The Paleoenvironment and Lithic Taphonomy of Shi’Bat Dihya 1, a Middle Paleolithic Site in Wadi Surdud,Yemen     

Luca Sitzia  Pascal Bertran  Stphane Boulogne  Michel Brenet  Rmy Crassard  Anne Delagnes  Marine Frouin  Christine Hatt  Jacques Jaubert  Lamya Khalidi  Erwan Messager  Norbert Mercier  Alain Meunier  Stphane Peign  Alain Queffelec  Chantal Tribolo  Roberto Macchiarelli 《Geoarchaeology》2012,27(6):471-491

The Shi'bat Dihya 1 site in western Yemen, dated by optically stimulated luminescence to 55 ka, provides insight into the Middle Paleolithic peopling of the Arabian Peninsula. The archaeological layer is interstratified within thick, sandy silt floodplain deposits filling a piedmont basin. Luminescence dates, lack of soil development, and gypsum precipitation indicate a high accretion rate of the floodplain during Marine Isotope Stage 3, in connection with a (semi)‐arid environment. Rapid overbank sedimentation was likely a result of the remobilization of loess material deposited on the Yemeni Great Escarpment at the periphery of the adjacent Tihama coastal sand desert or of other sources. Fabric and size analyses of the lithic artifacts, together with spatial projections, indicate site modifications by floods. Primary modifications include (1) selective accumulation of medium‐sized lithic pieces as a result of hydraulic sorting, (2) bimodal orientation of artifacts, and (3) ripple‐like arrangement of lithics and bone/tooth fragments. The overrepresentation of teeth may also be a consequence of sorting. Although floods have distorted the original site patterning, long‐distance transport of artifacts by water can be excluded, as indicated by relatively high refitting rate, close proximity of artifacts derived from the same block of raw material, and lack of abrasion of the pieces. Therefore, the site is considered “geologically” in situ because its remobilization by water occurred shortly after human abandonment. This study also stresses that the effective preservation of a site cannot be assessed without careful taphonomic study, even in a potentially favorable depositional context such as silty alluvium.  相似文献   

Carbonate diagenesis and feldspar alteration in fracture-related bleaching zones (Buntsandstein,central Germany): possible link to CO<Subscript>2</Subscript>-influenced fluid–mineral reactions     

Jens Wendler  Jens Köster  Jens Götze  Norbert Kasch  Norbert Zisser  Jonas Kley  Dieter Pudlo  Georg Nover  Reinhard Gaupp 《International Journal of Earth Sciences》2012,101(1):159-176

Fracture-related bleaching of Lower Triassic Buntsandstein red beds of central Germany was related to significant carbonate diagenesis and feldspar alteration caused by CO₂-rich fluids. Using cathodoluminescence microscopy and spectroscopy combined with electron microprobe analysis and stable carbon isotope study, two major fluid–mineral interactions were detected: (1) zoned, joint-filling calcites and zoned pore-filling calcite cements, the latter replacing an earlier dolomite, were formed during bleaching. During the calcite formation and dolomite–calcite transformation, iron was incorporated into the calcite cement crystal cores due to Fe availability from the coeval bleaching. The dedolomitisation was ultimately associated with a volume increase. The related permeability decrease implies a certain degree of sealing and increasing retention of CO₂, and the volume increase offers a minor CO₂ sink. Carbonate-rich sandstone, therefore, can provide advantages for underground CO₂ storage especially when situated in the fringes of the reservoir. (2) Alkali-feldspar alteration due to the bleaching fluids is reflected in cathodoluminescence spectra predominantly by the modulation of a brown luminescence emission peak (~620 nm). This peak represents a newly discovered effect related to alkali-feldspar alteration not solely associated with bleaching. Its modulation by the bleaching is interpreted to be due to Na depletion or a lattice defect in the Si–O bonds of the SiO₄-tetrahedron. Alteration reflected by this luminescence feature has a destructive effect on the feldspars implying the possibility of diminished rock integrity due to bleaching and, hence, CO₂-rich fluids. Two further CL spectral changes related to bleaching occur, (a) decreased intensity between around 570 nm assigned to Mn-depletion, and (b) increased amplitude and wavelength shift of the red (~680 nm) band. Converging evidence from carbonate and feldspar diagenesis, stable carbon isotope data and analysis of fracture directions suggests that CO₂ fluids contributed to a significant extent to the bleaching phenomena and alteration in the studied Buntsandstein strata.  相似文献   

Considerations on a suction drill for lunar surface drilling and sampling: II. experimental tests in vacuum conditions     

J?rg Fa?wald  Norbert I. K?mle  Mark S. Bentley  Peter Weiss 《Acta Geotechnica》2012,7(2):115-127

Drilling devices with the ability to create narrow, but deep, boreholes in a planetary surface are important tools for the exploration of the structure and properties of planetary surface layers. Therefore, they are usually proposed for planetary landers for the Moon, Mars, Venus or small planetary bodies. A method based on the use of a cold gas flow for ejecting debris particles from the borehole has recently been suggested and investigated theoretically (K?mle et al. in Acta Geotech 3:201–214, 2008a). The current paper reports on laboratory experiments designed to validate this method under vacuum or low pressure conditions. Two different sample materials were used: (1) glass beads in the sub-millimeter size range, and (2) the certified lunar analog material JSC-1A, a finely crushed basaltic rock. For both materials, the suction process for removing the particles from a simulated borehole worked well and with a moderate gas consumption.  相似文献   

Quantitative reconstruction of climate variability during the Eemian (Merkinė) and Weichselian (Nemunas) in Lithuania     

Vaida Šeirienė  Norbert Kühl  Dalia Kisielienė 《Quaternary Research》2014

Little is known concerning climate changes in the Eastern Baltic region during the last interglacial–glacial cycle and in particular, climate changes during the Weichselian. In this study, a quantitative reconstruction of the mean January and July temperature for the Medininkai-117 site in Lithuania is presented. The reconstruction is based on pollen and plant macrofossils from this site, which reveal that the vegetation was characteristic of many northern Europe sites during the Eemian and Early Weichselian. Gradual evolution of the vegetation suggests that relatively uniform climate conditions existed during the Eemian. Our reconstructions support the view of a relatively stable Eemian, with short cooling phases of low amplitude. A strong increase in temperature was apparent during the beginning of the interglacial and decrease during the transition to the Weichselian. Reconstructed July temperatures of the Eemian interglacial were approximately 2 °C higher than today (18.5 °C; today: 16.2 °C) and were similar to today for January (− 5.2 °C; today: − 5.1 °C). July temperatures during the Early Weichselian were only ~ 2°C lower than during the Eemian, whereas the January temperatures gradually decreased. Winter temperatures were relatively high (above − 10 °C) during the Early Weichselian.  相似文献   

Mapping subvertical discontinuities in rock cuts using a 400-MHz ground penetrating radar antenna     

Adnan Aqeel  Neil Anderson  Norbert Maerz 《Arabian Journal of Geosciences》2014,7(5):2093-2105

Hidden subvertical discontinuities oriented parallel to subparallel to the exposed faces of outcropping sandstone were effectively mapped at three different study sites in central Missouri using a ground-penetrating radar system (GPR) equipped with a 400-MHz monostatic antenna and a survey wheel. At each site, a suite of 2-D ground-penetrating radar profiles were acquired along multiple closely spaced traverses on relatively smooth exposed rock surfaces. Time-zero correction was applied to the raw GPR data which were then processed using band-pass filtering, range and display gain, color transformation, and deconvolution techniques. Pseudo 3D images of each identified discontinuity at each site were constructed based on the interpretation of the nonmigrated ground-penetrating radar profiles. These pseudo 3D images were hand-migrated and transformed into true 3D images which depict variable depths at “perpendicular horizontal distance” to each discontinuity relative to the exposed rock face. The results demonstrate that GPR can be used to detect and map hidden discontinuities. This information can then be used for rock slope stability analysis and rock engineering purposes.  相似文献   

Sporadic formation of slope streaks on Mars     

Norbert Schorghofer  Christina M. King 《Icarus》2011,216(1):159-168

Slope streaks are a form of gravity-driven mass-movements that frequently occur on Mars today. The cause of slope streak formation remains unclear; both, dry and wet processes have been suggested. Here, we observationally constrain the time of the year during which slope streaks form. Imagery from four Mars-orbiting cameras is mined to identify locations that have been imaged repeatedly, and the overlapping images are surveyed for streak activity. A search algorithm automatically finds the locations on the surface that have been imaged most often based on a graph representation. Dark slope streaks are found to form sporadically throughout the Mars year. At one study site in the Olympus Mons Aureole, observations constrain slope streak formation to at least five distinct time intervals within a single Mars year. New slope streaks form spatially isolated or in small groups within a few kilometers of one another. The observations suggest that slope streak triggering is unrelated to season and not caused by any large regional events. Most slope streaks are caused by sporadic events of small spatial extent.  相似文献   

World space observatory-ultraviolet among UV missions of the coming years     

Boris Shustov  Mikhail Sachkov  Ana I. Gómez?de?Castro  Klaus Werner  Norbert Kappelmann  Alexander Moisheev 《Astrophysics and Space Science》2011,335(1):273-282

Continuous access to the UV domain has been considered of importance to astrophysicists and planetary scientists since the mid-sixties. However, the future of UV missions for the post-HST era is believed by a significant part of astronomical community to be less encouraging. We argue that key science problems of the coming years will require further development of UV observational technologies. Among these hot astrophysical issues are: the search for missing baryons, revealing the nature of astronomical engines, properties of atmospheres of exoplanets as well as of the planets of the Solar System etc. We give a brief review of UV-missions both in the past and in the future. We conclude that UV astronomy has a great future but the epoch of very large and efficient space UV facilities seems to be a prospect for the next decades. As to the current state of the UV instrumentation we think that this decade will be dominated by the HST and coming World Space Observatory-Ultraviolet (WSO-UV) with a 1.7 m UV-telescope onboard. The international WSO-UV mission is briefly described. It will allow high resolution/high sensitivity imaging and high/low resolution spectroscopy from the middle of the decade.  相似文献   

First Late Triassic Record of a Paleoentomofauna from South America(Malargüe Basin,Mendoza Province,Argentina)   总被引：1，自引：0，他引：1  

Carsten BRAUCKMANN  Oscar F. GALLEGO  Norbert HAUSCHKE  Rafael G. MARTINS-NETO  Elke GROENING  Jan-M. ILGER  María B. LARA 《《地质学报》英文版》2010,84(4):915-924

<正>Late Middle Triassic to early Late Triassic insects from Argentina have been previously described from the Bermejo and Cuyana Basins where they have been recovered from the Ischichuca-Los Rastros and Potrerillos-Cacheuta Formations,respectively.The insect fauna discussed herein was collected during field studies in 1986/1987 from the Llantenes section(Norian to Rhaetian? Late Triassic),which is situated in the Malargue Basin in southern Mendoza province.The insect remains were found in the upper part of the Llantenes section (Llantenes Formation),which is built up of two coarsening-upwards cycles reflecting a deltaic progradation of a fluvial into a lacustrine environment(lower part),succeeded by repeated progradations into a floodplain-dominated environment(upper part;with finds of insects,conchostracans,fish remains,plant fragments,and drifted logs).The new finds represent the youngest Triassic insect records described from Argentina and even from South America in its entirety.There is only one contemporaneous fossil assemblage in Gondwana:in the Clarence/Moreton Basin(Aberdare Conglomerate;Late Norian)in Australia.The new Triassic insects include an impression of an isolated Mecopterida-like wing(Mendozachorista volkheimeri gen.et sp.nov.; Mendozachoristidae fam.nov.),coleopteran elytra of the Permosynidae(Ademosyne rosenfeldi sp.nov.and Ademosyne llantenesensis sp.nov.)and other isolated body fragments.This new Late Triassic entomofauna from Argentina is of considerable importance in the reconstruction of the biotic recovery of continental environments in Gondwana after the catastrophic mass extinction at the P/T boundary.  相似文献   

Sedimentological evidence for environmental changes since 34,000 years BP from Lago di Mezzano, central Italy     

Antje Ramrath  Norbert R. Nowaczyk  Jörg F.w. Negendank 《Journal of Paleolimnology》1999,21(4):423-435

Sediment cores recovered from Lago di Mezzano, central Italy, were petrographically and geochemically (dry densitity, total organic carbon) investigated. A floating chronology was established with sedimentation rates derived from varve thickness measurements, and this chronology was both supported and extrapolated with calibrated AMS-14C-datings. The profile has a length of 29.7 m and comprises a total of 34,000 years.Late Pleistocene sediments consist of minerogenic-organic mud with few benthic diatoms and an organic carbon content of 2%, thus suggesting a high allochthonous input. The onset of the Late Glacial at 14,580 cal BP is documented by a lithologic change to more organic-dominated sedimentation. The Younger Dryas cold event is recorded between 12,650 and 11,400 cal BP and exhibits higher dry densities and minerogenic input. These dates agree with records from other lacustrine archives in Europe and the Greenland ice cores.The early Holocene comprises a laminated organic diatom gyttja deposited at a time of climatic amelioration and increased primary productivity. The establishment of an anoxic hypolimnion enhanced the varve and organic matter preservation. Since 3700 varve years BP the sedimentation pattern has been strongly influenced by human impact, as documented by the increase in minerogenic sediments and turbidites as well as higher sedimention rates. The onset of this influence coincides with a Bronze Age settlement at the lake shore.  相似文献   

The response of vegetation cover and dune activity to rainfall,drought and fire observed by multitemporal satellite imagery     

Adrian Fisher  Paul P. Hesse 《地球表面变化过程与地形》2019,44(15):2957-2967

The stable longitudinal dunes in the northern Simpson Desert, Australia, were observed in satellite imagery to become more active after vegetation cover was reduced by fire and drought. Subsequent rainfall events also resulted in significant vegetation regrowth and dune stabilization. These switches between more active and stable conditions have not been previously described in the largely vegetated dune fields of central Australia. The observations, made on 12 dune sites, relied on high spatial resolution satellite imagery to observe dune crest activity, and seasonal Landsat fractional cover imagery to observe vegetation cover changes. The non-photosynthetic vegetation (NPV) component of the fractional vegetation cover images revealed significant changes in hummock grass cover on the dunes between 1988 and 2018, with a positive relationship with the three-year cumulative rainfall, disrupted by two periods of patchy burning. Only those sites that had burnt became active, and only after vegetation cover had remained low (NPV < 16%) during the ‘Millennium Drought’. There is no threshold in vegetation cover, below which dune crests become active, but active dune features require four-years of low NPV cover (< 16%) to develop. The large rainfall event that ended the drought increased NPV cover, stabilizing the dunes. Similar hummock grass covered dunes are present across large areas of the arid zone, and are likely to respond in similar ways, given that fire and drought are common occurrences in Australia. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.  相似文献