Eocene-Pliocene time scale and stratigraphy of the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB)

We present a general stratigraphic synthesis for the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB) from Eocene to Pliocene times. The stratigraphic data were compiled both from literature and from research carried out by the authors during the past 6 years ; an index of the stratigraphically most important localitites is provided. We distinguish 14 geographical areas from the Helvetic domain in the South to the Hanau Basin in the North. For each geographical area, we give a synthesis of the biostratigraphy, lithofacies, and chronostratigraphic ranges. The relationships between this stratigraphic record and the global sea-level changes are generally disturbed by the geodynamic (e.g., subsidence) evolution of the basins. However, global sea-level changes probably affected the dynamic of transgression–regression in the URG (e.g., Middle Pechelbronn Beds and Serie Grise corresponding with sea-level rise between Ru1/Ru2 and Ru2/Ru3 sequences, respectively) as well as in the Molasse basin (regression of the UMM corresponding with the sea-level drop at the Ch1 sequence). The URGENT-project (Upper Rhine Graben evolution and neotectonics) provided an unique opportunity to carry out and present this synthesis. Discussions with scientists addressing sedimentology, tectonics, geophysics and geochemistry permitted the comparison of the sedimentary history and stratigraphy of the basin with processes controlling its geodynamic evolution. Data presented here back up the palaeogeographic reconstructions presented in a companion paper by the same authors (see Berger et al. in Int J Earth Sci 2005).     

Synergy and fusion of optical and synthetic aperture radar satellite data for underwater topography estimation in coastal areas

A method to obtain underwater topography for coastal areas using state-of-the-art remote sensing data and techniques worldwide is presented. The data from the new Synthetic Aperture Radar (SAR) satellite TerraSAR-X with high resolution up to 1 m are used to render the ocean waves. As bathymetry is reflected by long swell wave refraction governed by underwater structures in shallow areas, it can be derived using the dispersion relation from observed swell properties. To complete the bathymetric maps, optical satellite data of the QuickBird satellite are fused to map extreme shallow waters, e.g., in near-coast areas. The algorithms for bathymetry estimation from optical and SAR data are combined and integrated in order to cover different depth domains. Both techniques make use of different physical phenomena and mathematical treatment. The optical methods based on sunlight reflection analysis provide depths in shallow water up to 20 m in preferably calm weather conditions. The depth estimation from SAR is based on the observation of long waves and covers the areas between about 70- and 10-m water depths depending on sea state and acquisition quality. The depths in the range of 20 m up to 10 m represent the domain where the synergy of data from both sources arises. Thus, the results derived from SAR and optical sensors complement each other. In this study, a bathymetry map near Rottnest Island, Australia, is derived. QuickBird satellite optical data and radar data from TerraSAR-X have been used. The depths estimated are aligned on two different grids. The first one is a uniform rectangular mesh with a horizontal resolution of 150 m, which corresponds to an average swell wavelength observed in the 10 × 10-km SAR image acquired. The second mesh has a resolution of 150 m for depths up to 20 m (deeper domain covered by SAR-based technique) and 2.4 m resolution for the shallow domain imaged by an optical sensor. This new technique provides a platform for mapping of coastal bathymetry over a broad area on a scale that is relevant to marine planners, managers, and offshore industry.     

Late glacial and Holocene Ostracoda from the Melilla cold-water coral mound field

The ostracod assemblages from sediment core TTR17-401G recovered from the Melilla cold-water coral mound field in the eastern Alboran Sea spanning the last 13 ka are analysed quantitatively, taxonomically and palaeoecologically. The core can be subdivided in three distinct assemblages linked to environmental shifts during the Younger Dryas and the Bølling–Allerød interstadial. A total of 9 ostracod species is recorded, Paracypris polita is dominant throughout the core. Common accessory taxa Cytherella robusta, Echinocythereis vidua and Macromckenziea ligustica characterize the well-oxygenated ostracod assemblage 2 affected by the Younger Dryas. Favourable growth conditions for ostracods during the latter are indicated by large-sized Krithe praetexta specimens.     

Novel basin modelling concept for simulating deformation from mechanical compaction using level sets

As sedimentation progresses in the formation and evolution of a depositional geologic basin, the rock strata are subject to various stresses. With increasing lithostatic pressure, compressional forces act to compact the porous rock matrix, leading to overpressure buildup, changes in the fluid pore pressure and fluid flow. In the context of petroleum systems modelling, the present study concerns the geometry changes that a compacting basin experiences subject to deposition. The purpose is to track the positions of the rock layer interfaces as compaction occurs. To handle the challenge of potentially large geometry deformations, a new modelling concept is proposed that couples the pore pressure equation with a level set method to determine the movement of lithostratigraphic interfaces. The level set method propagates an interface according to a prescribed speed. The coupling term for the pore pressure and level-set equations consists of this speed function, which is dependent on the compaction law. The two primary features of this approach are the simplicity of the grid and the flexibility of the speed function. A first evaluation of the model concept is presented based on an implementation for one spatial dimension accounting for vertical effective stress. Isothermal conditions with a constant fluid density and viscosity were assumed. The accuracy of the implemented numerical solution for the case of a single stratigraphic unit with a linear compaction law was compared to the available analytical solution [38]. The multi-layer setup and the nonlinear case were tested for plausibility.     

The position of the Rupelian/Chattian boundary in the southern Upper Rhine Graben based on new records of microfossils

This study analyses the regressive phase of the marine Froidefontaine Subgroup and the subsequent fluvio-lacustrine Niederroedern formation in the southern Upper Rhine Graben during the Late Rupelian and the position of the Rupelian/Chattian boundary. The study is based on the sedimentary record and several microfossil groups from two boreholes, with a focus on new records of fish otoliths, Bolboforma and Charophyta. The biostratigraphic evaluation of these groups provides evidence for a position of the Rupelian/Chattian boundary within the upper Niederroedern Formation. This is contrary to the results from a previous sedimentological approach, which places the boundary at the base of the Niederroedern Formation. The fish fauna indicates a biogeographic relation to southern France, the Molasse Basin of Switzerland and southern Germany.     

New biostratigraphical data for the Burdigalian Montchaibeux Member at the locality Courrendlin-Solé (Canton of Jura,Switzerland)

Geological surveys were carried out in the Miocene deposits at the place known as “En Solé” east of the village Courrendlin (Delémont Basin, Canton of Jura, Switzerland). This resulted in the discovery of new Miocene small mammal assemblages. The association of the rodents Megacricetodon aff. collongensis and Melissiodon sp. allows to biochronostratigraphically correlate for the first time the so-called “Rote Mergel des Mont Chaibeux” representing the lower part of the Montchaibeux Member of the Bois de Raube Formation to the regional M. collongensis–Keramidomys interval zone (MN 4; early Miocene).     

Paleogeography of the Upper Rhine Graben (URG) and the Swiss Molasse Basin (SMB) from Eocene to Pliocene

Twenty paleogeographic maps are presented for Middle Eocene (Lutetian) to Late Pliocene times according to the stratigraphical data given in the companion paper by Berger et al. this volume. Following a first lacustrine-continental sedimentation during the Middle Eocene, two and locally three Rupelian transgressive events were identified with the first corresponding with the Early Rupelian Middle Pechelbronn beds and the second and third with the Late Rupelian Serie Grise (Fischschiefer and equivalents). During the Early Rupelian (Middle Pechelbronn beds), a connection between North Sea and URG is clearly demonstrated, but a general connection between North Sea, URG and Paratethys, via the Alpine sea, is proposed, but not proved, during the late Rupelian. Whereas in the southern URG, a major hiatus spans Early Aquitanian to Pliocene times, Early and Middle Miocene marine, brackish and freshwater facies occur in the northern URG and in the Molasse Basin (OMM, OSM); however, no marine connections between these basins could be demonstrated during this time. After the deposition of the molasse series, a very complex drainage pattern developed during the Late Miocene and Pliocene, with a clear connection to the Bresse Graben during the Piacenzian (Sundgau gravels). During the Late Miocene, Pliocene and Quaternary sedimentation persisted in the northern URG with hardly any interruptions. The present drainage pattern of the Rhine river (from Alpine area to the lower Rhine Embayment) was not established before the Early Pleistocene.