Calc-alkaline volcanic rocks from NW Sardinia: Evaluation of a fractional crystallization model

The volcanic centre of Monte Seda Oro, N. W. Sardinia, representative of a Cenozoic calc-alkaline andesitic suite of rocks is composed of a variety of rocks ranging from high alumina basalts to dacites. The minerals of basaltic, andesitic and dacitic rocks show only limited variation in chemical composition. The geochemical data suggest that the various rock-types are related by a crystal-liquid fractionation. Least-squate numerical calculations, using major element data, support the derivation of andesites with SiO₃ content ranging from 53.8 to 59.0% from basalts having about 48.7% of SiO₂ by low pressure crystal fractionation of the phenocryst phases present in these rocks. However, the origin of dacites cannot be readily explained by this mechanism.     

Palaeogeography and tectonic structure of allochthonous units in the German part of the Rheno-Hercynian Belt (Central European Variscides)

New information on palaeogeography, orogenic evolution, tectonic structure, and boundaries of allochthonous units in the Rheno-Hercynian Belt is based on provenance analyses of clastic sediments and field studies. ⁴⁰K/⁴⁰Ar dating of detrital muscovites proved to be a particularly useful method because Cadomian, Caledonian and Early Variscan provenances of detrital material can be distinguished. Cadomian muscovite cooling ages are restricted to allochthonous units whereas Caledonian ages dominate within par-autochthonous and shortly displaced allochthonous units. The largest and uppermost preserved nappe, the Gießen-Harz Nappe, is derived from an oceanic flysch basin, which was not reached by Caledonian detritus. The other allochthonous units form a duplex-like structure sandwiched between the Gießen-Harz Nappe and par-autochthonous units at its base. The thick and heterogeneous roof- and floor-thrusts of this structure were previously often misinterpreted as olistostromes. The northern margin of allochthonous units is the steeply dipping Hörre-Gommern Zone. It consists of three sub-units derived from deep-water areas between the shelf at the southern margin of the Old Red Sandstone Continent and an oceanic basin to the south. The southeastern part of the duplex-structure (Harzgerode Zone) shows close affinities to Armorican terranes.     

Stability of Mg-Ca carbonates

In this article a diagram is constructed in which the stability of Mg-Ca-carbonates can be represented as a function of only two parameters. By means of this diagram the relative stability of the various carbonates can be easily compared.     

白刺不同果实性状的遗传力估计及优良亲本选择

亲子回归法研究白刺果实不同性状遗传力的结果表明,果径、果形、果色、果味、核形和果实出肉率等性状指标的遗传力较高,说明这些性状变异的遗传贡献较大,可作为白刺果实类型划分的主要指标,其中果径、果味和出肉率可作为白刺果实品质评价和优良亲本选择的主要依据。以果径和出肉率为指标,用家系选择法选择优良亲本可获得较大的遗传增益,且两指标选择的亲本一致,选择效果满意。     

A continental analysis of correlations between tree patterns in African savannas and human and environmental variables

This study analyses possible relationships between natural processes taking place in savannas and the tree patterns found in savannas. This can lead to new hypotheses about which processes are driving savanna physiognomy. To do so tree patterns were quantified for African savannas from historical aerial photographs applying frequently used landscape metrics. Also, additional data for these areas were collected to quantify the processes taking place at these locations. Correlations between tree pattern indices and explaining factors were analysed. We found a negative trend between tree cover and density of sheep and goats, but no relationship between tree cover and density of cattle, suggesting that small livestock have an effect on tree cover, but that larger livestock (or obligate grazers) do not. Also, a positive correlation between human population density and tree cover was found. Possible explanations for the found relations are discussed. Subsequent ways to analyse the latter correlation are discussed, and the potential of the presented historical database of aerial photographs is highlighted.     

Development of a modelling methodology for simulation of long-term morphological evolution of the southern Baltic coast

The Darss–Zingst peninsula at the southern Baltic Sea is a typical wave-dominated barrier island system which includes an outer barrier island and an inner lagoon. The formation of the Darss–Zingst peninsula dates back to the Littorina Transgression onset about 8,000 cal BP. It originated from several discrete islands, has been reshaped by littoral currents, wind-induced waves during the last 8,000 years and evolved into a complex barrier island system as today; thus, it may serve as an example to study the coastal evolution under long-term climate change. A methodology for developing a long-term (decadal-to-centennial) process-based morphodynamic model for the southern Baltic coastal environment is presented here. The methodology consists of two main components: (1) a preliminary analysis of the key processes driving the morphological evolution of the study area based on statistical analysis of meteorological data and sensitivity studies; (2) a multi-scale high-resolution process-based model. The process-based model is structured into eight main modules. The two-dimensional vertically integrated circulation module, the wave module, the bottom boundary layer module, the sediment transport module, the cliff erosion module and the nearshore storm module are real-time calculation modules which aim at solving the short-term processes. A bathymetry update module and a long-term control function set, in which the ‘reduction’ concepts and technique for morphological update acceleration are implemented, are integrated to up-scale the effects of short-term processes to a decadal-to-centennial scale. A series of multi-scale modelling strategies are implemented in the application of the model to the research area. Successful hindcast of the coastline change of the Darss–Zingst peninsula for the last 300 years validates the modelling methodology. Model results indicate that the coastline change of the Darss–Zingst peninsula is dominated by mechanisms acting on different time scales. The coastlines of Darss and the island of Hiddensee are mainly reshaped by long-term effects of waves and longshore currents, while the coastline change of the Zingst peninsula is due to a combination of long-term effects of waves and short-term effects caused by wind storms.     

Rainfall trends in the Brazilian Amazon Basin in the past eight decades

Rainfall series at 18 stations along the major rivers of the Brazilian Amazon Basin, having data since 1920s or 1930s, are analyzed to verify if there are appreciable long-term trends. Annual, rainy-season, and dry-season rainfalls are individually analyzed for each station and for the region as a whole. Some stations showed positive trends and some negative trends. The trends in the annual rainfall are significant at only six stations, five of which reporting increasing trends (Barcelos, Belem, Manaus, Rio Branco, and Soure stations) and just one (Itaituba station) reporting decreasing trend. The climatological values of rainfall before and after 1970 show significant differences at six stations (Barcelos, Belem, Benjamin Constant, Iaurete, Itaituba, and Soure). The region as a whole shows an insignificant and weak downward trend; therefore, we cannot affirm that the rainfall in the Brazilian Amazon basin is experiencing a significant change, except at a few individual stations. Subregions with upward and downward trends are interspersed in space from the far eastern Amazon to western Amazon. Most of the seasonal trends follow the annual trends, thus, indicating a certain consistency in the datasets and analysis.     

A spatiotemporal calculus for reasoning about land-use trajectories

Earth observation images are a powerful source of data about changes in our planet. Given the magnitude of global environmental changes taking place, it is important that Earth Science researchers have access to spatiotemporal reasoning tools. One area of particular interest is land-use change. Using data obtained from images, researchers would like to express abstractions such as ‘land abandonment’, ‘forest regrowth’, and ‘agricultural intensification’. These abstractions are specific types of land-use trajectories, defined as multi-year paths from one land cover into another. Given this need, this paper introduces a spatiotemporal calculus for reasoning about land-use trajectories. Using Allen’s interval logic as a basis, we introduce new predicates that express cases of recurrence, conversion and evolution in land-use change. The proposed predicates are sufficient and necessary to express different kinds of land-use trajectories. Users can build expressions that describe how humans modify Earth’s terrestrial surface. In this way, scientists can better understand the environmental and economic effects of land-use change.