Australasian microtektites from Antarctica: XAS determination of the Fe oxidation state

The Fe oxidation state and coordination number of 29 impact glass spherules recently recovered from the Transantarctic Mountains (Antarctica) have been determined by X‐ray absorption near edge structure (XANES) spectroscopy. Based on geochemical, isotopic, and fission track data, these spherules are considered as microtektites from the Australasian tektite/microtektite strewn field. Their find location is the farthest so far discovered from the possible source crater region, and their alkali content is the lowest compared with other published data on Australasian microtektite glasses. The Fe³⁺/(Fe²⁺+Fe³⁺) ratio, determined from the analysis of the pre‐edge peak energy position and integrated intensity, is below 0.1 (±0.04) for all the samples, and is comparable to that of most tektites and microtektites from the Australasian strewn field. Also, the pre‐edge peak integrated intensity, which is sensitive to the average Fe coordination geometry, is comparable to that of other Australasian microtektites reported in the literature. The agreement of the Fe oxidation state and coordination number, between the Transantarctic Mountain microtektites (TAM) and the Australasian tektites and microtektites, further confirms the impact origin of these glass spherules and provides an independent suggestion that they represent a major extension southeastward of the Australasian strewn field. The fact that similar redox conditions are observed in tektites and microtektites within the Australasian strewn field regardless of the distance from the source crater area (up to approximately 11000 km) could be an important constraint for better understanding the different processes affecting microtektite formation and transport. The fact that the Fe oxidation state of microtektites does not increase with distance, as in the case of North American microtektites, means that thermal and redox histories of Australasian and TAM microtektites could differ significantly from those of North American microtektites.     

Analysis of occurrence patterns and biological factors of cetaceans based on long‐term and fine‐scale data from platforms of opportunity: Madeira Island as a case study

Management and conservation issues are addressed through the identification of areas of particular importance, which requires the acquisition of baseline information on species distribution and dynamics. These types of data are particularly difficult to obtain at high resolution for large marine vertebrates like cetaceans, given that dedicated surveys are complex and logistically expensive. This study uses daily presence–absence sighting data of cetaceans collected year‐round from whale‐watching boats to support the theory that fine‐scale data obtained from platforms of opportunity can provide valuable information on species occurrence and group dynamics. Data from 7,551 (daily) sightings comprising 22 species were collected from 3,527 surveyed days over 11 years (mean of 321 days per year, SD = 17) in the pelagic environment of Madeira Island. Cetaceans were observed on 92% of the surveyed days, and a mean of 15.4 (SD = 1.5), 8.2 (SD = 2.0) and 2.1 (SD = 1.2) species were recorded per year, month, and day, respectively. There were significant differences in the number of species per month (p < .001), with the highest diversity recorded in June. At least nine species, comprising 96% of all sightings, were found to use the Madeiran waters on a regular basis, such as the Atlantic spotted dolphin (Stenella frontalis), the short‐beaked common dolphin (Delphinus delphis), the bottlenose dolphin (Tursiops truncatus), and others featured in the Red List of the International Union for Conservation of Nature as Endangered, Vulnerable, and Data Deficient. In addition, 10 species were found to use the Madeiran waters for travelling, feeding, resting, socializing and calving, which suggests that the southern and southeastern waters of Madeira Island constitute an area of interest for cetaceans. This study characterizes the cetaceans’ community structure (occurrence, aggregation sizes, behaviours, proportion of calves, and inter‐specific relationships) of a poorly studied region, providing important information for managers. Finally, the advantages and limitations of using fine‐scale data from a type of platform of opportunity that is increasing along coastlines globally are discussed.     

Effects of coastal orientation and depth on the distribution of subtidal benthic assemblages

A better understanding of biological systems can only be gained if we understand what processes are important and how they operate to determine the distribution of organisms. Coastal orientation and depth can influence environmental conditions, including the degree of water motion and availability of light, which in turn may influence the horizontal and vertical patterns of organism distribution. Here, we used a mixed‐model design to examine the effects of coastal orientation and depth on the structure of benthic assemblages by comparing the abundance and distribution of macroalgae and invertebrates in shallow and deep waters on the opposing coasts of São Miguel. Generally, coastal orientation had little influence on the distribution of most taxa. In contrast, significant differences were generally associated with depth, although patterns were spatially variable at the scale of locations. This study suggests that depth, and processes operating at the scale of location, but not at the scale of the coast, have an important influence on these assemblages, and that failure to recognise such a scale of variability may hamper our ability to better understand the processes that structure these communities.     

Mafic inclusions in the silica-rich rocks of the Tolfa-Ceriti-Manziana volcanic district (Tuscan Province,Central Italy): Chemistry and mineralogy

Summary A chemical and mineralogical study of magmatic inclusions in the silica-rich rocks of the Tolfa-Ceriti-Manziana sector (Tuscan Province, Central Italy) shows that they can be grouped according to their degree of alkalinity. We distinguish: TCM latites (TCML) with an alkaline-potassic affinity; Ceriti latites (CL) with calc-alkaline affinity; and Manziana shoshonites and latites (MS-ML) with an affinity intermediate between alkaline and subalkaline. The latter are hybrid rocks originating from the mixing of two magmas with slightly different geochemical affinities.These magmas may represent liquids derived by partial melting of a heterogeneous mantle, metasomatized by a crustal source. The most alkaline magmas (TCML) are associated with the largest degree of metasomatism which, if more pronounced, could lead to the production of the potassic magmas of the Roman Province.

---

Mafische Einschlüsse in den Si-reichen Gesteinen des vulkanischen Distriktes von Tolfa-Ceriti-Manziana (Toskanische Provinz, Zentralitalien): chemie und mineralogie

Zusammenfassung Eine chemische und mineralogische Untersuchung der magmatischen Einschlüsse in den sauren Gesteinen des Tolfa-Ceriti-Manziana Sektors (Toskanische Provinz, Zentralitalien) zeigt, daß sie nach dem Grad der Alkalinitdt unterteilt werden können. Wir unterscheiden TCM latite (TCML) mit einer Alkali-Kalium Affinität; Ceriti Latite (CL) mit einer kalkalkalischen Affinität und Manziana Shoshonite und Latite (MS-ML) mit einer Affinität die zwischen alkalisch und subalkalisch liegt. Die Letztgenannten sind Mischgesteine, die durch die Mischung zweier Magmen mit verschiedenen geochemischen Affinitäten entstanden sind.Diese Magmen, die genetisch nicht mit den Wirtsgesteinen in Beziehung stehen, dürften Schmelzen repräsentieren, die auf teilweise Aufschmelzung eines heterogenen Mantels, der durch eine krustale Quelle metasomatisiert wurde, zurückgehen. Die am meisten alkalischen Magmen (TCML) sind mit dem höchsten Grad der Metasomatose assoziiert, der wiederum, wenn noch stärker entwickelt, zur Entstehung der kalireichen Magmen der römischen Provinz führen könnte.

---

---

With 9 Figures     

Projection of runoff characteristics as a response to regional climate change in a Central/Eastern European catchment

ABSTRACT

The impact of climate change on runoff characteristics is investigated for the Upper Tisza basin, in eastern Central Europe. For a reliable estimation of uncertainty, an appropriate stochastic weather generator is embedded into a Monte Carlo cycle capable of generating any large number of independent, equally probable, 100-year-long daily sequences of synthetic data with which a hydrological model is driven in order to obtain the hydrological responses to the meteorological data sequences. According to our results, a decrease of daily average runoff is likely to occur in the future in the Upper Tisza basin, especially in July and August. The occurrence of water levels below the critical low level is estimated to increase between July and October. Level-3 flood warnings are projected to be less frequent in the future; however, they will tend to be more severe than in the historical period.     

Analyzing the genesis, intensity, and tracks of western Mediterranean cyclones

Midlatitude cyclones are analyzed on a selected region covering most of southern Europe and the western part of the Mediterranean Sea (35–50°N, 10°W–25°E). On the basis of mean sea level pressure fields of the ECMWF (European Centre for Medium-range Weather Forecast) Reanalysis Dataset (ERA-40), detailed evaluation of Mediterranean cyclones is accomplished for the period between 1957 and 2002 on a 1° horizontal resolution grid. Cyclone centers are identified and their paths are tracked with a 6-h time step (using 00 UTC, 06 UTC, 12 UTC, and 18 UTC). Decadal, annual, and seasonal statistical analysis of cyclone tracks includes the study of the genesis, frequency, and activity of the Mediterranean cyclones as well as the variability of cyclone tracks. The results suggest that the cyclone frequency in the western Mediterranean region increased in summer and autumn, and decreased in winter and spring. A special belt-shaped area is identified, which plays a special role in cyclogenesis, and also, the cyclone tracks often remain within this belt. An overall decreasing trend is detected in winter and spring in the entire Mediterranean belt, while cyclone frequency increased in autumn. The largest positive and negative trend coefficients are identified in summer.     

The Taraklı Flysch in the Boyali area (Sakarya Terrane,northern Turkey): Implications for the tectonic history of the IntraPontide suture zone

In the Boyal? area, northern Turkey, the tectonic units of the ?stanbul–Zonguldak Terrane and the IntraPontide suture zone are thrust over the deposits at the top of the Sakarya Terrane, known as Tarakl? Flysch. It consists of Early Maastrichtian–Middle Paleocene turbidite and mass-gravity deposits, whose source mainly corresponds to the ?stanbul–Zonguldak Terrane, and, with a lesser extent, to the IntraPontide suture zone. These deposits were sedimented in a foredeep basin developed during the convergence between Sakarya and Eurasian continental microplates. In the Late Paleocene–Early Eocene time span, the Tarakl? Flysch was deformed (D1 phase) during the closure of the foredeep basin. In the Miocene time, the strike-slip tectonics (D2 phase) related to the North-Anatolian fault produced further deformations of the Tarakl? Flysch.     

Hydrological regimes in different slope environments and implications on rainfall thresholds triggering shallow landslides

Natural Hazards - Assessing hazard of rainfall-induced shallow landslides represents a challenge for the risk management of urbanized areas for which the setting up of early warning systems, based...