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Comparative architectural analysis of large fluvial fan successions in humid vs arid settings: Styles of aggradation, channel belt avulsion and oberbank organisation

English title Comparative architectural analysis of large fluvial fan successions in humid vs arid settings: Styles of aggradation, channel belt avulsion and oberbank organisation
Applicant Moscariello Andrea
Number 175762
Funding scheme Project funding
Research institution Département des sciences de la Terre Université de Genève
Institution of higher education University of Geneva - GE
Main discipline Geology
Start/End 01.05.2018 - 31.12.2022
Approved amount 450'000.00
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All Disciplines (4)

Discipline
Geology
Geochemistry
Geochronology
Mineralogy

Keywords (9)

autogenic processes; fluvial avulsion; sedimentary processes ; clay minerals; geochemical signatures; chemostratigraphy; climate forcing; fluvial fans; radiogenic isotopes

Lay Summary (Italian)

Lead
Le conoidi fluviali (note anche come "sistemi fluviali distributivi") sono sempre più riconosciuti come sistemi deposizionali fondamentali responsabili dell'accumulo di ingenti volumi di sedimenti clastici nei bacini continentali. A questo proposito rimangono delle domande fondamentali sull'origine di questi sistemi e sui meccanismi che regolano l'evoluzione delle loro reti di drenaggio. La migrazione laterale dei canali fluviali, frequentemente osservata sulle conoide attive, è il processo fondamentale che intendiamo indagare descrivendo e riconoscendo le sue caratteristiche stratigrafiche.
Lay summary

Soggetto e obiettivi
Il nostro obiettivo principale è quello di contribuire a una migliore comprensione del comportamento dei grandi sistemi fluviali formati ai piedi delle montagne. In particolare, (i) miglioreremo la caratterizzazione morfologica e composizionale dei sistemi fluviali con modelli distributivi a forma di conoide; (ii) amplieremo la comprensione della composizione e delle relazioni sedimentarie con le dinamiche fluviali; (iii) metteremo in relazione lo sviluppo dei sistemi fluviali e la storia del sollevamento orogenico.
Contesto socio-scientifico
Una delle principali implicazioni della nostra ricerca riguarderà la relazione tra gli effetti dell’avulsione fluviale e i loro modelli temporali e spaziali nelle antiche successioni stratigrafiche che si verificano in conoidi fluviali (megafan) attualmente attivi in varie regioni e paesi densamente popolati (ad es. India del nord, Cina meridionale, Paraguay, sud-est del Brasile), dove esse formano vaste distese di terreni agricoli, ospitano complesse reti di trasporto tra centri economici locali e centri demografici, e la loro idrografia superficiale viene spesso modificata antropicamente per gestire le risorse idriche ad uso civile, agricolo e industriale. Cambiamenti drammatici ricorrenti di idrografia della superficie del conoide caratterizzano l'evoluzione di questi grandi sistemi alluvionali, comunemente accompagnati da alluvioni catastrofiche che interrompono i trasporti, la produttività economica e portano a gravi perdite di vita e di risorse, come riconosciuto anche dai registri archeologici. Imparare a leggere la registrazione stratigrafica di tali cambiamenti dalle successioni fluviali e a riconoscere i loro modelli in diversi contesti paleoambientali e in parti distinte di questi sistemi (ad esempio, prossimale o distale) migliorerà la nostra capacità di prevedere zone propense alla pericolosità su conoidi moderni e per interpretare i segnali geomorfici presenti di imminenti cambiamenti ambientali.

Direct link to Lay Summary Last update: 19.01.2018

Lay Summary (English)

Lead
Fluvial fans and megafans (also known as ‘distributive fluvial systems’) are increasingly recognized as fundamental depositional systems responsible for the accumulation of probably the largest volumes of terrestrial clastic sediments in continental basins. Fundamental questions remain on the origin of these systems and on mechanisms governing the evolution of their drainage networks.Lateral switching of river channels, frequently observed on active fans, is the fundamental process which we intend to investigate by describing and recognising its stratigraphic signatures in detail.
Lay summary

Subject and objectives
Our main objective is to contribute to a better understanding of the behavior of large fluvial systems formed at the foothills of mountains areas. In particular, (i) we will improve the morphological and compositional characterization of river systems with fan-shaped distributive patterns; (ii) will broaden the understanding of sedimentary composition and relationships with river dynamics; (iii) we will constraints the relationship between the development of river systems and the history of the orogenic relief.

Socio-scientific context
A major implication of our research will address the relationship between fluvial avulsion signatures and their temporal and spatial patterns in ancient stratigraphic successions is that presently active fluvial (mega)fans occur in various densely populated regions and countries (e.g. northern India, southern China, Paraguay, southeast Brazil), where they form vast expanses of farmlands, host complex transport networks between local economic hubs and demographic centers, and their surface hydrography is frequently modified anthropically to manage water resources for civil, agricultural and industrial use. Recurrent dramatic changes of fan-surface hydrography tipify the evolution of these large alluvial systems, commonly accompanied by catastrophic floods that disrupt transportation, economic productivity, and lead to major life and resource losses, as recognized also from archeological records. Learning to read the stratigraphic record of such changes from fluvial-fan successions and to recognize their patterns in different paleoenvironmental contexts and in distinct parts of these systems (for ex., proximal vs. distal) will enhance our ability to predict hazard-prone belts on modern fans and to interpret present geomorphic signals of impending change and environmental disruption.

Direct link to Lay Summary Last update: 19.01.2018

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Associated projects

Number Title Start Funding scheme
146736 The Miocene Mariño formation (central argentinian foreland, Mendoza region): a high-resolution integrated study of sedimentary and palaeoenvironmental responses to tectonic and climatic forcing. 01.11.2013 Project funding

Abstract

Fluvial fans and megafans (also known as ‘distributive fluvial systems’) are increasingly recognized as fundamental depositional systems responsible for the accumulation of probably the largest volumes of terrestrial clastic sediments in continental basins. Recent developments in fluvial geomorphology and sedimentology show that very thick successions of dominantly (but not exclusively) alluvial origin can be attributed to, or closely affected by, long-term progradation of large fluvial fans in all tectonic settings of prolonged subsidence and steady sediment supply, and in various climate contexts. Fundamental questions remain on the origin of these systems and on mechanisms governing the evolution of their drainage networks. Avulsion, frequently observed on active fans, is the fundamental process driving the areal distribution of runoff and sediment transport on fan surfaces over long timespans. However, stratigraphic signatures of autogenic avulsive events in fluvial-fan successions have not yet been investigated in detail.This project follows our investigation of fluvial-fan stratigraphy in Miocene dryland deposits of the central Argentinian foreland. It aims: 1) to provide criteria for the recognition of avulsion events at channel-belt and system scale in ancient fan records; 2) to estimate the variability of such avulsion mechanisms through time and space (from proximal to distal domains); 3) to carry out a comparative analysis of avulsion dynamics for two systems developed in ancient arid and humid settings, thus subject to markedly distinct paleohydrologic dynamics. The workflow is based on architectural analysis of large-scale photopanels of extensive outcrops, acquired by means of drone surveys, providing information at multi-kilometric scale and to be integrated with ground surveys at key locations and stratal intervals of relevant complexity. The project further promotes the line of integrated sedimentological research for the Geneva group, supporting field-based sedimentology with parallel, high-resolution, multi-proxy analyses of sediment composition, provenance, and chemostratigraphic characterization, fundamental for correlation in extensive coarse-clastic successions and for the recognition of allogenic forcing. This comparative study will be carried out on the Miocene record of the Argentinian foreland as example of fluvial-fan development in arid paleoclimate, and on well-known Paleocene-Eocene successions of the Uinta Basin (Utah, U.S.A.), as example of a humid paleoclimate setting.This project has fundamental relevance for an improved understanding of the autogenic dynamics driving the evolution and progradation of large fluvial-fan systems, thus underlying the basic architectural heterogeneity of extensive stratigraphic records in terrestrial settings. Whereas most research aims at recognizing the effects of long-term allogenic forcing on stratigraphy, distinguishing these from continuously superimposed effects of inherent system autodynamics will improve our ability to interpret the origin of stratigraphic variability and help redirect inferences on fluvial genetic stratigraphy. In addition, avulsions are cause for major environmental and infrastructural disruption and life loss on modern, densely populated fluvial fans, especially in tropical regions. Stratigraphic analysis provides a long-term record of avulsion dynamics, frequency and spatial distribution, providing basic information to guide prediction of recurrent hydrological hazard in such regions.
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