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  • 1
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    Oldest entirely preserved sponges and other fossils from the Lowermost Cambrian and a new facies reconstruction of the Yangtze platform (China) (2018)
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    Publikationsdatum: 2021-04-27
    Beschreibung: Eine Faziesrekonstruktion W1d Korrelation obersinischer-unterkambrischer Schichten der Yangtze-Plattform (Südchina) wird vorgestellt. Dabei wird zwischen geschütztem Becken, Schwelle W1d tiefem Becken unterschieden. Die unterkambrische Schwarzschiefer-Transgression, der "Badaowan" Event, wird als diachron gekennzeichnet. Nach Untersuchungen der Lithologie W1d Geochemie der unterkambrischen Sedimente, vorwiegend Schwarzschiefer des Profils Sansha (nahe Dayong. N-Hunan), kann zwischen Sedimenten, die unter teilweise anoxischen Bedingungen oder im stagnierenden Becken abgelagert wurden, unterschieden werden. Schwammnadeln sind im untersten Unterkambrium Zentralchinas weit verbreitet. Neufimde vollständiger hexactinellider Schwämme Sanshadictya microreticulata gen. et sp. 0., Hyalosinica archaica gen. et sp.o., Triticispongia diagonata gen. et sp. n., Solactiniella plumata gen. et sp. 0., Hunanospongia sp. QIAN & DING, 1988, Hexactinellida indet., eines fraglichen vertreters der Demospongiae, Saetaspongia densa gen. et sp. 0. sowie eines Vertreters der Malacostraca Perspicaris sp., W1d einer unbenannten A1genfonn, werden vorgestellt. Schwammnadeln wurden ebenfalls neu in Gesteinen des Shibantan Mb. (Dengying Fm., Ob. Proterozoikum) vom Straßenaufschluß Liantuo (nahe Yichang. S-Hubei) gefunden. Die Fauna vorwiegend hexactinellider Schwämme von Sansha wird im Zusammenhang mit den taphonornisch AhnIichen Spongienfaunen des Red Hil1s Quarry (Mitteldevon, Nevada) und des Arnager Kalkes (Kreide, Bomholm) diskutiert.
    Beschreibung: A facies reconstruction and correlation ofUpper Sinian - Lower Cambrian strata ofthe Yangtze platform (South China) is presented. Protected basin, uplift and deep basin development may be distinguished. The Lower Cambrian black shale transgression, the "Badaowan" Event, is characterized as diachronous. As a result of these investigations of lithology and geochemistry of the Lower Cambrian sediments (mainly black shales ofthe Sansha section, near Dayong. N. Hunan), sediments deposited under partially anoxic conditions or in a stagnant basin have been recognized. Sponge spicules are widely distributed in the lowennost Lower Cambrian of CentraI China. Recently discovered more or less complete sponges, including Sanshadictya microreticulata gen. et sp. 0., Hyalosinica archaica gen. et sp. 0., Triticispongia diagonata gen. et sp. 0., Solactiniella plumata gen. et sp. 0., Hunanospongia sp. QIAN & DING, 1988, Hexactinellida indet., a questionable demosponge, Saetaspongia densa gen. et sp. 0., and the Malacostraca Perspicaris sp., and an unnamed a1ga are described. Sponge spicules additionally were found in rocks of the Shibantan Mb. (Dengying Fm., Upper Proterozoic) from the road section of Liantuo (near Yichang. S.Hubei province). The fauna ofmainly hexactinellid poriferans from Sansha is discussed with regard to the similar taphonomy ofthe sponge faunas from the Red Hills Quarry (MiddIe Devonian ofNevada) and from the Arnager Iirnestooe (Cretaceous, Bomholm).
    Schlagwort(e): Paläontologie: Allgemeines ; 551 ; VU 000 ; 38.20 ; 38.2
    Sprache: Englisch
    Materialart: article , publishedVersion
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  • 2
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    A review of air–ice chemical and physical interactions (AICI): liquids, quasi-liquids, and solids in snow (2018)
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    Publikationsdatum: 2021-03-29
    Beschreibung: Snow in the environment acts as a host to rich chemistry and provides a matrix for physical exchange of contaminants within the ecosystem. The goal of this review is to summarise the current state of knowledge of physical processes and chemical reactivity in surface snow with relevance to polar regions. It focuses on a description of impurities in distinct compartments present in surface snow, such as snow crystals, grain boundaries, crystal surfaces, and liquid parts. It emphasises the microscopic description of the ice surface and its link with the environment. Distinct differences between the disordered air–ice interface, often termed quasi-liquid layer, and a liquid phase are highlighted. The reactivity in these different compartments of surface snow is discussed using many experimental studies, simulations, and selected snow models from the molecular to the macro-scale. Although new experimental techniques have extended our knowledge of the surface properties of ice and their impact on some single reactions and processes, others occurring on, at or within snow grains remain unquantified. The presence of liquid or liquid-like compartments either due to the formation of brine or disorder at surfaces of snow crystals below the freezing point may strongly modify reaction rates. Therefore, future experiments should include a detailed characterisation of the surface properties of the ice matrices. A further point that remains largely unresolved is the distribution of impurities between the different domains of the condensed phase inside the snowpack, i.e. in the bulk solid, in liquid at the surface or trapped in confined pockets within or between grains, or at the surface. While surface-sensitive laboratory techniques may in the future help to resolve this point for equilibrium conditions, additional uncertainty for the environmental snowpack may be caused by the highly dynamic nature of the snowpack due to the fast metamorphism occurring under certain environmental conditions. Due to these gaps in knowledge the first snow chemistry models have attempted to reproduce certain processes like the long-term incorporation of volatile compounds in snow and firn or the release of reactive species from the snowpack. Although so far none of the models offers a coupled approach of physical and chemical processes or a detailed representation of the different compartments, they have successfully been used to reproduce some field experiments. A fully coupled snow chemistry and physics model remains to be developed.
    Schlagwort(e): air, ice, liquids, quasi-liquids, solids; snow ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
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  • 3
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    Optimized extraction of dimension stone blocks (2018)
    Springer-Verlag | Berlin/Heidelberg
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    Publikationsdatum: 2021-03-29
    Beschreibung: The profitable production of dimension stone mainly depends on the extractable block size. The regularity and volume of the blocks are of critical importance, and are controlled by the three-dimensional pattern of the discontinuity system. Therefore, optimization of block size has to be the aim when quarrying for natural stone. This is mainly connected to the quantification of joints and fractures, i.e., their spacing and orientation. The problem of finding unfractured blocks within arbitrarily oriented and distributed planes can be solved effectively by a numerical algorithm. The main effects of joint orientations on block sizes and shapes will be presented in this article. Quantification of unfractured blocks with the aim of optimization is illustrated by detailed studies on several quarries. The algorithm used in this study can be applied as a powerful tool in the planning of a quarry and the future exploitation of dimension stone. Application of the described approach is demonstrated on practical examples of quarrying natural stones, namely, sandstone, granite, rhyolite, etc. Block quarrying can be optimized by using the new 3D-BlockExpert approach. The quantification of unfractured rock masses is also shown to contribute to a more ecological protection and the sustainable use of natural resources.
    Schlagwort(e): Production of dimension stones; Joints and fractures; Block sizes; Optimization ; 551 ; Earth Sciences; Geology
    Sprache: Englisch
    Materialart: article , publishedVersion
    Format: application/pdf
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  • 4
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    Physical weathering of building stones induced by freeze–thaw action: a laboratory long-term study (2018)
    Springer-Verlag | Berlin/Heidelberg
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    Publikationsdatum: 2021-03-29
    Beschreibung: Damages to natural building stones induced by the action of frost are considered to be of great importance. Commonly, the frost resistance of building stones is checked by standardised freeze–thaw tests before using. Corresponding tests normally involve 30–50 freeze–thaw action cycles. In order to verify the significance of such measurements, we performed long-term tests on four selected rocks over 1,400 freeze–thaw action cycles. Additionally, numerous petrophysical parameters were analysed to compare the behaviour of rocks in the weathering tests according to the current explanatory models of stress formation by growing ice crystals in the pore space. The long-term tests yield more information about the real frost sensibility of the rocks. A clear deterioration cannot be determined in most cases until 50 weathering cycles have been completed. In the freeze–thaw tests, the samples are also stressed by changing temperature and moisture, indicating that different decay mechanisms can interfere with each other. Thus, thermohygric and moisture expansion are important damage processes.
    Schlagwort(e): Freeze–thaw action; Natural building stones; Microfabric; Pore space properties ; 551 ; Earth Sciences; Geology
    Sprache: Englisch
    Materialart: article , publishedVersion
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  • 5
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    Direct linking of Greenland and Antarctic ice cores at the Toba eruption (74 ka BP) (2018)
    Details
    Publikationsdatum: 2021-03-29
    Beschreibung: The Toba eruption that occurred some 74 ka ago in Sumatra, Indonesia, is among the largest volcanic events on Earth over the last 2 million years. Tephra from this eruption has been spread over vast areas in Asia, where it constitutes a major time marker close to the Marine Isotope Stage 4/5 boundary. As yet, no tephra associated with Toba has been identified in Greenland or Antarctic ice cores. Based on new accurate dating of Toba tephra and on accurately dated European stalagmites, the Toba event is known to occur between the onsets of Greenland interstadials (GI) 19 and 20. Furthermore, the existing linking of Greenland and Antarctic ice cores by gas records and by the bipolar seesaw hypothesis suggests that the Antarctic counterpart is situated between Antarctic Isotope Maxima (AIM) 19 and 20. In this work we suggest a direct synchronization of Greenland (NGRIP) and Antarctic (EDML) ice cores at the Toba eruption based on matching of a pattern of bipolar volcanic spikes. Annual layer counting between volcanic spikes in both cores allows for a unique match. We first demonstrate this bipolar matching technique at the already synchronized Laschamp geomagnetic excursion (41 ka BP) before we apply it to the suggested Toba interval. The Toba synchronization pattern covers some 2000 yr in GI-20 and AIM- 19/20 and includes nine acidity peaks that are recognized in both ice cores. The suggested bipolar Toba synchronization has decadal precision. It thus allows a determination of the exact phasing of inter-hemispheric climate in a time interval of poorly constrained ice core records, and it allows for a discussion of the climatic impact of the Toba eruption in a global perspective. The bipolar linking gives no support for a long-term global cooling caused by the Toba eruption as Antarctica experiences a major warming shortly after the event. Furthermore, our bipolar match provides a way to place palaeoenvironmental records other than ice cores into a precise climatic context.
    Schlagwort(e): Greenland; Antarctic ice cores; Toba eruption ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
    Format: 18
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  • 6
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    Ancient Origin of the Modern Deep-Sea Fauna (2018)
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    Publikationsdatum: 2021-03-29
    Beschreibung: The origin and possible antiquity of the spectacularly diverse modern deep-sea fauna has been debated since the beginning of deep-sea research in the mid-nineteenth century. Recent hypotheses, based on biogeographic patterns and molecular clock estimates, support a latest Mesozoic or early Cenozoic date for the origin of key groups of the present deep-sea fauna (echinoids, octopods). This relatively young age is consistent with hypotheses that argue for extensive extinction during Jurassic and Cretaceous Oceanic Anoxic Events (OAEs) and the mid-Cenozoic cooling of deep-water masses, implying repeated re-colonization by immigration of taxa from shallow-water habitats. Here we report on a well-preserved echinoderm assemblage from deep-sea (1000–1500 m paleodepth) sediments of the NE-Atlantic of Early Cretaceous age (114 Ma). The assemblage is strikingly similar to that of extant bathyal echinoderm communities in composition, including families and genera found exclusively in modern deep-sea habitats. A number of taxa found in the assemblage have no fossil record at shelf depths postdating the assemblage, which precludes the possibility of deep-sea recolonization from shallow habitats following episodic extinction at least for those groups. Our discovery provides the first key fossil evidence that a significant part of the modern deep-sea fauna is considerably older than previously assumed. As a consequence, most major paleoceanographic events had far less impact on the diversity of deep-sea faunas than has been implied. It also suggests that deep-sea biota are more resilient to extinction events than shallow-water forms, and that the unusual deep-sea environment, indeed, provides evolutionary stability which is very rarely punctuated on macroevolutionary time scales.
    Beschreibung: Open-Access-Publikationsfonds 2012
    Schlagwort(e): deep-sea fauna ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
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  • 7
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    Degradation of Root Community Traits as Indicator for Transformation of Tropical Lowland Rain Forests into Oil Palm and Rubber Plantations. (2018)
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    Publikationsdatum: 2021-03-29
    Beschreibung: Conversion of tropical forests into intensely managed plantations is a threat to ecosystem functions. On Sumatra, Indonesia, oil palm (Elaeis guineensis) plantations are rapidly expanding, displacing rain forests and extensively used rubber (Hevea brasiliensis) agro-forests. Here, we tested the influence of land use systems on root traits including chemical traits (carbon, nitrogen, mineral nutrients, potentially toxic elements [aluminium, iron] and performance traits (root mass, vitality, mycorrhizal colonization). Traits were measured as root community-weighed traits (RCWTs) in lowland rain forests, in rubber agro-forests mixed with rain forest trees, in rubber and oil palm plantations in two landscapes (Bukit Duabelas and Harapan, Sumatra). We hypothesized that RCWTs vary with land use system indicating increasing transformation intensity and loss of ecosystem functions. The main factors found to be related to increasing transformation intensity were declining root vitality and root sulfur, nitrogen, carbon, manganese concentrations and increasing root aluminium and iron concentrations as well as increasing spore densities of arbuscular mycorrhizas. Mycorrhizal abundance was high for arbuscular and low for ectomycorrhizas and unrelated to changes in RCWTs. The decline in RCWTs showed significant correlations with soil nitrogen, soil pH and litter carbon. Thus, our study uncovered a relationship between deteriorating root community traits and loss of ecosystem functionality and showed that increasing transformation intensity resulted in decreasing root nutrition and health. Based on these results we suggest that land management that improves root vitality may enhance the ecological functions of intense tropical production systems.
    Beschreibung: Oüpen-Access Publikationsfonds 2015
    Schlagwort(e): Agricultural soil science; Ecosystem functioning; Forests; Jungles; Land use; Oil palm; Rainforests; Rubber ; 551
    Sprache: Englisch , Englisch
    Materialart: article , publishedVersion
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  • 8
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    Large, heterometallic coordination cages based on ditopic metallo-ligands with 3-pyridyl donor groups (2018)
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    Publikationsdatum: 2021-03-29
    Beschreibung: Ditopic N-donor ligands with terminal 4-pyridyl groups are omnipresent in coordination-based selfassembly. The utilization of ligands with 3-pyridyl donor groups is significantly less common, because the intrinsic conformational flexibility of these ligands tends to favor the formation of small aggregates. Here, we show that large Pd6L12 12+ cages can be obtained by reaction of Pd(II) salts with metallo-ligands L bearing terminal 3-pyridyl groups. The easy-to-access metallo-ligands contain an Fe(II) clathrochelate core. These sterically demanding clathrochelate complexes prevent the formation of smaller aggregates, which is observed for less bulky analogous building blocks. The cages were shown to bind BF4 and BPh4 anions in aqueous solvent mixtures, whilst the lateral size of the clathrochelate significantly affects their guest encapsulation behavior.
    Schlagwort(e): Ditopic N-donor ligands; metallo-ligand; ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
    Format: 7
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  • 9
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    Formin Is Associated with Left-Right Asymmetry in the Pond Snail and the Frog (2018)
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    Publikationsdatum: 2021-03-29
    Beschreibung: While components of the pathway that establishes left-right asymmetry have been identified in diverse animals, from vertebrates to flies, it is striking that the genes involved in the first symmetry-breaking step remain wholly unknown in the most obviously chiral animals, the gastropod snails. Previously, research on snails was used to show that left-right signaling of Nodal, downstream of symmetry breaking, may be an ancestral feature of the Bilateria [1, 2]. Here, we report that a disabling mutation in one copy of a tandemly duplicated, diaphanousrelated formin is perfectly associated with symmetry breaking in the pond snail. This is supported by the observation that an anti-formin drug treatment converts dextral snail embryos to a sinistral phenocopy, and in frogs, drug inhibition or overexpression by microinjection of formin has a chirality-randomizing effect in early (pre-cilia) embryos. Contrary to expectations based on existingmodels [3–5],wediscovered asymmetric gene expression in 2- and 4-cell snail embryos, preceding morphological asymmetry. As the formin-actin filament has been shown to be part of an asymmetry-breaking switch in vitro [6, 7], together these results are consistent with the view that animals with diverse body plans may derive their asymmetries from the same intracellular chiral elements [8].
    Schlagwort(e): Formin; Left-Right Asymmetry; Pond Snail; Frog ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
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  • 10
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    Mass Occurrences of the Brachiopod Halorella in Late Triassic Methane-Seep Deposits, Eastern Oregon (2018)
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    Publikationsdatum: 2021-04-25
    Beschreibung: The temporally and geographically scattered Phanerozoic record of methane-seep deposits hampers reconstruction of the evolution of life in chemosynthesis-based ecosystems. Unlike modern, Cenozoic, and late Mesozoic seeps, many of the known older seep deposits are typified by assemblages with profuse rhynchonellide brachiopods. Late Triassic (Norian) limestone bodies in eastern Oregon are enclosed in deep-water strata, extend laterally for up to a few hundred meters, and contain the dimerelloid rhynchonellide Halorella in rock-forming quantities. The analysis of two large limestone bodies in the Rail Cabin Member of the Vester Formation exposed near Graylock Butte, Grant County, Oregon, fosters the reconstruction of the paleoenvironmental setting of these unusual Halorella deposits, resulting in the first recognition of Triassic methane-seep deposits. The faunal assemblage includes few fossils other than Halorella. Although occasionally found at seeps, the recognized nuculanids are not seep-endemic bivalves. A Nucinella-like bivalve and a possible permophorid bivalve were likely endemic to this chemosynthesis-based environment; related bivalves lived at Jurassic and Cretaceous seeps. The superabundant, mostly articulated brachiopod shells are enclosed in a variety of micrites, including peloidal to clotted micrite. Early fibrous cement, forming banded and botryoidal crystal aggregates, preferentially occurs at the margin of the large limestone bodies but is scarce overall. Peloidal to clotted micrite and banded and botryoidal cement are common constituents of methane-seep limestones. Their negative d13C values as low as 36‰ reveal that carbonate formation was induced by the oxidation of methane. The presence of pyrobitumen (i.e., metamorphosed crude oil) in the limestones may indicate that the seepage fluids contained oil in addition to methane. Apart from the diagnostic 13C-depleted carbonate phases, mud injections recognized in one of the two limestone bodies also bear testament to former seepage activity.
    Schlagwort(e): Brachiopod; Halorella; Late triassic; Methane-Seep Deposits; ; 551
    Sprache: Englisch
    Materialart: article , publishedVersion
    Format: 14
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