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Earth Surface Signaling Systems: Upstream versus downstream propagation of climatic signals from source-to-sink, in nature and experiments

Applicant Castelltort Sébastien
Number 182017
Funding scheme Project funding (Div. I-III)
Research institution Section des Sciences de la Terre et de l'environnement Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geology
Start/End 01.04.2019 - 31.03.2023
Approved amount 719'906.00
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All Disciplines (2)

Discipline
Geology
Other disciplines of Earth Sciences

Keywords (5)

Environmental signals; stratigraphic cycles; Landscape response; Fluvial systems; Source to sink

Lay Summary (French)

Lead
“Facts from the Past”: les géologues explorent comment d’anciennes rivières ont répondu à un réchauffement climatique global il y a 40 Millions d’années.
Lay summary

Dans ce projet nous nous intéressons à des affleurements exceptionnels de roches sédimentaires d’origine fluviatile dans les Pyrénées espagnoles car elle préservent un enregistrement de l’évolution des rivières au cours d’un événement de réchauffement global il y a 40.5 Millions d’années, connu sous le nom de MECO pour “Middle Eocene Climatic Optimum” et qui dura 500 mille ans. Sur le terrain nous mesurons la géométrie des chenaux et la taille des sédiments en transport dans les roches avant, pendant et après le MECO. De plus nous prélevons des échantillons de la plaine d’inondation qui jouxtait ces anciennes rivières afin de mesurer sa composition en isotopes stables de l’oxygène et du carbone. Celle-ci nous renseigne sur la position précise des sédiments étudiés dans le cadre temporel du réchauffement. Grâce à ces données nous pouvons documenter l’impact du réchauffement global sur le système de rivières à cette époque, notamment répondre à la question de l’augmentation de la fréquence des événements extrêmes et de leur intensité. Ce réchauffement s’est il traduit par de plus longues sécheresses et des crues plus extrêmes, ou au contraire est-on passé à un climat moins saisonnier? 

Un deuxième volet du projet consiste à recréer des petites rivières en laboratoire et à les soumettre à des perturbations simples, notamment de précipitation, afin de simuler différents scénarios de changement climatique et documenter de manière directe leur impact sur les rivières. Ces expériences servent ensuite de point de comparaison pour comprendre les observations de terrain. 

Direct link to Lay Summary Last update: 13.02.2019

Responsible applicant and co-applicants

Employees

Project partner

Associated projects

Number Title Start Funding scheme
191614 ClimatiZENs - Climats du passé pour citoyens de demain 01.01.2021 Agora
161652 Experimental river response to grain size change 01.05.2015 International short research visits
146822 Earth surface signaling systems: natural and controlled experiments of tectonic and climatic extremes 01.01.2014 Project funding (Div. I-III)
146822 Earth surface signaling systems: natural and controlled experiments of tectonic and climatic extremes 01.01.2014 Project funding (Div. I-III)

Abstract

The Earth’s surface, on which we live, is evolving in response to environmental signals that are perturbations of its boundary conditions such as sea level, tectonic uplift or subsidence, and climatic processes. This evolution is slow and normally imperceptible to the human eye, but it leaves a record, on geological time scales, in sedimentary successions and erosional landscapes. The challenge of stratigraphy is to deconvolve past signals from this sedimentary record.By analogy with Cell Signaling in Biology, Earth Surface Signaling Systems is the study of the transmission of environmental signals and flow of information through interconnected networks of individual elements of the Earth’s surface, in the frame of a holistic "Systems" approach. Earth surface signaling requires a combination of experimental and theoretical researches that allow extracting concrete narratives of diverse climates from landscapes and sedimentary successions. By understanding ESSS, risk associated with environmental perturbations will be assessed better, and general circulation models more thoroughly constrained.SNSF project ESSS (2014-2017) was concerned with river network response to extreme tectonic deformation and fluvial systems response to extreme climate change. The present research project falls under the broad banner of my long-term Earth Surface Signaling Systems research line, but new developments in the field lead me to propose here to shift the focus to an outstanding gap of Earth Surface Signaling: to what extent discharge and sediment supply signals, through their influence on the river equilibrium profile, control aggradation, degradation and stratigraphic architecture of alluvial systems? In other words, how do upstream and downstream controls interact to determine the stratigraphic architecture of fluvial systems? Addressing such questions upholds fundamental insight on the filtering role of floodplains with respect to upstream signals and has crucial implication for the interpretation of ancient alluvial sequences. This focus shift stems from the emerging possibility to leverage 1) the recent development of methods for quantifying paleoslope in ancient fossil channel deposits, and 2) the newly built Surface Dynamics Laboratory at the University of Geneva, to test hypotheses of controls on aggradation, degradation and channel architecture. We propose to apply these methods, complemented with magnetostratigraphy and isotope and clay analyses on fine-grained sediments to generate independent correlations and climatic data, within well-constrained Late Eocene successions of the South-Pyrenean foreland basin in Spain, where exceptional outcrop conditions provide access to nearly 6 millions of years of correlative stratigraphy through continental to marine segments of a unique sediment routing system.In sub-project §1, we will collect grain size, channel geometry and floodplain isotope data in coeval sections of the alluvial fan, fluvial and deltaic sub-systems of the Late-Eocene Escanilla routing system. These data will be the basis to testing hypotheses of upstream versus downstream controls on alluvial sequence architecture and signal propagation. In parallel, two new magnetostratigraphic sections will be performed to trace robust timelines between the different segments of the S2S system and propose a high-frequency sequence stratigraphic framework.In sub-project §2, we will set up and run experiments of climate-induced water discharge and sediment supply perturbation in laboratory rivers. The experiments will serve to explore changes in channel geometry and stacking pattern through climate cycles, thus enabling improved reading of ancient alluvial records.
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