German Molasse Basin Research Articles

Feeding preferences of Gomphotherium subtapiroideum (Proboscidea, Mammalia) from the Miocene of Sandelzhausen (Northern Alpine Foreland Basin, southern Germany) through life and geological time: evidence from dental microwear analysis

The objective of this study is to estimate changes in feeding preferences of the proboscidean species Gomphotherium subtapiroideum (Schlesinger 1917) by means of dental microwear analyses. The dietary changes are first evaluated through the ontogeny of this species, between juveniles and adults, and are then studied through geological time, from early Middle Miocene (MN5) to middle Late Miocene (MN8–9) localities of the German Molasse Basin. The microwear patterns of juvenile and adult individuals of G. subtapiroideum from Sandelzhausen (MN5) differ merely by the variable “length of scratches”, emphasizing longer jaw movements during mastication in adults. The microwear signatures of G. subtapiroideum do not vary significantly between the two geological time periods studied, but reflect mixed feeding preferences in both cases. These results imply that, despite an important environmental change at that time (drying and opening), the ecology of G. subtapiroideum and, especially, its feeding habits were not affected. Its dental microwear pattern is then compared with those of other species of Proboscidea from the Middle-Late Miocene of Germany, namely Deinotherium giganteum and Gomphotherium steinheimense.

Present-day stress orientation in the Molasse Basin

The present-day state of stress in Western Europe is considered to be controlled by forces acting at the plate boundaries. It is assumed that the Alpine orogen only influence the regional pattern of present-day stress in Western Europe within the Alps themselves. We examine the present-day maximum horizontal stress orientation in the Molasse Basin in the Alpine foreland in order to investigate the possible influence of the Alps on the far-field stress pattern of Western Europe. Four-arm caliper and image logs were analysed in 137 wells, in which a total of 1348 borehole breakouts and 59 drilling-induced fractures were observed in 98 wells in the German Molasse Basin. The borehole breakouts and drilling-induced fractures reveal that stress orientations are highly consistent within the Molasse Basin and that the present-day maximum horizontal stress orientation rotates from N–S in southeast Germany (002°N ± 19°) to approximately NNW–SSE in southwest Germany and the Swiss Molasse Basin (150°N ± 24°). The present-day maximum horizontal stress orientation in the Molasse Basin is broadly perpendicular to the strike of the Alpine front, indicating that the stress pattern is probably controlled by gravitational potential energy of Alpine topography rather than by plate boundary forces. The present-day maximum horizontal stress orientations determined herein have important implications for the production of hydrocarbons and geothermal energy in the German Molasse Basin, in particular that hydraulically-induced fractures are likely to propagate N–S and that wells deviated to the north or south may have reduced wellbore instability problems.

Wetland paradise lost: Miocene community dynamics in large herbivorous mammals from the German Molasse Basin

Questions: What was the distribution of fossil mammal taxa in the Miocene German Molasse Basin? Were there changes in community structure during the terrestrial development of the Molasse Basin? Were community dynamics similar in the Molasse Basin to those in the rest of Europe? Data: We gathered the available Miocene large mammal herbivore occurrences from the southern German Molasse Basin [museum data mainly from Munich (Germany), with additional data from museums in Stuttgart (Germany) and Vienna (Austria)]. We used public data from NOW (Neogene of the Old World database, http://www.helsinki.fi/science/now) for comparison and as the source of ecological data for the species. Methods: We combined ecological data from the NOW database with distributions of herbivorous mammals within the Molasse Basin. We plotted the occurrences of taxa on a base map, and used the associated body size and dietary categories to plot these data on the map. We investigated the differences in the structure of communities in different time periods. We compared different time periods and differences among areas. We also compared the Molasse Basin and NOW data. Conclusions: The evolution of large-mammal communities in the Molasse Basin occurred in two phases: build up and decline. The build-up phase was characterized especially by a high abundance of small-sized browsers and mixed feeders. The diversity was especially high during the built-up phase, indicating a highly differentiated wetland habitat. The decline phase saw a very different community structure with fewer mixed feeders and with larger sized mammals dominating. The difference between these phases was largely the consequence of regional extinctions of species and genera. The Molasse Basin community dynamics also differ from those of the rest of Europe (NOW data).

A community of Middle Miocene Ruminantia (Mammalia, Artiodactyla) from the German Molasse Basin

A community of Middle Miocene Ruminantia (Mammalia, Artiodactyla) from the German Molasse Basin

Biota, palaeoenvironments and biostratigraphy of continental Oligocene deposits of the South German Molasse Basin (Penzberg Syncline)

Six charophyte, 13 mollusc, four ostracod and nine fish otolith taxa are taxonomically described, and one fruit, one seed and two foraminiferal taxa are briefly noted from the Lower Cyrena Beds and the Lower Coloured Molasse of the Sindelsdorf section near Penzberg (approximately 50 km south of Munich). Our palaeoecological and lithological data from the Lower Cyrena Beds suggest a delta plain with lagoons, estuaries, slowly flowing rivers, lakes and swamps. Faunal and floral elements of the Lower Coloured Molasse indicate lacustrine environments. The gastropod Tympanotonos and the tropical to subtropical fish fauna (Eleotridae, Ambassidae and Cyprinodontidae) suggest a warm, at least subtropical climate. Furthermore, Tympanotonos suggests comparisons with Recent molluscan faunas of the mangrove swamps of the West African coast, and thus hints at mangrove vegetation bordering the coasts of the Upper Bavarian Molasse Sea. A biostratigraphical classification for the Oligocene Molasse deposits of the Penzberg Syncline is established for the first time based on otoliths and charophytes. The Lower Cyrena Beds are attributed to the newly defined otolith zone OT‐O1/2 and probably correspond to the oldest part of the Chara microcera Zone. The lowermost part of the Lower Coloured Molasse can be correlated both with otolith zone OT‐O2 and the Chara microcera Zone. The Sindelsdorf section lies within the Rupelian–Chattian transition zone and thus the chronostratigraphic age is approximately 29–28 Ma.

Eustatic versus tectonic controls on Alpine foreland basin fill: sequence stratigraphy and subsidence analysis in the SE German Molasse

Abstract A sequence-stratigraphic and subsidence analysis in the SE German Molasse basin was carried out based on well and seismic data. The sequence-stratigraphic study revealed that the basin fill is composed of five second-order sequences. Sequences 3 and 4 can be subdivided into several third-order sequences. Seismic facies maps illustrate the temporal and spatial evolution of the study area. Comparison of an accommodation curve of the Molasse basin with the eustatic sea-level curve of Haq et al . ( Science , 1987, 235 , 1156–1167) showed, that the sequence stratigraphic subdivision was mainly controlled by eustatic sea-level fluctuations. Subsidence analysis revealed a major flexural event in the SE German Molasse basin from late Eocene to early Miocene (late Egerian), followed by a possible visco-elastic relaxation of the lithosphere responsible for the formation of an angular unconformity between the two classical transgressive-regressive megacycles of the Molasse stratigraphy (early Miocene, late Egerian-Eggenburgian boundary). A phase of relatively uniform, decreasing subsidence followed until the end of Molasse sedimentation, when an isostatic rebound resulted in the uplift of the basin. The subsidence analysis also revealed, that even though eustacy controlled sequence boundary formations, the interplay between subsidence and sedimentation rates, both governed by tectonics, controlled the transgressive-regressive megacycles. However, the coupling of the two factors depends on the tectonic process.

Seismic Stratigraphy and Stratigraphic Modelling of the South-Eastern German Molasse Basin: ABSTRACT

Although the German Molasse Basin can be regarded as a mature hydrocarbon province, no regional sequence stratigraphic analysis has been carried out so far. We have studied seismic lines and well data from the region between the Isar and Inn rivers (SE Germany) that have been generously supplied by German oil companies (DEE, BEB, Mobil, RWE-DEA and Wintershall). Initial work indicates that five major seismic sequences within three main depositional cycles are developed. The Alpine thrust belt to the south serves as the primary sediment source in the foreland basin. However, sedimentary infill mainly took place parallel to the basin axis. Our analysis suggests that the stratigraphic development of the Molasse Basin was mainly controlled by eustatic sea-level changes which caused the shoreline to shift in the W-E direction. The shifting of the depocenter axis in a N-S direction was controlled by the tectonic evolution of the thrust belt. The sea-level curve determined by seismic stratigraphy and well-derived subsidence curves have been used as input parameters for stratigraphic modelling, using the programs GeoMOD and PHIL. Basin-fill simulations with PHIL are in good agreement with the main features of the sequence stratigraphy and the distribution of the systems tracts observed inmore » the study area. The qualitative sea-level curve for the German Molasse Basin derived from the seismostratigraphic analysis could be quantified by the stratigraphic exercises.« less

Sequence stratigraphy and depositional history in the south-eastern German Molasse Basin

A study of seismic lines and well data from the region between the Isar and Inn rivers (SE Germany) indicates the presence of three main depositional cycles in the Molasse Basin: Upper Eocene-Chattian Sands, Upper Chattian Marls-Aquitanian Sandstone-Shale Series and Aquitanian Fish Shales-Upper Freshwater Molasse. The flexural subsidence caused by thrust loading has the greatest influence in increasing/reducing the accommodation space for the deposition, which controlled the displacement of the depositional axis in a N-S direction. However, eustatic sea-level changes, which caused the shoreline to shift in a W-E direction, have a strong impact on the stratigraphic development of this typical foreland basin.

Structure and Prospects of Alpine Basins and Foredeep

The sedimentary history of the German Molasse basin is characterized by three stages separated by major unconformities: (1) Permian-Carboniferous siliciclastic graben sedimentation, (2) Mesozoic mixed carbonate-siliciclastic shelf sedimentation, and (3) Tertiary siliciclastic foredeep sedimentation. The southern-most part of the basin was overthrust by the Alpine nappes. The hydrocarbon source rocks are Toarcian and Oligocene shales as well as Permian-Carboniferous coals. Most of the oil kitchen is to the north of the thrust front, whereas the gas kitchen is primarily in the subthrust zone. Some biogenic gas occurs in the shallower northeastern parts of the basin. The chief reservoir rocks are Triassic and Jurassic sandstones in the central and western part, and Tertiary sandstones and carbonates in the eastern part of the basin. They are commonly sealed by marine shales. Most traps are on the upthrown side of basin-parallel antithetic normal faults. The Molasse basin is in a mature stage of exploration, with relatively low remaining recoverable reserves. Additional exploration potential is inferred in stratigraphic traps in the foreland basin, as well as in structural traps in the subthrust zone and the nappes.

Upper Carboniferous source rocks north and south of the Variscan Front (NW and Central Europe)

Some topical aspects of Upper Carboniferous source rocks within the three main tectonic settings in NW and Central Europe are described. These are likely to offer an effective tool for reduction of risk in future exploration. In the foreland, the main geological factors responsible for the nitrogen content of gas accumulations and for the isotopic composition of methane are outlined. It will probably be possible to predict the molecular and isotopic composition of gas accumulations in the future. In addition, the application of the dynamics of diffusion processes to the loss of gas accumulations over geological time offers the possibility of predicting hydrocarbon fill in some areas of the basin. In the Variscan fold belt, the model of thin-skin tectonics suggests that the lowermost, parautochthonous low rank thrust sheets are more likely to be source rocks than are allochthonous, high rank thrust sheets. Additionally young subsidence is required in order to meet the conditions of gas dynamics. The possible source rock potential of the Permo-Carboniferous fills of the intramontane grabens south of the Variscan front are reported here for the first time. Some promising discoveries below the Swiss and German Molasse basin as well as in the eastern Paris Basin mean that the intramontane grabens are now an interesting exploration'objective.

Das Forschungsvorhaben "Hydrogeothermische Energienutzung und Grundwasserhaushalt des Malmkarsts im süddeutschen Molassebecken" - Ziele und Zwischenergebnisse

Das Forschungsvorhaben "Hydrogeothermische Energienutzung und Grundwasserhaushalt des Malmkarsts im süddeutschen Molassebecken" - Ziele und Zwischenergebnisse

A three-dimensional crustal model of southwest Germany derived from seismic refraction data

From densely covered seismic refraction data obtained in 1978 (Urach experiment) and 1984 (“Schwarzer Zollern-Wald” experiment) and from seismic reflection data and results from previous refraction investigations, a three-dimensional crustal model of southwest Germany was derived. Travel-time and amplitude information of seismic refraction data were interpreted with two-dimensional forward modeling (ray tracing) to calculate two crustal cross sections in southwest Germany. These results fill a gap in the existing data and enabled the construction of a detailed three-dimensional crustal model. While seismically the upper crust is laterally homogeneous (5.9–6.0 km/s) throughout the area, the middle and lower crust show pronounced lateral variations in thickness, velocity, and reflectivity. The Moho is a flat surface at a relatively shallow depth (25–26 km). We classify the middle and lower crust of southwest Germany into two characteristic crustal types. Type I consists of a mid-crustal low-velocity zone (5.4–5.8 km/s) overlying a thick (> 10 km), high-velocity (6.6–6.8 km/s) lower crust. Type II has no prominent mid-crustal low-velocity zone, and a thin (< 10 km), low-velocity (6.3–6.4 km/s) lower crust. The crustal types correlate with the major geologic units exposed in the area: Type I is present beneath the Black Forest, forming the eastern flank of the Rhinegraben and beneath the Swabian Jura, while Type II is present beneath the intervening Triassic sediments. Beneath the South German Molasse Basin, a low-velocity zone is also present in the upper middle-crust. Seismic reflection investigations have shown that the lower crust in southwest Germany comprises a stack of layers of alternating high- and low-velocities. The lateral variation of the reflectivity of this laminated lower crust has been recognized even on refraction data. We found that high-reflectivity of the lower crust correlates to high average velocity (6.7–6.8 km/s) in the lower crust (Type I). Thus, the average velocity of the lower crust in southwest Germany seems to be an indicator of the intensity of its lamination. The uppermost mantle has a velocity of 8.3 km/s in the area and a strong, positive velocity gradient.

Genetic Characterization of Natural Gases

Natural gases can be characterized genetically using four properties: C2+ concentration, carbon and hydrogen isotope variations in methane, and carbon isotope variation in ethane. Three diagrams for genetic characterization of gases have been designed in which the carbon isotopic composition of methane is correlated with the other parameters. In these diagrams, compositional fields have been defined for primary gases (biogenic, thermogenic associated, and thermogenic nonassociated) and for gases which result from mixing of these gases. These fields are strictly empirical and comprise compositional variations found in about 500 natural gases. The isotopic and compositional variations in natural gases can be described in terms of (1) processes during formation of the gases such as bacterial fermentation or maturation of organic matter, and (2) processes during secondary migration. Mixing of primary gases is an important and common process. Migration of gases predominantly affects the C2+ concentration, whereas the isotopic properties of gaseous hydrocarbons primarily remain unchanged, allowing an assessment of the origin of migrated gases and properties of their source rocks. The formation of gas from humic organic matter and coals is not yet clear from published data. The diagrams use data from various basins and areas. Interstitial gases from the Gulf of California are entirely of bacterial origin: traces of thermogenic gases are formed only in the vicinity of dolerite sills; gases in the south German Molasse basin and in the Vienna basin are of bacterial, mixed, and thermogenic origins. Data from the north Italian Po basin provide examples for genetic characterization of migrated gases.

Correlation of crude oils and source rocks in the German Molasse basin : Applicability of chromatographic techniques

Chromatographic techniques can be applied successfully in organic geochemical research. Taking the oil—oil and oil—source rock correlations in the German Molasse basin as examples, it is demonstrated how classical column chromatography can help in oil—oil correlation work. Secondary alteration of oils can be detected by analysing the fraction of saturated hydrocarbons by means of capillary column gas chromatography. Aromatic hydrocarbons are less affected by biodegradation. The high-performance liquid chromatographic separation of this group of compounds is also demonstrated. Final conclusions in oil—oil correlations can be drawn from gas chromatographic—mass spectrometric (GC—MS) analyses of biomarker components (steranes, triterpanes). Preliminary results of oil—source rock correlations were obtained by using thermochromatographic methods (pyrolysis—GC) for pre-selecting potential source rocks and GC—MS investigations of steranes.

Correlation studies on crude oils and source-rocks in the German Molasse Basin

Abstract Three types of oils can be distinguished in the German Molasse Basin according to their distributions of alkanes and aromatic hydrocarbons. GC-MS investigations, which till now have been restricted mainly to the analysis of steranes, have revealed the presence of only 2 oil families for which 2 different source-rocks must be assumed. We have tentatively concluded that the Tertiary oils have originated from Jurassic source-rocks of the “Germanic” facies, whereas the Triassic oils show some resemblance to Jurassic rocks of the “Helvetian” facies. The Tertiary foreland sediments have not yet been heated sufficiently to have generated oil.

Chemical composition and stable carbon isotopic ratios of crude oils from Southern Germany

Thirty crude oils were sampled in the South German Molasse Basin. The crude oils were chemically separated into five component groups and their stable carbon isotopic ratios were determined by mass spectrometry. A distinct differentiation of four regionally connected groups can be inferred from the results of the δ 13C values and chemical analyses. This grouping is in accordance with the present geologic information on the origin of crude oils in the Molasse Basin. The chemistry of crude oils seems to have been influenced by secondary processes in the eastern part of the Molasse Basin.

Geochemisch-paläogeographische Untersuchungen im süddeutschen Molassebecken

Geochemisch-paläogeographische Untersuchungen im süddeutschen Molassebecken

Das Süddeutsche Molassebecken - ein Überblick

Das Süddeutsche Molassebecken - ein Überblick