance changes. From this novel and multi-method proxy approach the researchers will test different hypotheses relating to onset, duration, and cessation of climate-enhanced erosion, quantify magnitude of erosion, and parse out the relative contribution of both tectonic and surface processes.

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.