Bertran Pascal, Lenoble Arnaud, Todisco Dominique, Desrosiers Pierre M, Sørensen Mikkel, . (2012). Particle size distribution of lithic assemblages and taphonomy of Palaeolithic sites
. J. Archaeol. Sci., 39(10), 3148–3166.
Abstract: Lithic debris derived from knapping and used tools can be assimilated to simple sedimentary particles that may undergo size sorting when exposed to geomorphic processes such as streamflow or overland flow. Sorting can be identified by comparing the size distribution of archaeological assemblages to that of experimental core reduction sequences. A new database including different types of raw material (mainly flint and quartzite) and Palaeolithic debitage (blade, Levallois, discoid, on anvil, and shaping) has been built for this purpose. Palaeoeskimo data have also been added to illustrate microlithic industries. For all the debitages and raw materials, the particle size of knapping products >2 mm in width fits with a power-law distribution and shows only minor fluctuations, the range of which is always <15% between experiments (all steps of the chaîne opératoire included up to the final tool). A lithic assemblage derived from block/core knapping or blank/preform production will display a particle size distribution close to the experimental distributions if not subsequently modified. Modifications may originate either from sedimentary processes or from anthropogenic factors. To help distinguishing amongst these, data on the impact of both water flows on sedimentary particles or experimental assemblages, and anthropogenic processes such as importation-exportation (of core, preforms or finished tools) or uneven spatial distribution of the different steps in core reduction and tool production within a site, are reviewed. By contrast to anthropogenic modifications, sedimentary processes are generally typified by strong impoverishment in or selective accumulation of fine-grained (<10 mm) artefacts together with a low intra-site variability (spatial homogenization) or a downslope size trend. Archaeological case studies taken from French Palaeolithic site are then detailed. Evidence for lithic redistribution implies that care should be taken in archaeological site analysis since sorting may impact significantly the initial techno-typological balance of the assemblage.
Keywords: Lithic taphonomy, Water flow, Experimental knapping, Size sorting, Palaeolithic, Site formation processes,
Programme: 1080
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Picard G, Domine F, Krinner G, Arnaud L, Lefebvre E,. (2012). Inhibition of the positive snow-albedo feedback by precipitation in interior Antarctica. Bachelor's thesis, Nature Publishing Group, .
Abstract: This study uses satellite data to study snow grain size–albedo relationships over the whole Antarctic Plateau. The findings suggest that increased precipitation resulting from climate change will effectively compensate for the decreased albedo that should have resulted from warming, thereby inhibiting the expected ice–albedo feedback.
Keywords: limate change Cryospheric science
Programme: 1013
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Yves Cherel, Evgeny V. Romanov, Pavanee Annasawmy, Delphine Thibault, Frédéric Ménard. (2020). Micronektonic fish species over three seamounts in the southwestern Indian Ocean (Vol. 176).
Abstract: Taxonomic composition, abundance and biological features of micronektonic fish were investigated using pelagic trawls conducted near and over the summits of three seamounts located in the western Indian Ocean (La Pérouse, MAD-Ridge and Walters Shoal). Mesopelagic fish from three families accounted for 80% by number of the total catch (5714 specimens, 121 taxa), namely myctophids (59%), gonostomatids (12%) and sternoptychids (9%). Whereas the gonostomatid Sigmops elongatus was the most abundant species around La Pérouse seamount, myctophids were the most diverse and dominant group by number in all three studied areas. Most myctophids were high-oceanic species, which included the numerically dominant Benthosema suborbitale, Ceratoscopelus warmingii, Diaphus perspicillatus, Hygophum hygomii, and Lobianchia dofleini. The few remaining myctophids (Diaphus suborbitalis being the most abundant) were pseudoceanic fish, highlighting the association with landmasses. The study adds one myctophid species new to the Indian Ocean (Diaphus bertelseni), and a second record in the literature of the recently described sternoptychid Argyripnus hulleyi.
Keywords: Lanternfish Tropical waters
Programme: 109
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MAJ Emilie. (2009). Des tournants spatiaux : approche diachronique de la sémiotique du paysage en Sibérie, l’exemple de la République Sakha (Iakoutie)]. GéoCité, 1.
Abstract: About the evolution of worlddview and conception of landscape in Yakut culture:
Based on geographical and anthropological litterature and on the field data collected during the missions Ethnoequid 2003-2006 and Festivethno 2009.
Keywords: Landscape, Siberia, Republic Sakha (Yakutia), Sakha, Yakut, Siberian minoritites,Turkic people, semiotic, temporality, space, history, place, taiga, domestication
Programme: 1024
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Lev Vinnik, Elena Kozlovskaya, Sergey Oreshin, Grigoriy Kosarev, Katerina Piiponen, Hanna Silvennoinen. (2016). The lithosphere, LAB, LVZ and Lehmann discontinuity under central Fennoscandia from receiver functions (Vol. 667).
Abstract: P- and S-wave velocity profiles (Vp and Vs) from the Earth's surface to a depth of 300km are obtained by simultaneous inversion of P- and S-wave receiver functions for the temporary POLENET/LAPNET array in northern Finland and 5 permanent stations in southern Finland. The obtained Vp/Vs velocity ratio in the uppermost mantle is anomalously low (1.65–1.70 versus the standard 1.8). This ratio can be explained by a high (~30%) fraction of orthopyroxene in the depleted upper mantle. An increase of ~4% in the Vs values is detected at a depth of 110–130km. Under southern Finland the high-velocity mantle keel may extend beyond the depth of 300km, but under northern Finland we detect a low-Vs zone (LVZ) with the top at a depth of 160km. This depth corresponds to the intersection of the geotherm with the wet solidus of peridotite at a temperature near ~1100°C, and suggests partial melting as an explanation for the origin of the LVZ. The bottom of the LVZ (the Lehmann discontinuity) is found at a depth of 240km. The fast direction of seismic azimuthal anisotropy beneath northern Finland in the depth interval from 200–240km to 320km is parallel to the current APM direction (60°) but in the interval from 160km to 200–240km the fast direction (150°) appears to be normal to the APM direction (Vinnik et al., 2014). The present study indicates that the fast direction of 150° confines to the LVZ where the flow in the direction normal to the APM direction is unlikely. More likely, the flow direction is parallel to the APM direction and normal to the fast direction of anisotropy, as suggested by experiments with sheared peridotite-type rocks containing melt.
Keywords: LAB Lehmann discontinuity Low-velocity zone Partial melting Receiver functions Seismic anisotropy
Programme: 1021
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Demay Jérémie, Delord Karine, Thiebot Jean-Baptiste, Barbraud Christophe, . (2014). First breeding record of the northern giant petrel Macronectes halli at Ile Amsterdam
. Antarct. Sci., 26(04), 369–370.
Keywords: KW -,
Programme: 109
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Friedt J-M, Tolle F, Bernard É, Griselin M, Laffly D, Marlin C, . (2012). Assessing the relevance of digital elevation models to evaluate glacier mass balance: application to Austre Lovénbreen (Spitsbergen, 79°N)
. Polar Record, 48(Special Issue 01), 2–10.
Abstract: The volume variation of a glacier is the actual indicator of long term and short term evolution of the glacier behaviour. In order to assess the volume evolution of the Austre Lovénbreen (79° N) over the last 47 years, we used multiple historical datasets, complemented with our high density GPS tracks acquired in 2007 and 2010. The improved altitude resolution of recent measurement techniques, including phase corrected GPS and LiDAR, reduces the time interval between datasets used for volume subtraction in order to compute the mass balance. We estimate the sub-metre elevation accuracy of most recent measurement techniques to be sufficient to record ice thickness evolutions occurring over a 3 year duration at polar latitudes.
The systematic discrepancy between ablation stake measurements and DEM analysis, widely reported in the literature as well as in the current study, yields new questions concerning the similarity and relationship between these two measurement methods.
The use of Digital Elevation Model (DEM) has been an attractive alternative measurement technique to estimate glacier area and volume evolution over time with respect to the classical in situ measurement techniques based on ablation stakes. With the availability of historical datasets, whether from ground based maps, aerial photography or satellite data acquisition, such a glacier volume estimate strategy allows for the extension of the analysis duration beyond the current research programmes. Furthermore, these methods do provide a continuous spatial coverage defined by its cell size whereas interpolations based on a limited number of stakes display large spatial uncertainties. In this document, we focus on estimating the altitude accuracy of various datasets acquired between 1962 and 2010, using various techniques ranging from topographic maps to dual frequency skidoo-tracked GPS receivers and the classical aerial and satellite photogrammetric techniques.
Keywords: KW
Programme: 304
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Pitman RobertL, Durban JohnW, Greenfelder Michael, Guinet Christophe, Jorgensen Morton, Olson PaulaA, Plana Jordi, Tixier Paul, Towers JaredR, . (2011). Observations of a distinctive morphotype of killer whale (Orcinus orca), type D, from subantarctic waters
. 0722-4060, 34(2), 303–306-.
Abstract: Studies have shown that killer whale (Orcinus orca) communities in high latitudes regularly comprise assemblages of sympatric ‘ecotypes’—forms that differ in morphology, behavior, and prey preferences. Although they can appear superficially similar, recent genetic evidence suggests that breeding is assortative among ecotypes within individual communities, and species-level divergences are inferred in some cases. Here, we provide information on a recently recognized ‘type D’ killer whale based on photographs of a 1955 mass stranding in New Zealand and our own six at-sea sightings since 2004. It is the most distinctive-looking form of killer whale that we know of, immediately recognizable by its extremely small white eye patch. Its geographic range appears to be circumglobal in subantarctic waters between latitudes 40°S and 60°S. School sizes are relatively large (mean 17.6; range 9–35; n = 7), and although nothing is known about the type D diet, it is suspected to include fish because groups have been photographed around longline vessels where they reportedly depredate Patagonian toothfish (Dissostichus eleginoides).
Keywords: Killer whale, Orcinus orca, Subantarctic, Type D,
Programme: 109
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Bascou J, Delpech G, Vauchez A, Moine B N, Cottin J Y, Barruol G, . (2008). An integrated study of microstructural, geochemical, and seismic properties of the lithospheric mantle above the Kerguelen plume (Indian Ocean)
. Geochem. Geophys. Geosyst., 9(4), Q04036–.
Abstract: Peridotite xenoliths brought up to the surface by the volcanism of the Kerguelen Islands represent a mantle that has been affected by a high degree of partial melting followed by intense melt percolation above the Kerguelen plume. These xenoliths are therefore particularly suitable to investigate effects of melt-rock interaction on crystallographic fabrics (lattice-preferred orientation (LPO)) of peridotite minerals and on the LPO-induced seismic properties of peridotites above a mantle plume. We have studied a suite of 16 ultramafic samples representative of different degrees of partial melting and magma-rock interaction among which the protogranular harzburgites are the least metasomatised xenoliths and dunites are the ultimate stage of metasomatism. Olivine LPO is characterized by high concentration of [010] axes perpendicular to the foliation and [100] axes close to the lineation or distributed in the foliation plane in harzburgites, whereas the high concentration of [100] axes is parallel to the lineation and [010] axes is perpendicular to the assumed foliation in dunites. Olivine LPO in harzburgites is interpreted as being due to a deformation regime in axial compression or transpression. The fabric strength of olivine decreases progressively from protogranular to poikilitic harzburgites and finally to dunites, for which it remains nevertheless significant (J index $\geq$ 3.8). Seismic properties calculated from LPO of minerals indicate that metasomatism at higher melt/rock ratio lowers the P wave velocities. The most significant difference between harzburgites and dunites corresponds to the distribution of S wave anisotropy. Harzburgites display the maximum of anisotropy within the foliation plane and the minimum of anisotropy perpendicular to the foliation plane, whereas the lowest anisotropy is parallel to the lineation for dunites. These modifications of seismic properties as a result of metasomatic processes may induce seismic heterogeneities in the mantle above the Kerguelen plume. In addition, assuming a lithospheric mantle primarily harzburgitic and structured with a horizontal foliation, the seismic properties calculated for the Kerguelen xenoliths reconcile the rather high anisotropy evidenced by the horizontally propagating surface waves with the apparent isotropy revealed by the absence of splitting of vertically propagating teleseismic SKS waves recorded by the GEOSCOPE Kerguelen station.
Keywords: Kerguelen, mantle plume, seismic anisotropy, metasomatism, crystallographic fabric, lithosphere, 8121 Tectonophysics: Dynamics: convection currents, and mantle plumes, 8030 Structural Geology: Microstructures, 7208 Seismology: Mantle,
Programme: 133;444
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Park Young‐Hyang, Durand Isabelle, Kestenare Elodie, Rougier Gilles, Zhou Meng, d'Ovidio Francesco, Cotté Cédric, Lee Jae‐Hak. (2014). Polar Front around the Kerguelen Islands: An up‐to‐date determination and associated circulation of surface/subsurface waters (Vol. 119).
Abstract: Abstract The circulation of iron?rich shelf waters around the Kerguelen Islands plays a crucial role for a climatically important, annually recurrent phytoplankton spring bloom over the sluggish shelf region and its downstream plume area along the Antarctic circumpolar flow. However, there is a long?standing confusion about the Polar Front (PF) in the Kerguelen region due to diverse suggestions in the literature for its geographical location with an extreme difference over 10° of latitude. Based on abundant historical hydrographic data, the in situ hydrographic and current measurements during the 2011 KEOPS2 cruise, satellite chlorophyll images, and altimetry?derived surface velocity fields, we determine and validate an up?to?date location of the PF around the Kerguelen Islands. Artificial Lagrangian particle trajectories computed from altimetric velocity time series are analyzed for the possible pathways and sources of different surface/subsurface waters advected into the chlorophyll bloom area east off the islands studied during the KEOPS2 cruise. The PF location determined as the northernmost boundary of the Winter Water colder than 2°C, which is also associated with a band of strong currents, appears to be primarily controlled by topography. The PF rounds the Kerguelen Islands from the south to deflect northward along the eastern escarpment up to the northeastern corner of the Kerguelen Plateau before making its southward retroflection. It is shown that the major surface/subsurface waters found within the deep basin east of the Kerguelen Islands originate from the shelf around the Heard Island, rather than from the shallow shelf north of the Kerguelen Islands.
Keywords: Kerguelen Polar Front Southern Ocean
Programme: 688
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