EAR-PF: Unravelling climate and tectonic signatures using a landscape evolution modelling framework to interpret stable isotope and thermochronology records

When geologists use rocks to go back in time to understand what Earth was like in the past, it can be challenging to pull apart the competing effects of climate and tectonics (i.e. mountain building). For example, in the Northern Patagonian Andes, the scientific community has previously noted observations that indicate the region got colder and drier during the Miocene Epoch.

But, it is hard to know if that apparent cold climate is because the Northern Patagonian Andes were at high elevations in the Miocene (causing the local climate to be cold) or if the local environment was responding to changes in global climate. There are two major portions of this postdoctoral fellowship. In the first part, PI Havranek will use three different geochemistry tools, all of which were developed in the last 15 – 20-years, that can each shed light on different aspects of the climate and tectonics system of the Northern Patagonian Andes in the Miocene.

Because the tools PI Havranek intends to use are so new, the interpretation of these kinds of data has always been done separately from each other. To be able to interpret them together, PI Havranek will create a landscape evolution model. These kinds of models are intended to describe the ways that landforms (like mountain ranges) change through time.

The model will be capable of predicting what the geochemical data should be based on different hypothesized climate and tectonic scenarios. Then it is possible to evaluate which hypothesis best fits all of the geochemical data. The final goal of this project is to shed light on which came first, a cold climate that enabled the growth of the Northern Patagonian Andes, or the uplift of a mountain range that locally cooled the climate.

If successful, this kind of approach could be extended to different places around the world. As a part of the field work associated with this project, PI Havranek will lead a short course on stable isotope geochemistry for students at Universidad de La Plata. To make both the field sites and laboratory settings used for this project more accessible, PI Havranek will produce a series of video tours of those spaces.

Two high-school students, recruited through the University of Idaho Upward Bound TRIO-INSPIRE program will help assess the videos and make them accessible to a wide range of viewers.

The geoscience community has long recognized that climate and tectonics are inextricably linked and feedback on each other via erosion and landscape evolution. Over geologic timescales, tectonics can modulate climate through silicate weathering, and climate can influence deep-crustal processes by controlling the extent of weathering and erosion. It is particularly challenging to disentangle the primary driver, climate or tectonics, of observations in the rock record.

For example, if a paleoenvironment cooled over time, that cooling could be driven by either surface uplift or by cooling of the global climate. Many of the proxy tools geochemists have developed to target questions about climate and tectonics target either past climatic conditions or rates of rock exhumation. Furthermore, geochemical proxy data are frequently interpreted in isolation to independently constrain either climatic and tectonic histories without considering their concurrent evolution.

In this project, the aim is to co-interpret the climatic and tectonic history of the Paso del Sapo Basin in the Northern Patagonian Andes (Chubut Province, Argentina). The Paso del Sapo basin in the Broken Foreland of the Argentine Andes provides a unique opportunity to develop a framework for integrating thermochronology, stable isotope geochemistry, and landscape evolution modeling because there is a well-documented geologic context, and clear, testable tectonic and climatic hypotheses exist.

PI Havranek will create a record of 1) paleoclimate using carbonate clumped isotope thermometry and volcanic glass stable isotope geochemistry and 2) exhumation using low temperature thermochronology (detrital apatite (U-Th)/He). Then, PI Havranek will create a landscape evolution model capable of predicting both stable isotope geochemistry and low temperature thermochronology data.

This model will be used to test previously proposed tectonic and climatic hypotheses of the Paso del Sapo Basin. This project would provide a proven framework for future coupled stable isotope and thermochronology studies. The project will support: 1) the implementation of a stable isotope geochemistry short course at Universidad de La Plata; 2) the creation of accessible geoscience education videos; and 3) mentorship of two high school students through the University of Idaho TRIO-INSPIRE Upward Bound Program.

This project is jointly funded by the Earth Sciences Postdoctoral Fellowship program and the Established Program to Stimulate Competitive Research (EPSCoR).

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.