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Les dépôts littoraux pleistocènes et holocènes: une clé pour déchiffrer les séries sédimentaires anciennes et pour gérer l'évolution future des côtes

English title Pleistocene and Holocene coastal deposits: a key for deciphering ancient sedimentary sequences and for managing future coastal evolution
Applicant Davaud Eric
Number 119777
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 01.04.2008 - 31.03.2012
Approved amount 198'730.00
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Keywords (14)

sedimentary geology; coastal deposits; Pleistocene; Holocene; global changes; sea-level changes; eolianite; carbonate; coastal dune; forward modelling; image analysis; sedimentology eolianite petroleum; geology paleoclimatology sealevel; changes Quaternary Holocene Pleistocene

Lay Summary (French)

Lead
Lay summary
Dans la plupart des régions semi-arides les cordons dunaires littoraux pléistocènes et holocènes constituent d’importants aquifères et peuvent former des digues naturelles limitant l’impact d’une élévation du niveau marin. Ces dépôts sableux qui s’étendent souvent sur de très longues distances sont soumis à une diagenèse météorique très active qui les consolide mais favorise simultanément le développement d’une porosité secondaire pouvant amplifier leur capacité à héberger des fluides. Ces corps sédimentaires éoliens, très fréquents dans le Quaternaire, n’ont que très rarement été signalés dans les séries sédimentaires plus anciennes où ils pourraient constituer des réservoirs d’hydrocarbures importants. Cette absence est classiquement imputée à un faible potentiel de préservation ou à des facteurs climatiques ou environnementaux. Les nombreuses observations dont nous disposons sur le bassin méditerranéen, le golfe Persique, l’Australie et le Maroc montrent cependant que ces dépôts, qui peuvent se lithifier très rapidement, sont susceptibles de résister à l’érosion lors de phases d’élévation rapide du niveau marin. Leur prétendue absence dans les séries sédimentaires anciennes s’expliquerait donc par la difficulté qu’il y a à les distinguer de dépôts marins classiques. L’objectif de ce projet est de trouver des critères de reconnaissance univoques permettant d’identifier ce type de dépôts dans les séries sédimentaires pré-Quaternaires et de comprendre les processus et les conditions environnementales qui sont à l’origine de leur formation et de leur préservation. Les résultats attendus de cette recherche pourraient avoir des implications dans le domaine de la géologie pétrolière (géométrie et hétérogénéités internes des réservoirs d’hydrocarbures carbonatés) et et dans le domaine de l’environnement (comportement des zones littorales face à l’élévation du niveau marin et variations paléoclimatiques).
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Name Institute

Publications

Publication
An aeolianite in the upper Dalan member (Khuff formation), South pars field, Iran.
Frébourg G., Davaud E., Virgone A., Gaillot J., Kamali M. (2010), An aeolianite in the upper Dalan member (Khuff formation), South pars field, Iran., in Journal of Petroleum Geology, 33, 141-154.
Carbonate coastal dunes: potential reservoir rocks ?
Frébourg G. (2010), Carbonate coastal dunes: potential reservoir rocks ?, in Terre et Environnement, 92, 1-178.
Catastrophic event recorded among Holocene eolianites (Sidi Salem Formation, SE Tunisia).
Frébourg G., Hasler C.A., Davaud E. (2010), Catastrophic event recorded among Holocene eolianites (Sidi Salem Formation, SE Tunisia)., in Sedimentary Geology, 224, 38-48.
Facies and characteristics in carbonate eolianites.
Frébourg G., Hasler C.A., Le Guern P., Davaud E. (2008), Facies and characteristics in carbonate eolianites., in Facies, 54(2), 175-191.
Anatomy, internal heterogeneities, and early fracture network of a Pleistocene carbonate coastal dune (Rejiche Formation, southeastern Tunisia)
Hasler C.A., Frébourg G., Davaud E., Anatomy, internal heterogeneities, and early fracture network of a Pleistocene carbonate coastal dune (Rejiche Formation, southeastern Tunisia), in Facies.
Uplifted marine terraces of the Akamas Peninsula (Cyprus): evidence of climatic conditions during the Late Quaternary highstands.
Frébourg G., Hasler C.A., Davaud E., Uplifted marine terraces of the Akamas Peninsula (Cyprus): evidence of climatic conditions during the Late Quaternary highstands., in Sedimentology.

Scientific events

Active participation

Title Type of contribution Title of article or contribution Date Place Persons involved
20th Meeting of Swiss Sedimentologists 25.02.2012 Fribourg, Switzerland
AAPG Annual Convention and Exhibition 2011 15.04.2011 Houston, Texas
27th European Meeting of the IAS 20.09.2009 Alghero, Sardaigne
AAPG Annual Convention and Exhibition 2009 10.06.2009 Denver, Colorado
26th International Meeting of the IAS 13.09.2008 Bochum, Germany
14th Geology Conference 20.06.2008 San Salvador, Bahamas


Associated projects

Number Title Start Funding scheme
113356 Sea-level and climate events during the past 500'000 years: the record from fossil reefs, coastal deposits and paleosols from the southeastern Bahamas 01.04.2007 Project funding
107694 Les dépôts littoraux pleistocènes et holocènes: une clé pour déchiffrer les séries sédimentaires anciennes et pour gérer l'évolution future des côtes 01.04.2005 Project funding

Abstract

Eolianites form huge sand bodies extending in some places over hundreds of kilometres along Holocene and Pleistocene coastlines, but they have been very seldom reported in pre Quaternary sedimentary sequences. This paradox has prompted several authors to suggest that eolianites only form during ice ages and are genetically related to rapid glacio-eustatic fluctuations of sea level.Several clues indicate, however, that eolian limestones are much more frequent in the fossil record than suggested, and that their apparent scarcity results from the difficulty of distinguishing them from shallow marine deposits.There are two main reasons why a better understanding of the climatic/eustatic conditions in which these deposits are preserved, and why the development of tools to identify them in the fossil record at the core or thin section scale are important:- from an economic perspective, eolianites represent huge and continuous volumes of sand that are characterized by high primary and secondary porosity. In the fossil record, they could constitute important aquifers and oil or gas reservoirs.- from an ecological viewpoint, carbonate coastal dunes may lithify very quickly and form hydrodynamic barriers that slow down coastal erosion. Their preservation along the present-day coastlines could reduce the devastating effects of a rising sea level.During the previous project (107694/1), we demonstrated that classical petrographic criteria to recognise eolian sediments (well sieved, fine grained and laminated sands) are exceptional in carbonate dunes, as wind carbonate deposits are mainly heterogeneous in size and often coarse-grained. Our experimental works on the influence of percolating fluid on grains packing have shown that the fluid affects grain orientation, but the major reorganising phase take place during evaporation, and can significantly reduce porosity. We have also studied the interaction between fluids and sediments in the field, and important results have been obtained on the eolianites’ early diagenesis: preferential precipitation of carbonate cement around quartz has been observed for the first time, and is presented as a new indicator of vadose diagenesis. The importance of primary depositional facies on early cements and fractures has also been quantified. A detailed study of the sedimentary sequence of carbonate coastal dunes allowed us to recognise seasonal trends. Our project’s aim is to continue and extend the work done in the previous project by:- comparing the petrographic composition of present day and Holocene eolianites;- testing the icehouse hypothesis on the climatic/eustatic conditions surrounding the formation of eolianites by re-examining shallow-water facies for a possible eolian origin in the pre-Quaternary sedimentary record at the outcrop level and on cores (Cretaceous Delphino-Helvetic units, Mesozoic Middle East oil fields);- complete the laboratory experiments on the role of percolation of fluids and desiccation of sediment on grain packing, test the value of this post-depositional criterion as a paleoclimatic proxy and study its influence on reservoir properties;- looking for the presence of submerged eolian ridges developed during the last post-glacial transgression using existing echo-sounding, side-scan sonar, and high resolution seismic data-sets;- evaluating the petrophysical heterogeneities and the reservoir potential of eolianites by studying their diagenetic evolution of subaerial exposure through time;- improving the recognition criteria at core and thin section scale;- introducing onshore transportation as an important process in 2D simulation models.
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