Effect of the thermal gradient variation through geological time on basin modeling; a case study: The Paris basin.

Many studies investigated the thermal modeling of the Paris basin for petroleum interests during the 1970s. Most of the softwares developed by oil companies or research centers were based on the assumption of a constant thermal gradient. In order to take into consideration the variation of the thermal gradient during basin evolution, we developed the TherMO's Visual Basic 1D program. We applied our model to twenty boreholes located along a cross-section roughly running EW over 150 km in the center of the Paris basin. The numerical results were calibrated with organic matter maturity data. TherMO's simulates the amount of heat provided to the sedimentary organic matter. The heat parameter simulated shows lateral variation along the cross-section. It decreases from Rambouillet to Trou Aux Loups boreholes (87–66 mW/m2) at about 100 km more to the east whereas the heat flux value simulated is 73 mW/m2 in St. Loup borehole. The mean thermal gradient calculated for liassic horizons at 87 My for the Rambouillet well is 50.4 °C/km. This value is similar to previously published results. By integrating the calculation of the thermal gradients and conductivities related to the burial of each stratigraphic sequence, our approach points out variations in the thermal regimes the sedimentary organic matter (SOM) has been subjected to through geological time

Implications of spatial and temporal evolutions of thermal parameters in basin modelling

International audienceThis paper presents the Paris Basin numerical modelling at a high sequential resolution scale (1–5 my). Simulations were carried out from the computation of thermal gradients and conductivities varying with the burial of genetic units. Geologic heating rates are also calculated throughout the burial of the stratigraphic sequences. Thermal energies are then deduced. The Paris Basin is well known for its hydrocarbon potential in Liassic sediments. This study is focused on an east–west cross-section through the basin. The results show spatial and temporal variations of thermal parameters from the western to the eastern part of the profile. The reactivation of Hercynian fracture systems during the Mesozoic may be responsible for the computed variations in thermal conductivities and thermal gradients. Major geodynamic events also played a role in the simulated thermal history. Variations of the thermal energy are observed and are well correlated with the burial history of the basin. We suggest linking the simulated thermal energies to the thermal cracking of the organic matter. Our results are consistent with the prediction of hydrocarbon potential in the Cretaceous period. Consequently, this approach provides new insights to improve petroleum generation modelling issues

Seismic stratigraphic framework and depositional history for Cretaceous and Cenozoic contourite depositional systems of the Mozambique Channel, SW Indian Ocean

International audienceThis study describes previously unrecognized contourite depositional systems (CDSs) in the Mozambique Channel which constrain palaeoceanographic models for this area. The stratigraphic stacking patterns record nine seismic units (SU1 to SU9) separated by eight major discontinuities (a to h, oldest to youngest). Key seismic markers in CDS evolutionary history occur during Aptian-Albian (~122 Ma), late Cenomanian (94 Ma), early (38.2–36.2 Ma) and late (25–23 Ma) Oligocene, and early-middle Miocene (~17–15 Ma) epochs. These record onset (~122 to 94 Ma), growth (94 to 25–23 Ma), maintenance (25–23 to 17–15 Ma), and burial (17–15 Ma to the actual time) stages for CDSs. CDSs first develop during the onset stage which coincides with the opening and deepening of the African-Southern Ocean gateway (at 122 and 100 Ma, respectively). The growth stage, beginning in the late Cenomanian (94 Ma), correlates with the opening and deepening of the Equatorial Atlantic gateway. During the growth stage, two major shifts in sedimentary stacking pattern occur which coincide with palaeoceanographic changes during the early (38.2–36.2 Ma) and late (25–23 Ma) Oligocene. These in turn coincide with the onset and local enhancement of Antarctic water masses. CDS growth continued until the early-middle Miocene during the maintenance stage (~17–15 Ma). Most CDS growth ceased at the end of the maintenance stage. Circulation of the North Atlantic water mass into the Southern Hemisphere led to a deepening of Antarctic water masses in the area

Origin and propagation of sedimentary sequences throughout the Escanilla fluvial routing system (South Pyrenean foreland basin)

EGU2020: Sharing Geoscience Online, 4-8 may 2020During middle Eocene, the Escanilla fluvial system transported and deposited material from East to West in the southern Pyrenees foreland basin. The paleogeography and sedimentology of the source to sink system is well established. The temporal framework is made of scattered low resolution magnetostratigraphies, and a robust temporal framework in the most distal (Olson) and most proximal (Sis) parts of the system. We built a new high resolution magnetostratigraphy from the middle part of the system, the Lascuarre section. The correlation of Lascuarre with the high resolution magnetostratigraphies and the integration of these data with other available chronological constraints results into a robust complete temporal framework from source to sink. Sedimentological analyses of the Lascuarre section allow recognizing a set of sedimentary sequences throughout the record. Here we present the result of the analyses, and discuss the relative weight of the different forcing. Particularly, we elucidate the role of tectonics in relation to subsidence distribution patterns, and also the distinct expression of climate. Eventually, we identify and explore the signal propagation mechanisms of climate aberrations and of quasi-regular orbital variations along the routing system

Modélisation 3D des transports de sel et de chaleur au cours des 248 Ma d’évolution du bassin de Paris : implications diagénétiques

Un modèle de bassin 3D a été développé sur le bassin de Paris, reconstituant ses 248 Ma d’histoire géologique depuis le Trias jusqu’à l’actuel. Cette modélisation s’appuie sur une base de données stratigraphique et lithologique détaillée constituée d’environ 1100 forages pétroliers. Ce modèle, d’échelle régionale, couvre un domaine de 700 000 km2, plus vaste que l’extension actuelle du bassin, afin de prendre en compte l’évolution paléogéographique de la plaque européenne. Cette histoire géologique est simulée à l’aide du modèle numérique NEWBAS de l’Ecole des Mines de Paris. Le modèle simule la sédimentation, l’érosion, la compaction, les écoulements de fluides et les processus de transport de solutés et de chaleur. L’objet du présent article est de montrer l’intérêt d’une telle modélisation pour l’estimation et la quantification de l’importance des circulations de fluides dans les processus géologiques. Les études sur les ciments diagénétiques des réservoirs Dogger et Keuper du bassin de Paris ont souvent conduit leurs auteurs à invoquer des circulations de fluides régionales. Ces études, qui fournissent des estimations de paléotempératures et de paléosalinités, apportent des contraintes à la modélisation, mais en retour la modélisation peut apporter un calage dans le temps de ces événements et une estimation des processus pertinents. La reconstitution des transports de chaleur et de sel proposée dans cet article permet ainsi de cerner l’influence de l’hydrodynamique sur ces processus. L’histoire thermique et saline du bassin est présentée à différentes étapes sur une coupe NW-SE représentative d’une ligne d’écoulement actuelle également valable au cours du Tertiaire. On montre l’importance de la paléotopographie pour expliquer les fortes salinités dans les réservoirs et le rôle de la faille de Bray pour l’évolution de la salinité dans le Dogger. Le basculement et l’érosion de la base tertiaire crée un écoulement gravitaire qui se substitue au régime d’écoulement en compaction, permettant ainsi la migration de saumures depuis la formation salifère à l’est du bassin vers les réservoirs du Keuper à l’ouest. La recharge des aquifères aux affleurements et la mise en charge des systèmes permet une migration ascendante des eaux salées depuis le Keuper vers le Dogger en considérant une perméabilité plus importante au niveau de la faille de Bray. Bien que dominé par la composante conductive, le transport de chaleur est également influencé par l’hydrodynamique avec un effet de refroidissement convectif possible lors de la mise en charge des aquifères à la fin de l’érosion tertiaire, pouvant expliquer une partie de l’excès de température déduit des inclusions fluides du Keuper entre l’état thermique à la fin du dépôt de la craie et l’actuel. D’après nos simulations, la base du Tertiaire est la période la plus compatible avec les observations diagénétiques, pour des raisons thermiques (maximum d’enfouissement et effet de refroidissement convectif) et chimique (topographie favorable aux migrations de saumures dans le Keuper et le Dogger)

A compilation of global bio-optical in situ data for ocean colour satellite applications – version three

A global in situ data set for validation of ocean colour products from the ESA Ocean Colour Climate Change Initiative (OC-CCI) is presented. This version of the compilation, starting in 1997, now extends to 2021, which is important for the validation of the most recent satellite optical sensors such as Sentinel 3B OLCI and NOAA-20 VIIRS. The data set comprises in situ observations of the following variables: spectral remote-sensing reflectance, concentration of chlorophyll-a, spectral inherent optical properties, spectral diffuse attenuation coefficient, and total suspended matter. Data were obtained from multi-project archives acquired via open internet services or from individual projects acquired directly from data providers. Methodologies were implemented for homogenization, quality control, and merging of all data. Minimal changes were made on the original data, other than conversion to a standard format, elimination of some points, after quality control and averaging of observations that were close in time and space. The result is a merged table available in text format. Overall, the size of the data set grew with 148 432 rows, with each row representing a unique station in space and time (cf. 136 250 rows in previous version; Valente et al., 2019). Observations of remote-sensing reflectance increased to 68 641 (cf. 59 781 in previous version; Valente et al., 2019). There was also a near tenfold increase in chlorophyll data since 2016. Metadata of each in situ measurement (original source, cruise or experiment, principal investigator) are included in the final table. By making the metadata available, provenance is better documented and it is also possible to analyse each set of data separately. The compiled data are available at https://doi.org/10.1594/PANGAEA.941318 (Valente et al., 2022)

The topography of North Namibian Margin during the Meso-Cenozoic

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The North Namibian margin during the Meso-Cenozoic : deformation and topography

Poste