Growth rhythms,evolution of the Earth's interior,and origin of the Metazoa

Growth patterns preserved in the accretionary skeletons of fossils provide the only known method of directly measuring the rate of the Earth's rotation in the distant past. From seasonal and tidal growth patterns of fossils, one can determine the number of days per year and per month, respectively, in the distant past. Together, these values can be used to distinguish the effects of moment of inertia changes on the length of day from those of tidal friction. When the Metazoan accretionary skeleton originated in the Late Precambrian-Cambrian, the length of day determined from fossils was approximately 19 hr. This value requires that density differentiation of the Earth was essentially complete well the end of the Precambrian. The growing length of day, as well as prior differentiation of oxygenated outer layers (atmosphere, hydrosphere, and crust) from the Earth's dense layers within, were prerequisites for the origin of the Metazoa. Circadia (=approximatelly 24 hr) rhythms in living Metazoa do not readily adapt to environemtal cycles less than about 19hr. Prokaryotes generally lack circadian rhythms because their generation times are less than a day; prokaryotes were well-adapted to Precambrian days less than 19 hr duration, as well as to oxygen-poor environments. As the length of day increased to 19 hr or more during the Late Precambrian, eukaryotes with life spans substantially longer than a day (and consequently with an ability to postpone energyusage beyond a day) evolved. During the Phanerozoic, moment of inertia changes were relatively small, so that lunar tidal friction became the most important cause of changing length of day. However, some researchers believe that even the former may have left an imprint on fossil growth patterns. This conclusion is difficult to confirm, given the uncertainties of growth pattern analyses. But facies-by-facies comparisons of growth patterns can help reduce this uncertainty: presumed tidal growth patterns should change systematically with depth of habitat, for example. Preliminary analyses for Late Ordovician brachiopods from Indiana suggest that this approach will be productive, and may help evaluate the suggestion that the Late Ordovician-Silurian was a time of unusual evolution of the Earth's moment of inertia during the Phanerozoic.     

Radiophysical investigations of sea roughness (radiooceanography) at the Ukrainian Academy of Sciences

Experiments on the scattering of radio waves in the range 200 m to 3 cm from a rough sea surface are described. Amplitude, frequency, and space-time characteristics of scattered radio signals at different states of the sea surface are presented. It is shown that the problem of the short and medium wave scattering from the sea can be solved by the perturbance method. In this case the mechanism of scattering is of "resonant" character. The intensity of the backscatter signals is proportional to the density of the spatial spectrum on the half-length of the radio waves. The high frequency radio wave scattering is well described by a two-scale model of the scattering surface, "ripple on the large wave." The intensity of scattered radio signals is also proportional to the spectrum density of "ripples" whose length is approximately equal to half a radio wave. The effect of the large waves is to modulate the amplitude of a scattered radio signal and to broaden its frequency spectrum. Methods of solution of the reverse problem were considered. This allowed determination of parameters of sea roughness by characteristics of scattered radio signals. The principles of design of the corresponding equipment are described.     

Hydro-economic models: Concepts, design, applications, and future prospects

Future water management will shift from building new water supply systems to better operating existing ones. The variation of water values in time and space will increasingly motivate efforts to address water scarcity and reduce water conflicts. Hydro-economic models represent spatially distributed water resource systems, infrastructure, management options and economic values in an integrated manner. In these tools water allocations and management are either driven by the economic value of water or economically evaluated to provide policy insights and reveal opportunities for better management. A central concept is that water demands are not fixed requirements but rather functions where quantities of water use at different times have varying total and marginal economic values. This paper reviews techniques to characterize the economic value of water use and include such values in mathematical models. We identify the key steps in model design and diverse problems, formulations, levels of integration, spatial and temporal scales, and solution techniques addressed and used by over 80 hydro-economic modeling efforts dating back 45-years from 23 countries. We list current limitations of the approach, suggest directions for future work, and recommend ways to improve policy relevance.     

Assessment of marine benthic quality change in gradients of disturbance: Comparison of different Scandinavian multi-metric indices

Three multi-metric benthic macrofauna indices were used to assess marine benthic ecological quality status (EcoQS) according to the European Water Framework Directive, in seven pollution gradients mainly, western Scandinavia. The impacts included organic load, hypoxia, metals, urban effluents and physical disturbance. The indices responded in a similar threshold fashion, irrespective of impact factor identity. Usually, the border between Good and Moderate EcoQS (G/M), is determined as some deviation from a reference situation. References, however, are difficult to find. An alternative procedure is described to estimate the G/M border, not requiring reference data. Thresholds, where faunal structure deterioration commences, were identified from non-linear regressions between indices and impact factors. Index values from the less impacted side of the thresholds were assumed to come from environments of Good and High EcoQS, and the 5th percentile of these data, was defined as the G/M border. Estimated G/M borders compared well with previous studies.     

The effects of sulfidation and oxidation during metamorphism on compositionally varied rocks adjacent to the Bleikvassli Zn–Pb–(Cu) deposit, Nordland, Norway

Petrographic, electron microprobe, and bulk-rock geochemical analyses indicate that the distribution and composition of ferromagnesian silicates (biotite, garnet, and staurolite) in and adjacent to the metamorphosed Bleikvassli Zn–Pb–(Cu) volcanogenic massive sulfide deposit, Norway, are dependent upon the competing effects of f O₂–f S₂ and host-rock composition. The enrichment in magnesium content of these silicates within the orebody and at distances of as much as 5–10 m away is due to the increased f O₂ and f S₂ conditions imposed on the silicates in zones subject to minor hydrothermal alteration during regional metamorphism. Alternatively, within pelitic country rocks at distances >5–10 m from ore, the host-rock chemistry controls the composition of metamorphic silicate minerals. Also, country rocks within a few meters of ore are distinguished by the common presence of zinc-bearing staurolite (up to 9 wt% ZnO) coexisting with biotite ± garnet. Rocks in the Bleikvassli deposit were hydrothermally enriched in zinc and fluorine prior to metamorphism. The fluorine resides mainly in biotite, which is an additional contributing factor to the magnesium enrichment of that mineral due to Fe²⁺–F avoidance. Our inference that the sulfidation–oxidation halo around the Bleikvassli ore deposit is only meters in width contrasts with the view of Maiga (1983), who proposed the effects of sulfidation could be identified at distances >159 m from ore. It is evident that the delineation of a sulfidation–oxidation halo bordering a metamorphosed massive sulfide deposit must be done carefully in order to discriminate between the effects due to variations in primary rock composition versus those resulting from a sulfur and oxygen fugacity gradient between the massive sulfides and the sulfur-poor country rocks. Received: 1 March 1998 / Accepted: 3 May 2000     

Chemostratigraphy of upper Jurassic reservoir sandstones,Danish Central Graben,North Sea

A chemostratigraphic study of Upper Jurassic sandstones in the northern Danish Central Graben has been undertaken within the framework of a well-defined stratigraphic/sedimentological model based particularly on cored well sections. Two reservoir sandstone units are recognised, the transgressive marginal marine to shoreface sandstone of the Gert Member and the regressive to transgressive shoreface sandstone of the Ravn Member. Both members belong to the Heno Formation, which is equivalent to the Fulmar Formation (UK) and the Ula Formation (Norway).     

Pre-orogenic upper crustal softening by lower greenschist facies metamorphic reactions in granites of the central Pyrenees

Pre-kinematic greenschist facies metamorphism is often observed in granites and basement units of mountain belts, but rarely dated and accounted for in orogenic cycle reconstructions. Studying pre-kinematic alteration is challenging because of its usual obliteration by subsequent syn-kinematic metamorphism often occurring at conditions typical of the brittle–ductile transition. It is, however, to be expected that pre-kinematic alteration has major implications for the rheology of the upper crust. In the 305 Ma-old Variscan basement of the Bielsa massif (located in the Axial Zone of the Pyrenees), successive fluid–rock interaction events are recorded in granites below 350°C. Combined microstructural and petrographic analysis, low-T thermobarometry and in situ U–Th/Pb dating of anatase, titanite and monazite show extensive pre-orogenic (pre-Alpine) and pre-kinematic alteration related to feldspar sericitization and chloritization of biotite and amphibole at temperatures of 270–350°C at 230–300 Ma. This event is followed by a second fluid–rock interaction stage marked by new crystallization of phyllosilicates at 200–280°C and is associated with the formation of mylonitic shear zones and fractures parallel to the shear planes. U–Pb anatase and monazite ages as well as the microtextural relationships of accessory minerals suggest an age for this event at 40–70 Ma, consistent with independent regional geology constraints. The Variscan basement was therefore softened at late to post-Variscan time, at least 150–200 Ma before the main Alpine shortening while Alpine-age compression (c. 35–50 Ma) leads to the formation of a dense net of mylonites. The associated deformation, both distributed at the scale of the Bielsa massif and localized at decametric scale in mylonitic corridors, precedes the strain localization along the major thrusts of the Axial Zone. The Bielsa massif is a good example where inherited, pre-orogenic upper crustal softening controls the deformation patterns in granitic basement units through low-grade metamorphic reactions.     

A local spatial decision support system for developing countries based on MCA,fuzzy sets and OWA – case study of a municipality in Cuba

This paper presents a Spatial Decision Support System for local governments of developing countries. It allows municipality government, enterprises, scientific community and civil society to address decision problems using GIS. The framework is supported by four modules of information technologies: Environmental Decision Support Database, Data Manipulation, Decision Support, and Mapping. A case study is presented covering the implementation of this framework in one municipality of Cuba. An example of land suitability planning for coconut crops is used to evaluate the system performance and usability. Results show local municipalities are able to use this framework to solve local decision problems using state of the art decision making even with low infrastructure development.