The origin of metalliferous argillites in the Shoal Arm Formation of north-central Newfoundland

The Middle Ordovician Shoal Arm Formation, which is located in the central volcanic belt of north-central Newfoundland, is a tripartite assemblage of hematitic argillites, grey cherts, and black shales directly underlying a flysch sequence. The hematitic argillites are enriched in Fe, Mn, Ni, Pb, and Co. Factor analysis and principal component analysis indicate the presence of a hydrothermal component, presumably derived from hydrothermal activity in the coeval Lawrence Head volcanics. Unusual, (?) calcareous Mn-Fe-oxide nodules are present in the top parts of turbidites in the hematitic argillites. Electron microprobe analysis of a color transition from a red to a green argillite indicates fractionation of Mn from Fe by diagenetic mobilization of Mn and subsequent precipitation as Mn-carbonate in adjacent green, calcareous argillites. The detrital component of the Shoal Arm Formation is influenced by several, geochemically different, clastic sources. The top part of the Shoal Arm Formation is characterized by a Zr-, Nb-, and Y-rich clastic component that may reflect either erosion or volcanic activity of lateral equivalents of the Lawrence Head volcanics. The hydrothermal component disappeared with erosion of these volcanics. The overlying grey, mottled and laminated cherts reflect a biogenic bloom, which preceded euxinification of the depositional basin. Synchronous and diachronous depositional models are proposed to explain the tectonic history of the Shoal Arm Formation. The synchronous model emphasizes the high biological productivity and limited circulation in a restricted basin as the cause for the observed euxinification. The diachronous model explains the black shale facies with a prograding, deep-water anoxic layer that developed during rapid basin subsidence as the result of thrust-loading. In this model, the black shales were deposited in front of flysch sediments derived from a southeastward prograding thrust stack. The Middle Ordovician Taconic sequence of New York (i.e., the upper part of the Poultney Formation, the Indian River, and the Mt. Merino Formations) exhibits hematitic argillites in a similar lithostratigraphic position relative to black shale and flysch as the Shoal Arm Formation. Comparison of the Shoal Arm Formation with this part of the Taconic sequence indicates that the two tectonic models are also applicable to this sequence. Both the Indian River Formation and the Mt. Merino Formation are slightly enriched in Fe, Mn, and the trace elements Pb and Ni. This modest metal enrichment is explained either by recycling of Fe and Mn into the seawater in expanded oxygen minimum zones and subsequent precipitation at oxic/anoxic interfaces, or by a distal hydrothermal component. A continental source of Fe is excluded. Minor enrichment of biogenically derived material in the Mt. Merino Formation suggests that biological productivity may not have been the determining factor for euxinification. The comparison with Precambrian sequences that contain Superior-type banded iron-formations and black shales in comparable stratigraphic positions indicates little geochemical similarity with the two Ordovician sequences. Enrichments of Fe, Mn, Pb, Ni, Co, and Cr in both iron-formations and black shales are generally stronger than in the Ordovician cases. Interpretations of biological productivity are hampered by the insufficient knowledge of inorganic element associations with biological matter in Precambrian oceans. As a consequence, it is difficult to test the proposed tectonic models with the available geochemical data. Comparisons to that point have to rely upon field observations alone

The origin of metalliferous argillites in the Shoal Arm Formation of north-central Newfoundland

The Middle Ordovician Shoal Arm Formation, which is located in the central volcanic belt of north-central Newfoundland, is a tripartite assemblage of hematitic argillites, grey cherts, and black shales directly underlying a flysch sequence. The hematitic argillites are enriched in Fe, Mn, Ni, Pb, and Co. Factor analysis and principal component analysis indicate the presence of a hydrothermal component, presumably derived from hydrothermal activity in the coeval Lawrence Head volcanics. Unusual, (?) calcareous Mn-Fe-oxide nodules are present in the top parts of turbidites in the hematitic argillites. Electron microprobe analysis of a color transition from a red to a green argillite indicates fractionation of Mn from Fe by diagenetic mobilization of Mn and subsequent precipitation as Mn-carbonate in adjacent green, calcareous argillites. The detrital component of the Shoal Arm Formation is influenced by several, geochemically different, clastic sources. The top part of the Shoal Arm Formation is characterized by a Zr-, Nb-, and Y-rich clastic component that may reflect either erosion or volcanic activity of lateral equivalents of the Lawrence Head volcanics. The hydrothermal component disappeared with erosion of these volcanics. The overlying grey, mottled and laminated cherts reflect a biogenic bloom, which preceded euxinification of the depositional basin. Synchronous and diachronous depositional models are proposed to explain the tectonic history of the Shoal Arm Formation. The synchronous model emphasizes the high biological productivity and limited circulation in a restricted basin as the cause for the observed euxinification. The diachronous model explains the black shale facies with a prograding, deep-water anoxic layer that developed during rapid basin subsidence as the result of thrust-loading. In this model, the black shales were deposited in front of flysch sediments derived from a southeastward prograding thrust stack. The Middle Ordovician Taconic sequence of New York (i.e., the upper part of the Poultney Formation, the Indian River, and the Mt. Merino Formations) exhibits hematitic argillites in a similar lithostratigraphic position relative to black shale and flysch as the Shoal Arm Formation. Comparison of the Shoal Arm Formation with this part of the Taconic sequence indicates that the two tectonic models are also applicable to this sequence. Both the Indian River Formation and the Mt. Merino Formation are slightly enriched in Fe, Mn, and the trace elements Pb and Ni. This modest metal enrichment is explained either by recycling of Fe and Mn into the seawater in expanded oxygen minimum zones and subsequent precipitation at oxic/anoxic interfaces, or by a distal hydrothermal component. A continental source of Fe is excluded. Minor enrichment of biogenically derived material in the Mt. Merino Formation suggests that biological productivity may not have been the determining factor for euxinification. The comparison with Precambrian sequences that contain Superior-type banded iron-formations and black shales in comparable stratigraphic positions indicates little geochemical similarity with the two Ordovician sequences. Enrichments of Fe, Mn, Pb, Ni, Co, and Cr in both iron-formations and black shales are generally stronger than in the Ordovician cases. Interpretations of biological productivity are hampered by the insufficient knowledge of inorganic element associations with biological matter in Precambrian oceans. As a consequence, it is difficult to test the proposed tectonic models with the available geochemical data. Comparisons to that point have to rely upon field observations alone

Alternsgerechte Quartiere

Angesichts des zunehmenden Anteils Älterer an der Bevölkerung stehen Städte und Gemeinden vor neuen Anforderungen an Versorgung, Verkehr und öffentliche Räume. Der Gestaltung eines Wohnumfelds für ein gesundes und aktives Altern kommt eine hohe Bedeutung zu, da Ältere hier besonders viel Zeit verbringen. Ein fußgänger- und radfahrfreundliches Quartier, das Rastmöglichkeiten und sichere Straßenquerungen bietet, schafft die Voraussetzungen für aktive Fortbewegung und eine Vielzahl außerhäuslicher Aktivitäten und unterstützt somit die gesellschaftliche Teilhabe Älterer. Internationale Leitlinien, nationale Initiativen und lokale Aktivitäten quartiersbezogener Ansätze zur Gesundheitsförderung im Alter geben bereits gute Beispiele für die Umsetzung. Eine differenzierte Betrachtung des Alterns und eine Fokussierung auf gesundheitsförderliche Verhältnisse verdeutlichen die Notwendigkeit eines gemeinsamen Handelns von Gesundheitsförderung und Stadtplanung zur Gestaltung alternsgerechter Quartiere.In the face of an ageing population, cities and communities are confronted with new requirements concerning daily supply, transport and public space. The supportive design of neighbourhoods for active and healthy ageing is extremely important as elderly people spend most of their time in the immediate surroundings. Walkable and bikeable neighbourhoods that offer places to rest and safe street crossings enable the elderly to remain active and pursue many outside activities, thereby enhancing their social participation. There are international guidelines, national initiatives and local neighbourhood-related approaches to health promotion in old age that serve as good examples for implementation. A differentiated view on ageing and a focus on healthy environments underscore the necessity of joint action by health promotion and urban planning to design age-friendly neighbourhoods

Seasonal oxygen, nitrogen and phosphorus benthic cycling along an impacted Baltic Sea estuary: regulation and spatial patterns

The regulatory roles of temperature, eutrophication and oxygen availability on benthic nitrogen (N) cycling and the stoichiometry of regenerated nitrogen and phosphorus (P) were explored along a Baltic Sea estuary affected by treated sewage discharge. Rates of sediment denitrification, anammox, dissimilatory nitrate reduction to ammonium (DNRA), nutrient exchange, oxygen (O-2) uptake and penetration were measured seasonally. Sediments not affected by the nutrient plume released by the sewage treatment plant (STP) showed a strong seasonality in rates of O-2 uptake and coupled nitrification-denitrification, with anammox never accounting for more than 20 % of the total dinitrogen (N-2) production. N cycling in sediments close to the STP was highly dependent on oxygen availability, which masked temperature-related effects. These sediments switched from low N loss and high ammonium (NH4 (+)) efflux under hypoxic conditions in the fall, to a major N loss system in the winter when the sediment surface was oxidized. In the fall DNRA outcompeted denitrification as the main nitrate (NO3 (-)) reduction pathway, resulting in N recycling and potential spreading of eutrophication. A comparison with historical records of nutrient discharge and denitrification indicated that the total N loss in the estuary has been tightly coupled to the total amount of nutrient discharge from the STP. Changes in dissolved inorganic nitrogen (DIN) released from the STP agreed well with variations in sedimentary N-2 removal. This indicates that denitrification and anammox efficiently counterbalance N loading in the estuary across the range of historical and present-day anthropogenic nutrient discharge. Overall low N/P ratios of the regenerated nutrient fluxes impose strong N limitation for the pelagic system and generate a high potential for nuisance cyanobacterial blooms

Methane fluxes from coastal sediments are enhanced by macrofauna

Methane and nitrous oxide are potent greenhouse gases (GHGs) that contribute to climate change. Coastal sediments are important GHG producers, but the contribution of macrofauna (benthic invertebrates larger than 1 mm) inhabiting them is currently unknown. Through a combination of trace gas, isotope, and molecular analyses, we studied the direct and indirect contribution of two macrofaunal groups, polychaetes and bivalves, to methane and nitrous oxide fluxes from coastal sediments. Our results indicate that macrofauna increases benthic methane efflux by a factor of up to eight, potentially accounting for an estimated 9.5% of total emissions from the Baltic Sea. Polychaetes indirectly enhance methane efflux through bioturbation, while bivalves have a direct effect on methane release. Bivalves host archaeal methanogenic symbionts carrying out preferentially hydrogenotrophic methanogenesis, as suggested by analysis of methane isotopes. Low temperatures (8 °C) also stimulate production of nitrous oxide, which is consumed by benthic denitrifying bacteria before it reaches the water column. We show that macrofauna contributes to GHG production and that the extent is dependent on lineage. Thus, macrofauna may play an important, but overlooked role in regulating GHG production and exchange in coastal sediment ecosystems

Sulfide oxidation in deep Baltic Sea sediments upon oxygenation and colonization by macrofauna

Coastal and shelf sediments affected by transient or long-term bottom water anoxia and sulfidic conditions undergo drastic changes in macrofauna communities and abundances. This study investigates how early colonization by two macrofaunal functional traits (epifauna vs. infauna) affects oxygen, sulfide, and pH dynamics in anoxic sediment upon recent bottom water oxygenation. Large mesocosms (area 900 cm 2) with 150-m-deep Baltic Sea soft sediments were exposed to three treatments: (1) no animals; (2) addition of 170 polychaetes (Marenzelleria arctia); (3) addition of 181 amphipods (Monoporeia affinis). Porewater chemistry was investigated repeatedly by microsensor profiling over a period of 65 days. Colonization by macrofauna did not significantly deepen penetration of oxygen compared to the animal-free sediment. Bioturbation by M. affinis increased the volume of the oxidized, sulfide-free sediment by 66% compared to the animal-free control already after 13 days of incubation. By the end of the experiment M. affinis and M. arctia increased the oxidized sediment volume by 87 and 35%, respectively. Higher efficiency of epifaunal amphipods in removing hydrogen sulfide than deep-burrowing polychaetes is likely due to more substantial re-oxidation of manganese and/or nitrogen compounds associated with amphipod mixing activity. Our results thus indicate that early colonization of different functional groups might have important implications for the later colonization by benthic macrofauna, meiofauna and microbial communities that benefit from oxidized and sulfide-free sediments

Methane emissions offset atmospheric carbon dioxide uptake in coastal macroalgae, mixed vegetation and sediment ecosystems

Publisher Copyright: © 2023, The Author(s).Coastal ecosystems can efficiently remove carbon dioxide (CO2) from the atmosphere and are thus promoted for nature-based climate change mitigation. Natural methane (CH4) emissions from these ecosystems may counterbalance atmospheric CO2 uptake. Still, knowledge of mechanisms sustaining such CH4 emissions and their contribution to net radiative forcing remains scarce for globally prevalent macroalgae, mixed vegetation, and surrounding depositional sediment habitats. Here we show that these habitats emit CH4 in the range of 0.1 – 2.9 mg CH4 m−2 d−1 to the atmosphere, revealing in situ CH4 emissions from macroalgae that were sustained by divergent methanogenic archaea in anoxic microsites. Over an annual cycle, CO2-equivalent CH4 emissions offset 28 and 35% of the carbon sink capacity attributed to atmospheric CO2 uptake in the macroalgae and mixed vegetation habitats, respectively, and augment net CO2 release of unvegetated sediments by 57%. Accounting for CH4 alongside CO2 sea-air fluxes and identifying the mechanisms controlling these emissions is crucial to constrain the potential of coastal ecosystems as net atmospheric carbon sinks and develop informed climate mitigation strategies.Peer reviewe

Computertomographische Untersuchungen und Druckversuche an Robinienrundholz (KIT Scientific Reports ; 7610)

Robinienholz eignet sich wegen seiner hohen Festigkeit und ausgezeichneten Dauerhaftigkeit für tragende frei bewitterte Bauteile. Die natürliche Stammform mit ihren teilweise zahlreichen Krümmungen erschwert jedoch die Abschätzung der Tragfähigkeit. In dieser Arbeit wird auf der Grundlage der Ergebnisse von computertomographischen Untersuchungen und von Druckversuchen an natürlich gewachsenen Robinienstammabschnitten ein Modell zur Berechnung der Tragfähigkeit entwickelt

Nitrous Oxide Dynamics in the Siberian Arctic Ocean and Vulnerability to Climate Change

Nitrous oxide (N2O) is a strong greenhouse gas and stratospheric ozone-depleting substance. Around 20% of global emissions stem from the ocean, but current estimates and future projections are uncertain due to poor spatial coverage over large areas and limited understanding of drivers of N2O dynamics. Here, we focus on the extensive and particularly data-lean Arctic Ocean shelves north of Siberia that experience rapid warming and increasing input of land-derived nitrogen with permafrost thaw. We combine water column N2O measurements from two expeditions with on-board incubation of intact sediment cores to assess N2O dynamics and the impact of land-derived nitrogen. Elevated nitrogen concentrations in water column and sediments were observed near large river mouths. Concentrations of N2O were only weakly correlated with dissolved nitrogen and turbidity, reflecting particulate matter from rivers and coastal erosion, and correlations varied between river plumes. Surface water N2O concentrations were on average close to equilibrium with the atmosphere, but varied widely (N2O saturation 38%–180%), indicating strong local N2O sources and sinks. Water column N2O profiles and low sediment-water N2O fluxes do not support strong sedimentary sources or sinks. We suggest that N2O dynamics in the region are influenced by water column N2O consumption under aerobic conditions or in anoxic microsites of particles, and possibly also by water column N2O production. Changes in biogeochemical and physical conditions will likely alter N2O dynamics in the Siberian Arctic Ocean over the coming decades, in addition to reduced N2O solubility in a warmer ocean.publishedVersio

Biological nitrate transport in sediments on the Peruvian margin mitigates benthic sulfide emissions and drives pelagic N loss during stagnation events

Highlights • Very high rates of dissimilatory nitrate reduction to ammonium by Thioploca. • Non-steady state model predicts Thioploca survival on intracellular nitrate reservoir. • Ammonium release by Thioploca may be coupled to pelagic N loss by anammox. • Thioploca may contribute to anammox long after bottom water nitrate disappearance. • Model indicates that benthic foraminifera account for 90% of benthic N2 production. Abstract Benthic N cycling in the Peruvian oxygen minimum zone (OMZ) was investigated at ten stations along 12oS from the middle shelf (74 m) to the upper slope (1024 m) using in situ flux measurements, sediment biogeochemistry and modelling. Middle shelf sediments were covered by mats of the filamentous bacteria Thioploca spp. and contained a large ‘hidden’ pool of nitrate that was not detectable in the porewater. This was attributed to a biological nitrate reservoir stored within the bacteria to oxidize sulfide to sulfate during ‘dissimilatory nitrate reduction to ammonium’ (DNRA). The extremely high rates of DNRA on the shelf (15.6 mmol m-2 d-1 of N), determined using an empirical steady-state model, could easily supply all the ammonium requirements for anammox in the water column. The model further showed that denitrification by foraminifera may account for 90% of N2 production at the lower edge of the OMZ. At the time of sampling, dissolved oxygen was below detection limit down to 400 m and the water body overlying the shelf had stagnated, resulting in complete depletion of nitrate and nitrite. A decrease in the biological nitrate pool was observed on the shelf during fieldwork concomitant with a rise in porewater sulfide levels in surface sediments to 2 mM. Using a non-steady state model to simulate this natural anoxia experiment, these observations were shown to be consistent with Thioploca surviving on a dwindling intracellular nitrate reservoir to survive the stagnation period. The model shows that sediments hosting Thioploca are able to maintain high ammonium fluxes for many weeks following stagnation, potentially sustaining pelagic N loss by anammox. In contrast, sulfide emissions remain low, reducing the economic risk to the Peruvian fishery by toxic sulfide plume development