Late glacial and early Holocene hydroclimate variability in northwest Iran (Talesh Mountains) inferred from chironomid and pollen analysis

We reconstructed the paleohydrologic and climatic history of the Lake Neor region, NW Iran, from the end of the late glacial to the middle Holocene (15,500–7500 cal yr BP). Subfossil chironomid and pollen assemblages in a sediment core from a peatland located south of Lake Neor enabled identification of four main hydrologic phases. The period 15,500–12,700 cal yr BP was characterized by a relatively dry climate with an open landscape, suggested by the abundance of Irano-Turanian steppe plants (e.g. Amaranthaceae, Artemisia and Cousinia). Dominance of several shallow-water and semi-terrestrial chironomid taxa (e.g. Pseudosmittia, Smittia/Parasmittia and Paraphaenocladius/Parametriocnemus) during this period is indicative of lower water tables in the wetland. Between 12,700 and 11,300 cal yr BP, chironomid taxa indicate higher wetland water tables, as suggested by the presence of Zavrelia, Chironomus anthracinus/plumosus-type and Micropsectra, which are inhabitants of open-water, lacustrine areas. The open-steppe vegetation remained dominant in the watershed during this time. Increasing wetland moisture could be explained by: (1) cool summers that reduced the evaporation rate; and/or (2) a decrease in duration of the summer dry season. The period 11,300–8700 cal yr BP was characterized by lower wetland moisture, contemporaneous with a delay in the expansion of deciduous forest, suggesting persistent dry climate conditions throughout the beginning of the Holocene, which may have been related to the intensified seasonality of precipitation. Around 8700 cal yr BP, higher wetland water levels, inferred from chironomids, occurred simultaneously with the onset of regional deciduous forest expansion, probably caused by a shortening of the summer dry period. We concluded that chironomids are appropriate paleoecological proxies to investigate global and local hydrologic variability in the Middle East.     

Observations of Doppler oscillations in a solar prominence

We report on the observation of Doppler oscillations in a quiescent limb prominence. Fourier analysis of the data reveals an oscillatory period of 7.5 min, whose phase varies linearly at 16 consecutive points (7280 km) along the slit. This yields an upper limit for the perturbation wavelength of 20000 km. Wavelet analysis confirms the above period and indicates an oscillation lifetime of 12 min. Moreover, the disturbance appears to travel at a speed greater than 4.4 km s^-1. A comparison of these results with the predictions of some theoretical models is made.     

A Finite Element Method for Cracked Components of Structures

1 .IntroductionOffshoreplatformsarelargescalesteelorconcretestructures.Theyexperiencevariouskindsofdamagessuchasdents ,corrosionpits ,cracks ,deformation ,etc .,afteryearsofenvironmentalimpactofwinds ,waves ,currents ,soilreactions ,earthquakesandice (DuanandLiu ,1 995) .Thesafetyofthestructureshasalwaysbeenthemostimportantissueconcerned ,anditdependsontheassessmentoftheintegrityofthestructures,orspecificallyontheassessmentofthedamagesinthestructures .Riclesetal.( 1 994)experimentallyinvestig…     

The Wuqbah peridotite, central Oman Ophiolite: Petrological characteristics of the mantle in a fossil overlapping ridge setting

The Wuqbah peridotites (Wuqbah massif, central Oman Ophiolite) constitute the mantle part of a complete ophiolitic sequence and their field deformation geometry is thought to reflect mantle dynamics in a fossil overlapping ridge settings (Girardeau et al., 2002). These peridotites comprise dominantly residual harzburgites and dunites. Nearly 70% of the harzburgites are clinopyroxene-free, and the rest contains less than 1%. The mineral chemistry of olivine, pyroxenes and spinel, and whole rock major and rare-earth element data, indicate that the Wuqbah peridotites are all strongly refractory and that they record a major percolation event, marked by strong enrichments in incompatible elements. At the massif scale, the Central Zone contains rocks with the most refractory features (20% melt extraction), as expected in an area of mantle upwelling. In the overlapping ridge senario, it corresponds to the overlap zone whose formation is discussed.     

Methodical considerations on the statistical operations concerning climatic variations

Summary The reading of the monograph, mentioned in the title and rather fully described in the text, gave rise to some statistical remarks and a few operations with chance data. Lysgaard obtained several high correlation coefficients. It could be proved that these large values were due to the smoothing of the original series.Perhaps a novum in statistics is shown in Fig. 1. The overlapping 60 respectively 90 year normals of precipitation (Copenhagen 1821–1947) have contradictory trends.In addendum 2, ten random permutations of the years 1800 to 1966 are given. These can be used for any period of 167 years or less. I randomized with them the mean year temperatures of Copenhagen (1801–1935) and then computed overlapping 30 year means. If the recent climatic variations are real, the curve of the original overlapping 30 year means (curve 11 of fig. 2) must show a course decidedly different from that of the random curves 1–10 of fig. 2. It appears that there is a difference, but not an exceptional one.In addendum 4 an interesting demonstration of the caprices of chance is given.

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Zusammenfassung Die Lektüre der im Titel erwähnten Monographie, deren Inhalt im Text beschrieben wird, gab mir Veranlassung zu einigen statistischen Bemerkungen und zu Rechenoperationen mit Zufallsdaten. Es wird gezeigt, daß einige vonLysgaard gefundene hohe Korrelationskoeffizienten durch Ausgleichung der Originalbeobachtungsreihen verursacht wurden. Eine Kuriosität der Statistik ist aus Abb. 1 zu ersehen, in der die übergreifenden 60jährigen Mittelwerte der Niederschläge von Kopenhagen in ihrem Verlauf eine zum Gang der übergreifenden 90jährigen Mittelwerte entgegengesetzte Tendenz zeigen. Im Anhang 2 werden Zufallspermutationen der Jahre 1800 bis 1966 angegeben, die für Perioden von 167 oder weniger Jahren verwendet werden können. Ich ordnete damit nach dem Zufall die mittleren Jahrestemperaturen von Kopenhagen von 1801 bis 1935 und berechnete dann übergreifende 30jährige Mittelwerte. Wenn die neuzeitlichen Klimaschwankungen reell sind, muß erwartet werden, daß die Kurve der übergreifenden 30jährigen Mittel der Originalbeobachtungswerte (Abb. 2, Kurve 11) einen Verlauf zeigt, der von den Zufallskurven (Abb. 2, Kurven 1–10) sich deutlich unterscheidet. Es zeigen sich zwar Unterschiede, doch sind sie nicht sehr auffällig. Ferner wird im Anhang 4 ein interessantes Beispiel für ein Spiel des Zufalls gezeigt.

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Résumé La lecture de la monographie mentionnée dans le titre et dont on donne ici l'essentiel a fourni à l'auteur l'occasion de quelques remarques et de calculs de phénomènes aléatoires. On montre que certains coefficients élevés de corrélation trouvés parLysgaard résultent de compensations des séries originales d'observations. La fig. 1 illustre un fait statistique curieux, savoir que les moyennes mobiles par périodes de 60 ans des précipitations à Copenhague présentent une tendance opposée à celle qui se fonde sur la période mobile de 90 ans. En appendice 2 on donne des permutations aléatoires des années 1800 à 1966 que l'on peut employer pour des périodes de 167 ans ou moins. L'auteur a ordonné de cette façon les températures annuelles moyennes de Copenhague de 1801 à 1935 et calculé les moyennes mobiles par 30 ans. Si les variations climatiques récentes sont réelles, on doit s'attendre que la courbe de ces moyennes mobiles par 30 ans (fig. 2, courbe 11) se distingue nettement des courbes purement aléatoires (fig. 2, courbes 1 à 10). Il y a en fait des différences, mais elles ne sont pas exceptionelles. Enfin l'appendice 4 contient un exemple intéressant du jeu du hasard.

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With 3 figures.

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Folia Geograph. Dan. t. V. Copenhagen 1949, 215 p.     

The Eaux-Bonnes landslide (Western Pyrenees,France): overview of possible triggering factors with emphasis on the role of groundwater

The purpose of this study is to achieve an understanding of the failure mechanisms which caused the Eaux-Bonnes landslide. The geological investigations carried out on the slope of the landslide showed that the sliding mass was cut by numerous faults. The factors controlling the landslide failure were complex, and it is known that neither earthquakes nor heavy precipitation could have triggered the disruption. The groundwater within the solid rock mass has been surveyed, because significant precipitation events during the 2 years preceding the beginning of the paroxysmal phase of the landslide could have led to an increase in pore water pressure along these fractures, thereby triggering the landslide. In order to achieve a full understanding of the failure mechanism, and to identify the origin of the groundwater, a hydrogeochemical survey was carried out over a period of 1 year. The results reveal the existence of high sulphate concentrations in the groundwater originating in springs located at the bottom of the landslide. The sulphate concentrations are correlated with high calcium concentrations, and clearly indicate the presence of gypsum in the vicinity of the lower reaches of the landslide. The presence of gypsum in this area of the Pyrenees suggests that deep groundwater played a role in triggering the landslide.     

Unplanned urban growth: land use/land cover change in the Guwahati Metropolitan Area,India

Unplanned urban growth, particularly in developing countries has led to changes in land use/land cover (LULC). Numerous Indian cities face problems of unplanned LULC change due to nominal or non-existent planning efforts compounded by rapid urban population growth. The Guwahati Metropolitan Area (GMA) is one such urban centre. The present study assesses the trajectories of LULC change using Landsat imageries acquired in 1976, 1989, 2002 and 2015. Natural and semi natural vegetated area and artificial and natural water bodies decreased while built-up areas, cultivated and managed areas, and natural and semi natural non-vegetated areas increased. The built-up area increased from 23.9 in 1976 to 115.1 km² in 2015 becoming the dominant land cover class accounting for 41.8% of the total geographical area. During this period, natural and semi natural vegetated land were reduced by 88.9 km² at an annual rate of 2.2 km². Over the years there was an increasing trend of built-up land and cultivated and managed areas in the peripheral areas of the city while natural and semi natural vegetated land diminished. Consequently, as in many other developing countries, there is an urgent need for the governmental authorities and other stakeholders to implement effective urban planning policies.