Thèses passées

Thèse 2025

Michiel Arts. Cyclostratigraphic insights into Silurian climate dynamics - time scale, astronomical forcing, and climatic events during the Silurian

The Silurian Period (443 to 419 million years ago) represents a critical interval in Earth's history, marked by major climatic shifts, repeated biogeochemical events, and substantial carbon isotope excursions. Yet, the Silurian remains relatively poorly understood due to a lack of high-resolution (cyclo)stratigraphic frameworks. The result is some of the largest
chronological uncertainties of the entire Phanerozoic timescale. To address these issues, stratigraphic correlation, cyclostratigraphy, and radiometric dating were integrated to improve the spatial and temporal resolution of Silurian successions. The results provide increased fidelity into the Silurian, allowing us to study the role that astronomical cycles might have
played in pacing Silurian biogeochemical events.

To get better spatial constraints on Silurian successions, we developed a new stratigraphic correlation framework for Gotland's subsurface based on a set of gamma-ray logs. The combination of Dynamic Time Warping and Barycenter Averaging techniques enabled a semiautomated correlation of the well-logs. The resulting correlation enabled the identification of major biogeochemical events in the subsurface and contributed to refining the stratigraphic architecture of Gotland across a ~60-kilometre transect.

To improve temporal constraints and understand the role of astronomical pacing, the type Silurian Cellon section in the Carnic Alps of Austria, spanning the Ludlow to Pridoli intervals, was studied. High-resolution pXRF proxy records and induration patterns from this section were processed using the newly developed WaverideR R package, allowing us to uncover the imprint of astronomical cycles, enabling the tracking period (m) of the 405-kyr eccentricity cycle in continuous wavelet transform scalograms. Monte Carlo simulations incorporating external age constraints were then used to generate an astrochronologically constrained numerical age model. The age model yields new numerical ages for Silurian stage boundaries and conodont zonations. The cyclostratigraphic study also shows that astronomical cycles could have paced Linde, Klev, and Silurian-Devonian boundary events, since these events all occur after a 2.4-Myr eccentricity minima. In contrast, the Lau event appears to be decoupled from this pacing.

To establish more precise numerical age constraints and evaluate the role of astronomical forcing during the Silurian, we developed a Monte Carlo-based model that integrates astrochronological constraints, floating astrochronologies, and Bayesian U-Pb age-depth models. This model was applied to the Telychian-Homerian interval of the Altajme core from
Gotland, Sweden. The new method reduced age uncertainties by an average of 62% compared to using the Bayesian U-Pb Bchron model alone. The model produced refined ages and durations for the Ireviken and Mulde biogeochemical events and the Llandovery Wenlock boundary. The age model also indicates that the maximum rate of change in the δ¹³Ccarb record reached 0.025‰/kyr and 0.045‰/kyr for the Ireviken and Mulde biogeochemical events, respectively. The age-calibrated proxy records show the imprint of astronomical cycles, indicating that the Ireviken and Mulde events could have been paced, since both events occur after a 2.4-Myr eccentricity minimum.

Together, these case studies demonstrate that the integration of astrochronology, U-Pb geochronology, and stratigraphic correlation provides a powerful tool for improving Silurian chronostratigraphy. They further support the hypothesis that long-period astronomical cycles could have paced Silurian biogeochemical events.

 

Thèse 2024

Imen Arfaoui. Multidisciplinary assessment of unconventional reservoir potential in Tunisia: Case studies of Silurian hot shales and Ypresian limestones. 

Unconventional reservoir properties vary depending on their regional and global depositional context and lithological variety (shale, limestones). Therefore, their understanding becomes crucial to improve hydrocarbon exploration worldwide as global energy demand intensifies. The research carried out in this thesis addresses the growing interest in unconventional
reservoirs, particularly in underexplored North African basins. A comprehensive multidisciplinary investigation of two key potential unconventional hydrocarbon reservoirs within the Jeffara Basin (southern Tunisia) and the Tellian Numidian Zone (Northwestern Tunisia) is done in the framework of this thesis. It is focused on two primary good source rocks, the Silurian Hot Shales and the early Eocene Bou Dabbous Formation.

The research integrates fieldwork, sedimentology, petrographic analysis, mineralogical identification, organic and elemental geochemistry, and petrophysical analyses. Based on the results, this research study aims to provide an understanding of these formations depositional environments, diagenetic processes, and reservoir potential, thereby contributing to the broader field of unconventional hydrocarbon exploration.

The Silurian Hot Shales, analyzed through borehole samples from three wells, reveal high organic carbon content ranging between 0.54 wt.% and 23.86 wt.%, Tmax up to 460 ◦C, and biomarkers ratio (0.4 < Ts/ (Ts + Tm) < 0.65), favorable geochemical properties for shale gas/oil production. They witnessed an early mature to mature organic matter that is placed within an oil/gas generation window, with an average transformation ratio (TR) of 30%, an oil saturation index (OSI) exceeding 100% in some target saturated layers, and an average hydrocarbon generation potential (HGP) for the three studied wells of 20.37 kg HC/ton rock. Detailed mineralogical assessments highlight the presence of quartz-rich layers important to the hydraulic fracability, indicating significant potential for unconventional hydrocarbon extraction.

Meanwhile, the Eocene limestone deposits, particularly the Bou Dabbous (source rock) Formation and its lateral equivalent, the El Garia (reservoir) Formation, are scrutinized through outcrop analogs (three studied cross-sections). The second part of this study elucidates the complex interplay of depositional settings and tectonic dynamics that shaped their reservoir
characteristics and contributed to organic matter preservation. Stratigraphic and diagenetic analyses reveal the critical influence of tectonic subsidence, eustatic sea-level changes, and pressure-induced compaction on the reservoir properties (low permeability and significant many types of identified porosity). Despite challenges posed by post-depositional diagenetic processes (cementation, dissolution, compaction, ...) that lead to porosity destruction, the Bou Dabbous Formation holds good organic matter richness (with maximum recorded TOC = 1.11 wt.%, 2.75 wt.%, in TS and OK section respectively), that is marginally mature to mature, with Tmax ranging from 433°C to 454°C, intraparticle/interparticle and fracture porosities. These parameters witness promising prospects for unconventional hydrocarbon exploration. The brittleness index (BI) for the Bou Dabbous Formation, determined based on carbonate fractions, detrital content, and TOC percentages, ranges between 0.84 and 0.98, suggesting a high fracturing sensitivity among the studied areas rocks.

This dissertation underscores the importance of multidisciplinary approaches, combining advanced techniques to evaluate unconventional reservoirs. The findings enhance the understanding of Tunisias petroleum systems and provide insights relevant to global discussions on shale gas/oil and tight reservoirs, thereby supporting future exploration strategies in similar geological settings worldwide.

 

 

Thèses 2022

Mouna Rachdi.  Sédimentologie de la plate-forme carbonatée nummulitique ypréso-lutétienne au nord et au sud de la Téthys.

ABSTRACT. Various sedimentological analysis have been carried out on the Ypresian to Lutetiandeposists in two different regions, located in northern and southern parts of the Tethian domain. Four sections were logged in north Tunisia and two sections were logged in the southern part of France. Lithological and magnetic signal studies allowed to make correlations and deposit environment reconstructions in the two sectors. A range of 12 microfacies in the southern part of the Tethian domain, and 13 microfacies, in the northern part was identified. The ypresio-lutetian deposits were characterized by nummulitids and discocyclinid-rich grainstones and packstones deposited belang the inner ramp zone. In the transitional central zone of the study area, the observed microfacies are composed of coral-rich floatstones and  nummulithoclast-rich packstones and grainstones, showing a mid-ramp depositional environments. The most distal microfacies are characterized of globigerinid and radiolarian-rich mudstones and wackestones showing the outer ramp environments. In this work, the role of the intense tectonic activity was highlighted with the variation in thicknesses and nature of the deposits in the southern sector of the Tethian domain. The northern part of the Tethian domain shows coastal depositional environments, formed of Orbitolitids, Miliolids, Ceretids and oolithe-rich packstones and grainstones. This deposit is followed of an inner platform sedimentation, composed of Nummulitid and Alveolinid-rich packstones and grainstones. Further, the carbonate platform profile shows a submarine middle platform Solenomeris-rich framestones and rudstones, followed by the most distal outer platform deposits, composed of Globigerinid-rich mudstones associated with rare bioclastic debris. The magnetic signal helped us to make correlations between the MS and the sea level changes. This method has often been used as a correlation tool, indeen, in the most common case, the magnetic signal tends to increase with the most proximal environments. In this work, we were able to determine that the magnetic signal increases also with the distal environments, which is related to the sedimentation rates and the presence of glauconia.

 

Sébastien Wouters. Evaluating the replicability in cyclostratigraphy.

Cyclostratigraphy is the study of sedimentary cycles, i.e., patterns that are found to repeat themselves in the sedimentary geologic records. Those sedimentary cycles can be used to establish the chronology of the rocks’ formation in two ways:
- by considering that given cycles are representative of the same geologic time in different records.
- by using cycles linked to the regular astronomical cycles to quantify geological intervals’ durations.
However, the use of sedimentary cycles for these stratigraphic purposes can be inconsistent; primarily because cycles can easily be confused for one another, and due to the imprecision and scarcity of independent stratigraphic constraints that could solve such ambiguity. Cycles’ ambiguity comes from the repetitive nature of sedimentary cycles. The lack of stratigraphic constraints takes roots from the reality of the field; their imprecision originates from their potential to have an offset from one record to another. Still, countermeasures and replicability studies can be implemented; throughout the thesis, a discussion is proposed on how effectively replicability can be applied to cyclostratigraphic studies. This involves the development of new tools and concepts, which are meant to survey the potential failure points of cyclostratigraphic studies, and establish their replicability. A formalisation proposal is made on how to conduct stratigraphic correlation, taking explicitly into account the ambiguity of cycles and the offsets of stratigraphic constraints. This involves defining an interval inside which, despite any offset, a given stratigraphic event must occur beyond any
reasonable doubt. Within equivalent intervals, the ability of cycles to be uniquely recognisable in separate records can be established. Overall, cyclostratigraphic interpretations should propose tests able to distinctively confirm or falsify them. This can be supported by making the computerisation of the stratigraphic process more accessible to geologists. In this endeavour, data formats and data processing procedures were established with the idea of making all necessary data storable, and machine-readable. Equally, the output of the data processing procedures is set so that it can be reversible, i.e, reversed back into its original form, to make it more intuitively understandable by geologists. A reversible cyclostratigraphic signal processing method is developed in the thesis. The method is based on decompositions, i.e., ensembles of sub-signals that can reconstruct the initial signal when summed with one another. Inside decompositions, sub-signals can cross-cancel one another, underlining that in sub-signals, wiggles not present in the original signal can occur. These wiggles are particularly susceptible to be misinterpreted in cyclostratigraphic signals due to sedimentation rate fluctuations, and to the amount and nature of processes able to affect the signal. Therefore, the amount and location of cross-cancellation should be determined. The “wiggle-in-signal approach” is presented; it aims at making the sub-signals in the decomposition more representative of the expression, wiggle by wiggle,
of all the processes affecting the signal. This means reducing the amount of cross-cancellation, while still untangling the various processes involved in the cyclostratigraphic signals. Empirical Mode Decomposition (EMD) is shown to be especially fit for this purpose. Cross-cancellation occurs in any signal processing method, but can currently only be quantified in a decomposition. Furthermore, decompositions are representative of entire content of signals, as they allow a flawless reconstruction. Decompositions can thus give a comprehensive overview of how all the properties of a given signal are interpreted. It is proposed that decompositions could be used as a practical standard output for the analytical interpretation of cyclostratigraphic signals. The StratigrapheR package was developed throughout the thesis, as a proof of concept on how to process and visualise lithological data in the R scripting environment. The package permits the automation of drawing lithologs and eases the development of lithological data processing software. The pmob universal format for palaeomagnetic data (which stands for PalaeoMagnetic OBject), is proposed. It can integrate any information the user wants to add on any measurement, and it standardises the processing of mainstream palaeomagnetic data. Overall, the development of standardised data formats and of associated data processing tools, especially in an open source and free environment, could greatly ease the task of replicating cyclostratigraphic interpretations.

 

Thèse 2019

Hocine Djouder. Silurian succession from North Africa: Sedimentology, ichnology and thermal history for a new era of hydrocarbon exploration.

ABSTRACT. The economic potential for unconventional shale oil and gas production in the Silurian of the Berkine – Ghadames and Illizi basins (BGI) was recently confirmed through exploration drilling in south-eastern Algeria. The research of this thesis focusses on the southern margin of the prolific BGI basins, i.e. the Tassili n’Ajjer plateau, and aims to understand and characterize in great detail the depositional environments and sequences of the entire Silurian deposits, as well as to reconstruct the diagenetic and thermal history of the region.
Over the Tassili n’Ajjer plateau, Silurian succession is composed of three Formations, namely from bottom to top: the Oued Imihrou Formation, overlained by the Atafaïtafa and the Oued Tifernine Fm. The 400 m-thick clastic strata of this succession, laterally traceable over kilometers, are showing progressively a general trend of thickening- and coarsening-upward (shallowing-upward) with exceptional variability of depositional environments, as evidenced by their numerous associated sedimentological and ichnological features. Indeed, the wealth of outcrop data within the Silurian succession enables us to distinguish thirteen facies (facies A-M), ranging from shallow-to marginal-marine facies. Furthermore, the sequential analysis of this succession was carried out following the identified characteristics of each facies and ichnofacies, as well as the integration of magnetic susceptibility, gamma-ray spectrometry, and geochemical results. Using this multidisciplinary approach, six 3rd-order sequences have been identified (in ascending order, Si-1 to Si-6). Most, if not all, of the levels with abnormally high values of magnetic susceptibility and gamma-ray, correspond to key surfaces of the aforementioned depositional sequences, i.e. the maximum flooding surfaces, therefore, highlighting the global sea-level rises within the Silurian Period.
Investigation of the diagenesis- and thermal maturity-evolution of the Silurian succession during the present study led to significant conclusions. Our results and interpretations, both on graptolite-derived organic matter maturity and evolution of clay minerals, reveal an important relationship between kerogen maturation with episodic illite crystallization and the structural evolution in SE Algeria. Indeed, the repeatedly reactivated N-S lineaments and mega-shear zones, during the Phanerozoic orogeneses and rifting phases, constituted migration pathways for hot potassium-rich fluids. These migration pathways, notably at the westernmost part of the Tassili n’Ajjer plateau, induced thermal anomaly or brief ‘heat spike’ as revealed by higher organic maturation level and subsequent precipitation of authigenic clay minerals.
Lastly, from the standpoint of Silurian oil and shale gas future exploration in the eastern Sahara, it is important to highlight that the areas of interest ‘Plays’ could be most likely those bordering major Precambrian lineaments, i.e. Amguid-El Biod-Messaoud axis, where thermal maturation and unrestricted hydrothermal fluids are high and frequently reported. In other words, these promising areas are undoubtedly offering the highest potential with more discoveries of natural resources in Algeria.

 

Thèse 2017

Hanene Belghiti. Sédimentologie et contrôle eustatique. Cas du Miocène, Tunisie Centre Nord.

RESUME. En Afrique du Nord, au Néogène, la compression qui affecte le domaine atlasique témoigne de la convergence Afrique-Europe et se marque par des dépôts de séries silicoclastiques du Miocène pauvres en faune. Le travail s'intéresse à caractériser les variations spatiotemporelles des faciès, les variations eustatiques et les corrélations de ces séries miocènes. A cette fin, on observe et analyse les différents mécanimes sédimentaires afin d'identifier des surfaces remarquables corrélables basées sur l'analyse séquentielle et les variations de la susceptibilité magnétique. Sur la base des données obtenues, l'objectif est de proposer un modèle sédimentologique, étudier les variations eustatiques à l'échelle régionale, établir des corrélations et élaborer un modèle paléogéographique des séries du Miocène en Tunisie.

 

Thèse 2016

Mehrdad Sardar Abadi. Lower Carboniferous shallow marine sequences from the Central Alborz Basin, Iran (north-eastern margin of Gondwana): sedimentology, biostratigraphy and rock–magnetic studies.

ABSTRACT. The Lower Carboniferous Mobarak Formation records the development of a carbonate platform on the southern Paleo-Tethyan passive margin. This pervasive carbonate factory was deposited following the opening of the Paleo-Tethys Ocean into the Alborz Basin along the northern margin of Gondwana. The depositional facies range from the most proximal to the most distal and include coastal environments, inner ramp peritidal facies, peloidal to crinoidal shoals, storm to fair-weather influenced mid-ramps, proximal to distal shell beds and low energy outer ramps. Storms clearly played a dominant role in the distribution of skeletal and non-skeletal shoals on the carbonate ramp. Sedimentological analyses complemented with foraminiferal biostratigraphy reveal four events which are interpreted to represent the principal factors controlling carbonate platform evolution in the Alborz Basin during the Lower Carboniferous: 1) A transgression linked to global temperature rise in the Early Tournaisian (Middle Hastarian) resulted in the formation of thick-bedded argillaceous limestones. 2) the Hastarian-Ivorian boundary glaciation phase, 3) Upper Ivorian-Lower Visean? tectonic block faulting. 4) the Visean-Serpukhovian glaciation phase. The three foraminiferal assemblages encountered in the Tournaisian interval of the Mobarak Formation are restricted to specific periods within the Ivorian. The occurrence of specific foraminiferal taxa in Alborz is tightly governed by transgressions and migration of North Paleo-Tethyan biotic elements as response to the thermal period.
We also combined proxies for ambient paleothermometry in addition to the indications for arid conditions and arid conditions and the presence of foraminiferal taxa with a North Paleo-Tethyan affinity in the Lower Carboniferous Mobarak Formation to suggest a paleo-position for the Alborz Basin at lower latitudes than approximately 45°-50° southern paleolatitude reported thus far. Magnetic susceptibility (cin) was measured and compared with facies from the same sample. There is a clear link between cin and facies, and the average cin values are higher for distal facies than for proximal ones. The cin profile of Lower Carboniferous carbonate sequence reflects stratigraphic variations in response to relative sea level changes and detrital input. In the context of the sequence stratigraphic framework, the average cin values for lowstand and transgressive system tracts deposits are higher than for the highstand system tracts deposits. The clear link between cin and facies points to at least partly preserved primary cin signal, related to detrital inputs. In respect to the hysteresis measurements the cin signal is mainly carried by low coercivity ferromagnetic minerals such as magnetite, with a mixture of relatively coarse grains (detrital fraction) and ultra-fine grains (probably formed during diagenesis).

 

Thèse 2015

Damien Pas. Sedimentary development and correlation of long-term off-reef to shallow-water Devonian carbonate records in Europe.

ABSTRACT. The Devonian Period coincides with the largest carbonate platform development of the Phanerozoic Eon. Sedimentary records of this Period are consequently significant archives of past life, climate and environment. In the Pre-Mesozoic massifs of Europe, these records are exceptionally well-exposed and -preserved. In this research, we use an integrated sedimentological approach, with emphasis on facies analysis, to illustrate the diversity of depositional settings that shaped three of the most remarkable European carbonate platforms (e.g., Ardennes, Rheinisches Schiefergebirge and Carnic Alps) and to reconstruct their long-term environmental development throughout the Mid-Late Devonian. Based on the large amount of material from the different locations, we have carried out an in-depth study on the reliability of magnetic susceptibility as a tool for palaeoenvironmental reconstruction and long-distance correlation in marine carbonates.

 

Thèse 2012

Jonathan Michel. Lithostratigraphie, sédimentologie et analyse séquentielle du quartzite de Berlé (Emsien supérieur, Grand Duché de Luxembourg).

RESUME. Ce travail intègre différentes approches dédiées au Quartzite de Berlé: terrain, analyse microscopique, palynologie, analyse séquentielle, susceptibilité magnétique et analyse diagénétique. Un complexe estuarien a ainsi été identifié dans l'Emsien du Bassin de Neufchâteau-Wiltz-Eifel. Trois types d'environnement y sont reconnus: alluvial, tidal et marin distal. La combinaison de l'analyse sédimentologique détaillée et de la stratigraphie séquentielle est à la base de la modélisation des variations verticales et latérales du domaine estuarien. Dans le modèle proposé, le Quartzite de Berlé correspond à une barre sableuse tidale et passe latéralement aux grès à flaser bedding du sommet des Couches de Clervaux. La reconstitution diagenétique permet une meilleure compréhension des mécanismes à l'origine des caractéristiques présentes du quartzite, grâce à l'identification de différents ciments et minéraux authigènes. Les relations temporelles entre ces différents constituants sont intégrées dans une séquence paragénétique qui comporte quatre phases: une phase éogénétique, une phase mésogénétique, une phase métamorphique et une phase télogénétique. La minéralogie des argiles (cristallinité de l'illite) montre que le Quartzite de Berlé a subi des conditions d'enfouissement variables à l'échelle régionale, liées à la phase de rift pré-varisque du bassin rhéno-hercynien. Enfin, l'interprétation du signal de susceptibilité magnétique suggère qu'en domaine détritique proximal, ce signal est principalement contrôlé par les paramètres environnementaux (agitation, taux de sédimentation) et par la diagenèse.

 

Thèses 2008

Cédric Mabille. Dynamique sédimentaire de l'Eifelien et de la base du Givétien en Belgique et dans les régions limitrophes.

RESUME. Ce travail est basé sur l'étude sédimentologique, magnétique et géochimique de 14 coupes, totalisant près de 1650 m de faciès carbonatés, détritiques ou mixtes. La sédimentation s'effectue sur des rampes et plate-forme montrant une grande variété d'environnements. Les comparaisons des courbes de susceptibilité magnétique (SM) et de faciès permettent de mettre en évidence trois types de comportements : (1) certaines coupes ne montrent aucun lien entre SM et faciès, la SM restant relativement constante ; (2) un parallélisme peut être observé entre SM et faciès et (3), une opposition peut être observée entre les deux types de courbes. Une fois identifiés et interprétés en terme de modèle de dépôt, ces comportements relativement cohérents permettent l'utilisation de la susceptibilité magnétique à des fins de corrélation haute résolution. Les courbes de SM peuvent également servir de proxy du signal eustatique.

L'intégration de l'ensemble des données et interprétations aboutit à la proposition d'un canevas de statigraphie séquentielle. La généralisation de ce canevas à l'ensemble du bord sud du Synclinorium de Dinant permet une meilleure compréhension du passage latéral entre la Formation de Couvin et la Formation de Jemelle et mène à la reconstitution de l'installation de la plate-forme carbonatée à la transition Eifelien-Givétien.

 

Benoît Hubert. Les stromatopores givétiens et frasniens de l'Ardenne méridionale et du Boulonnais (France et Belgique): sédimentologie, paléobiodiversité et paléobiogéographie. Benoît Hubert, 2008, thèse de doctorat en cotutelle ULg-Université de Lille I.

ABSTRACT: The Devonian stromatoporoids developped in Ardenne mainly during the Givetian. They are also well represented during the Frasnian. The aim of the work is to analyse the biodiversity of stromataoporoids in southern Ardenne during these two periods and to compare the results with what is known from the Boulonnais. Stromatoporoids are constrained to the nature of sediments (i.e. carbonated facies). Preliminary studies of sedimentological environments are necessary to approach biodiversity. During the Givetian, the southern Ardenne is mainly characterized by shallow water and carbonated shelves. Abundant reefs found the best conditions for their development. They are distributed at different scales and through different times. Some differences are observed between Givetian and Frasnian reefs. Some specialized species seems to dominate in different reef units. Finally, stromatoporoids of southern Ardenne seems to have affinities with fauna distributed along the same plate, but also with fauna from the Gondwana.

 

Thèse 2004

Anne-Christine da Silva. Sédimentologie de la plate-forme carbonatée frasnienne belge.

ABSTRACT: This work reflects the integration of different techniques, such as field observations, petrography, magnetic susceptibility measurements, isotopic analyses and sequence stratigraphy. The combination of these results allows us to reconstruct the environmental evolution of the shallow water Frasnian carbonate deposits of Belgium. The sedimentological analysis provides different facies models, each characterized by its own geographical and stratigraphical position. The Lower part of the Frasnian corresponds to a ramp, with shales and crinoidal layers. The Middle part of the Frasnian is divided in two platform areas (north and south). The external zone of the platform is dominated by crinoidal deposits, the intermediate part shows biostroms with stromatoporoids and the internal zone presents sub- to supratidal deposits. The Upper part of the Frasnian is a ramp with external deposits made by shales, intermediate belt of rugose coral biostromes and the shallowest part of the platform is characterized by oncoids and peloids. The major control on facies distribution is the result of sea level variations, which imply cyclic sedimentation (third and fourth order). Control on lateral variations is related to tectonic movements which imply morphological variations of the platform. We recognized different sequences and each tract of these sequences is characterized by facies, magnetic susceptibility, isotopic and cyclic pattern variations. The sequences defined on the platform are compared to the sequences defined in the basinal area. Finally magnetic susceptibility is used mainly for precise correlations (fourth order). We have showned that magnetic susceptibility signal is directly related to facies, fourth order cycles and third order sequences. The amount of magnetic minerals is probably related to lithogenic inputs.