Multiple mechanisms driving detachment folding as deduced from 3D reconstruction and geomechanical restoration: the Pico del Águila anticline (External Sierras,Southern Pyrenees)

Three‐dimensional (3D) modelling allows observation of geological features that may not be evident by classical two‐dimensional approaches. This is particularly important in the Pico del Águila anticline (Central External Sierras, Southern Pyrenees, Spain), a structure characterized by important geometrical variability in 3D. The Pico del Águila is a N–S‐trending fold, transverse to the E–W‐trending South‐Pyrenean thrust front, with well‐exposed growth strata that record the evolution of the structure and the influence of the South‐Pyrenean thrust front. Fold kinematics is complex and not precisely quantified. It is characterized by multiple folding mechanisms acting simultaneously in a heterogeneous stratigraphic sequence. To better understand the fold's structural evolution, 3D reconstruction and geomechanical restoration of the structure were performed. The restoration takes into account rock mechanical properties without assuming a specific kinematic model. Our work suggests that the growth of the structure was characterized by variable uplift/sedimentation rates through time and between fold limbs. The restoration also reveals that a combination of multiple folding mechanisms operated simultaneously in different units and structural domains during anti‐clinal growth. This has major implications in the understanding of detachment folds with associated growth strata, as such structures are described in many settings as potential traps for hydrocarbons and natural resources.     

OH point defects in olivine from Pakistan

The infrared (IR) spectra of gem-quality olivine crystals from Pakistan, formed in serpentinised dunitic rocks, are characterised by strongly pleochroic absorption bands at 3,613, 3,597, 3,580 and 3,566 cm^?1. These bands are assigned to O-H stretching vibrations of OH point defects corresponding to H₂O concentrations of about 35 wt ppm. Unlike other olivine spectra, the dominating bands are strongly polarised parallel to the b-axis. The unusual spectra type, excludes the presence of planar defects. This finding is supported by transmission electron microscopy. The 3,613 cm^?1 band is related to vacant Si sites, the slightly lower energetic bands preferentially to vacant M2 sites. The exclusive presence of these bands is not only a characteristic feature of olivines treated under high P,T conditions equivalent to mantle environment, the presence of these bands in untreated natural olivine also indicates formation conditions equivalent to crustal rocks.     

Quasi-satellite orbits in the general context of dynamics in the 1:1 mean motion resonance: perturbative treatment

Our investigation is motivated by the recent discovery of asteroids orbiting the Sun and simultaneously staying near one of the Solar System planets for a long time. This regime of motion is usually called the quasi-satellite regime, since even at the times of the closest approaches the distance between the asteroid and the planet is significantly larger than the region of space (the Hill’s sphere) in which the planet can hold its satellites. We explore the properties of the quasi-satellite regimes in the context of the spatial restricted circular three-body problem “Sun–planet–asteroid”. Via double numerical averaging, we construct evolutionary equations which describe the long-term behaviour of the orbital elements of an asteroid. Special attention is paid to possible transitions between the motion in a quasi-satellite orbit and the one in another type of orbits available in the 1:1 resonance. A rough classification of the corresponding evolutionary paths is given for an asteroid’s motion with a sufficiently small eccentricity and inclination.     

Study of the Influence of the Indirect Effect of Ocean Tides and of the Direct Deformation Effect of the Atmosphere on the Results of GPS Observations

The geodynamic interpretation of the results of GPS observations among the permanently operating stations which establish the frame for defining and conserving the coordinate system and simultaneously for describing the fundamental tendencies of dynamics in the area represented by them, should be deprived of the effects of geodynamic phenomena, which can be either periodic or short-term (even non-periodic) so that secular changes may be found. Some of these influences are included in scientific processing software, others have to be modelled later. The purpose of this project is to determine the influences of the indirect effect of ocean tides and the direct deformational effect of the atmosphere on the results of GPS observations, performed at stations Pecný (Czech Republic), Wettzell (FRG) and Graz (Austria), and also for the GPS stations of the Central Europe Regional Geodynamic Project (CERGOP) in the region of Central and East Europe. On the basis of analyses and results it is possible to claim that at the present accuracy of GPS observations the influence of ocean loading and atmospheric pressure effects for geodynamic campaigns in the region of the Czech Republic is negligible. For campaigns in larger regions (i.e. Central Europe) atmospheric corrections will have to be applied to height differences. These corrections, however, due to their periodicity have negligible influence on secular changes.     

Palaeoecology of well-preserved coral communities in a siliciclastic environment from the Late Pleistocene (MIS 7), Kish Island, Persian Gulf (Iran): the development of low-relief reef frameworks (biostromes) in increasingly restricted environments

Major changes in community structure and depositional relief of high-latitude coral communities in the southern Persian Gulf between marine isotope stage (MIS) 7 and the present day suggest that the area has become increasingly restricted. Corals and bivalves from outcrops on Kish Island, Iran, were identified in order to interpret the Late Pleistocene palaeoenvironmental setting. U/Th disequilibrium dating was used to constrain the ages of the stratigraphic units. During MIS 7, two coral-bearing sequences were deposited on what is now Kish Island. The lower sequence is dated as MIS 7.5 and changes laterally from an assemblage dominated by Cyphastrea sp. and Platygyra daedalea in the west to one characterized by branching Montipora in the east. By contrast, the upper sequence, dated as MIS 7.1, transitions from an assemblage dominated by platy Montipora in the west to a diverse assemblage of Platygyra and other faviids in the east. The assemblages of both sequences are within a marl matrix and bounded by thin lithified mollusc-rich layers. Corals and bivalves indicate that the sequences were deposited on gentle slopes in sheltered environments less than 20 m deep. The MIS 7 deposits may be classified as coral carpets or biostromes that developed a low-relief framework. During MIS 5, coral communities were no longer framework building and are now limited to an Acropora-rich layer of coral rubble that covers large parts of the island, and two small incipient reefs with sparse faviids. Similarities between the MIS 5 and modern nearshore coral communities suggest that the environmental conditions during MIS 5 were comparable to those of today. The late Pleistocene coral carpets and non-framework coral communities of the southern Persian Gulf may serve as models for coral biostromes in the fossil record, which formed under restricted environmental conditions such as elevated terrigenous input, high turbidity, and strong seasonal changes in temperature and/or salinity.     

Integral risk management: steps on the way from theory to practice

The best strategy to cope with natural hazards is the integral risk management, which involves all participants, decides on the basis of risks and also accepts a residual risk. Therefore, a substantial risk dialogue is essential not only to encourage self-responsibility. Even if throughout the Alpine perimeter this is accepted by the administration and the experts, the difficulties lie in the detail on the way to a full implementation of the effective risk management into practice. Therefore, a series of expert hearings and workshops was carried out in Bavaria to highlight the status of risk dialogue and point out the need for further development. In the beginning, an expert hearing dealt with the status of torrential risk management and worked out recommendations, focusing on the phases of reconstruction, preparation and prevention. On this basis, a practitioner workshop developed solution concepts for two case studies regarding all elements of the integral risk management. One of these was further regarded in a final workshop together with the municipality to encourage risk awareness, risk dialogue and to estimate the benefit of the measures. The activities and the results are described and summarized in the following article.     

Input of organic carbon as determinant of nutrient fluxes,light climate and productivity in the Ob and Yenisey estuaries

Spectral light attenuation profiles and concentrations of total and dissolved carbon (C), nutrients and chlorophyll a (Chla) were studied along transects running from the river mouth to the Kara Sea during late summer 2003 for the Yenisey and fall 2005 for the Ob estuaries. Earth Observation data were used to generate composite images of water color and Chla distribution over the estuaries and the Kara Sea to reveal the spatial impact of the river efflux in terms of optical properties.