An overview on source rocks and the petroleum system of the central Upper Rhine Graben

International Journal of Earth Sciences - The petroleum system of the Upper Rhine Graben (URG) comprises multiple reservoir rocks and four major oil families, which are represented by four distinct...     

Suppression of Periodic Disturbances in Seismic Aftershock Recordings for Better Localisation of Underground Explosions

For precise localisation of a potential underground nuclear explosion, the Comprehensive Nuclear-Test-Ban Treaty Organization, during an on-site inspection, can set up seismic sensors to find the very small signals from aftershocks. These signals can be masked by periodic disturbances from, for example, helicopters. We present a new method to characterise every such disturbance by the amplitude, frequency and phase of the underlying sine in the time domain using a mathematical expression for its Hann-windowed discrete Fourier transform. The contributions of these sines are computed and subtracted from the complex spectrum sequentially. Two examples show the performance of the procedure: (1) synthetic sines superposed to a coal-mine induced event, orders of magnitude stronger than the latter, can be removed successfully, (2) removal of periodic content from the signals of a helicopter overflight reduces the amplitude by a factor 3.3 when the frequencies are approximately constant. The procedure cannot yet cope with peaks that change frequency too fast, for example by the Doppler effect when passing, and with peaks that lie too close to each other. Improvement to solve these problems seems possible.     

White mica 40Ar/39Ar age spectra and the timing of multiple episodes of high‐P metamorphic mineral growth in the Cycladic eclogite–blueschist belt,Syros, Aegean Sea,Greece

New geochronology from Syros in the Cycladic eclogite–blueschist belt, Aegean Sea, Greece, shows that ⁴⁰Ar/³⁹Ar geochronology consistently dates microstructural events in metamorphic rocks. We demonstrate that the age spectra depend on microstructure in a predictable and systematic way. Ages can be inferred by applying the method of asymptotes and limits to data from the step ‐ heating experiments. The results are consistent with previously published estimates for the timing of a sequence of distinct and discrete episodes of high ‐ P metamorphic mineral growth observed regionally across this belt. Arrhenius plots from these experiments imply that phengitic white mica is highly retentive of argon, and therefore (if these data can be extrapolated to the natural environment) the ages can be interpreted as recording the timing of episodic deformation and metamorphism. Porphyroblastic growth begins: (i) for omphacite – jadeite–eclogite facies parageneses at c. 53 Ma; and (ii) for garnet – glaucophane facies parageneses at c. 47 Ma. The Kini Shear Zone started as an extensional post ‐ epidote–albite‐transitional–blueschist facies shear zone that had completed operation by c. 31 Ma. The scatter in ages is due to the effect of deformation, recrystallization and multiple growth events in shear zones that continued operating for 3 – 6 million years from the start of each episode.     

Quantifying two-way influences between the Arctic and mid-latitudes through regionally increased CO2 concentrations in coupled climate simulations

Climate Dynamics - In which direction is the influence larger: from the Arctic to the mid-latitudes or vice versa? To answer this question, CO2 concentrations have been regionally increased in...     

Towards a science of past disasters

It is widely recognised that natural disasters emerge in the interplay between extreme geophysical events and the human communities affected by them. Whilst detailed natural scientific knowledge of a given event is critical in understanding its impacts, an equally thorough understanding of the affected communities, their economies, ecologies, religious structures, and how all of these have developed over time is arguably as important. Many extreme events leave methodologically convenient traces in the geological and archaeological records in the form of discrete stratigraphic layers often associated with both accurate and precise dates. This paper focuses on volcanic eruptions and draws on matched case studies to illustrate the usefulness of a two-step, quasi case–control comparative method for examining vulnerability and impacts in the near- and far-fields of these eruptions. Although issues of data resolution often plague the study of past disasters, these limitations are counterbalanced by the access to unique long-term information on societies and their material expressions of livelihood, as well as a similarly long-term perspective on the critical magnitude/frequency relationship of the geophysical trigger(s) in question. By drawing together aspects of contemporary Disaster Risk Reduction research, archaeology, and volcanology, this paper sketches out a methodological roadmap for a science of past disasters that aims to be relevant for not only understanding vulnerabilities and impacts in the deep past, but for also better understanding vulnerability in the present.     

Use of Systematic, Palaeoflood and Historical Data for the Improvement of Flood Risk Estimation. Review of Scientific Methods

The catastrophic floods recently occurring in Europe warn of the critical need forhydrologic data on floods over long-time scales. Palaeoflood techniques provideinformation on hydrologic variability and extreme floods over long-time intervals(100 to 10,000 yr) and may be used in combination with historical flood data (last1,000 yr) and the gauge record (last 30–50 yr). In this paper, advantages anduncertainties related to the reconstruction of palaeofloods in different geomorphologicalsettings and historical floods using different documentary sources are described.Systematic and non-systematic data can be combined in the flood frequency analysisusing different methods for the adjustment of distribution functions. Technical toolsintegrating multidisciplinary approaches (geologic, historical, hydraulic and statistical)on extreme flood risk assessment are discussed. A discussion on the potential theoreticalbases for solving the problem of dealing with non-systematic and non-stationary data ispresented. This methodology is being developed using new methodological approachesapplied to European countries as a part of a European Commission funded project (SPHERE).