De nouvelles mesures d'âges au strontium par isochrones sur roches totales ont mis en évidence, dans le socle du Togo et du Bénin, un métamorphisme d'âge pan-africain pouvant atteindre le faciès des amphibolites et affectant une série volcano
-sédimentaire d'âge inconnu, des syénites alcalines pan-africaines, des granites éburnéens, et des diorites quartziques éburnéennes ou antérieures.
Distribution patterns of gypsum and kalistrontite in a dry lake basin of the southwestern Kalahari (Omongwa pan, Namibia)
The studied basin is a pan of the southwestern Kalahari, in eastern central Namibia. The distribution patterns of gypsum and kalistrontite are mainly determined by groundwater depth and by the lithological composition of the deposits. Gypsum occurs
Late Pan-African syenite-granite plutons in NW Nigeria
The Pan-African (800-500 Ma) Older Granite suite of Nigeria is dominated by calc-alkaline, I-type magmatism and is a product of subduction processes at the eastern margin of the West African craton. The Kanoma and Sabon Gida composite plutons of NW
Les pans du Kalahari méridional sont des cuvettes pouvant contenir des lacs éphémères et recouvertes d'argiles calcaires salines ou sablonneuses déposées en périodes de précipitations. Deux dunes en croissant au sud de ces dépressions sont
Pan-national identities : representations of the Philippine diaspora on the world wide web
Les AA. montrent comment la Toile (web) mondiale peut faciliter la mutation d'une identité trans-nationale en une identité globale et pan-nationale. Le concept de tahanang est spécifique de la diaspora philippine, le chez-soi servant de métaphore
pour une identité philippine pan-nationale. Le web ne facilite pas seulement les interactions spatiales des communautés en diaspora, mais il nourrit la représentation de l'identité nationale. Dans le cas de cette diapora, les réseaux de sociabilité
Identification of dominant climate factor for pan evaporation trend in the Tibetan Plateau
In this paper, a derivation based approach has been used to quantitatively assess the contribution rate of climate factors to the observed pan evaporation paradox across the Tibetan Plateau. The results showed that a decrease in wind speed
was the dominant factor for the decreasing pan evaporation, followed by an increasing vapor pressure and decreasing solar radiation, all of which offset the effect of increasing temperature across the Tibetan Plateau.
Anthropogenically-triggered iron pan formation in some Irish soils over various time spans
This paper synthesises existing and new research into the influence of man on the development of iron pans in Irish soils. The common theme in this work is the influence of organic matter, directly or indirectly, on the fate of iron and on its
, the development of an iron pan is a relatively modern process, superimposed on an earlier generation of distinctly different horizons.
The nature of calcareous deposits along pan margins in eastern central Namibia
This report describes a mainly petrographical study of calcareous deposits that are associated with pan basins in eastern central Namibia, aimed at establishing the mode of development of this common type of formation. Some observations are also
pedogenic origin should also be considered for calcareous deposits that commonly occur along pan margins in other parts of southern Africa.
Les nappes précambriennes du Gourma dans la chaîne pan-africaine du Mali
Gourma ; Géographie de l'Afrique ; Géologie régionale ; Mali ; Métamorphisme de HP/BT ; Nappe ; Nappe de charriage ; Pan-Africain ; Précambrien
Situé à l'Ouest du fossé crétacé de Gao, le Gourma oriental appartient à la chaîne pan-africaine du Mali. Il correspond à de grandes nappes pelliculaires mises en place vers l'W-SW à la bordure du craton ouest africain. Les nappes internes portent
Programmes pan-européens de recherche sur les modifications des paysages
Author reports on Pan-European research programmes and networks specialised in the field of landscape ecology. The main aim of these programmes is to clarify the relations between physical geographical conditions, anthropogenic effects and land use
Trend in pan evaporation and its attribution over the past 50 years in China
This study analyzes pan evaporation data from 671 stations in China over the past 50 years in order to reveal the trends of it and the corresponding trend attribution. Mann-Kendall test shows a significant declining trend in pan evaporation for most
stations. Complete correlation coefficients of pan evaporation with 7 climate factors were computed, and decreases in diurnal temperature range (DTR), SD (sunshine duration) and wind speed were found to be the main attributing factors in the pan evaporation
Peroxyacetyl nitrate (PAN) in relation to ozone and some meteorological parameters at Delft in the Netherlands
Depuis 1972, la teneur de l'air en nitrate de péroxyacétyl PAN, l'un des produits de la pollution photochimique de l'atmosphère, est mesurée toutes les 15minutes à Delft. Les AA. décrivent les techniques utilisées, et présentent à titre
d'illustration les résultats de 48journées. Pour connaître le cycle diurne de la pollution d'origine photochimique, il se confirme que les concentrations moyennes semi-horaires en PAN fournissent des indications plus satisfaisantes que les teneurs correspondantes
en ozone. Toutefois, si l'on veut étudier le transport sur une grande échelle des produits de la pollution photochimique, il semble indispensable de mesurer à la fois l'ozone et le PAN, et de disposer de plusieurs stations d'alerte. (J. P. Besancenot).
Comparison of pan evaporation and actual evaporation estimated by land surface model in Xinjiang from 1960 to 2005
In this paper, the trends of pan evaporation and actual evaporation are investigated using observational data and observation-constrained simulation results using NCAR Community Land Model (CLM) in Xinjiang from 1960 to 2005. The results suggest
that decrease of pan evaporation indicates an increase of actual evaporation in Xinjiang in the past half century. The correlation analysis shows that diurnal temperature range, wind speed, low cloud cover and precipitation are the most likely driving forces
for the reduced pan evaporation and the ascending actual evaporation.
The Boteti palaeo-estuary in northern Botswana is located where the endoreic Boteti river, an overflow from the regional Okavango river system, enters the Makgadikgadi pans. The aims are to help identify precursor conditions for the origin
of microcrystalline silcrete–calcrete intergrade deposits while developing insight into pene-contemporaneous silica and calcite matrix formation. General precursor conditions require the presence of cyclical endoreic freshwater inflow into a saline pan. The pan should
be deep enough to sustain a permanent watertable under climatic conditions sufficient to cause carbonate fractionation within the groundwater. Freshwater inflow into a saline pan drives the geochemistry of the system (from freshwater to saline, from
neutral to high pH). The geochemistry is controlled by the periodicity of inflow relative to salinity levels of phreatic groundwater in the receptor saline pan.
La phase tectonique majeure (environ 700m.a.) de l'orogenèse pan-africaine est caractérisée, dans le Kerdous, par l'individualisation de larges zones mylonitiques. Elles sont associées dans plusieurs cas à des structures chevauchantes montrant le
cisaillement se fait du SSE vers le NNW, obliquement à l'axe des mégastructures. Au point de vue géodynamique et dans un cadre de tectonique des plaques dont l'existence est reconnue, au Pan-Africain, dans l'Anti-Atlas nord-oriental, la zone du Kerdous présente
Geomorphological and sedimentological considerations are used to evaluate the interaction of wind and water in shaping contemporary lunette processes. It is considered that like other pans in the area, groundwater activity influences pan floor
sediment avaibility and transport, that the present highly seasonal climatic regime permits the interaction of aeolian transport of sediment to the dune and its return to the pan floor by water during storm events, creating a cycling process favoured
Pans and dunes in the southwstern Kalahari (Namibia) : geomorphology and evidence for Quaternary paleoclimates
The AA.present a detailed geomorphic study on the formation of pans and dunes along the southwestern Kalahari margin (Tses-Keetmanshoop-Aroab). Field observations and the interpretation of aerial photographs were accompanied by sedimentological
L’institutionnalisation de la région alpine à travers l’étude de deux réseaux pan-alpins (Alliance dans les Alpes et Alparc)
Cet article veut, à travers l'analyse de deux réseaux pan-alpins, montrer comment les Alpes sont en train de s'institutionnaliser, d'émerger en tant que région transnationale. Il s'agit ici avant tout de saisir les mécanismes de fonctionnement de