36 research outputs found
Las formaciones Plio-Cuaternarias de El Abalario, en el litoral de la provincia de Huelva
Local diversity in settlement, demography and subsistence across the southern Indian Neolithic-Iron Age transition: site growth and abandonment at Sanganakallu-Kupgal
The Southern Indian Neolithic-Iron Age transition demonstrates considerable regional variability in settlement location, density, and size. While researchers have shown that the region around the Tungabhadra and Krishna River basins displays significant subsistence and demographic continuity, and intensification, from the Neolithic into the Iron Age ca. 1200Â cal. BC, archaeological and chronometric records in the Sanganakallu region point to hilltop village expansion during the Late Neolithic and âMegalithicâ transition period (ca. 1400â1200Â cal. BC) prior to apparent abandonment ca. 1200Â cal. BC, with little evidence for the introduction of iron technology into the region. We suggest that the difference in these settlement histories is a result of differential access to stable water resources during a period of weakening and fluctuating monsoon across a generally arid landscape. Here, we describe well-dated, integrated chronological, archaeobotanical, archaeozoological and archaeological survey datasets from the Sanganakallu-Kupgal site complex that together demonstrate an intensification of settlement, subsistence and craft production on local hilltops prior to almost complete abandonment ca. 1200Â cal. BC. Although the southern Deccan region as a whole may have witnessed demographic increase, as well as subsistence and cultural continuity, at this time, this broader pattern of continuity and resilience is punctuated by local examples of abandonment and mobility driven by an increasing practical and political concern with water
TESTING FOR GENETIC EVIDENCE OF POPULATION EXPANSION AND CONTRACTION: AN EMPIRICAL ANALYSIS OF MICROSATELLITE DNA VARIATION USING A HIERARCHICAL BAYESIAN MODEL
La géochimie organique des sédiments marins profonds. Mission orgon 3, 1976 (Mauritanie, Sénégal, Iles du Cap-Vert). Généralités et résultats obtenus à la mer. Organic Geochemistry of Deep Marine Sediments. Orgon 3 Mission, 1976 (Mauritania,Senegal,Cape Verde Islands). General and Results Obtained At Sea
Sept articles distincts traitent, le premier des gĂ©nĂ©ralitĂ©s sur la mission ORLON 3, le second du cadre gĂ©ologique gĂ©nĂ©ral, les cinq autres des rĂ©sultats obtenus Ă la mer dans les domaines de l'interprĂ©tation des profils d'Ă©chosondeur, de la descrip-tion des carottes, de l'examen de la matiĂšre organique figurĂ©e, de l'Ă©tude des gaz occlus et enfin de la microbiologie. Les profils d'Ă©chosondeur permettent de prĂ©ciser la topographie des fonds, qui apparaissent comme entaillĂ©s de canyons. Ils permettent aussi de dĂ©celer les glissements sĂ©dimentaires qui apparaissent comme un processus normal de mise en place des sĂ©diments dans la rĂ©gion Ă©tudiĂ©e. La description immĂ©diate des carottes a permis, en particulier, de mettre en Ă©vidence des niveaux turbiditiques Ă Ă©lĂ©ments bioclastiques subsistant sous la lysocline, ce qui, entre autres, confirme les considĂ©rations prĂ©cĂ©dentes. L'examen de la matiĂšre organique figurĂ©e fait soupçonner l'importance de l'apport dĂ©tritique Ă©olien, ce qui est une nouveautĂ©. L'Ă©tude des gaz occlus oppose nettement la rĂ©gion Nord (radiale de Nouadhibou), au Sud (rĂ©gion des fleuves cĂŽtiers et du canyon de Kayar). Dans cette derniĂšre, les gaz ne contiennent pratiquement que du mĂ©thane comme hydrocarbure ; les teneurs sontirrĂ©guliĂšrement rĂ©parties et ne montrent aucune corrĂ©lation, ni avec la teneur en carbone organique, ni avec la richesse microbienne des niveaux. Au Nord, le mĂ©thane est un peu moins prĂ©dominant (l'Ă©thane reprĂ©sente quelques centiĂšmes du mĂ©thane, les homologues supĂ©rieurs sont Ă l'Ă©tat de traces). S'il n'y a pas corrĂ©lation avec la richesse microbienne, il y en a par contre avec la teneur en carbone organique et les teneurs s'accroĂźssent rĂ©guliĂšrement en profondeur pour atteindre le double des teneurs mesurĂ©es au Sud. L'interprĂ©tation de ces donnĂ©es n'est pas Ă©vidente. La microbiologie a mis en Ă©vidence un phĂ©nomĂšne dĂ©jĂ entrevu aux prĂ©cĂ©dentes missions ORLON. A la pauvretĂ© gĂ©nĂ©rale en bactĂ©ries des sĂ©diments Ă©tudiĂ©s, jointe Ă la disparition totale de ces bactĂ©ries trĂšs rapidement dans la profondeur des carottes, se superpose ici, dans des niveaux profonds diffĂ©rents suivant les carottes, une microflore trĂšs abondante et active (non sporulĂ©e). L'importance gĂ©ologique de cette dĂ©couverte ne saurait ĂȘtre sous-estimĂ©e. <br> Seven separate articles will be published on the ORLON 3 mission.The first will deal with general aspects, the second with the general geological setting and the other five with the results obtained at sea in the fields of interpreting echosounder profiles, describing tore samples, observing parriculote organic motter, examining entrapped gas and investigating microbiology. Echosounder profiles describe the topography of the sea bed which appears to be slashed by canyons. They also detect sedimentary sliding which appears as a normal process of sediment deposition in the region being investigated. The im.nediate description of core samples in particular revealed turbidite levels with bioclastic elements subsisting under the lysocline, thus confirming the preceding considerations among others. An examination of the figured elements in the organic matter suggests the importance of eolian detrital influx, which is something new. An analysis of the entrappeci gas gives rise ta clearcut opposition between the northern region (radial of Nouadhibou) and the southern region (a region of coastal rivers and the Kayar canyon). In the latter region, the gas contains almost nothing other thon methane as a hydrocarbon. The amounts of methane in the gas are irregularly distributed and show no correlation either with the organic carbon contents or with the microbial richness of the levels. In the north the methane is slightly less predominant (ethane represents a few hundredths of methane, and the upper homo-logous series have merely traces). Although there is no correlation witb the microbial richness, there is nonetheless one with the organic carbon content which increases regularly at depth to attain double the amounts measured in the south. The interpretation of such data is not obvious.Microbiology revealed a phenomenon thot had already been glimpsed during preceding ORLON missions. In addition ta the general bacterial poverty of the sediments analyzed, combined with the total disappearance of such bacteria very quickly as depth increases in the cores, is here superimposed the presence of some discrete levels, at depths depending on the cores, where thrives a very abundant and active (unsporulated) microflora
Coupled transport and poro-mechanical properties of a heat-treated mortar under confinement
International audienceThis experimental investigation focuses on a mortar heated/cooled up to 105, 200, 300 or 400 °C. The reference state for the material corresponds to mass stabilization at 60 °C oven-drying. Extensive (and tortuous) micro-crack development is shown by SEM and FIB/SEM imaging after heating-cooling up to 400 °C. Poro-mechanical performance is significantly affected after 400 °C heat-treatment, as plastic straining develops with increasing hydrostatic stress Pc; simultaneously, intrinsic gas permeability Kint decreases irreversibly after a first loading, and remains significantly lower whatever the subsequent Pc loading. These results are mainly attributed to the irreversible closure of heat-induced micro-cracks. This interpretation, based on our micro structural analysis, is validated experimentally under hydrostatic loading: a dedicated static gas experiment provides directly the pore volume under given Pc. By comparison with experimental data on heat-treated cement paste, we conclude that the irreversible pore closure of heat-treated mortar is related to that of micro-cracks mainly located at the paste/aggregate interface
Phytolith analysis reveals the intensity of past land use change in the Western Ghats biodiversity hotspot
This paper presents a study of phytoliths (opal silica bodies from plants) from sediment sequences obtained from two tropical forest patches in the Western Ghats of India: a sacred grove (sequence covers last 550 cal BP) and a forest patch in a plantation (sequence covers last 7500 cal BP). The sites are located at mid-elevation (c. 650â1400 m above sea level) in a mosaic landscape showing anthropogenic open habitats and plantation as well as some evergreen forests. The aim of this paper is to evaluate the landscape composition of grassland and forest over time in the region, grassland being invariably shaped by anthropogenic activities, particularly fire for cultivation. In particular, we compare the phytolith record with the previously published pollen record from the same cores in order to improve our understanding of grass diversity and abundance over time. We identified and classified phytoliths into 34 morphotypes from five taxonomic groups: Poaceae (grasses), Cyperaceae (sedges), Arecaceae (palms), Pteridopsida (ferns) and woody dicotyledons (broad-leaved trees and shrubs). We also calculated the humidityâaridity index (Iph). First, our results show that grasses are the most represented phytolith types in both sites, followed by broad-leaved trees and shrubs, palms, sedges, and ferns. Second, the highly variable climatic index Iph over the last 1000 years suggest that changes in phytolith percentage (e.g. broad-leaved trees) might be caused by human agro-pastoral activities, such as clearing through fires and irrigation. Prior to these human activities, the phytolith signal for early Holocene climate is congruent with the existing literature. Finally, this study compares new phytolith results with previous pollen data from the same sites. We find good agreement between these two botanical proxies throughout, thus validating our findings. We provide important evidence regarding the history of environmental change due to anthropogenic activities in the Western Ghats. This has important implications because it provides insights into how tropical forest will respond to increased intensity of human activities