Climate forcing due to the 8200 cal yr BP event observed at Early Neolithic sites in the eastern Mediterranean     

Bernhard Weninger  Eva Alram-Stern  Eva Bauer  Lee Clare  Uwe Danzeglocke  Olaf Jris  Claudia Kubatzki  Gary Rollefson  Henrieta Todorova  Tjeerd van Andel 《Quaternary Research》2006,66(3):401-420

We explore the hypothesis that the abrupt drainage of Laurentide lakes and associated rapid switch of the North Atlantic thermohaline circulation 8200 yr ago had a catastrophic influence on Neolithic civilisation in large parts of southeastern Europe, Anatolia, Cyprus, and the Near East. The event at 8200 cal yr BP is observed in a large number of high-resolution climate proxies in the Northern Hemisphere, and in many cases corresponds to markedly cold and arid conditions. We identify the relevant archaeological levels of major Neolithic settlements in Central Anatolia, Cyprus, Greece and Bulgaria, and examine published stratigraphic, architectural, cultural and geoarchaeological studies for these sites. The specific archaeological events and processes we observe at a number of these sites during the study interval 8400–8000 cal yr BP lead us to refine some previously established Neolithisation models. The introduction of farming to South-East Europe occurs in all study regions (Thrace, Macedonia, Thessaly, Bulgaria) near 8200 cal yr BP. We observe major disruptions of Neolithic cultures in the Levant, North Syria, South-East Anatolia, Central Anatolia and Cyprus, at the same time. We conclude that the 8200 cal yr BP aridity event triggered the spread of early farmers, by different routes, out of West Asia and the Near East into Greece and Bulgaria.  相似文献   

Environmental changes and the Migration Period in northern Germany as reflected in the sediments of Lake Dudinghausen     

Mirko Dreßler  Uwe Selig  Sven Adler  Thomas Hübener 《Quaternary Research》2006,66(1):25-37

Paleolimnological techniques were used to identify environmental changes in and around Lake Dudinghausen (northern Germany) over the past 4800 yr. Diatom-inferred total phosphorus (DI-TP) changes identify four phases of high nutrient levels (2600-2200 BC, 1050-700 BC, 500 BC-AD 100 and AD 1850-1970). During these high DI-TP phases, fossil pollen, sediment geochemistry and archaeological records indicate human activities in the lake catchment. Although the same paleo-indicators suggest increased human settlement and agriculture activity during the late Slavonic Age, the Medieval Time and the Modern Time (AD 1000-1850), DI-TP levels were low during this period. In the sediments, iron and total phosphorus were high from ∼AD 100 to 1850, likely due to increased inflow of iron-rich groundwater into the lake. Increased iron input would have lead to a simultaneous binding and precipitation of phosphate in the upper sediment and overlying water column. As a result, anthropogenic impact on Lake Dudinghausen was masked by these phosphorus-controlling processes from AD 1000 to 1850 and was not evident by means of DI-TP. In accordance with fossil pollen, sediment geochemistry and limited archaeological records, DI-TP levels were low from AD 100-1000. Groundwater levels likely rose during this period as the climate gradually changed toward colder and/or moister conditions. Such climate change likely led to reduced settlement activities and forest regeneration in the catchment area. Our results are concordant with similar studies from central Europe which indicate rapid decreasing settlement activities from AD 100 to 1000.  相似文献   

An OSL, radiocarbon and tephra isochron-based chronology for Birdlings Flat loess at Ahuriri Quarry, Banks Peninsula, Canterbury, New Zealand     

Peter C. Almond  Fiona L. Shanhun  Uwe Rieser  James Shulmeister 《Quaternary Geochronology》2007,2(1-4):4-8

OSL, radiocarbon dating of pedogenic carbonate and tephrochronology have been used in an attempt to provide a detailed and reliable chronology for Birdlings Flat loess, a thick, proximal loess found on the lower flanks of Banks Peninsula, Canterbury, New Zealand. In a ca 15 m thick section at Ahuriri Quarry the Kawakawa tephra isochron of 26,500 cal. yr BP is identified at a depth of ca. 1.35 m on the basis of glass counting and electron microprobe fingerprinting. Radiocarbon ages of filamentous or root pseudomorph carbonate increase down section from ca. 10,000 cal. yr BP at 2.80 m to ca. 30,000 ¹⁴C yr BP at 10.90 m. Ages from carbonate lining cracks are often out of sequence, indicating deep percolation by bypass flow down preferential flow paths. OSL ages show reversals with respect to each other, carbonate radiocarbon ages, and with the position and accepted age of Kawakawa tephra. Coincident radiocarbon and OSL ages at 3.85 m depth indicate that OSL ages are underestimates by at least 20%. Before OSL can be deemed a high accuracy dating method of the quatzo-feldspathic loess of South Island, New Zealand, more research into the causes of age underestimation and age reversals must be carried out. The last major episode of loess accumulation on the flanks of Banks Peninsula in Canterbury began before ca. 30,000 ¹⁴C yr BP (ca. 35,000 cal. yr BP) and possibly before 43,000 yr based on OSL.  相似文献   

Optically stimulated luminescence dating of sublittoral and intertidal sediments from Dubai, UAE: Radioactive disequilibria in the uranium decay series   总被引：1，自引：0，他引：1  

Anja Zander  Detlev Degering  Frank Preusser  Haino Uwe Kasper  Helmut Brückner 《Quaternary Geochronology》2007,2(1-4):123-128

Shallow marine and intertidal shell rich sediments from the low coastal plain of Dubai were dated by optically stimulated luminescence. Combined high-resolution gamma spectrometry and ICP–MS analyses revealed significant disequilibria in the ²³⁸U decay series. Time dependent dose rates were modelled for two scenarios including a closed system and an open system with linear U and Ra uptake. OSL ages that were calculated using the linear uptake model are in good agreement with archaeological evidence and radiocarbon datings on shells and wood. The presented results illustrate that luminescence-dating techniques are suitable to set up a chronostratigraphic frame for calcareous coastal environments if an appropriate model is applied to consider the influence of radioactive disequilibria and time dependent dose rates. A comprehensive radionuclide analysis of the sediments is thought necessary to perform geochemically supported dose rate simulations.  相似文献   

The effect of land surface changes on Eemian climate     

Guy Schurgers  Uwe Mikolajewicz  Matthias Gröger  Ernst Maier-Reimer  Miren Vizcaíno  Arne Winguth 《Climate Dynamics》2007,29(4):357-373

Transient experiments for the Eemian (128–113 ky BP) were performed with a complex, coupled earth system model, including atmosphere, ocean, terrestrial biosphere and marine biogeochemistry. In order to investigate the effect of land surface parameters (background albedo, vegetation and tree fraction and roughness length) on the simulated changes during the Eemian, simulations with interactive coupling between climate and vegetation were compared with additional experiments in which these feedbacks were suppressed. The experiments show that the influence of land surface on climate is mainly caused by changes in the albedo. For the northern hemisphere high latitudes, land surface albedo is changed partially due to the direct albedo effect of the conversion of grasses into forest, but the indirect effect of forests on snow albedo appears to be the major factor influencing the total absorption of solar radiation. The Western Sahara region experiences large changes in land surface albedo due to the appearance of vegetation between 128 and 120 ky BP. These local land surface albedo changes can be as much as 20%, thereby affecting the local as well as the global energy balance. On a global scale, latent heat loss over land increases more than 10% for 126 ky BP compared to present-day.  相似文献   

Magmatic source and metamorphic grade of metavolcanic rocks from the Granjeno Schist: was northeastern Mexico a part of Pangaea?     

Sonia Alejandra Torres Snchez  Carita Augustsson  Jos Rafael Barboza Gudio  Uwe Jenchen  Juan Alonso Ramírez Fernndez  Michael Abratis  Anders Scherstn 《Geological Journal》2016,51(6):845-863

The geochemistry of the metavolcanic rocks from the Granjeno Schist in northeastern Mexico indicates an origin in different tectonic environments: mid‐ocean ridge and ocean island. High ratios of Hf/Th and Th/Nb (4.4–14 and 0.08–0.15), low ratios of LaN/YbN and LaN/SmN (0.74–1.7 and 0.60–1.4) and depleted LREE patterns in metabasalt display mid‐ocean ridge characteristics. In contrast, the pattern of trace‐element ratios and REEs in metabasalt and metapillow lava 60 km to the west indicates a magma source with ocean‐island basalt characteristics. Both areas were metamorphosed during the Late Carboniferous (300 ± 4 Ma). Estimated metamorphic conditions deduced from white mica and chlorite compositions, distinguish greenschist facies (350 °C and 4 kbar) for the mid‐ocean ridge basalt, and prehnite–pumpellyite facies (250 °C and 2.5 kbar) for the ocean‐island‐type basalt. This metamorphism took place at an active continental margin during Pennsylvanian time. Our new tectonic model, which differs from earlier models, suggests that the origin of the Granjeno Schist is related to a subduction zone located at the western margin of Pangaea, active after Laurentia–Gondwana collision. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

A Meta‐Analysis on the Return on Investment of Geospatial Data and Systems: A Multi‐Country Perspective          下载免费PDF全文

Natalie Trapp  Uwe A. Schneider  Ian McCallum  Steffen Fritz  Christian Schill  Maria Teresa Borzacchiello  Christine Heumesser  Max Craglia 《Transactions in GIS》2015,19(2):169-187

The availability, quality and accessibility of Geographic Information (GI) have significant socio‐economic and environmental benefits, but the collection and maintenance of GI require substantial investments. Cost‐benefit assessments (CBAs) attempt to justify the costs of geospatial data investments, applying different methodologies and focusing on diverse areas. Therefore, the Returns on Investment (ROI) vary considerably across studies, regions and sectors. The objective of this study is to explain some of the variation in the average ROI of GI by conducting a meta‐analysis of 82 cost‐benefit assessments between 1994 and 2013. In a first step, CBAs are systematically reviewed and relevant information is extracted. Particular emphasis is given to investment conditions and study characteristics. In a second step, multivariate regression methods are used to assess the size, significance and direction of individual effects. The results suggest that regional factors have the largest impact on the profitability of GI. Returns in Australia and New Zealand, for example, are four times larger than in Europe. In addition, small‐scale regional investments have a 2.5 times lower return than large‐scale international investments. Overall, the expected benefits of GI investments are approximately 3.2 times larger than the costs.  相似文献   

Ichthyofauna in the upper Rhine River close to the city of Karlsruhe as determined by the analysis of fish impingement by cooling-water intakes of a power plant     

Frankie Thielen  Uwe Weibel  Jürgen Hirt  Marcel Münderle  Michael Marten  Horst Taraschewski  Bernd Sures 《Limnologica》2008,38(1):76-85

The fish fauna in the northern part of the upper river Rhine close to the city of Karlsruhe (Germany) was analyzed by collecting fish from the cooling-water intake of a power plant (impingement method) between 1989 and 2001. With this method a total of 36 fish species were recorded. The results were compared between the years as well as with other studies on the fish fauna in this area. Particularly with regard to the physical structure of the river bed and banks, the pre-technical situation of the river Rhine has not been restored. However, the number of fish species has been augmented since the 1970s mainly due to improvements in the water quality and almost all autochthonous fish species are present again. Altogether only three introduced fish species (Sander lucioperca L., Lepomis gibbosus L., and Carassius auratus gibelio were found in this study. Among the long-distance migrating species three freshwater spawners (Lampetra fluviatilis, Petromyzon marinus and Salmo trutta trutta) were detected in addition to the catadromous eel. The eudominant fish species varied between years, i.e. the European eel, Anguilla anguilla, was the eudominant species 1989, whereas this species occurred in much lower numbers during the subsequent sampling campaigns. This clearly indicates that the high dominance of eels is mainly caused by stocking activities in the upper Rhine. In the following years roach, Rutilus rutilus was the eudominant fish species. Overall a positive development of the fish fauna in the upper Rhine over the last 15 years could be observed in terms of fish populations as well as in terms of species richness.  相似文献   

Miocene to Quaternary basin evolution at the southeastern Andean Plateau (Puna) margin (ca. 24°S lat,Northwestern Argentina)     

Heiko Pingel  Ricardo N. Alonso  Uwe Altenberger  John Cottle  Manfred R. Strecker 《Basin Research》2019,31(4):808-826

The Andean Plateau of NW Argentina is a prominent example of a high‐elevation orogenic plateau characterized by internal drainage, arid to hyper‐arid climatic conditions and a compressional basin‐and‐range morphology comprising thick sedimentary basins. However, the development of the plateau as a geomorphic entity is not well understood. Enhanced orographic rainout along the eastern, windward plateau flank causes reduced fluvial run‐off and thus subdued surface‐process rates in the arid hinterland. Despite this, many Puna basins document a complex history of fluvial processes that have transformed the landscape from aggrading basins with coalescing alluvial fans to the formation of multiple fluvial terraces that are now abandoned. Here, we present data from the San Antonio de los Cobres (SAC) area, a sub‐catchment of the Salinas Grandes Basin located on the eastern Puna Plateau bordering the externally drained Eastern Cordillera. Our data include: (a) new radiometric U‐Pb zircon data from intercalated volcanic ash layers and detrital zircons from sedimentary key horizons; (b) sedimentary and geochemical provenance indicators; (c) river profile analysis; and (d) palaeo‐landscape reconstruction to assess aggradation, incision and basin connectivity. Our results suggest that the eastern Puna margin evolved from a structurally controlled intermontane basin during the Middle Miocene, similar to intermontane basins in the Mio‐Pliocene Eastern Cordillera and the broken Andean foreland. Our refined basin stratigraphy implies that sedimentation continued during the Late Mio‐Pliocene and the Quaternary, after which the SAC area was subjected to basin incision and excavation of the sedimentary fill. Because this incision is unrelated to baselevel changes and tectonic processes, and is similar in timing to the onset of basin fill and excavation cycles of intermontane basins in the adjacent Eastern Cordillera, we suspect a regional climatic driver, triggered by the Mid‐Pleistocene Climate Transition, caused the present‐day morphology. Our observations suggest that lateral orogenic growth, aridification of orogenic interiors, and protracted plateau sedimentation are all part of a complex process chain necessary to establish and maintain geomorphic characteristics of orogenic plateaus in tectonically active mountain belts.  相似文献   

Localized shock-induced melting of sandstone at low shock pressures (<17.5 GPa): An experimental study          下载免费PDF全文

Matthias Ebert  Astrid Kowitz  Ralf Thomas Schmitt  Wolf Uwe Reimold  Ulrich Mansfeld  Falko Langenhorst 《Meteoritics & planetary science》2018,53(8):1633-1643

Shock-induced recovery experiments were performed to investigate melt formation in porous sandstones in the low shock pressure regime between 2.5 and 17.5 GPa. The sandstone shocked at 2.5 and 5 GPa is characterized by pore closure, fracturing of quartz (Qtz), and compression and deformation of phyllosilicates; no melting was observed. At higher pressures, five different types of melts were generated around pores and alongside fractures in the sandstone. Melting of kaolinite (Kln), illite (Ill), and muscovite (Ms) starts at 7.5, 12, and 15 GPa, respectively. The larger the amount of water in these minerals (Kln ~14 wt%, Ill ~6–10 wt%, and Ms ~4 wt% H₂O), the higher the shock compressibility and the lower the shock pressure required to induce melting. Vesicles in the almost dry silicate glasses attest to the loss of structural water during the short shock duration of the experiment. The compositions of the phyllosilicate-based glasses are identical to the composition of the parental minerals or their mixtures. Thus, this study has demonstrated that phyllosilicates in shocked sandstone undergo congruent melting during shock loading. In experiments at 10 GPa and higher, iron melt from the driver plate was injected into the phyllosilicate melts. During this process, Fe is partitioned from the metal droplets into the surrounding silicate melts, which induced unmixing of silicate melts with different chemical properties (liquid immiscibility). At pressures between 7.5 and 15 GPa, a pure SiO₂ glass was formed, which is located as short and thin bands within Qtz grains. These bands were shown to contain tiny crystals of experimentally generated stishovite.  相似文献