Intercomparison of Boron Isotope and Concentration Measurements. Part I: Selection, Preparation and Homogeneity Tests of the Intercomparison Materials

In 1999 the Istituto di Geoscienze e Georisorse (IGG), with the support of the International Atomic Energy Agency (IAEA), undertook the collection, preparation and distribution of eight geological materials intended for a blind interlaboratory comparison of measurements of boron isotopic composition and concentration. The materials came from Italian sources and consist of three natural waters (Mediterranean seawater and two groundwaters) and five rocks and minerals (tourmaline, basalt, obsidian, limestone and clay). The solid materials were crushed, milled and mixed, in preparation for distribution. Extensive assays performed at the IGG on these materials demonstrated that their boron isotopic and chemical compositions are homogeneous.
Additional homogeneity tests were carried out on solid material fragments at the GeoForschungsZentrum Potsdam, with the specific objective of investigating the suitability of some of them for the calibration in situ of micro-analytical techniques. Two materials, B4 (tourmaline) and B6 (obsidian), proved to be isotopically homogeneous and may become excellent references for in situ microanalyses of boron isotopes.
The materials described here were used as the basis of a major laboratory intercomparison study and are now available for further distribution from either the IAEA (solid materials) or the IGG (waters).     

Hydrothermal gases offshore Milos Island, Greece

Hydrothermal fluids emerge from the seafloor of Paleohori Bay on Milos. The gases in these fluids contain mostly CO₂ but CH₄ concentrations up to 2% are present. The stable carbon isotopic composition of the CO₂ (near 0%) indicates an inorganic carbon source (dissociation of underlying marine carbonates). The carbon and hydrogen isotopes of most CH₄ samples are enriched in the heavy species (δ¹³C = −9.4 to −17.8‰; δD = −102 to −189‰) which is believed to be characteristic for an abiogenic production of CH₄ by CO₂-reduction (Fischer-Tropsch reactions). Depletions in the deuterium content of three CH₄ samples (to −377%) are probably caused by unknown subsurface rock alteration processes. Secondary hydrogen isotope exchange processes between methane, hydrogen and water are most likely responsible for calculated unrealistic methane formation temperatures.

We show that excess helium, slightly enriched in ³He, is present in the hydrothermal fluids emerging the seafloor of Paleohori Bay. When the isotopic ratio of the excess component is calculated a ³He/⁴He_excess of 3.6 · 10⁻⁶ is obtained: This indicates that the excess component consists of about one third of mantle helium and two thirds of radiogenic helium. We infer that the mantle-derived component has been strongly diluted by radiogenic helium during the ascent of the fluids to the surface.     

Tectonic style and pressure distribution at the northern margin of the Alps between Lake Constance and the River Inn

Hydrocarbon exploration in the Molasse basin and the Alpine thrust belt has provided new information on the tectonic structure of the foreland margin of the overthrust belt. Two N-S cross-sections show the front of the Folded Molasse as a so-called Triangle Zone in the area north of the Hindelang 1 well (Bavaria) and the Sulzberg 1 well (Vorarlberg). The Triangle Zone was described and defined byJones (1982) for the Alberta Foothills in Canada.Oil and gas wells commonly encountered overpressured zones with pressure gradients up to 2.5 bar/10 m. The pressure profiles from the Sulzberg1, Hindelang1, Staffelsee1, Miesbach 1 and Bromberg 1 wells were analysed stratigraphically and lithologically with respect to the tectonics of the region. It can be concluded that the overpressures in the Foreland Molasse were caused by compaction, where those within the thrust belt were caused by tectonics.

---

Zusammenfassung Die von der Erdöl- und Erdgasindustrie im Bereich des Alpennordrandes durchgeführten Untersuchungsarbeiten brachten neue Ergebnisse zum tektonischen Bau. So stellt sich in zwei N-S-Profilen nördlich von Hindelang (Bayern) und über die Tiefbohrung Sulzberg 1 (Vorarlberg) die Stirn der Faltenmolasse als Triangelzone dar, wie sie von Jones (1982) aus den Foothills der Rocky Mountains beschrieben wird.Tiefbohrungen auf Erdöl und Erdgas haben verbreitet überhydrostatische Porendrücke mit Gradienten bis 2,5 bar/10 m angetroffen. Es wurden Druckprofile aus den Bohrungen Sulzberg 1, Hindelang 1, Staffelsee 1, Miesbach 1 und Bromberg 1 nach stratigraphisch-lithologischen Gesichtspunkten analysiert, regionaltektonisch zugeordnet und interpretiert. Es zeigt sich, daß die Überdrücke in der Vorlandmolasse durch Kompaktion entstanden sind, während diejenigen unter den Decken tektonische Ursachen haben.

---

Résumé Les travaux d'exploration entrepris par l'industrie du pétrole dans le bassin molassique et dans la bordure septentrionale des Alpes ont conduit à de nouveaux résultats en ce qui concerne les structures tectoniques de cette région. Dans deux profils nord — sud établis dans la région, respectivement au nord de Hindelang (Bavière) et au nord de Sulzberg (Vorarlberg), le front de la molasse plissée se présente comme une »zone triangulaire« du type défini parJones (1982) dans les Foothills d'Alberta au Canada.Des forages pétroliers profonds ont fréquemment recontré des pressions interstitielles hyperhydrostatiques avec des gradients pouvant atteindre 2,5 bars / 10 m.Les profils de pression relevés dans les sondages de Sulzberg 1, Hindelang 1, Staffelsee 1, Miesbach 1 et Bromberg 1 ont été analysés au point de vue stratigraphique et lithologique et placés dans le cadre tectonique de la région. Il en résulte que les surpressions dans la molasse d'avant-pays (Vorlandmolasse) sont dues à la compaction et que celles des formations recouvertes par les nappes sont d'origine tectonique.

---

, - , . , Hindelang / /, Sulzberg 1 / Vorarlberg / , Jones' 1982 Foothills . 2.5 /10 . , . , , - .

     

Reconstruction of the late Quaternary paleoenvironments of the Nussloch loess paleosol sequence,Germany, using n-alkane biomarkers

This study contributes to the paleoenvironmental reconstruction of the loess–paleosol sequence of Nussloch, Germany, by using n-alkanes as plant leaf-wax-derived lipid biomarkers. We found that n-alkane patterns and concentrations in the Saalian loess and the last interglacial Eemian paleosol of Nussloch point to very strong degradation and prevailing deciduous vegetation. Degradation effects in the overlying paleosols and loess layers are less pronounced and allow for the application of an end-member mixing model to estimate vegetation changes semi-quantitatively. Our findings highlight the potential for the interpretation of degradation-corrected n-alkane ratios. n-Alkane modelling results for loess layers, paleosols and an in-filled paleochannel dated to ~ 60–32 ka suggest that up to ~ 50% of the n-alkanes were derived from deciduous trees or shrubs. This finding is in agreement with the abundant occurrence of wood fragments and indicates a highly variable and dynamic landscape dominated by tundra shrubland. On the other hand, deciduous trees or shrubs did not contribute significantly to the soil organic matter in the late Weichselian loess layers and the intercalated Gelic Gleysols (~ 32–18 ka).     

The Regensburg Model: reference values for the (I)NDCs based on converging per capita emissions†

A core question still remains after the Paris Agreement: who receives how much of the remaining CO₂ budget (resource/burden/effort sharing), so that the increase in the global average temperature is kept to well below 2°C above pre-industrial levels? If converging per capita emissions serve as a possible answer to this question, the discussion focuses primarily on the approach ‘Contraction and Convergence’ (C&C). The Regensburg Model now offers a further option for the mathematical implementation of converging per capita emissions. The authors identify features common to C&C and differences from C&C. They show that, of the convergence models they examined, the Regensburg Model is the most favourable option for industrialized countries.

Policy relevance

In politics, the concept of converging per capita emissions is often accepted at the abstract level. Civil society in particular can then take politicians at their word wherever they take values calculated using the Regensburg Model as points of reference; then prosperous developed countries in particular whose nationally determined contributions do not come up even to these reference values will find it difficult to justify their contributions.     

Seismicity and structural investigations of the Romanian Vrancea Region: Evidence for azimuthal variations of p-wave velocity and poisson's ratio

A study of the shallow and intermediate depth seismicity of the Romanian Vrancea region in the period 1964–1981 has been performed. The seismic events have been relocated by a standard location procedure using a regional velocity model. From the temporal and spatial distribution of the seismic activity, aspects of the seismicity before the large March 4, 1977 earthquake are treated, in particular the seismic gap in space and time prior to this event, found by Mârze (1979), which is critically discussed and revised. The concept of the precursor time/magnitude relationships of different authors is applied and its validity to the Vrancea region assessed. The hypocentral distribution shows that the intermediate depth seismic activity is confined to a small volume with dimensions of only some tens of kilometers. The results are interpreted in terms of the tectonics of the region. From an analysis of the travel-time residuals at different local stations, evidence for lateral velocity heterogeneities beneath the region is obtained e.g. a high velocity zone southeastwards of the Carpathian chain. Finally mean ratios, (i.e. Poisson's ratios), for various stations are calculated from P- and S-wave travel times. They show azimuthal variations of up to 6% for stations within the area where the intermediate seismic activity occurs in comparison with the station Focsani, situated eastwards in the Carpathian foredeeps. All these results are compatible with the plate tectonic concept for the Vrancea region, that is the subduction of an oceanic lithospheric slab under the Carpathian mountain arc, giving rise to such a highly active seismic zone.     

KINEMATICS OF QUATERNARY EXTENSION IN THE PAMIR

KINEMATICS OF QUATERNARY EXTENSION IN THE PAMIR1　BurtmanVS ,MolnarP .GeologicalandgeophysicalevidencefordeepsubductionofcontinentalcrustbeneaththePamir[J].SpecPapGeolSocAm ,1993,2 81:76 . 2　StreckerMR ,FrischW ,HamburgerMW ,etal.QuaternarydeformationintheEasternPamirs ,TadzhikistanandKyrgyzs tan[J].Tectonics,1995 ,14(5 ) :10 6 1～ 10 79.…     

Climate control on the evolution of Late Pleistocene alluvial‐fan and aeolian sand‐sheet systems in NW Germany

The Late Pleistocene was characterized by rapid climate oscillations with alternation of warm and cold periods that lasted up to several thousand years. Although much work has been carried out on the palaeoclimate reconstruction, a direct correlation of ice‐core, marine and terrestrial records is still difficult. Here we present new data from late Middle Pleniglacial to Lateglacial alluvial‐fan and aeolian sand‐sheet deposits in northwestern Germany. Records of Late Pleniglacial alluvial fans in central Europe are very rare, and OSL dating is used to determine the timing of fan aggradation. In contrast to fluvial systems that commonly show a delay between climate change and incision/aggradation, the small alluvial‐fan systems of the Senne area responded rapidly to climatic changes and therefore act as important terrestrial climate archives for this time span. The onset of alluvial‐fan deposition correlates with the climate change from warm to cold at the end of MIS 3 (29.3±3.2 ka). Strong fan progradation started at 24.4±2.8 ka and may be related to a period of higher humidity. The vertical stacking pattern of sedimentary facies and channel styles indicate a subsequrent overall decrease in water and sediment supply, with less sustained discharges and more sporadic runoffs from the catchment area, corresponding to an increasing aridity in central Europe during the Late Pleniglacial. Major phases of channel incision and fan aggradation may have been controlled by millennial‐scale Dansgaard–Oeschger cycles. The incision of channel systems is attributed to unstable climate phases at cold–warm (dry–wet) or warm–cold (wet–dry) transitions. The alluvial‐fan deposits are bounded by an erosion surface and are overlain by aeolian sand‐sheets that were periodically affected by flash‐floods. This unconformity might be correlated with the Beuningen Gravel Bed, which is an important marker horizon in deposits of the Late Pleniglacial resulting from deflation under polar desert conditions. The deposition of aeolian sand‐sheet systems (19.6±2.1 to 13.1±1.5 ka) indicates a rapid increase in aridity at the end of the Late Pleniglacial. Intercalated flash‐floods deposits and palaeosols (Finow type) point to temporarily wet conditions during the Lateglacial. The formation of an ephemeral channel network probably marks the warm‐cold transition from the Allerød to the Younger Dryas.     

Social and ecological constraints on decision making by transhumant pastoralists: a case study from the Moroccan Atlas Mountains

Transhumant pastoralism is an important activity in southern Morocco. Migration pattern of transhumant pastoralists can be affected by physical factors (e.g. droughts and diseases) or socioeconomic factors (e.g. schooling options for children and migration costs). We studied the spatio-temporal rangeland usage of the three tribes Ait Mgoun, Ait Zekri, and Ait Toumert in the south-central Atlas region with a two-fold approach. First, we tracked the migration movements of one representative transhumant herd using the Advanced Research and Global Observation Satellite (ARGOS) collars, which record coordinates from satellite signals. Second, we interviewed herders to obtain information about general grazing practices of the respective tribe and to gain more direct information on motivations underlying decisions. For each tribe we observed small-, medium- and large-scale movements. We found that the most important drivers of migration decisions were seasonal fodder availability and weather conditions in combination with herd-specific risk and cost assessment, as well as personal factors. In conclusion, general migration patterns vary in time, both between and within the tribes, but according to a regulatory framework. Moreover, it appears that both the customary rules and its flexible adaptation to physical constraints are generally beneficial in terms of conservation of the arid and semiarid rangeland resources.