147-7 Apatite fission-track as a potential proxy for changes in paleo-erosion during paleoclimatic excursions

Session: Climate, Ocean and Environmental Changes Through Earth History: From Marine and Terrestrial Proxies to Model Assessments (Posters)

Presenting Author:

Authors:

Abstract:

Detrital apatite fission track (AFT) is a well-established thermochronological tool which has been used primarily to gauge recorded unroofing histories of sedimentary rocks. Typically, it has been used to resolve exhumation of the temporal scale of 10⁶ – 10⁷ years. Here we explore the use of AFT to retrieve information about surface processes that occur on much shorter timescales (10⁵ years) during episodes of extreme global warming.

To test this hypothesis, we focused on Paleocene Eocene Thermal Maximum (PETM) strata. These are ideal sequences due to their well-defined stratigraphy and isotopic compositions, as well as the PETM’s short duration and importance as a climate analogue for current climate conditions.

We sampled outcrops of pre-, syn- and post-PETM sequences from the Tremp-Graus Basin in the foreland of the Pyrenees Mountains.  Pre-PETM deposits consist primarily of alluvial fan paleosols; syn-PETM sequences are dominated by fluvial deposits, which transition post-PETM into marine carbonate-rich sequences.

The increase in atmospheric temperature syn-PETM caused increased precipitation and subsequent heightened weathering and erosion at the paleolatitude of the studied area. We will examine if the erosional response caused by the PETM can be described quantitatively. Sandstone samples have been separated for future AFT lag time thermochronology (time of cooling minus time of deposition) to test this hypothesis. To provide more context and aid in interpreting AFT data, we also investigated paleosol chemical compositions and detrital zircon U-Pb geochronology.

Preliminary zircon U-Pb analyses indicate zircon provenance stays relatively consistent across all six Pyrenean samples spanning pre-, syn- and post-PETM detrital record. However, a brief shift occurs in zircon provenance within the post-PETM, specifically in sandstone layers deposited subsequent to the transition to marine conditions. Notably, there is a significant increase in Variscan-derived zircon grains relative to those found in pre- and syn-PETM intervals, as well as when compared to a younger post-PETM sample. This transient change in zircon sourcing corresponds with predicted erosional responses. Further constraining quantitative erosional rates based on AFT data holds promise for enhancing current paleoclimate reconstructions and advancing climate forward-modelling efforts.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-5997

© Copyright 2025 The Geological Society of America (GSA), all rights reserved.