@article{HoehnFrimmelPrince2021, author = {H{\"o}hn, Stefan and Frimmel, Hartwig E. and Prince, Westley}, title = {Syn-metamorphic sulfidation of the Gamsberg zinc deposit, South Africa}, series = {Mineralogy and Petrology}, volume = {115}, journal = {Mineralogy and Petrology}, number = {6}, issn = {1438-1168}, doi = {10.1007/s00710-021-00764-w}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-268574}, pages = {709-728}, year = {2021}, abstract = {The Mesoproterozoic Aggeneys-Gamsberg ore district, South Africa, is one of the world´s largest sulfidic base metal concentrations and well-known as a prime example of Broken Hill-type base metal deposits, traditionally interpreted as metamorphosed SEDEX deposits. Within this district, the Gamsberg deposit stands out for its huge size and strongly Zn-dominated ore ( >14 Mt contained Zn). New electron microprobe analyses and element abundance maps of sulfides and silicates point to fluid-driven sulfidation during retrograde metamorphism. Differences in the chemistry of sulfide inclusions within zoned garnet grains reflect different degrees of interaction of sulfides with high metal/sulfur-ratio with a sulfur-rich metamorphic fluid. Independent evidence of sulfidation during retrograde metamorphism comes from graphic-textured sulfide aggregates that previously have been interpreted as quenched sulfidic melts, replacement of pyrrhotite by pyrite along micro-fractures, and sulfides in phyllic alteration zones. Limited availability of fluid under retrograde conditions caused locally different degrees of segregation of Fe-rich sphalerite into Zn-rich sphalerite and pyrite, and thus considerable heterogeneity in sphalerite chemistry. The invoked sulfur-rich metamorphic fluids would have been able to sulfidize base metal-rich zones in the whole deposit and thus camouflage a potential pre-metamorphic oxidation. These findings support the recently established hypothesis of a pre-Klondikean weathering-induced oxidation event and challenge the traditional explanation of Broken Hill-type deposits as merely metamorphosed SEDEX deposits. Instead, we suggest that the massive sulfide deposits experienced a complex history, starting with initial SEDEX-type mineralization, followed by near-surface oxidation with spatial metal separation, and then sulfidation of this oxidized ore during medium- to high-grade metamorphism.}, language = {en} } @article{Ibebuchi2021, author = {Ibebuchi, Chibuike Chiedozie}, title = {Revisiting the 1992 severe drought episode in South Africa: the role of El Ni{\~n}o in the anomalies of atmospheric circulation types in Africa south of the equator}, series = {Theoretical and Applied Climatology}, volume = {146}, journal = {Theoretical and Applied Climatology}, number = {1-2}, issn = {1434-4483}, doi = {10.1007/s00704-021-03741-7}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-268569}, pages = {723-740}, year = {2021}, abstract = {During strong El Ni{\~n}o events, below-average rainfall is expected in large parts of southern Africa. The 1992 El Ni{\~n}o season was associated with one of the worst drought episodes in large parts of South Africa. Using reanalysis data set from NCEP-NCAR, this study examined circulation types (CTs) in Africa south of the equator that are statistically related to the El Ni{\~n}o signal in the southwest Indian Ocean and the implication of this relationship during the 1992 drought episode in South Africa. A statistically significant correlation was found between the above-average Nino 3.4 index and a CT that features widespread cyclonic activity in the tropical southwest Indian Ocean, coupled with a weaker state of the south Indian Ocean high-pressure. During the analysis period, it was found that the El Ni{\~n}o signal enhanced the amplitude of the aforementioned CT. The impacts of the El Ni{\~n}o signal on CTs in southern Africa, which could have contributed to the 1992 severe drought episode in South Africa, were reflected in (i) robust decrease in the frequency of occurrence of the austral summer climatology pattern of atmospheric circulation that favors southeasterly moisture fluxes, advected by the South Indian Ocean high-pressure; (ii) modulation of easterly moisture fluxes, advected by the South Atlantic Ocean high-pressure, ridging south of South Africa; (iii) and enhancement of the amplitude of CTs that both enhances subsidence over South Africa, and associated with the dominance of westerlies across the Agulhas current. Under the ssp585 scenario, the analyzed climate models suggested that the impact of radiative heating on the CT significantly related to El Ni{\~n}o might result in an anomalous increase in surface pressure at the eastern parts of South Africa.}, language = {en} } @article{Ibebuchi2021, author = {Ibebuchi, Chibuike Chiedozie}, title = {Circulation pattern controls of wet days and dry days in Free State, South Africa}, series = {Meteorology and Atmospheric Physics}, volume = {133}, journal = {Meteorology and Atmospheric Physics}, number = {5}, issn = {1436-5065}, doi = {10.1007/s00703-021-00822-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-268552}, pages = {1469-1480}, year = {2021}, abstract = {Atmospheric circulation is a vital process in the transport of heat, moisture, and pollutants around the globe. The variability of rainfall depends to some extent on the atmospheric circulation. This paper investigates synoptic situations in southern Africa that can be associated with wet days and dry days in Free State, South Africa, in addition to the underlying dynamics. Principal component analysis was applied to the T-mode matrix (variable is time series and observation is grid points at which the field was observed) of daily mean sea level pressure field from 1979 to 2018 in classifying the circulation patterns in southern Africa. 18 circulation types (CTs) were classified in the study region. From the linkage of the CTs to the observed rainfall data, from 11 stations in Free State, it was found that dominant austral winter and late austral autumn CTs have a higher probability of being associated with dry days in Free State. Dominant austral summer and late austral spring CTs were found to have a higher probability of being associated with wet days in Free State. Cyclonic/anti-cyclonic activity over the southwest Indian Ocean, explained to a good extent, the inter-seasonal variability of rainfall in Free State. The synoptic state associated with a stronger anti-cyclonic circulation at the western branch of the South Indian Ocean high-pressure, during austral summer, leading to enhanced low-level moisture transport by southeast winds was found to have the highest probability of being associated with above-average rainfall in most regions in Free State. On the other hand, the synoptic state associated with enhanced transport of cold dry air, by the extratropical westerlies, was found to have the highest probability of being associated with (winter) dryness in Free State.}, language = {en} } @article{Hardaker2021, author = {Hardaker, Sina}, title = {Platform economy: (dis-) embeddedness processes in urban spaces}, series = {Urban Transformations}, volume = {3}, journal = {Urban Transformations}, issn = {2524-8162}, doi = {10.1186/s42854-021-00029-x}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-271329}, pages = {1-13}, year = {2021}, abstract = {Digital platforms, understood as multi-sided matchmakers, have amassed huge power, reimagining the role of consumers, producers, and even ownership. They increasingly dictate the way the economy and urban life is organized. Yet, despite their influential and far-reaching role in shaping our economic as well as sociocultural world, our understanding of their embeddedness, namely how their activities are embedded in systems of social and societal relationships and how they conceptualize their main functions and actions in relation to their wider setting, remains rudimentary. Consequently, the purpose of this frontier paper is threefold. Firstly, it reveals the need to discuss and evaluate (dis-)embedding processes in platform urbanism in order to understand the underlying dynamics of platform power and urban transformation. Secondly, it aims to reveal the main reasons in regard to the difficulties in pinpointing digital platforms embeddedness. Thirdly, it seeks to propose future research unravelling the (dis-)embeddedness of the platform economy. This paper argues for three main reasons namely unawareness, unaccountability and non-transparency of digital platforms that drive the lack of embeddedness and reaffirms platform power. This is mainly based on the configuration of new commodities, platforms' strategic avoidance of labour protections and other regulatory frameworks as well as platforms' secrecy in which they operate. This frontier paper argues that transferring the concept of embeddedness to the platform economy might serve as a valuable tool to understand and pinpoint essential dynamics and relationships at play, therefore proposing embeddedness as a basis for future research on the platform economy. It strongly argues that a more detailed understanding is urgently needed, in order to be able to understand, accompany and actively influence the development of the platform economy in regulatory terms.}, language = {en} } @article{MeyerPetersThieletal.2021, author = {Meyer, Constantin and Peters, Jan Christoph and Thiel, Michael and Rathmann, Joachim and Job, Hubert}, title = {Monitoring von Freifl{\"a}cheninanspruchnahme und -versiegelung f{\"u}r eine nachhaltige Raumentwicklung in Bayern}, series = {Raumforschung und Raumordnung}, volume = {79}, journal = {Raumforschung und Raumordnung}, number = {2}, doi = {10.14512/rur.40}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-261622}, pages = {172-189}, year = {2021}, abstract = {Im Freistaat Bayern wird intensiv diskutiert, wie die nach wie vor hohe Freifl{\"a}cheninanspruchnahme f{\"u}r Siedlungs- und Verkehrszwecke reduziert werden kann. Wissenschaftliche Grundlage f{\"u}r Steuerungsans{\"a}tze in der Stadt- und Regionalentwicklung sollte ein verbessertes staatliches Fl{\"a}chenmonitoring sein, welches {\"u}ber die amtliche Statistik und deren Hauptindikator "Siedlungs- und Verkehrsfl{\"a}che" hinaus auch die qualitative Dimension der Fl{\"a}cheninanspruchnahme einbezieht. Daf{\"u}r stellt dieser Beitrag methodische Erweiterungsans{\"a}tze f{\"u}r das Fl{\"a}chenmonitoring vor, welche kleinr{\"a}umige Analysen der Zersiedelung, Freiraumstruktur, Fl{\"a}chenversiegelung und {\"O}kosystemleistungen am Beispiel des Landkreises Rh{\"o}n-Grabfeld aufzeigen. Diese werden im Kontext der Debatte zu Ursachen und Steuerung der Freifl{\"a}cheninanspruchnahme sowie zu aktuellen Anforderungen an das Fl{\"a}chenmonitoring diskutiert. Betont wird deren Bedeutung f{\"u}r das Monitoring rechtlicher Vorgaben und politischer Ziele zur nachhaltigen Fl{\"a}chennutzung.}, language = {de} } @article{RauchTaubenboeckKnoppetal.2021, author = {Rauch, S. and Taubenb{\"o}ck, H. and Knopp, C. and Rauh, J.}, title = {Risk and space: modelling the accessibility of stroke centers using day- \& nighttime population distribution and different transportation scenarios}, series = {International Journal of Health Geographics}, volume = {20}, journal = {International Journal of Health Geographics}, doi = {10.1186/s12942-021-00284-y}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-261228}, year = {2021}, abstract = {Purpose Rapid accessibility of (intensive) medical care can make the difference between life and death. Initial care in case of strokes is highly dependent on the location of the patient and the traffic situation for supply vehicles. In this methodologically oriented paper we want to determine the inequivalence of the risks in this respect. Methods Using GIS we calculate the driving time between Stroke Units in the district of M{\"u}nster, Germany for the population distribution at day- \& nighttime. Eight different speed scenarios are considered. In order to gain the highest possible spatial resolution, we disaggregate reported population counts from administrative units with respect to a variety of factors onto building level. Results The overall accessibility of urban areas is better than in less urban districts using the base scenario. In that scenario 6.5\% of the population at daytime and 6.8\% at nighttime cannot be reached within a 30-min limit for the first care. Assuming a worse traffic situation, which is realistic at daytime, 18.1\% of the population fail the proposed limit. Conclusions In general, we reveal inequivalence of the risks in case of a stroke depending on locations and times of the day. The ability to drive at high average speeds is a crucial factor in emergency care. Further important factors are the different population distribution at day and night and the locations of health care facilities. With the increasing centralization of hospital locations, rural residents in particular will face a worse accessibility situation.}, language = {en} } @article{LatifiHolzwarthSkidmoreetal.2021, author = {Latifi, Hooman and Holzwarth, Stefanie and Skidmore, Andrew and Brůna, Josef and Červenka, Jaroslav and Darvishzadeh, Roshanak and Hais, Martin and Heiden, Uta and Homolov{\´a}, Lucie and Krzystek, Peter and Schneider, Thomas and Star{\´y}, Martin and Wang, Tiejun and M{\"u}ller, J{\"o}rg and Heurich, Marco}, title = {A laboratory for conceiving Essential Biodiversity Variables (EBVs)—The 'Data pool initiative for the Bohemian Forest Ecosystem'}, series = {Methods in Ecology and Evolution}, volume = {12}, journal = {Methods in Ecology and Evolution}, number = {11}, doi = {10.1111/2041-210X.13695}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-262743}, pages = {2073-2083}, year = {2021}, abstract = {Effects of climate change-induced events on forest ecosystem dynamics of composition, function and structure call for increased long-term, interdisciplinary and integrated research on biodiversity indicators, in particular within strictly protected areas with extensive non-intervention zones. The long-established concept of forest supersites generally relies on long-term funds from national agencies and goes beyond the logistic and financial capabilities of state- or region-wide protected area administrations, universities and research institutes. We introduce the concept of data pools as a smaller-scale, user-driven and reasonable alternative to co-develop remote sensing and forest ecosystem science to validated products, biodiversity indicators and management plans. We demonstrate this concept with the Bohemian Forest Ecosystem Data Pool, which has been established as an interdisciplinary, international data pool within the strictly protected Bavarian Forest and Šumava National Parks and currently comprises 10 active partners. We demonstrate how the structure and impact of the data pool differs from comparable cases. We assessed the international influence and visibility of the data pool with the help of a systematic literature search and a brief analysis of the results. Results primarily suggest an increase in the impact and visibility of published material during the life span of the data pool, with highest visibilities achieved by research conducted on leaf traits, vegetation phenology and 3D-based forest inventory. We conclude that the data pool results in an efficient contribution to the concept of global biodiversity observatory by evolving towards a training platform, functioning as a pool of data and algorithms, directly communicating with management for implementation and providing test fields for feasibility studies on earth observation missions.}, language = {en} } @article{MeisterLangeAthinodorouUllmann2021, author = {Meister, Julia and Lange-Athinodorou, Eva and Ullmann, Tobias}, title = {Preface: Special Issue "Geoarchaeology of the Nile Delta"}, series = {E\&G Quarternary Science Journal}, volume = {70}, journal = {E\&G Quarternary Science Journal}, doi = {10.5194/egqsj-70-187-2021}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-261195}, pages = {187-190}, year = {2021}, abstract = {No abstract available.}, language = {en} } @article{KunzKneisel2021, author = {Kunz, Julius and Kneisel, Christof}, title = {Three-dimensional investigation of an open- and a closed-system Pingo in northwestern Canada}, series = {Permafrost and Periglacial Processes}, volume = {32}, journal = {Permafrost and Periglacial Processes}, number = {4}, doi = {10.1002/ppp.2115}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-257678}, pages = {541-557}, year = {2021}, abstract = {The present study presents three-dimensional investigations of a hydrostatic pingo in the Mackenzie Delta region and a hydraulic pingo in the Ogilvie Mountains and contributes to a better understanding about the internal structures of the two pingo types. A combined approach using quasi-three-dimensional electrical resistivity tomography, ground-penetrating radar and frost probing allowed a clear delineation of frozen and unfrozen areas in the subsurface. At the hydrostatic pingo a massive ice core as well as a surrounding talik could be detected, but the location of the ice core and the talik differs from previous published assumptions. In contrast to acknowledged theory, at our site the massive ice core is not located in the center of the pingo but at the western edge, whereas the eastern flank is underlain by a talik, which surrounds the massive ice core. At the hydraulic pingo, the expected internal structure could be confirmed and the pathway of upwelling water could also be detected. The combined approach of the applied methods represents the first known three-dimensional geoelectrical investigation of pingos and provides new insights into the internal structure and architecture of the two different pingo types. The chosen approach allows further conclusions on the formation of these permafrost-affected landforms.}, language = {en} } @article{GeyerLanding2021, author = {Geyer, Gerd and Landing, Ed}, title = {The Souss lagerstatte of the Anti-Atlas, Morocco: discovery of the first Cambrian fossil lagerstatte from Africa}, series = {Scientific Reports}, volume = {11}, journal = {Scientific Reports}, number = {1}, doi = {10.1038/s41598-021-82546-0}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259236}, pages = {3107}, year = {2021}, abstract = {Episodic low oxygenated conditions on the sea-floor are likely responsible for exceptional preservation of animal remains in the upper Amouslek Formation (lower Cambrian, Stage 3) on the northern slope of the western Anti-Atlas, Morocco. This stratigraphic interval has yielded trilobite, brachiopod, and hyolith fossils with preserved soft parts, including some of the oldest known trilobite guts. The "Souss fossil lagerstatte" (newly proposed designation) represents the first Cambrian fossil lagerstatte in Cambrian strata known from Africa and is one of the oldest trilobite-bearing fossil lagerstatten on Earth. Inter-regional correlation of the Souss fossil lagerstatte in West Gondwana suggests its development during an interval of high eustatic levels recorded by dark shales that occur in informal upper Cambrian Series 2 in Siberia, South China, and East Gondwana.}, language = {en} }