Academic literature on the topic 'Messinian salt'

ABSTRACT A multi-client 2-D seismic survey, consisting of 6,770 line-kilometer of 2-D data, was acquired by Norway’s PGS Geophysical offshore Cyprus in 2006. It was followed in 2006 and 2007 by the acquisition of two 3-D surveys, located offshore Lebanon (1,500 square kilometers), and offshore Lebanon and Cyprus (1,300 square kilometers). Further, in 2008 an additional 2-D survey was acquired offshore Cyprus to fill in the existing 2006 seismic 2-D grid. The 2008 2-D survey consist of 6,500 line-kilometer and was acquired with the PGS dual sensor GeoStreamer® technology (The 2008 2D data is still being processed so no GeoStreamer® examples are shown in this article). Since 2007, some of the deep-water areas (1,500–2,000 meters deep) offshore Cyprus have been offered for exploration and producing bid licenses by the government, while the Lebanese government is in the stage of preparing its offshore region for exploration and licensing. In this paper, several representative seismic lines are shown to illustrate the quality of the seismic data over this large region. The data shows that a Pliocene to Recent succession overlies a thick Upper Miocene evaporite section, known as the Messinian Salt. The blanketing salt-dominated interval is up to one kilometer thick and provides a regional seal over the area; although some faults are known to penetrate the salt and may allow seepage to occur. The pre-Messinian Salt section is highly structured, with both horsts-and-grabens as well as large folds. In particular, several examples of seismic reflections are presented, which are interpreted as possible Direct Hydrocarbon Indicators (DHI). Some four-way structural closures are highly prospective as they are characterized by multiple DHIs; for example, a bright spot at the base of the Messinian Salt overlying a flat spot. Other examples consist of phase changes, dim spots, velocity pull-downs, low-frequency shadow zones and gas chimneys. Also shown are how some of these interpreted DHIs can be characterized in the 3-D surveys. The 3-D example illustrate a correlation between pre-Messinian four-way structural closure and the root-mean square amplitude of the base Messinian Salt reflection.

We use 3D seismic reflection data from the Levant margin, offshore Lebanon to investigate the structural evolution of the Messinian evaporite sequence, and how intra-salt structure and strain varies within a thick salt sheet during early-stage salt tectonics. Intra-Messinian reflectivity reveals lithological heterogeneity within the otherwise halite-dominated sequence. This leads to rheological heterogeneity, with the different mechanical properties of the various units controlling strain accommodation within the deforming salt sheet. We assess the distribution and orientation of structures, and show how intra-salt strain varies both laterally and vertically along the margin. We argue that units appearing weakly strained in seismic data may in fact accommodate considerable subseismic or cryptic strain. We also discuss how the intra-salt stress state varies through time and space in response to the gravitational forces driving deformation. We conclude that efficient drilling through thick, heterogeneous salt requires a holistic understanding of the mechanical and kinematic development of the salt and its overburden. This will also enable us to build better velocity models that account for intra-salt lithological and structural complexity in order to accurately image sub-salt geological structures.

The definition of pre-Messinian source rocks in the eastern Mediterranean is of paramount importance for hydrocarbon exploration because of the ability of salt to act as a high-quality seal rock. This research evaluates the organic geochemical features of the Upper Miocene (Tortonian—Messinian) sedimentary succession onshore Crete Island, Greece. The study employs original (Messinian, Agios Myron Fm) and published (Tortonian, Viannos Fm, Skinias Fm, Moulia Fm, and Messinian Ploutis section) results from organic geochemical analyses of mudstone samples. One hundred and one samples were examined using standard organic geochemistry methodology (Rock-Eval II and VI-TOC) to define the origin, type, and degree of organic matter maturity. The data indicate that the studied samples have poor to fair gas-prone source rock potential. These possible source rock units have not experienced great temperatures during burial, and, thus, their organic matter is thermally immature. The sub-salt (Tortonian—Messinian) source rock units are likely to be of higher thermal maturity in the western and eastern south Cretan trenches because of tectonic subsidence and a thicker sedimentary overburden. Several traps can grow in these regions, associated with normal faults, rotated blocks and unconformities (both below and above the unconformities). This research provides a basis for the further evaluation of the hydrocarbon potential in Crete Island. It is an area that shares geological similarities with the surrounding regions that contain proven reserves and is of crucial economic and strategic importance.

This study investigates the interplay of evolving tectonic and submarine sedimentation processes in the northwest Aegean Sea using marine multichannel seismic profiles. We identify an extensive basin developing in the Thermaikos Gulf inner shelf, outer shelf, and slope leading to the 1500 m deep West North Aegean Trough (NAT). We establish the unconformable extent of Eocene and Oligocene sequences on the upper shelf and trace their continuation in the deeper shelf and slope of Thermaikos Gulf. The start of the Miocene and Middle Miocene developed below the well-established Messinian bounding reflectors that are mostly erosional. Important lateral variations are observed within the Messinian sequence, which is up to 0.8 s thick. Messinian prograding clinoforms are identified on the Thermaikos Gulf shelf and southeast of Chalkidiki, and a zone of irregular reflectors is attributed to the Messinian salt layer. The transpressional deformation of the Messinian in the southwestern margin constrains the timing of westward progradation of the North Anatolian Fault during Messinian. The Pliocene-Quaternary sediments are 0.6–1.8 s thick, showing the overwhelming effect of tectonics on sedimentation plus the northwards Quaternary activation at the Thermaikos apron.

ABSTRACT The deepwater area of the Nile Delta is within the eastern Mediterranean basin on the Nile Delta Cone between the Herodotus abyssal plain to the west and the Levant basin to the east. The complex evolution and interaction of the African, Eurasian and Arabian plates have shaped the Late Miocene to Recent Nile Cone and its substratum. The tectono-stratigraphic framework is controlled by deep-seated basement structures with distinct gravity and magnetic expressions, and by the interaction of the NW-trending Misfaq-Bardawil (Temsah) and NE-trending Qattara-Eratosthenes (Rosetta) fault zones. In addition, significant salt-induced deformation of a Messinian evaporitic sequence up to 4,000 m thick has occurred, together with large-scale rotational block movement. The deformational pattern is largely the result of multiphase tectonic movements along pre-existing basement faults on the continental margin of the Neo-Tethys ocean. The Nile Cone consists of late Paleogene to Late Miocene sediments that pre-date the Messinian evaporites, and Pliocene-Pleistocene sequences. In the east, the pre-salt deposits (as much as 3,000 m thick) are primarily deepwater sediments with local condensed sequences over syndepositional intrabasinal highs. Shale occurs westward across the Rosetta trend. The Messinian evaporitic sequence exhibits three distinct seismic facies suggesting cyclic deposition with the occurrence of interbedded anhydrite, salt and clastic sequences and pure halite deposition. During the Messinian salinity crisis, large-scale canyons were excavated that resulted in multiphase cut-and-fill clastic systems. The Pliocene-Pleistocene sequences were deposited in a slope to basin-floor setting. Exploration targets are the Pliocene-Pleistocene deepwater channel and basin-floor turbidite sands in a variety of structural settings. Water depths range from 800 to 2,800 m. The Upper Miocene sequence offers additional exploration objectives in the form of fluvial and/or turbidite sands. The focus of pre-salt exploration is the delineation of distal turbidities within the Serravallian to Tortonian sequence and the identification of new reservoir sequences deposited on pre-existing intrabasinal highs. Hydrocarbon charge has yet to be proven by drilling, but seismic amplitude anomalies and the occurrence of natural surface slicks suggest both gas and liquid charges from pre-salt source rocks through faults and salt-withdrawal windows.

Abstract Three-dimensional seismic imaging and well calibration reveal a large allochthonous mud edifice that is composed of several mud extrusions and covers an area >740 km2 on the outer shelf slope of the Nile Delta. The allochthonous material was sourced from beneath the ∼1-km-thick Messinian evaporites in the Eastern Mediterranean and extruded synchronously as eight large mud volcanoes directly on top of the Messinian evaporites in a catastrophic remobilization event at the end of the Messinian salinity crisis. These large extrusive flows coalesced to form a single edifice with an exceptional volume of ∼292 km3 that is connected to eight widely spaced conduits. We argue that this large mud body represents a new morphological type and scale of mud extrusion. We propose that mud extrusions that coalesce on a surface forming a multi-conduit-fed edifice be referred to as mud canopies, by analogy with salt canopies, with implications for basin reconstruction, paleo–overpressure release events, and fluid migration.

Based on the geodynamic context, two hypotheses of origin of salt in the subsurface of the Sahel area are worth being defended. The first suggests that the halokinesis activities, namely, of the Triassic evaporitic sedimentation, may still be until now influencing the functioning of the saline systems in the Sahel. The second integrates the Sahel area geodynamic evolution in the framework of the convergence between African and Eurasian plates. It suggests a link between the blockage of the subduction between African and Eurasian plates in North Tunisia, the Messinian Salinity Crisis, and eventually the concrete opening and evolution of the playa during the Quaternary. Such a suggestion is materialized by a geodynamic model relating successively these events. This scenario suggests that the Messinian Salinity Crisis constituted huge quantities of salt and/or salty water. This saline subsurface reserve is until now influencing the Sahel behavior as a whole. Through groundwater convergence, huge quantities of salt are accumulated within depressions of the Sahel area. Currently, the convergence of the plate between African and Eurasian plates results in a tectonic activity within these saline systems materialized by the formation of fault spring mounds along preferential orientation ensuring the surface-subsurface connectivity.

Entre 5.97 et 5.33Ma, à la fin du Miocène, un événement géologique exceptionnel aux conséquences majeures a affecté le bassin méditerranéen : la Crise de Salinité Messinienne (CSM). Cet épisode, dont le scénario exact reste encore énigmatique, est responsable du dépôt d’un volume considérable d’évaporites connu sous le nom de Géant Salifère de Méditerranée (GSM). Aujourd'hui, plus de 90 % des dépôts évaporitiques du MSG sont situés dans les bassins profonds de la Méditerranée et sont enfouis sous une épaisse couche de sédiments Plio- Quaternaire. Ces évaporites ont donc été étudiées principalement par imagerie sismique. Dans ce mémoire, nous nous intéressons aux dépôts de la crise enregistrés sur Promontoire des Baléares (BP), un haut topographique situé dans bassin de la Méditerranée occidentale. Du fait qu’il contient une succession de bassins en position intermédiaire stratégique, étagés entre les bassins marginaux du pourtour Méditerranéen et les bassins profonds, le BP se révèle un lieu unique avec des dépôts évaporitiques variés, ubiquistes et peu déformés tectoniquement, permettant d’accéder à une vision complète de l’enregistrement de la crise et pouvant mener à un scénario global cohérent.Cette thèse de doctorat a été réalisée dans le cadre d’un projet transdisciplinaire : « European Training Network (ETN) SaltGiant », dont l'objectif est de comprendre le GSM. Une approche pluridisciplinaire a été appliquée sur la zone d’étude choisie pour apporter des contraintes afin de répondre à certaines des nombreuses questions encore sans réponses sur la crise de salinité messinienne. Le travail de base a consisté en l'interprétation d'un large ensemble de données de sismique réflexion en Méditerranée occidentale, particulièrement concentré sur les dépôts messiniens du BP. Ceci a permis de préciser la cartographie des unités messiniennes de cette région et de définir leurs inter-relations géométriques. Une comparaison détaillée de ces unités évaporitiques avec celles du bassin messinien sicilien de Caltanissetta a été menée afin de reconstituer l'histoire de leur dépôt pour la confronter au modèle chrono-stratigraphique « consensuel » à trois phases. Pour reconstituer la paléo-bathymétrie de la dépression centrale de Majorque (CMD), le bassin le moins déformé situé dans sa partie centrale du BP, une interprétation structurale a permis d’identifier les principaux mouvements tectoniques post-MSC, modérés et localisés dans des corridors de décrochement. L'analyse par backstripping 2D et pseudo-3D, en collaboration avec d’autres collègues du projet SaltGiant, a alors permis de restaurer la paléo-bathymétrie de la CMD. Enfin, ces résultats ont été utilisés comme contraintes bathyétriques et de volumes pour modéliser le dépôt des évaporites observées, par des modèles physiques basés sur la théorie du contrôle hydraulique des détroits. Les résultats montrent que les unités messiniennes de la CMD pourraient constituer un analogue non déformé de celles qui affleurent à terre dans le bassin sicilien de Caltanissetta. Ils démontrent aussi qu'une baisse générale du niveau marin de grande amplitude (>850m) est nécessaire pour précipiter le volume de halite observé dans la CMD. Ces résultats, très bien contraints par ces études précises, remettent en cause certaines idées parfois encore largement acceptées. Ces doutes concernent en particulier l'apparition synchrone du sel à l'échelle du bassin méditerranéen, la profondeur maximale de dépôt du gypse inférieur primaire (PLG) et le moment de la formation du gypse inférieur resédimenté (RLG). En conclusion, ce mémoire montre la nécessité de réviser le scénario consensus actuel de la CSM, et l’importance de réaliser des forages en mer dans la région clef du BP, ce qui permettrait de révéler de nombreux mystères encore enfouis sous le géant salifère de Méditerranée
The Messinian Salinity Crisis (MSC; 5.97– 5.33 Ma) is one of the most controversial geological events that influenced the evolution of the Mediterranean Basin in the late Miocene, leaving behind an immense volume of evaporites known as the Mediterranean Salt Giant (MSG). Today, more than 90% of the MSG evaporitic deposits are located offshore, buried below thick sediments that are Pliocene to Quaternary in age, and have thus been studied mainly by marine seismic reflection imaging. The Balearic Promontory (BP), a prominent topographic high in the Western Mediterranean basin, contains a unique and tectonically poorly deformed MSC record that resembles the evaporitic record of other peri-Mediterranean marginal and intermediate basins.This PhD thesis was performed in the framework of the SaltGiant European Training Network (ETN), a cross-disciplinary project whose objective is to understand the formation of the MSG. The work of the thesis is focused on the MSC deposits of the BP. Multi-disciplinary approach was applied to answer some of the still open questions concerning the MSC event. As a first step, seismic interpretation of a wide seismic reflection dataset in the Western Mediterranean in general and in the BP in particular was performed, with the aim of refining the mapping of the Messinian units covering the area. To restitute the depositional history of the MSC evaporites of the BP, a detailed comparison with the Messinian evaporitic units of the Sicilian Caltanissetta Basin was carried out, in which a discussion on how this history matches the existing 3-stages chrono-stratigraphic ‘consensus model’ is illustrated. The next step consisted in the restoration of the paleo-bathymetry of the BP at the beginning of the MSC, focusing on the relatively less-deformed basin located in the central part of the BP and called the Central Mallorca Depression (CMD). To achieve this restoration, structural interpretation in the CMD area was done where the main post-MSC tectonic-related vertical movements that altered the MSC paleo-bathymetry were identified. Then 2D and pseudo-3D backstripping analysis were applied in collaboration with other colleagues from the SaltGiant project, to restore the paleo-bathymetry. In the final step, the paleo-bathymetry was used to model the deposition of the MSC evaporite volumes observed in the CMD using physics-based models built on strait hydraulic-control theory. The results show that the MSC units of the CMD could constitute an undeformed analog of those outcropping on-land in the Sicilian Caltanissetta Basin. Moderate post-MSC deformation acted along MSC strike-slip corridors in the CMD following the MSC evaporites deposition, thus altering only locally the paleo-bathymetry. A high amplitude drawdown (>850m) is required during the halite stage of the MSC. The results rise a series of doubts about the current consensus model, still widely accepted. Doubts concern the synchronous onset of salt at the basin scale, the maximum depth of deposition of the Primary Lower Gypsum (PLG) and the timing of formation of the Resedimented Lower Gypsum (RLG). All the results and discussions hint to the need of revision of the current MSC consensus model, as well as the importance of initiating drillings offshore over the BP area, which would help revealing many of the mysteries still buried with the MSG

During the Middle Miocene through the Pliocene the Appalachian Mountains underwent continued erosion and approached modern elevations. The Rocky Mountains had undergone uplift to half or more of their present elevation during the Late Cretaceous to Middle Eocene Laramide Revolution; after a lull during the Middle Eocene through the Early Miocene, there was increased tectonic activity beginning ~12 Ma and especially between 7 and 4 Ma. Locally some highlands may have approached or attained modern elevations. The increasingly high mountains and plateaus of Asia and North America deflected the major air streams southward, bringing colder polar air into the middle latitudes of North America. An extensive Antarctic ice sheet further cooled ocean waters and contributed to the spread of seasonally dry climates. The elimination of most of the Asian exotics from the North American flora dates to the Late Miocene-Pliocene as a result of a decline in summer rainfall. The Sierra Nevada attained about two-thirds of their present elevation within the past 10 Ma. They were appreciably elevated at ~5 Ma, stood at ~2100 m at 3 Ma, and have risen ~950 m since 3 Ma (Huber, 1981). The California Coast Ranges and Cascade Mountains attained significant heights by 3 Ma, and there was a rapid rise of the Alaska Range at ~6 Ma. Temperatures increased between ~18 and 16 Ma. In the absence of major plate reorganization and intense volcanic activity and with increased erosion from continued replacement of the dense evergreen forest by deciduous forest and shrubland (increasing albedo), atmospheric CO2 concentration decreased and a sharp lowering of temperature occurred in the Middle Miocene between 15 and 10 Ma. Eolian dust deposits increased in the Late Cenozoic, suggesting greater aridity (Rea et al., 1985). This is supported by kaolinite records from North Atlantic deep sea sediments (Chamley, 1979). At ~4.8~4.9 Ma global cooling and a marine regression of ~40~50 m combined to isolate the Mediterranean Basin from the ocean and to concentrate large volumes of salt as water evaporated. The biota was destroyed, giving rise to the term Messinian salinity crisis.

Abstract The offshore eastern Mediterranean region has received increased international interest in the last decade for its hydrocarbon potential in the pre-salt traps. The presence of a heterogeneous Messinian-age salt layer and complex pre-Messinian structures pose very difficult challenges in seismic imaging. In this paper, we provide a detailed workflow for seismic data preconditioning and imaging which resolves the subsurface challenges of the Mediterranean. Broadband acquisition was used to collect seismic data, which combines the responses of dual-sensor receivers to remove the effect of the receiver ghost. Adaptive source de-ghosting was then applied to address the source-side ghost. Data was processed using robust multiple attenuation and converted wave attenuation (CWA). A high-resolution velocity model building and imaging workflow was designed as follows: Diving waves full-waveform inversion (FWI) to capture detailed velocity for the complex overburden, followed by post-salt reflection tomography. Born modeling-based reflection FWI to update the velocity heterogeneities inside the salt body followed by reflection tomography for the deep section. Reverse time migration (RTM) to handle the waveform multi-pathing. De-ghosting corrected the wavelet phase and expanded the usable frequency bandwidth, resulting in a broadband dataset for imaging. Robust multiple attenuation and converted wave attenuation (CWA) techniques aided in revealing the true geological dips beneath the salt and facilitated picking accurate residual move-outs during the velocity model building. RTM in conjunction with the high-resolution velocity model significantly improved imaging of complex salt structures and pre-salt reservoirs. At well locations, our workflow resulted in a very good match between the available well data and surface seismic in terms of markers depths and velocity trends. This paper presents a novel approach for modelling the velocity heterogeneities inside the complex Messinian-age salt formation using the Born modeling-based reflection FWI. In addition, salt-related strong converted waves were successfully attenuated, whereas previously the presence of this energy misled interpreters and caused anomalous velocity updates in similar geological settings in the Mediterranean.