The MgCr2O4–MgFe2O4 solid solution series: effects of octahedrally coordinated Fe3+ on T–O bond lengths

The influence on the spinel structure of Fe³⁺ → Cr substitution was studied in flux-grown synthetic single crystals of the magnesiochromite–magnesioferrite (MgCr₂O₄–MgFe₂O₄) solid solution series. Samples were analysed by single-crystal X-ray diffraction, electron microprobe analyses, optical absorption and Mössbauer spectroscopy. With the exception of iron-poor samples (3–12 mol-% MgFe₂O₄), optical absorption and Mössbauer spectra show that iron occurs almost exclusively as trivalent Fe in the present samples. A very intense and broad absorption band at ca 7,800 cm^?1 dominates the optical absorption spectra of samples with higher Fe-contents. The appearance of this band is related to a distinct structural disorder of Fe³⁺ and a development of magnetic ordering as demonstrated by Mössbauer spectra. Profound composition-related changes are observed in the Mössbauer spectra, which are magnetically unsplit in the range 2–41 mol-% magnesioferrite, but become magnetically split in the range 59–100 mol-% magnesioferrite. Structural parameters a ₀ and M–O increase with magnesioferrite content and inversion degree, while u and T–O decrease. Our study confirms the previously reported (Lavina et al. 2002) influence of Fe³⁺ at the M site on T–O bond lengths in the spinel structure.     

Long-term summer temperature variations in the Pyrenees

Two hundred and sixty one newly measured tree-ring width and density series from living and dry-dead conifers from two timberline sites in the Spanish Pyrenees were compiled. Application of the regional curve standardization method for tree-ring detrending allowed the preservation of inter-annual to multi-centennial scale variability. The new density record correlates at 0.53 (0.68 in the higher frequency domain) with May–September maximum temperatures over the 1944–2005 period. Reconstructed warmth in the fourteenth to fifteenth and twentieth century is separated by a prolonged cooling from ∼1450 to 1850. Six of the ten warmest decades fall into the twentieth century, whereas the remaining four are reconstructed for the 1360–1440 interval. Comparison with novel density-based summer temperature reconstructions from the Swiss Alps and northern Sweden indicates decadal to longer-term similarity between the Pyrenees and Alps, but disagreement with northern Sweden. Spatial field correlations with instrumental data support the regional differentiation of the proxy records. While twentieth century warmth is evident in the Alps and Pyrenees, recent temperatures in Scandinavia are relatively cold in comparison to earlier warmth centered around medieval times, ∼1450, and the late eighteenth century. While coldest summers in the Alps and Pyrenees were in-phase with the Maunder and Dalton solar minima, lowest temperatures in Scandinavia occurred later at the onset of the twentieth century. However, fairly cold summers at the end of the fifteenth century, between ∼1600–1700, and ∼1820 were synchronized over Europe, and larger areas of the Northern Hemisphere.     

Atlantic surface water inflow to the Nordic seas during the Pleistocene–Holocene transition (mid–late Younger Dryas and Pre‐Boreal periods, 12 450–10 000 a BP)

The inflow of Atlantic Water to the Nordic seas from mid–late Younger Dryas to earliest Holocene (12 450–10 000 a BP) is reconstructed on the basis of a high‐resolution core (LINK14) from 346 m water depth on the east Faroe shelf. We have analysed the distribution of planktic and benthic foraminifera, stable isotopes and ice‐rafted debris (IRD), and calculated absolute temperatures and salinities by transfer functions. During the investigated time period there was almost continuous inflow of Atlantic Water to the Nordic seas. Deposition of IRD during the mid–late Younger Dryas and Pre‐Boreal coolings indicates the presence of melting icebergs and that summer sea surface temperatures were low. The east–west temperature gradient across the Faroe–Shetland Channel was much steeper than today. The cold conditions around the Faroe Islands are attributed to stronger East Greenland and East Icelandic currents than at present. The near‐continuous inflow of Atlantic Water is consistent with published evidence suggesting that deep convection took place in the Nordic seas, although the convection sites probably had shifted to a more easterly position than at present. Around the time of deposition of the Saksunarvatn Tephra c. 10 350 a BP, sea surface temperatures increased to the present level. Copyright © 2011 John Wiley & Sons, Ltd.     

Nahrungsfauna und Kanadische Seeforelle in Berner Gebirgsseen

Ohne Zusammenfassung English Summary: Lake trout and its prey fauna in Swiss mountain lakes) Die Nahrungsfauna wurde vonGrim⇘s, Nahrungs?kologie und Wachstum der Fische vonNilsson bearbeitet.     

Exploring changes in hydrogeological risk awareness and preparedness over time: a case study in northeastern Italy

ABSTRACT

Hydrogeological hazards are increasingly causing damage worldwide due to climatic and socio-economic changes. Building resilient communities is crucial to reduce potential losses. To this end, one of the first steps is to understand how people perceive potential threats around them. This study aims at exploring how risk awareness of, and preparedness to, face hydrological hazards changes over time. A cohort study was carried out in two villages in the northeastern Italian Alps, Romagnano and Vermiglio, affected by debris flows in 2000 and 2002. Surveys were conducted in 2005 and 2018, and the results compared. The survey data show that both awareness and preparedness decreased over time. We attribute this change to the fact that no event had occurred in a long time and to a lack of proper risk communication strategies. The outcomes of this study contribute to socio-hydrological modelling by providing empirical data on human behaviour dynamics.     

Neue Gesichtspunkte zum schwedischen Präkambrium

Zusammenfassung Seit dem Anfang dieses Jahrhunderts sind mehrere Versuche gemacht worden, die Gesteine des baltischen Schildes nach Bildungs- und Deformationsperioden (Zyklen, Orogenesen) einzuteilen. Heute sprechen die meisten schwedischen Petrologen von Präsvekofennokarelium (oder Präsvekokarelium; > 2500 M. J.), Svekofennokarelium (oder Svekokarelium; 1750–2500 M. J.), Gotium (1150 bis 1750 M. J.) und Dalslandium (900–1150 M. J.). Das Svekofennokarelium scheint mindestens zwei Orogenesen zu umfassen — die svekofennidische (1800–2000 M. J.) und eine ältere Orogenese. Dagegen soll das Gotium hauptsächlich eine anorogene Ära sein.Die meisten der gotischen Gesteine sind Vulkanite und Granitoide. Da unter den Vulkaniten Ignimbrite häufig sind, interpretiert man sie als anatektische Gesteine, die vom svekofennidischen Orogen stammen, was auch für die Mehrzahl der gotischen Granitoide gilt. Die Eruption der Vulkanite hat im Zeitraum zwischen 1600 und 1750 M. J. stattgefunden, die Intrusion der Granitoide zwischen 1450 und 1750 M. J. (nachWelin u. Mitarb.). Die jüngsten gotischen Granitoide sind die Karlshamn-Spinkamåla-Halengranite in Blekinge und Schonen sowie die zweite Generation der Linagranite in Norrbotten und Lappland. Im Gegensatz zu den anderen gotischen Graniten werden diese von beträchtlichen Pegmatitintrusionen begleitet und können deshalb als digitale palingenetische Produkte eines postsvekofennidischen Orogens gedeutet werden.Während des Gotiums haben auch Eruptionen basischer Magmen stattgefunden, was besonders auf den späteren Teil des Zeitabschnittes, das Jotnium (1150 bis 1300 M. J.), zutrifft, als die anatektischen Magmen erschöpft waren. Die jotnischen Basite sind Diabase mit wenig Chrom ( 0,006% in normalen Gesteinen). Im südlichen Schweden kommt eine ältere Diabasart mit schwarz pigmentiertem Plagioklas (Hyperit) vor, die um 1250 M. J. tektonisiert wurde, während die jüngeren jotnischen Diabase keine tektonischen Veränderungen zeigen.Die jotnischen Sandsteine und Konglomerate sind vom Verfasser in Härjedalen, mittleres Schweden, untersucht worden und sind dort durch Einlagerungen jaspilitischer und tuffitischer Art gekennzeichnet. Die Gerölle des basalen Konglomerats zeigen marginale thermale Umwandlungen (Abb. 2). Es scheint darum, daß sich die subjotnische vulkanische Aktivität bis ins Jotnium fortgesetzt hat. Da einer der jüngsten subjotnischen Porphyre in Dalekarlien und Härjedalen 1670 M. J. alt ist und da eine Probe dalekarlischen jotnischen Sandsteins die Alterszahl 1185 M. J. ergeben hat, muß man mit einer beträchtlichen Länge der jotnischen Sedimentationsperiode rechnen.

---

Since the early twentieth several attempts have been made to divide the rocks of the Baltic shield into periods of development and deformation, viz. geological cycles or orogenies. Nowadays most Swedish petrologists distinguish between the pre-Svecofennokarelian (or the pre-Svecokarelian; > 2,500 M. Y.), the Svecofennokarelian (or the Svecokarelian; 1,750–2,500 M. Y.), the Gothian (1,150 –1,750 M. Y.), and the Dalslandian (900–1,150 M. Y.). The Svecofennokarelian seems to comprise at least two orogenies — the Svecofennian one (1,800–2,000 M. Y.) and an older one. The Gothian, on the contrary, is essentially an anorogenic era.Most Gothian rocks are acid volcanics and granitoids. Among the former ignimbrites are common. They have thus been interpreted as anatectic rocks originating from the Svecofennian orogeny, as well as have most Gothian granitoids, too. The extrusion of volcanics have ranged between 1,600 and 1,750 M. Y., the intrusion of granitoids between 1,450 and 1,750 M. Y., according to Eric Welin and co-workers. Youngest among the latter are the Karlshamn-Spinkamåla-Halen granites in Blekinge and Scania as well as the second generation of Lina granite in Norrbotten and Lappland. Contrary to the other Gothian granitoids these are associated with considerable amounts of pegmatite and could accordingly be suspected to represent distal palingenic products of an orogeny younger than the Svecofennian one.During the Gothian basic magma has also erupted, especially in Jotnian time, near the end of the era (1,150–1,300 M. Y.), when the anatectic magma was exhausted. The Jotnian basites are dolerites poor in chromium (60 p.p.m. in undifferentiated rocks). In Southern Sweden an older variety of dolerite with black-pigmented plagioclase (hyperite) was tectonized about 1,250 M. Y. ago, whereas the younger dolerites have escaped tectonization.The Jotnian sandstone and conglomerate have been examined by the writer in Härjedalen, Central Sweden, and have there been shown to contain basal intercalations of jaspilite and tuffites. Furthermore, the pebbles of the basal conglomerates have marginal rims indicating thermal alterations (Fig. 2). The sub-Jotnian volcanic activity seems thus to have proceeded into the Jotnian. As one of the youngest sub-Jotnian porphyries in Dalecarlia and Härjedalen has given the figure 1,670 M. Y. and one sample of Dalecarlian Jotnian sandstone has an age as low as 1,185 M. Y., the period of sedimentation ought to have been very long.

---

Résumé Dès le début du XXème siècle, ont été faites plusieurs tentatives de subdivision des roches du Bouclier baltique en périodes de mise en place et de déformation, c'est-à-dire en cycles géologiques ou orogénèses. Actuellement, la plupart des pétrographes suédois font la distinction entre le Pré-Svécofennocarélien (ou Pré-Svécocaré lien: > 2,500 millions d'années), le Svécofennocarélien (ou Svécocarélien: 1,750–2,500 M. A.), le Gothien (1,150–1,750 M. A.) et le Dalslandien (900–1,150 M. A.). Le Svécofennocarélien semble comprendre au moins deux orogénèses: l'orogénèse svécofennique (1,800–2,000 M. A.) et une autre plus ancienne. Par contre, le Gothien ne correspond qu'à une seule orogénèse.Les roches du Gothien sont en majorité des granitoïdes et des Vulcanites acides; parmi ces dernières prédominent des ignimbrites: Elles ont été considérées comme des roches anatectiques provenant de l'orogénèse svécofennique. La plupart des roches granitoïdes du Gothien auraient la même origine. L'extrusion des Vulcanites a eu lieu dans une période de 1,750 à 1,600 M. A., l'intrusion des granitoïdes s'est produite entre 1,750 et 1,450 M. A. (d'après Eric Welin et ses collaborateurs). Parmi ces dernières roches, les plus jeunes sont les granites de Karlshamn-Spinkamåla-Halen en Blekinge et en Scanie ainsi que la deuxième génération du granite de Lina en Bothnie septentrionale et en Laponie. Contrairement aux autres roches granitoïdes du Gothien, celles-ci sont associées à de grandes quantités de pegmatites et pourraient, par conséquent, être considerées comme les produits palingénétiques provenau d'une orogénèse plus jeune que l'orogénèse svécofennique.Durant le Gothien — plus précisément en fin du Jotnien (1,150–1,300 M. A.) lorsque le magma anatectique s'éleva — ont fait éruption des masses magmatiques basiques. Les roches basiques du Jotnien sont des dolorites pauvres en chrome ( 60 ppm teneur en chrome des roches quelconques). En Suède méridionale, une variété plus ancienne de dolérites, avec plagioclase à pigment noir (hypérite), a été tectonisée il y a environ 1,250 millions d'années, tandis que les dolérites plus récentes n'ont subi aucune déformation.Les grès et les conglomérats du Jotnien, étudiés par l'auteur dans la vallées de Härje (Härjedalen) en Suède centrale, comportent des intercalations basales de jaspilites et de tuffites. De plus, les galets du conglomérat basal présentent des modifications corticales indiquant des altérations thermiques: l'activité volcanique sub-jotnienne semblerait donc s'être prolongée jusque dans le Jotnien. Comme l'une des plus jeunes porphyrites sub-jotniennes de Dalécarlie et de Härjedalen date de 1,670 millions d'années et qu'un échantillon de grès jotnien de Dalécarlie remonte à 1,185 millions d'années, il est possible d'affirmer que la période de sédimentation a dû être très longue.

---

( ), svekofennokarelium ( Präsvekokarelium 2500 ), Svekofennokarelium ( Svekokarelium; 1750–2500 ), Gotium (1150–1750 ) Dalslandium (900–1150 ). Svekofennokarelium , , - , : Svekofennidische (1800–2000 ) — . Gotium, , . Gotium . . . , , , Svekofennidmm'a, Gotium. 1600–1750 , — 1450–1750 ( WELIN .). KarlshamnSpmkamala-Halenga Blekinge Schonen, Lina** Norrbotten . , , postsvekofennidischen . , — Gotium (1150–1300 ), . Jotnium ( < 0,006 %) (), 1250 , Jotnium . Jotnium Härjedalen, , . (. 2). , , Jotnium, Jotnium. . . Dalekarlien Härjedalen 1670 , Dalekarlien — 1185 , Jotnium .

     

Optical Absorption Spectra of (Mg,Fe)SiO3 Silicate Perovskites

Electronic absorption spectra have been measured at room temperature and pressure for polycrystalline samples of (Mg, Fe)SiO₃ silicate perovskites synthesized by multi-anvil device. One strong near-infrared band at about 7000 cm^-1 and several weak bands in the visible region were found. The near-infrared band at 7000 cm^-1 is assigned to a spin-allowed transition of Fe²⁺ at the 8–12 coordinated site in perovskite. However, definite assignments of the weak bands in the visible region are difficult because of their low intensities and the scattering effect at the gain boundaries. Crystal field calculations for Fe²⁺ at different sites in perovskite have been carried out based on the crystal structure data. The results agree with the assignment of Fe²⁺ to the 8–12 coordinated site in perovskite. Crystal field stabilization energy of Fe²⁺ with coordination number of 8 in perovskite is 3332 cm^-1 which is small compared to the octahedral site of magnesiowüstite (4320 cm^-1), another important lower-mantle mineral.     

Earthquake magnitude — recent research and current trends

The magnitude recommendations adopted by the IASPEI Assembly at Zürich in 1967 have had both a stabilizing and a stimulating effect on magnitude determinations and related research. From 1967 onwards, one magnitude research paper has appeared on the average almost every week, thus making this parameter the most studied one in seismology. New facilities and more accurate methods, e.g., concerning instrumental equipment and interpretation techniques, have made it possible to improve earlier achievements. The application of magnitude scales has been extended in all respects, e.g., with regard to epicentral distances, focal depths, wave types and wave periods. Magnitude—frequency relations have become the most investigated equations within seismology, observationally as well as theoretically. They have wide applications, e.g., for estimating the maximum magnitudes of future earthquakes — an important item in earthquake prediction. The magnitudes provide significant information on other source parameters, such as wave energy, fault length, seismic moment. Relations between different types of magnitude yield valuable information on source properties. For instance, relations between magnitudes based on body and surface waves are used for efficient discrimination between earthquakes and underground explosions. It is our purpose to review the magnitude development in the post-Zürich period (1967–1980), partly for geologists, tectonophysicists and engineers, who need an overview, partly for seismologists, who need an introduction to an overwhelmingly comprehensive literature.     

Growth of Mytilus edulis in net bags transferred to different localities in a eutrophicated Danish fjord

The growth rate has been measured in Mytilus edulis transferred in net bags to seven localities in the brackish Danish fjord, Limfjorden, in which certain areas are heavily eutrophicated. The increase in shell length, shell weight and flesh body weight was measured after growth periods of 14–18 days. The increase in, e.g., flesh dry weight ranged from twice the start weight to a four-fold increase of the start weight. The net growth efficiencies were estimated to be between 54 and 73%. Algal concentration was in no case the limiting growth factor, but low growth rates were observed in areas with seasonal oxygen depletion and release of toxic H₂S from the sediments. It is suggested that measurements of actual growth in M. edulis can be a useful technique in the study of biological effects in marine recipients.     

Fracture risk estimation for Swedish earthquakes

For Swedish earthquakes, the average magnitude increases gently with the focal depth, whereas the seismic wave energy exhibits significant maxima at 15, 23 and 28 km depth. The earthquake fracture risk is estimated to be about 10^?6 for an underground storage facility in a carefully selected site.