Impact of an abrupt climate change on sediment distribution from source to sink, PETM, Southern Pyrenees (Spain)

 

Allogenic factors such as climate and tectonics are regulating the mechanisms involved in sediment generation, transport and deposition. A key challenge for modern society is to predict and better understand how sedimentary systems adapt to an abrupt change in climate. The geological record allows an insight on past climate crises and their registration in sediments.

This study focuses on the changes in physical sedimentary processes during the Paleocene-Eocene Thermal Maximum (PETM, 56 Myrs ago) in the Southern Pyrenees (Spain). A lengthening of the siliciclastic system has been shown to occur coevally to the PETM. Yet, connections throughout the sedimentary system from source to sink and reconstructions of the processes involved in this short-term lengthening lack constraints. Although higher seasonality in pluviometry is usually invoked to explain the increase in sedimentary export, this hypothesis is based on very few continental outcrops only and do not include any system-scale quantification. Here we propose to test this hydrology-based hypothesis thanks to (i) a better understanding of the source-to-sink system’s paleogeography, (ii) paleohydraulic quantifications applied on supplementary outcrops and (iii) grain-size used as a down-system common thread.

First, the sources are better constrained thanks to provenance analyses combining petrography and double dating on detrital zircons (U/Pb and (U-Th)/He). Then, reconstructions of paleohydraulics in several continental outcrops allow to compare paleoslopes and water discharges between pre- and syn-PETM deposits. Finally, studying grain-size along the whole system allows a quantitative estimation of the climate-related evolution of the system’s diffusivity.

This system-scale study provides quantitative insights on the changes in sediment transport processes during an abrupt climate change. The deduced landscape evolution is then a valuable tool to be applied on today’s systems.

 

This research is carried out in the scope of the lead author’s PhD project and is part of the S2S-FUTURE European Marie Skłodowska-Curie ITN.