During the final glaciation and following melting across the Carboniferous/Permian boundary, southern Gondwana experienced an icehouse to greenhouse transition at a relatively high palaeolatitude (ca. 60 degrees). Sediments deposited from around 300 to 280 Ma in the southern Karoo Basin are archives of this transition, but the evolution of their links to the flanking oceans is still a matter of debate. The aim here is to detail the deglaciation history by simulating early diagenetic processes both under melt and marine water conditions. For this, black shale core samples from three wells, which were drilled in the 1960s through the Lower Ecca Group into the Dwyka Group, were analysed for TOC contents, mineralogical composition and textural properties. The data allow extrapolations about the depositional mineralogy and early diagenesis that in turn serve as input parameters for hydrogeochemical models. The imaging and modelling results reveal that the organic carbon-lean shales associated with, and directly overlying the diamictite beds of the Dwyka Group (known as the Prince Albert Formation) can be interpreted as rhythmites (varves?) deposited under freshwater conditions in response to the deglaciation across southern Gondwana during the latest Carboniferous (similar to 300 to 280 Ma). Thereafter, in the early Permian (similar to 280 Ma) the first notable marine influence is revealed by the occurrence of Mg-bearing carbonate precipitates in black shales of the Whitehill Formation of the overlying Lower Ecca Group; and from the hydrogeochemical models. Preferential preservation of organic matter in these shales is interpreted to be due to marine water fluctuations from the south that created stratified water columns of dense anoxic cold bottom systems overlain by lighter freshwater. Directly above the Whitehill Formation, Mn-siderite in rhythmites of the Collingham Formation points to a recurring influx of fresh water from the north. Today, the black shales of the Lower Ecca Group are tight, and thermogenic gas accumulated in inter-particle pores, in intra-particle pores in albite, organic matter and dolomite, or adsorbed on organic matter in the Whitehill Formation. The brittleness of this prospective Whitehill Formation is weakened in places by high contents of chlorite and illite, but to a lesser degree elsewhere due to low contents of carbonate and quartz cements.

Summary The talk will present results about organic-inorganic interactions leading to porosity formation due to migration of source-rock-derived corrosive fluids through carbonate reservoirs. Two aspects will be covered: (i) detectable processes at the nanometer scale by imaging techniques, and (ii) generic hydrogeochemical modelling results of porosity creation at a play scale (from source rock to reservoir).

The Karoo Basin of South Africa was explored for conventional oil and gas in the 1960s, and during which 19 boreholes were drilled by SOEKOR-the Southern Oil Exploration Corporation. Ten of these boreholes in the southern part of the basin were deep, c. 2.3 to 5.5 km in depth. Geochemical, petrophysical and petrographic studies on the recovered cores from these drill holes concluded that the lower Karoo sequences were possibly prospective for thermogenic gas across the Karoo region immediately north of the Cape Mountains and south of the main concentration of dolerite intrusions flanking the Karoo Escarpment. Since then, very limited analytical work has been undertaken on these cores to gain new data and to extend the concepts towards potential shale gas plays. In the light of the recent interest in unconventional shale gas potential of the Karoo Basin, we re-examine this SOEKOR data and, together with new petrographic and geochemical analyses on 115 core samples from eight of the deep drill holes, we present new resource estimates of two possible reservoirs with recoverable shale gas of 10 to 50 Tcf (Source Rock 1) and 65 to 400 Tcf (Source Rock 2), respectively.

Interactions between the microbiota and distal gut are important for the maintenance of a healthy intestinal barrier; dysbiosis of intestinal microbial communities has emerged as a likely contributor to diseases that arise at the level of the mucosa. Intraepithelial lymphocytes (IELs) are positioned within the epithelial barrier, and in the small intestine they function to maintain epithelial homeostasis. We hypothesized that colon IELs promote epithelial barrier function through the expression of cytokines in response to interactions with commensal bacteria. Profiling of bacterial 16S ribosomal RNA revealed that candidate bacteria in the order Bacteroidales are sufficient to promote IEL presence in the colon that in turn produce interleukin-6 (IL-6) in a MyD88 (myeloid differentiation primary response 88)-dependent manner. IEL-derived IL-6 is functionally important in the maintenance of the epithelial barrier as IL-6−/− mice were noted to have increased paracellular permeability, decreased claudin-1 expression, and a thinner mucus gel layer, all of which were reversed by transfer of IL-6+/+ IELs, leading to protection of mice in response to Citrobacter rodentium infection. Therefore, we conclude that microbiota provide a homeostatic role for epithelial barrier function through regulation of IEL-derived IL-6.

Stylolites and the interfaces to the host limestone have been investigated by means of a multidisciplinary analytical approach (thin section microscopy, FIB-TEM, organic geochemistry and petrography). Carbonate dissolution assuming different boundary conditions was simulated by applying a generic hydrogeochemical modelling approach. It is the conceptual approach to characterize and quantify traceable organic-inorganic interactions in stylolites dependent on organic matter type and its thermal maturity, and to follow stylolite formation in carbonates as result of organic matter reactivity rather than pressure solution as a main control. The investigated stylolite samples are of Upper Permian (Lopingian, Zechstein), Middle Triassic (Muschelkalk) and Late Cretaceous (Maastrichtian) age and always contain marine organic matter. The thermal maturity of the organic matter ranges from the pre-oil generation zone (0.4-0.5% R-r) to the stage of dry gas generation (>1.3% R-r). The results of the generic hydrogeochemical modelling indicate a sharp increase of calcite dissolution and the beginning of stylolite formation at approximately 40 degrees C, which is equivalent to a depth of less than 800 m under hydrostatic conditions considering a geothermal gradient of 30 degrees C and a surface mean temperature of 20 degrees C. This temperature corresponds to the pre-oil window when kerogens release an aqueous fluid enriched in carbon dioxide and organic acids. This aqueous fluid may change the existing pore water pH or alkalinity and causes dissolution of carbonate, feldspar and quartz, and clay mineral precipitation along the stylolite. Dissolution of limestone and dolostone leads to reprecipitation of calcite or dolomite opposite of the dissolution side, which indicates only localized mass redistribution. All these integrated hydrogeochemical processes are coupled to the generation of water during organic matter maturation. In all of the calculated hydrogeochemical scenarios, H2O is a reaction product and its formation supports the suggested hypothesis.

Summary Isolated micro-environments may develop in shale or at interfaces to other lithologies. The isolation from the bulk matrix creates an environment in which specific hydrogeochemical conditions may develop due to organic-inorganic interactions. It is the conversion of labile organic matter during early diagenesis or during the early oil window in small natural reactors with or without the buffer potential of the bulk rock which leads to processes different from those at a bulk scale. During both early diagenesis and early oil window acidic and corrosive hydrogeochemical conditions develop due to the release of low molecular weight organic acids (e.g., acetic acid) or carbon dioxide, and lead to dissolution of labile minerals, but also to precipitation of solid solutions at equilibrium. In the talk two selected topics will be presented in form of a slide show with pictures presenting features on a nanometre scale. First, early diagenetic micro-environments for the formation of nano-sized titania polymorphs will be visualized. Second, the formation of stylolitic micro-environments at the interfaces to carbonates will be introduced which is controlled by the organic matter content and its conversion. The talk shall introduce micro-environments in shale, and their significance for geochemical processes apart from the bulk scale.

We report on geochemical and petrophysical properties of shales from the Prince Albert, Whitehill and Collingham Formations of the Lower Karoo Supergroup, near Jansenville in the Eastern Cape, close to the tectonic front of the Cape Fold Belt. Results are based on two boreholes sited on a southerly dipping limb of a shallowly plunging syncline. Structural, sedimentological, lithological, mineralogical, geochemical and petrophysical analyses provide detailed characteristics that have become the focus of interest for potential shale gas occurrences.The black shales of the Whitehill Formation are composed of quartz, illite, muscovite and chlorite, with lesser plagioclase and accessary pyrite. The Collingham Formation rocks have the largest proportion of quartz, which gives this formation a higher brittleness factor than that of the Prince Albert and Whitehill formations. Mercury porosimetry analyses yield average meso- and macroporosity values of 0.83% for black shales of the Whitehill Formation, confirming that these sediments are tightly packed. Layers of dolomite within the shales have porosities of 2.9%, and pores measuring 1.5 mu m wide.The black shales of the Whitehill Formation have an average total organic carbon (TOC) content of 4.5 weight % whereas the TOC content of shales in the Collingham and Prince Albert Formations is <1 weight %. The elemental composition and relatively higher delta C-13 and delta N-15 stable isotope values suggest that the Whitehill Formation was deposited under anoxic conditions, which led to the preservation of the mixed marine and terrestrial organic matter, whereas the Prince Albert and the Collingham Formations were deposited under oxidizing conditions.High maximum temperature values (Tmax average: 528 degrees C), low overall hydrogen and oxygen index values (all from Rock Eval analyses) and high reflectance measurements on bitumen (BRo= 4%) characterise these sedimentary rocks as over mature. As a consequence, they display few hydrocarbon yields in pyrolysis and thermovaporization experiments, and offer a minor late-gas potential.The main characteristics of black shales in the study area indicate that their overmaturity with respect to hosting gas deposits is attributed to the tectono-metamorphic overprinting during the Cape Orogeny (ca. 250 Ma, Halbich, 1993; Hansma et al., 2013).Rocks of the lower Karoo Supergroup outcropping within the area flanking the northern tectonic margin of the Cape Fold Belt therefore have limited potential for hosting shale gas deposits. This finding has implications for estimates of potential shale gas resources of the Karoo Basin.

Summary Acid gas generation by thermochemical sulfate reduction (TSR) evolves within a complex web of petroleum-water-rock-gas interactions in reservoirs under high temperature conditions of more than ca. 100°C. The interactions lead to the formation of toxic and corrosive hydrogen sulfide (free H2S gas and dissolved H2S). Such interactions are caused by the instability of hydrocarbons in the presence of water and a reactive reservoir rock matrix containing water-soluble anhydrite. The mass conversions of the inorganic water-rock-gas interactions which are triggered by the redox degradation of hydrocarbons establish a certain, thermodynamically defined state of chemical equilibrium. Any approach to geochemically model “acid gas generation” and “H2S-risk distribution” in petroleum systems should be based on a conceptual model that adequately reproduces the intimately interconnected and interdependent nature of all isochronous hydrogeochemical reactions, whether they are kinetically controlled or establish equilibrium species distributions. Such approaches rely (1) on the thermodynamical calculation of chemical equilibrium species distribution, (2) on the coupling of kinetically controlled oil degradation and sulfate reduction by oil-derived reductants to the equilibrium calculations, and (3) on the calculation of diffusive mass transport through the free pore water network and the irreducible water film. The key to model TSR, “acid gas generation, and “H2S-risk distribution” is not to consider and model any single, isolated reaction like the kinetically controlled sulfate reduction which depends on the thermal history. The actual key to model TSR, the fate and behavior of sulfidic sulfur, and a realistic “H2S-risk distribution” in petroleum reservoirs is an overall reproduction of the hydrogeochemical reactive transport processes which temporally and spatially evolve in a complex network of oil/petroleum-water-rock-gas interactions under reservoir conditions. Consequently, we perform 3D hydrogeochemical, multi-component and multi-species reactive mass transport modeling for a semi-generic case study by using the PHAST computer code (provided by the U.S. Geological Survey) and take the following boundary conditions into account: gas reservoir; carbonate (dolomite plus calcite) reservoir rocks; anhydrite seal; 140°C; 600 bar total pressure; kinetic rate constant for sulfate reduction by CH4 = 1.08 × 10–16 mol s-1 l-1 mass transport is restricted to diffusion; modeled time span is 10 Ma

Whereas gas production from unconventional reserves has greatly increased over the past decades, there is still a largely unexplored potential in the Paleozoic of Central Europe. For this area, the paper summarizes some important aspects of the geology of tight sandstone gas reservoirs, gas shales and coalbed methane. Tight sandstones with low permeabilities are especially present in the Permian (Rotliegend Formation) of The Netherlands and northern Germany, but also in the underlying Carboniferous. There is already active production from some of these reservoirs. Further development greatly depends on understanding of gas charge as well as the regional distribution of porosity and permeability which in turn depend on facies and diagenesis. In contrast exploration for gas shales is just at the very beginning. Whereas Mesozoic shales in the southern Lower Saxony Basin have to be regarded as prime targets due to thickness, maturity and organic matter content, there are additional targets in the Mississippian, but also in older rocks. Currently an international gas shale research programme (Gas shales in Europe, GASH) gathers relevant data for these units. Coalbed methane exploration started already about 20 years ago in the Ruhr Basin, but was not successful at that time due to small flow rates. On the other hand, production from abandoned coal mines provided substantial amounts of gas. Due to the abundance of coal seams and the suitable maturity conditions and gas contents, there is a high potential for future substantial coalbed methane in the area. Alors que l’extraction du gaz naturel des gisements non conventionnels a fortement augmenté ces dernières dizaines d’années, un large potentiel de ressources reste inexploré dans les couches paléozoïques de l’Europe Centrale. Cet article présente, pour cette région, quelques aspects importants de la géologie des grès de faible perméabilité (tight gas sands), des gaz de schiste (gas shales) et du gaz de houille (coalbed methane, CBM). Les grès de faible perméabilité se trouvent surtout parmi les couches permiennes (Rotliegend) aux Pays-Bas et dans le nord de l’Allemagne, mais aussi dans les couches du Carbonifère supérieur. La production est déjà active dans quelques-uns de ces réservoirs. Pour l’avenir, le développement dépendra principalement de l’amélioration de la compréhension du gaz en place et de la distribution régionale de la porosité et la perméabilité qui, d’ailleurs, dépendent du faciès lithologique et la diagénèse. La recherche de gaz dans les roches argileuses, par contre, vient juste de commencer. Les roches argileuses mésozoïques dans le sud du bassin de Basse-Saxe (Lower Saxony Basin) sont des objets d’exploration prioritaire à cause de leur épaisseur, de leur maturité et de leur teneur en matière organique. Mais il existe d’autres séries intéressantes dans le carbonifère inférieur et des couches plus anciennes. Actuellement, un projet de recherche international vise à acquérir des données géologiques sur ces systèmes. La recherche du gaz de houille (CBM) a commencé dans la bassin de la Ruhr il y a une vingtaine d’années, mais avec un succès très limité à cause de faibles débits de gaz. En revanche, le captage de grisou des mines de charbon abandonnées a fourni de considérables quantités de gaz. De par la multitude des filons houillers et des conditions de maturité et de teneurs en gaz favorables, il existe dans cette région un potentiel considérable de gaz de houille.

Unconventional Gas Resources in the Paleozoic of Central Europe - Whereas gas production from unconventional reserves has greatly increased over the past decades, there is still a largely unexplored potential in the Paleozoic of Central Europe. For this area, the paper summarizes some important aspects of the geology of tight sandstone gas reservoirs, gas shales and coalbed methane. Tight sandstones with low permeabilities are especially present in the Permian (Rotliegend Formation) of The Netherlands and northern Germany, but also in the underlying Carboniferous. There is already active production from some of these reservoirs. Further development greatly depends on understanding of gas charge as well as the regional distribution of porosity and permeability which in turn depend on facies and diagenesis. In contrast exploration for gas shales is just at the very beginning. Whereas Mesozoic shales in the southern Lower Saxony Basin have to be regarded as prime targets due to thickness, maturity and organic matter content, there are additional targets in the Mississippian, but also in older rocks. Currently an international gas shale research programme (Gas shales in Europe. GASH) gathers relevant data for these units. Coalbed methane exploration started already about 20 years ago in the Ruhr Basin, but was not successful at that time due to small flow rates. On the other hand, production from abandoned coal mines provided substantial amounts of gas. Due to the abundance of coal seams and the suitable maturity conditions and gas contents, there is a high potential for future substantial coalbed methane in the area.

The Shiranish Formation consists of mudstones and wackestones in the central Euphrates Graben which are rich in organic carbon. Here the Shiranish Formation is more than 700 m thick with a minor increase in organic maturity with depth. The Shiranish Formation sediments are characterized by a continuously increasing hydrogen index to the top whereas the oxygen index is markedly lower in the Upper Shiranish Formation (USF). The Lower Shiranish Formation (LSF) is characterized by lower hydrogen indices and higher oxygen indices relative to the USF. These organic geochemical characteristics enable a rough subdivision into a lower and an upper part of the Shiranish Formation. Furthermore, mineralogical results enable a subdivision of the USF into two parts (USF-1, lower part; USF-2, upper part) each with individual mineralogical signatures due to a modified depositional environment and differing diagenetic history. The LSF resembles mineralogically the USF-2. Ankerite, together with higher pyrite contents in the LSF and USF-2, reflect similar diagenetic pathways which were controlled by higher clay contents. During early diagenesis, a traceable conversion of metabolizable organic matter led to mineral assemblages due to significant methanogenesis. Intervals in the USF with total organic carbon (TOC) contents up to around 4% and hydrogen indexes up to 500 mg HC/g TOC indicate the presence of very good potential source rock intervals for oil generation. Additionally, intervals of the LSF also contain gas-prone organic material. Bulk kinetic investigations show a broad activation energy of the LSF and a narrow activation energy pattern for the USF for hydrocarbon generation. Furthermore, the predicted petroleum formation temperatures are 136 degrees C for the USF and 144 degrees C for the LSF, respectively. This corresponds to c. 630 m difference in burial depth for petroleum formation. These differences in activation energies and corresponding depth to reach oil window maturity are controlled by facies, and less by maturity.

The capture and geological storage of CO2 can be used to reduce anthropogenic greenhouse gas emissions. To assess the environmental impact of potential CO2 leakage from deep storage reservoirs on the abundance and functional diversity of microorganisms in near-surface terrestrial environments, a natural CO2 vent (>90% CO2 in the soil gas) was studied as an analogue. The microbial communities were investigated using lipid biomarkers combined with compound-specific stable carbon isotope analyses, the determination of microbial activities, and the use of quantitative polymerase chain reactions (Q-PCR). With this complementary set of methods, significant differences between the CO2-rich vent and a reference site with a normal CO2 concentration were detected. The δ13C values of the plant and microbial lipids within the CO2 vent demonstrate that substantial amounts of geothermal CO2 were incorporated into the microbial, plant, and soil carbon pools. Moreover, the numbers of Archaea and Bacteria were highest at the reference site and substantially lower at the CO2 vent. Lipid biomarker analyses, Q-PCR, and the determination of microbial activities showed the presence of CO2-utilising methanogenic Archaea, Geobacteraceae, and sulphate-reducing Bacteria (SRB) mainly at the CO2 vent, only minor quantities were found at the reference site. Stable carbon isotopic analyses revealed that the methanogenic Archaea and SRB utilised the vent-derived CO2 for assimilatory biosynthesis. Our results show a shift in the microbial community towards anaerobic and acidophilic microorganisms as a consequence of the long-term exposure of the soil environment to high CO2 concentrations.

Shale gas is produced from fine-grained siliciclastic sediments that are typically rich in organic carbon. Nearly all shales contain thermal gas generated in situ at mature to overmature levels of thermal alteration, although gas of biogenic origin is also produced from some shales. While shale gas production in the USA began in 1821, it is only in the last few years that it has become widely significant (currently about 8% of the domestic gas). In contrast, European shale gas exploration is still in its infancy. In general, European sedimentary basins offer the best potential for shale gas occurrence because thick, organic matter-rich sediments occur in nearly all Phanerozoic strata. Even so, there is little knowledge about the factors controlling shale gas generation and, more importantly, shale gas production in European basins. These factors are not necessarily the same as those that control commercial shale gas production in the USA. Palaeozoic sediments of Cambrian to Ordovician age are currently being tested for their shale gas potential and productivity in Sweden, as are those of Silurian age in Poland. Moreover, Lower and Upper Carboniferous sedimentary successions from England in the west to Poland in the east probably contain shale gas, but their depth, thickness and thermal maturity may be limiting factors for exploration in continental regions. Lower Carboniferous black shales in the Dniepr-Donets Basin of the Ukraine may also hold a significant potential. Moreover, organic-rich sediments of Oligocene/Miocene age in the Paratethyan Basin may offer shale gas potential, for example in the Pannonian Basin. At present, Upper Jurassic black shales are currently being tested for their shale gas potential in the Vienna Basin. European analogues of known biogenic shale gas systems may occur locally in organic-rich Lower Cretaceous sediments in the North German Basin with gas generation being related to Pleistocene glaciation/deglaciation cycles.

Different feldspar types control complex hydrogeochemical processes in hydrocarbon-bearing siliciclastic reservoirs, which have undergone different degrees of degradation. To test such processes generically, carbon dioxide equilibria and mass transfers induced by organic-inorganic interactions have been modelled for different hydrogeochemical scenarios. The approach is based on and compared with data from the Norwegian continental shelf (Smith & Ehrenberg 1989) and assumes local thermodynamic equilibrium among solids and fluids. Equilibrating mineral assemblages (different feldspar types, quartz, kaolinite, calcite) are based on the primary reservoir composition. Equilibration and coupled mass transfer were triggered by the addition and reaction of different amounts of CO2, CH4 and H-2 (plus acetic acid) at temperatures between 50 and 95 degrees C (323 and 368 K). These components occur in oil fields as products of anaerobic bacterial degradation, hydrolytic disproportionation of hydrocarbons and/or thermal maturation of kerogen. We apply two different computer codes and two different thermodynamic data bases to calculate the results. Reaction of 0.32-0.6 mol CO2, 0.16-0.3 mol CH4 and 0.8-1.5 mol H-2 with K-feldspar, quartz, kaolinite and calcite in 1 l of pore water results in modelled values of 0.3-2.3 mol% CO2 in a multicomponent gas phase that resembles measured data (0.2-1.5 mol%). Similar CO2 contents result from acetic acid addition (CO2, CH4, H-2 + 0.016 mol CH3COOH). Equilibration with albite or anorthite reduces the release of CO2 into the multicomponent gas phase dramatically, by 1 or 4 orders of magnitude compared with the equilibration with K-feldspar. Minor differences in the modelled CO2 content (0.1-0.2 mol%) result from calculations with different computer codes if the same thermodynamic data base is applied. Relevant differences (up to 1.9 mol% CO2) result from calculations using different thermodynamic data bases.

37 oil samples from 17 oil fields in the Austrian part of the Alpine Foreland Basin have been investigated with regard to biomarker composition. The differences in the composition of oil are generally minor reflecting a common lower Oligocene source rock (Schöneck Fm.) and homogenization during long-distance lateral migration. Nevertheless a regional subdivision into five oil groups is suggested by biomarker data. Variations in biomarker composition reflect a strong vertical facies zonation within the source rock (e.g. carbonate content) and different maturity of the source rock. Within the distinguished oil groups, the western one is most discrete. In comparison to the others it is characterized by relatively low maturity (0.7-0.8%Rr), low C28-/C29-steranes ratios, low Ts/Tm values, high hopane / moretane ratios and high sulphur contents. Probably, the oil is mainly derived from the middle part of the Schöneck Formation, which yields a sulphur rich oil during pyrolysis.

A classification of non-metallic and metallic deposits as well as energy resources has been performed for Central Europe. The Variscan metallogenesis in Central Europe outside the Alps with predominantly granitophile elements is denominated as an "ensialic metallogenesis", whereas the Alpine successor shows all the hallmarks of an "ensimatic metallogenesis". Part of the Variscan metallotect was re-activated during Alpine metallogenesis and incorporated into the Alpine metallotect. Classification schemes based on the age of formation, structure and sequence stratigraphic elements are discussed. Planar architectural elements in the various schemes such as unconformities, transgressive surfaces, flooding surfaces and sequence boundaries play a decisive role in siting ore traps and correlating mineral deposits.

Oligocene rocks are one of the most important sources of hydrocarbons within the Paratethyan realm. In the Alpine Foreland Basin (Central Paratethys) the main Oligocene source rock is the Schöneck Formation, but organic-rich rocks occur in the entire Lower Oligocene succession. Based on well-log calibration by core data, the spatial distribution and thickness variations of different Lower Oligocene source-rock facies are investigated. The deeper-water sediments are characterized by lateral continuity, but exhibit vertical variability. The latter reflects major palaeoceanographic changes in the Central Paratethys, such as the closure of seaways, basin-wide changes in salinity and in redox conditions. The upper shaly part of the Schöneck Formation has the highest source potential (>5% TOC, initial HI: 500–600 mgHC g −1 TOC) and reaches its maximum thickness ( c . 5 m) in a narrow belt parallel to the palaeo-shoreline. The present-day distribution of Lower Oligocene rocks is controlled by submarine erosion which affected the northern passive slope of the foreland basin. Erosion climaxed during the late Early Oligocene. The eroded material was re-deposited along the lower basin slope (Oberhofen facies). The source-rock potential of the re-deposited sediments is relatively low. The oil kitchen (4–7 km burial depth) is located beneath the Alpine nappes where the Lower Oligocene succession was removed locally by the advancing nappes. Both submarine erosion at the northern basin slope and tectonic erosion beneath the Alps have to be considered in the evaluation of the prospectivity of the basin. Because deposition of the Lower Oligocene succession in the Alpine Foreland Basin is controlled by basin-wide processes, it may serve as a model for source- rock deposition in foreland basins of the Paratethyan realm (e.g. Carpathians, Terek–Caspian Foredeep).

Deeper water black shales, overlain by coccolith-bearing marlstones representing the incipient Paratethys (example: Early Oligocene; Austrian Molasse Basin), have sedimentary characteristics similar to those of the Holocene Black Sea since 7500 years bp. Framboid pyrite size, biomarker and C-N-isotope data additionally indicate that isolation of the Paratethys resulted in Black Sea-type characteristics during nannoplankton zone NP 23.In contrast to the estuarine circulation across the Bosphorus since 7500 years bp, marine conditions prevailed in the incipient Paratethys during NP 21/22. Nitrogen was fixed and low organic carbon accumulation rates prevailed. In both settings a vertical density water-column stratification was accompanied by photic zone anoxia, and by anaerobic methane oxidation in the Paratethys. In the Paratethys increased run off, starting in NP 22, led to estuarine circulation during NP 23. During this period cyclic blooms of calcareous nannoplankton resulted in high calcite accumulation rates which diluted the coeval clay sedimentation. Similar sedimentary features in the Black Sea and the Paratethys during the earliest Oligocene are result from opposite paleoccanographic developments, both leading to estuarine circulation patterns. In the Black Sea, permanent photic zone anoxic conditions were established 7500 years bp in response to the first invasion of saline Mediterranean waters into the former freshwater lake. In contrast, brackish surface water in the Paratethys resulted from nutrient-rich freshwater diluting the marine water body. (c) 2005 Elsevier B.V. All rights reserved.