One million years of cultural evolution in a stable environment at Atapuerca (Burgos,Spain)     

J. Rodríguez  F. Burjachs  G. Cuenca-Bescós  N. García  J. Van der Made  A. Pérez González  H.-A. Blain  I. Expósito  J.M. López-García  M. García Antón  E. Allué  I. Cáceres  R. Huguet  M. Mosquera  A. Ollé  J. Rosell  J.M. Parés  X.P. Rodríguez  C. Díez  J. Rofes  E. Carbonell 《Quaternary Science Reviews》2011,30(11-12):1396-1412

The present paper analyses the evidence provided by three sites (Sima del Elefante, Gran Dolina, and Galería) located in the Trinchera del Ferrocarril of the Sierra de Atapuerca. These three sites are cave infillings that contain sediments deposited from approximately 1.2 Ma to 200 kyr. Pollen, herpetofauna, and small and large mammal remains are used as proxies to obtain a general picture of the environmental changes that occurred at the Sierra de Atapuerca throughout the one million-year period represented at these sites. Similarly, cultural changes are tracked analyzing the evidence of human behavior obtained from the study of several bone and lithic assemblages from these three sites. At least three periods with different cultural features, involving technology, subsistence and behavior, are determined from the available evidence. The first two periods correspond to the Mode 1 technology and Homo antecessor: the first is dated around 1.2 to 1.0 Ma and reflects opportunistic behavior both in technology and subsistence. The second period is around 800 kyr BP. Mode 1 technology is still maintained, but subsistence strategies include systematic hunting and the use of base camps. The third period is dated between 500 ka and 200 ka and corresponds to the Mode 2 technology and the acquisition of directional hunting and other organizational strategies by Homo heidelbergensis. A transition from Mode 2 to Mode 3 seems to appear at the end of this time-range, and may reflect the early phases of a fourth cultural change. With regard to the environment, our main conclusion is that there was an absence of extremely harsh conditions at Atapuerca throughout this time period. The presence of Mediterranean taxa was constant and the dominant landscape was a savannah-like open environment, probably with small forest patches. An alternation of Mediterranean and mesic species as the dominant component of the tree storey was induced by the climatic cycles, and steppes spread across the landscape during the drier periods. In any case, it is not possible to establish clear cut-off points separating entirely different environmental episodes. Our results show no evidence of any relationship between environmental change and cultural change at the Sierra de Atapuerca.  相似文献   

Development of a three‐dimensional watershed modelling system for water cycle in the middle part of the Heihe rivershed,in the west of China     

Jian Zhou  Bill X. Hu  Guodong Cheng  Genxu Wang  Xin Li 《水文研究》2011,25(12):1964-1978

A three‐dimensional numerical modelling system is developed to study transformation processes of water resources in alluvial fan and river basin along the middle reaches of the Heihe River Basin, Northwest China, an arid and semi‐arid region. Integrating land utilization, remote sensing and geographic information systems, we have developed a numerical modelling system that can be used to quantify the effects of land use and anthropogenic activities on the groundwater system as well as to investigate the interaction between surface water and groundwater. Various hydraulic measurements are used to identify and calibrate the hydraulic boundary conditions and spatial distributions of hydraulic parameters. In the modelling study, various water exchanges and human effects on the watershed system are considered. These include water exchange between surface water and groundwater, groundwater pumping, lateral water recharges from mountain areas, land utilization, and infiltration and evaporation in the irrigation and non‐irrigation areas. The modelling system provides a quantitative method to describe spatial and temporal distributions and transformations between various water resources, and it has application to other watersheds in arid and semi‐arid areas. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Hydrocarbon- and ore-bearing basinal fluids: a possible link between gold mineralization and hydrocarbon accumulation in the Youjiang basin,South China   总被引：5，自引：0，他引：5  

X.?X.?GuEmail author  Y.?M.?Zhang  B.?H.?Li  S.?Y.?Dong  C.?J.?Xue  S.?H.?Fu 《Mineralium Deposita》2012,47(6):663-682

The Youjiang basin, which flanks the southwest edge of the Yangtze craton in South China, contains many Carlin-type gold deposits and abundant paleo-oil reservoirs. The gold deposits and paleo-oil reservoirs are restricted to the same tectonic units, commonly at the basinal margins and within the intrabasinal isolated platforms and/or bioherms. The gold deposits are hosted by Permian to Triassic carbonate and siliciclastic rocks that typically contain high contents of organic carbon. Paragenetic relationships indicate that most of the deposits exhibit an early stage of barren quartz ± pyrite (stage I), a main stage of auriferous quartz + arsenian pyrite + arsenopyrite + marcasite (stage II), and a late stage of quartz + calcite + realgar ± orpiment ± native arsenic ± stibnite ± cinnabar ± dolomite (stage III). Bitumen in the gold deposits is commonly present as a migrated hydrocarbon product in mineralized host rocks, particularly close to high grade ores, but is absent in barren sedimentary rocks. Bitumen dispersed in the mineralized rocks is closely associated and/or intergrown with the main stage jasperoidal quartz, arsenian pyrite, and arsenopyrite. Bitumen occurring in hydrothermal veins and veinlets is paragenetically associated with stages II and III mineral assemblages. These observations suggest an intimate relationship between bitumen precipitation and gold mineralization. In the paleo-petroleum reservoirs that typically occur in Permian reef limestones, bitumen is most commonly observed in open spaces, either alone or associated with calcite. Where bitumen occurs with calcite, it is typically concentrated along pore/vein centers as well as along the wall of pores and fractures, indicating approximately coeval precipitation. In the gold deposits, aqueous fluid inclusions are dominant in the early stage barren quartz veins (stage I), with a homogenization temperature range typically of 230°C to 270°C and a salinity range of 2.6 to 7.2 wt% NaCl eq. Fluid inclusions in the main and late-stage quartz and calcite are dominated by aqueous inclusions as well as hydrocarbon- and CO₂-rich inclusions. The presence of abundant hydrocarbon fluid inclusions in the gold deposits provides evidence that at least during main periods of the hydrothermal activity responsible for gold mineralization, the ore fluids consisted of an aqueous solution and an immiscible hydrocarbon phase. Aqueous inclusions in the main stage quartz associated with gold mineralization (stage II) typically have a homogenization temperature range of 200–230°C and a modal salinity around 5.3 wt% NaCl eq. Homogenization temperatures and salinities of aqueous inclusions in the late-stage drusy quartz and calcite (stage III) typically range from 120°C to 160°C and from 2.0 to 5.6 wt% NaCl eq., respectively. In the paleo-oil reservoirs, aqueous fluid inclusions with an average homogenization temperature of 80°C are dominant in early diagenetic calcite. Fluid inclusions in late diagenetic pore- and fissure-filling calcite associated with bitumen are dominated by liquid C₂H₆, vapor CH₄, CH₄–H₂O, and aqueous inclusions, with a typical homogenization temperature range of 90°C to 180°C and a salinity range of 2–8 wt% NaCl eq. It is suggested that the hydrocarbons may have been trapped at relatively low temperatures, while the formation of gold deposits could have occurred under a wider and higher range of temperatures. The timing of gold mineralization in the Youjiang basin is still in dispute and a wide range of ages has been reported for individual deposits. Among the limited isotopic data, the Rb–Sr date of 206 ± 12 Ma for Au-bearing hydrothermal sericite at Jinya as well as the Re–Os date of 193 ± 13 Ma on auriferous arsenian pyrite and ⁴⁰Ar/³⁹Ar date of 194.6 ± 2 Ma on vein-filling sericite at Lannigou may provide the most reliable age constraints on gold mineralization. This age range is comparable with the estimated petroleum charging age range of 238–185 Ma and the Sm–Nd date of 182 ± 21 Ma for the pore- and fissure-filling calcite associated with bitumen at the Shitouzhai paleo-oil reservoir, corresponding to the late Indosinian to early Yanshanian orogenies in South China. The close association of Carlin-type gold deposits and paleo-oil reservoirs, the paragenetic coexistence of bitumens with ore-stage minerals, the presence of abundant hydrocarbons in the ore fluids, and the temporal coincidence of gold mineralization and hydrocarbon accumulation all support a coeval model in which the gold originated, migrated, and precipitated along with the hydrocarbons in an immiscible, gold- and hydrocarbon-bearing, basinal fluid system.  相似文献   

An Intercomparison Study of the Germanium Isotope Composition of Geological Reference Materials     

Raphaelle Escoube  Olivier J. Rouxel  Béatrice Luais  Emmanuel Ponzevera  Olivier F.X. Donard 《Geostandards and Geoanalytical Research》2012,36(2):149-159

Recent analytical developments in germanium stable isotope determination by multicollector ICP‐MS have provided new perspectives for the use of Ge isotopes as geochemical tracers. Here, we report the germanium isotope composition of the NIST SRM 3120a elemental reference solution that has been calibrated relative to internal isotopic standard solutions used in the previous studies. We also intercalibrate several geological reference materials as well as geological and meteoritic samples using different techniques, including online hydride generation and a spray chamber for sample introduction to MC‐ICP‐MS, and different approaches for mass bias corrections such as sample–calibrator bracketing, external mass bias correction using Ga isotopes and double‐spike normalisation. All methods yielded relatively similar precisions at around 0.1‰ (2s) for δ^74/70Ge values. Using igneous and mantle‐derived rocks, the bulk silicate Earth (BSE) δ^74/70Ge value was re‐evaluated to be 0.59 ± 0.18‰ (2s) relative to NIST SRM 3120a. Several sulfide samples were also analysed and yielded very negative values, down to ?4.3‰, consistent with recent theoretical study of Ge isotope fractionation. The strong heavy isotope depletion in ore deposits also contrasts with the generally positive Ge isotope values found in many modern and ancient marine sediments.  相似文献   

Effects of pH on ferri-cyanide uptake and assimilation by several plants     

X. Z. Yu  F. Li  K. Li 《International Journal of Environmental Science and Technology》2012,9(2):227-233

This paper presents an investigation of the capacity of four different plants to remove and assimilate ferri-cyanide at different pH conditions. Detached roots of weeping willows (Salix babylonica L.), rice (Oryza sativa L. cv. JY 98), soybean (Glycine max L. cv. WH) and maize (Zea mays L. var. HK) were hydroponically exposed to ferri-cyanide in a closed system at 25?±?0.5°C for 24?h kept under darkness. Almost all applied ferri-cyanide was in the complex form in the hydroponic solution at pH????7.0 in the absence of light, while dissociation of ferri-cyanide to free cyanide and iron in solution was detected at pH????6.5. All plant species used were found to be able to remove and assimilate ferri-cyanide efficiently. The uptake and assimilation rates appeared to be inversely related to the pH, in which positive effects were observed at pH 6.0 and 6.5. Remarkable decreases in the assimilation rates were found at pH 8.0. Results presented here suggest that changes in solution pH have a substantial influence on not only the speciation of ferri-cyanide in the plant growth media, but also the uptake and assimilation mechanisms of ferri-cyanide by plants.  相似文献   

Creep Failure of Roof Stratum Above Mined-Out Area   总被引：1，自引：0，他引：1  

J. -A. Wang  D. Z. Li  X. C. Shang 《Rock Mechanics and Rock Engineering》2012,45(4):533-546

By taking into account the rheological behavior of the rock mass, the creep failure of a roof stratum seated on pillars in mined-out area is analyzed through a newly developed visco-elastic model. The time-dependent deflection of the roof stratum is obtained by numerical inversion of Laplace transform. The study shows that when creep properties of both the pillars and roof stratum are considered, the expected deflection in the roof stratum increases with time. Consequently, the roof would fail when the critical tensile stress is reached as the result of the increased deflection. To demonstrate the present analytical procedure, the failure time of roof stratum of the Xingtai Gypsum Mine in China was estimated, and the results obtained agreed with the observation. The case study indicates that the analytic approach provides a new way to assess the potential impact of the time-dependence of the roof stratum deformation and is useful in predicting its stability above a mined-out area.  相似文献   

Analytical Study of Underground Explosion-Induced Ground Motion   总被引：1，自引：0，他引：1  

J. C. Li  G. W. Ma  Y. X. Zhou 《Rock Mechanics and Rock Engineering》2012,45(6):1037-1046

A theoretical approach is presented to study the ground motion induced by an underground tunnel explosion. The ground motion is caused by two coupled stress waves, i.e., the reflected body wave and the secondary surface wave or Raleigh wave. Based on the principle of conservation of momentum at the wavefronts, the reflected body waves along the ground surface are derived. The interaction of the body wavefront and the ground surface induces the secondary surface wave which transfers outwards on the ground. The particle velocity and particle acceleration on the ground surface are subsequently derived. The analytical results are compared with results from numerical simulations and empirical formulae with different material damping ratios. The effects of the loading density and the material damping on the ground motion are investigated. Finally, the limitations of the proposed theoretical approach for ground motion prediction are discussed.  相似文献   

Influence of redox conditions on iodide migration through a deep clay formation (Toarcian argillaceous rock,Tournemire, France)     

B. Frasca  S. Savoye  C. Wittebroodt  O.X. Leupin  M. Descostes  B. Grenut  J. Etep-Batanken  J.-L. Michelot 《Applied Geochemistry》2012

With a half-life of 15.7 Ma, a high mobility and the potential to accumulate in the biosphere, ¹²⁹I is considered, in safety assessment calculations for radioactive waste repositories, to be one of the main contributors to the radiological dose. Several authors have reported that, at low concentration, I⁻ is weakly retained on argillaceous rocks. This process is not yet well-understood and different hypotheses have been put forward as to whether reactive phases or experimental artifacts (e.g. pyrite oxidation) could be the reason for the retention of I⁻ observed at low concentration. The aim of this study was to investigate the effect on I⁻ mobility of (i) the redox conditions and (ii) the amount of pyrite and natural organic matter (NOM) contents of the rock. These questions were addressed by performing batch sorption, through-diffusion and out-diffusion experiments on rock samples of Toarcian argillaceous rock from Tournemire (Aveyron, France). One of the challenges faced during this study was to distinguish actual transport properties from experimental artifacts. A especially elaborate experimental set-up allowed limiting the (i) oxidation of both argillaceous rock and I⁻, and (ii) carbonate precipitation. A comparison of the batch sorption results obtained for two Toarcian clay specimens, that differed in their amount of pyrite and NOM, allowed relating I⁻ sorption to pyrite oxidation. However, no evidence was found to associate the I⁻ behavior to the NOM amounts. While the through-diffusion experiments showed a very slight sorption (distribution ratio (R_d) = 0.016 mL g⁻¹) for the lowest I⁻ concentration under oxic conditions, the out-diffusion tests performed after the through-diffusion experiments on the same cells showed significant sorption under both oxic and anoxic conditions, resulting in R_d ranging from 0.02 mL g⁻¹ to 1.25 mL g⁻¹. The range of R_d values was higher for the upstream reservoir under oxic conditions. The discrepancies observed between the through-diffusion and the out-diffusion experiments suggest a kinetic control of the I⁻ uptake by argillaceous rocks under oxic and anoxic conditions.  相似文献   

Formation and characteristics of post-earthquake debris flow: a case study from Wenjia gully in Mianzhu, Sichuan, SW China   总被引：3，自引：0，他引：3  

H. Y. Ni  W. M. Zheng  Y. B. Tie  P. C. Su  Y. Q. Tang  R. G. Xu  D. W. Wang  X. Y. Chen 《Natural Hazards》2012,61(2):317-335

During the three flood seasons following the Wenchuan earthquake in 2008, two catastrophic groups of debris flow events occurred in the earthquake-affected area: the 2008-9-24 debris flow events, which had a serious impact on rebuilding; and the 2010-8-13/14 debris flow events, which destroyed much of the progress made in rebuilding. The Wenjia gully is a typical post-earthquake debris flow gully and at least five debris flows have occurred there. As far as the 2010-8-13 debris flow is concerned, the deposits of the Wenjia gully debris flow reached a volume of 3.1 × 10⁶ m³ in volume and hundreds of newly built houses were buried. This study took the Wenjia gully debris flow as an example and discussed the formation and characteristics of post-earthquake debris flow on the basis of field investigations and a remote sensing interpretation. The conclusions drawn from the investigation and analysis were as follows: (1) Post-earthquake debris flows were a joint result of both the earthquake and heavy rainfall. (2) Gully incision and loose material provision are key processes in the initiation and occurrence of debris flows and a cycle can be presented as the following process: runoff—erosion—collapse—engulfment—debris flow—further erosion—further collapse—further engulfment—debris flow enlargement. (3) The amount of rainfall that triggered debris flows from the Wenjia gully was significantly less than the average daily rainfall, while the intraday rainfall threshold decreased by at least 23.3%. (4) The occurrence mechanism of Wenjia gully debris flow was an erosion type and there was a positive relationship between debris flow magnitude and rainfall, which fitted an exponential model. (5) There were five representative characteristics of Wenjia gully debris flow: the long duration of the occurring process; the long distance of deposition chain conversion during the process of damage; magnification in the scale of debris flow; and the high frequency of debris flow events.  相似文献   

Experimental and numerical analysis on the responses of slope under rainfall   总被引：1，自引：0，他引：1  

X. B. Lu  T. L. Ye  X. H. Zhang  P. Cui  K. H. Hu 《Natural Hazards》2012,64(1):887-902

Rainfall is an important factor to trigger the slope failure such as landslides and debris flows. First, the relationship between rainfall duration with the initiation of debris flow and rainfall intensity was mainly studied by the series tests in a box model. Then, the rainfall induced responses of slopes and the initiation of slope failure were simulated by using the software FLAC2D based on the soil parameters in Weijia Gully, Beichuan County, Sichuan Province. The effects of the slope angle, rainfall intensity, soil parameters on the development of the stress, and pore pressure in the soil of the slope were analyzed. It indicates that largest displacements in the slope are mainly located near the toe. With the increase of the rainfall intensity, the effective stress in the slope decreases and the displacement increases.  相似文献