Facies and depositional environments of the Upper Muschelkalk (Schinznach Formation, Middle Triassic) in northern Switzerland.

Subsurface sedimentary strata in northern Switzerland, such as the Middle Triassic Upper Muschelkalk, are attracting interest as potential reservoirs for CO2 sequestration and for geothermal energy production. Characterizing facies in such strata aids prediction of reservoir properties in unexplored areas. Although well studied elsewhere, the Swiss Upper Muschelkalk has received little attention despite containing the southern-most deposits of the Central European Basin. The Upper Muschelkalk represents the deposits of a storm-dominated, homoclinal carbonate ramp, developed during a basin-wide 3rd-order transgressive-regressive cycle. Our facies analyses of nine boreholes across northern Switzerland reveal 12 lithofacies, eight lithofacies associations and four types of metre-scale 5th-order cycles corresponding to at least 23 short orbital eccentricity cycles. During the 3rd-order transgression, crinoidal bioherms developed across Switzerland followed by deep-ramp environments. Subsequently, tempestites were deposited up to and after the basin-wide maximum flooding surface. Lateral tempestite correlations indicate that Switzerland lay within an open-marine, mid-ramp environment during almost half of the depositional history. Mid-ramp deposits pass upwards to prograding shelly shoals, which sheltered a back-shoal lagoon containing patchy oolitic shoals. At the top of the Upper Muschelkalk, back-shoal sediments give way to coastal sabkha facies, which were overlain by oolitic shoals during a marine transgression. Shortly thereafter the top of the Upper Muschelkalk was dolomitized by brines from an overlying hypersaline environment that was later removed by a basin-wide erosive event. Overall, the paucity of porous shoal facies, unlike in southern Germany, has resulted in poor primary reservoir properties in the Upper Muschelkalk of Switzerland.

The Close-Up Imager Onboard the ESA ExoMars Rover: Objectives, Description, Operations, and Science Validation Activities.

The Close-Up Imager (CLUPI) onboard the ESA ExoMars Rover is a powerful high-resolution color camera specifically designed for close-up observations. Its accommodation on the movable drill allows multiple positioning. The science objectives of the instrument are geological characterization of rocks in terms of texture, structure, and color and the search for potential morphological biosignatures. We present the CLUPI science objectives, performance, and technical description, followed by a description of the instrument's planned operations strategy during the mission on Mars. CLUPI will contribute to the rover mission by surveying the geological environment, acquiring close-up images of outcrops, observing the drilling area, inspecting the top portion of the drill borehole (and deposited fines), monitoring drilling operations, and imaging samples collected by the drill. A status of the current development and planned science validation activities is also given. Key Words: Mars-Biosignatures-Planetary Instrumentation. Astrobiology 17, 595-611.

Linking the diffusion of water in compacted clays at two different time scales: tracer through-diffusion and quasielastic neutron scattering.

Diffusion of water and solutes through compacted clays or claystones is important when assessing the barrier function of engineered or geological barriers in waste disposal. The shape and the connectivity of the pore network as well as electrostatic interactions between the diffusant and the charged clay surfaces or cations compensating negative surface charges affect the resistance of the porous medium to diffusion. Comparing diffusion measurements performed at different spatial or time scales allows identification and extraction of the different factors. We quantified the electrostatic constraint q for five different highly compacted clays (rhob = 1.85 +/- 0.05 g/cm3) using quasielastic neutron scattering (QENS) data. We then compared the QENS data with macroscopic diffusion data for the same clays and could derive the true geometric tortuosities G of the samples. Knowing the geometric and electrostatic factors for the different clays is essential when trying to predict diffusion coefficients for other conditions. We furthermore compared the activation energies Ea for diffusion at the two measurement scales. Because Ea is mostly influenced by the local, pore scale surroundings of the water, we expected the results to be similar at both scales. This was indeed the case for the nonswelling clays kaolinite and illite, which had Ea values lower than that of bulk water, but not for montmorillonite, which had values lower than that in bulk water at the microscopic scale, but larger at the macroscopic scale. The differences could be connected to the strongly temperature dependent mobility of the cations in the clays, which may act as local barriers in the narrow pores at low temperatures.

Translational diffusion of water and its dependence on temperature in charged and uncharged clays: A neutron scattering study.

The water diffusion in four different, highly compacted clays [montmorillonite in the Na- and Ca-forms, illite in the Na- and Ca-forms, kaolinite, and pyrophyllite (bulk dry density rho(b)=1.85+/-0.05 gcm(3))] was studied at the atomic level by means of quasielastic neutron scattering. The experiments were performed on two time-of-flight spectrometers and at three different energy resolutions [FOCUS at SINQ, PSI (3.65 and 5.75 A), and TOFTOF at FRM II (10 A)] for reliable data analysis and at temperatures between 27 and 95 degrees C. Two different jump diffusion models were used to describe the translational motion. Both models describe the data equally well and give the following ranking of diffusion coefficients: Na-montmorilloniteor=Na-montmorillonite>Ca-illite>Na-illite>or=kaolinite>pyrophyllite>or=water, in both jump diffusion models. For clays with a permanent layer charge (montmorillonite and illite) a reduction in the water content by a factor of 2 resulted in a decrease in the self-diffusion coefficients and an increase in the time between jumps as compared to the full saturation. The uncharged clay kaolinite exhibited no change in the water mobility between the two hydration states. The rotational relaxation time of water was affected by the charged clay surfaces, especially in the case of montmorillonite; the uncharged clays presented a waterlike behavior. The activation energies for translational diffusion were calculated from the Arrhenius law, which adequately describes the systems in the studied temperature range. Na- and Ca-montmorillonite (approximately 11-12 kJmol), Na-illite (approximately 13 kJmol), kaolinite and pyrophyllite (approximately 14 kJmol), and Ca-illite (approximately 15 kJmol) all had lower activation energies than bulk water (approximately 17 kJmol in this study). This may originate from the reduced number and strength of the H-bonds between water and the clay surfaces, or ions, as compared to those in bulk water. Our comparative study suggests that the compensating cations in swelling clays have only a minor effect on the water diffusion rates at these high densities, whereas these cations influence the water motion in non-swelling clays.