Contents of Volume 48     

Rudolf BráZdil  Christian Pfister  Heinz Wanner  Hans Von Storch  JüRg Luterbacher 《Climatic change》2001,48(4):653-655

Volume Contents

Contents of Volume 48  相似文献   

Composition of organic matter in subducted and unsubducted sediments off the Nicoya peninsula, Costa Rica (ODP Leg 170, Sites 1039 and 1040)     

Rüdiger Lutz  Birgit Gieren  Andreas Lückge  Heinz Wilkes  Ralf Littke 《Organic Geochemistry》2000,31(12)

Investigation of sediment samples from Sites 1039 and 1040 (ODP Leg 170) drilled off the Nicoya peninsula (Costa Rica) by organic geochemical and organic petrological methods has revealed that subduction has only little influence on the composition of the sedimentary organic matter. Organic carbon contents reached 1.5% in the Pleistocene samples but Miocene and Pliocene sediments had an average organic carbon content of less than 0.5%. Organic carbon/sulfur ratios are generally below 2.8, reflecting an intense sulfate reduction in the uppermost sediments which was enhanced by sulfate supply both from sea water and deeper strata. Microscopical examinations indicate that the organic matter is mainly derived from marine sources. A small amount of terrigenous organic matter is, however, present as well according to n-alkane and fatty acid distributions. The alkenone unsaturation index U₃₇^k′ shows only a slight decrease during the Miocene and Pliocene, and stronger variations in the Pleistocene, probably indicating more stable sea surface temperatures during the Miocene and Pliocene. Variations in the Pleistocene can possibly be related to glacial/interglacial changes.  相似文献   

Impact of managed aquifer recharge on the chemical and isotopic composition of a karst aquifer,Wala reservoir,Jordan   总被引：1，自引：1，他引：0  

Julian Xanke  Nadine Goeppert  Ali Sawarieh  Tanja Liesch  Jochen Kinger  Wasim Ali  Heinz Hötzl  Khair Hadidi  Nico Goldscheider 《Hydrogeology Journal》2015,23(5):1027-1040

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Degradation of algal lipids by deep-sea benthic foraminifera: An in situ tracer experiment     

Hidetaka Nomaki  Naohiko Ohkouchi  Petra Heinz  Hisami Suga  Yoshito Chikaraishi  Nanako O. Ogawa  Kouhei Matsumoto  Hiroshi Kitazato 《Deep Sea Research Part I: Oceanographic Research Papers》2009,56(9):1488-1503

We conducted an in situ feeding experiment using ¹³C-labeled unicellular algae in Sagami Bay, Japan (water depth, 1450 m), in order to understand the fate of lipid compounds in phytodetritus at the deep-sea floor. We examined the incorporation of excess ¹³C into lipid compounds extracted from bulk sediments and benthic foraminiferal cells. ¹³C-enriched fatty acids derived from ¹³C-labeled algae were exponentially degraded during 6 days of incubation in the sediment. Subsequent enrichments in ¹³C in sedimentary n-C_15, anteiso-C₁₇, and C₁₇ fatty acids indicated the microbial degradation of algal material and production of bacterial biomass in the sediment. We observed the incorporation of ¹³C-labeled algal phytol and fatty acids into foraminiferal cells. The compositions of ¹³C-labeled algal lipids in foraminiferal cells were different from those in the bulk sediments, indicating that foraminiferal feeding and digestion influenced the lipid distribution in the sediments. Furthermore, some sterols in Globobulimina affinis (e.g., 24-ethylcholesta-5,22-dien-3β-ol, 24-ethylcholest-5-en-3β-ol, and 23,24-dimethylcholesta-5,22E-dien-3β-ol) were newly produced via the modification of dietary algal sterols within 4–6 days. In addition to the effects of bacteria, feeding by benthic foraminifera can result in a significant reorganization of the composition of organic matter and influence benthic food webs and carbon cycling at the deep-sea floor.  相似文献   

Ureilite petrogenesis: A limited role for smelting during anatexis and catastrophic disruption     

Paul H. Warren  Heinz Huber 《Meteoritics & planetary science》2006,41(6):835-849

Abstract— A popular model for ureilites assumes that during anatexis in an asteroidal mantle, pressure‐buffered equilibrium smelting (partial reduction coincident with partial melting) engendered their conspicuous mafic‐silicate‐core mg diversity (75–96 mol%). Several mass‐balance problems arise from this hypothesis. Smelting inevitably consumes a large proportion of any plausible initial carbon while generating significant proportions of Fe metal and copious proportions of CO gas. The most serious problem concerns the yield of CO gas. If equilibrium smelting produced the ureilites' entire 21 mol% range in olivine‐core mg, the proportion of gas within the asteroidal mantle (assuming plausibly low pressure <˜80 bar) should have reached ≥85 vol%. Based on the remarkably stepwise cooling history inferred from ureilite texture and mineralogy, a runaway, CO‐leaky process that can loosely be termed smelting appears to have occurred, probably triggered by a major impact. The runaway scenario appears likely because, by Le Châtelier's principle, CO leakage would tend to accelerate the smelting process. Also, the copious volumes of gas produced by smelting would have led to explosive, mass‐leaky eruptions into the vacuum surrounding the asteroid. Loss of mass would mean diminution of interior pressure, which would induce further smelting, leading to further loss of mass (basalt), and so on. Such a disruptive runaway process may have engendered the ureilites' distinctive reduced olivine rims. But the only smelting, according to this scenario, was a short‐lived disequilibrium process that reduced only the olivine rims, not the cores; and the ureilites were cooling, not melting, during the abortive “smelting” episode.  相似文献   

German Democratic Republic — Regional structure and development     

Heinz Lüdemann 《GeoJournal》1984,8(1):4-6

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Remarks on the convergency of photospheric model conceptions and the solar quasi continuum     

Dietrich Labs  Heinz Neckel 《Solar physics》1972,22(1):64-69

A comparison is made of the observed intensity in the solar continuous spectrum with those predicted by some models. Arguments are given that the bend-off observed for < 0.6 is a real phenomenon, and due to a veiled line haze.  相似文献   

Environmental changes and carbon cycle perturbations at the Triassic–Jurassic boundary in northern Switzerland     

Nathan Looser  Elke Schneebeli-Hermann  Heinz Furrer  Thomas M. Blattmann  Stefano M. Bernasconi 《Swiss Journal of Geoscience》2018,111(3):445-460

The Triassic–Jurassic boundary is characterized by strong perturbations of the global carbon cycle, triggered by massive volcanic eruptions related to the onset of the Central Atlantic Magmatic Province. These perturbations are recorded by negative carbon isotope excursions (CIEs) which have been reported worldwide. In this study, Triassic–Jurassic boundary sections from the southern margin of the Central European Basin (CEB) located in northern Switzerland are analyzed for organic carbon and nitrogen isotopes in combination with particulate organic matter (POM) analyses. We reconstruct the evolution of the depositional environment from Late Triassic to Early Jurassic in northern Switzerland and show that observed negative shifts in δ¹³C of the total organic carbon (δ¹³C_TOC) in the sediment are only subordinately influenced by varying organic matter (OM) composition and primarily reflect global changes in the carbon cycle. Based on palynology and the stratigraphic positions of isotopic shifts, the δ¹³C_TOC record of the studied sections is correlated with the GSSP section at Kuhjoch (Tethyan realm) in Austria and with the St. Audrie’s Bay section (CEB realm) in southwest England. We also show that in contrast to POM analyses the applicability of organic carbon/total nitrogen (OC/TN) atomic ratios and stable isotopes of total nitrogen (δ¹⁵N_TN) for detecting changes in source of OM is limited in marginal depositional environments with frequent changes in lithology and OM contents.  相似文献   

<Superscript>10</Superscript>Be surface exposure dating of the last deglaciation in the Aare Valley,Switzerland     

Lorenz Wüthrich  Ezequiel Garcia Morabito  Jana Zech  Mareike Trauerstein  Heinz Veit  Christian Gnägi  Silke Merchel  Andreas Scharf  Georg Rugel  Marcus Christl  Roland Zech 《Swiss Journal of Geoscience》2018,111(1-2):295-303

The combined Rhone and Aare Glaciers presumably reached their last glacial maximum (LGM) extent on the Swiss Plateau prior to 24 ka. Two well-preserved, less extensive moraine stades, the Gurten and Bern Stade, document the last deglaciation of the Aare Valley, yet age constraints are very scarce. In order to establish a more robust chronology for the glacial/deglacial history of the Aare Valley, we applied ¹⁰Be surface exposure dating on eleven boulders from the Gurten and Bern Stade. Several exposure ages are of Holocene age and likely document post-depositional processes, including boulder toppling and quarrying. The remaining exposure ages, however yield oldest ages of 20.7 ± 2.2 ka for the Gurten Stade and 19.0 ± 2.0 ka for the Bern Stade. Our results are in good agreement with published chronologies from other sites in the Alps.  相似文献   

Discrete element simulation of geogrid-stabilised soil     

Michael Stahl  Heinz Konietzky  Lothar te Kamp  Hein Jas 《Acta Geotechnica》2014,9(6):1073-1084

A particle-based numerical simulation procedure is presented for the generation and calibration of geogrid-stabilised soil on the basis of experimental data. The paper describes how to simulate a biaxial geogrid depending on a specific particle and parallel bond model. Numerical and experimental pull-out tests have been performed to reproduce the pull-out force–strain behaviour of a biaxial geogrid specimen embedded in granular material under special consideration of the grain-size distribution, initial relative density, normal stress state as well as sample installation. Model analysis of soil mobilisation and geogrid deformation is presented to understand the significance of the interlocking effect as key mechanism for soil stabilisation. The procedure can be used for further investigations of the influence and effects of soil stabilisation depending on the significant properties of the interacting components (soils and geogrids).  相似文献