A thermochronological study of southern Fiordland, New Zealand

The Fiordland Block, in the southwestern part of the South Island of New Zealand, shows evidence of a complex tectonic evolution dominated by tectonic and intrusive events in the mid-Paleozoic and mid-Cretaceous and is thought to represent a fragment of the Paleozoic margin of Gondwana. Fiordland geology is dominated by the extensive granulite facies Cretaceous Western Fiordland Orthogneiss, which is surrounded by Paleozoic metasediments and intrusive rocks. This study concentrates on an area in southern Fiordland, where rocks of three crustal levels are exposed, separated by steep SW-NE trending faults (for example the Dusky Fault): the granulite facies (-9-12 kbar) Western Fiordland Orthogneiss, the amphibolite facies Cretaceous Supper Cove Orthogneiss which intruded into kyanite-grade ( -6-8 kbar) Paleozoic metasediments, and the andalusite to sillimanite-grade ( -3-4 kbar) Southwestern Fiordland Block. By determining and comparing the structural, metamorphic and thermochronological histories of the different crustal levels, a better understanding of the tectonic evolution of Fiordland, and of the exhumation of Fiordland in particular, has been gained. The Paleozoic history of Fiordland is characterised by andalusite to sillimanitegrade metamorphism and strong deformation associated with the emplacement of voluminous granitic intrusions. New U-Pb SHRIMP zircon dating of granitic intrusions in southern Fiordland yielded ages of ca 370 to 380 Ma, which are consistent with previously determined ages from other parts of Fiordland and from the once contiguous area of Westland-Nelson, in the northwestern part of the South Island of New Zealand. A ca 340 Ma U-Pb zircon age of a posttectonic pegmatite in the Southwestern Fiordland Block and a ca 335 Ma U-Pb zircon age from a weakly deformed metagabbro in the sillimanite-grade Central Fiordland Belt (to the east of the Southwestern Fiordland Block) constrain the younger age limit of the dominant tectonic event. The localised preservation of 220-270 Ma 40Ar-39 Ar hornblende and mica ages indicate that the area cooled to below -300°C by at least the Permian and give a minimum cooling rate of 3°-5°C/Ma for cooling following mid-Paleozoic metamorphic and deformation events. However, because most of the Paleozoic rocks are strongly affected by a Cretaceous thermal event, little is known about the tectonic and cooling history between the mid-Paleozoic and the mid-Cretaceous. The majority of the 40 Ar-39 Ar mica ages from the Paleozoic metasedimentary and intrusive sequence range between ca 100 and 120 Ma and indicate a strong thermal overprint in the Cretaceous. In the Southwestern Fiordland Block, the thermal event is associated with only very little deformation and with a localised, static, kyanite-grade overprint. No evidence for the presence of Cretaceous intrusions has been found in the Southwestern Fiordland Block. Immediately north of the Dusky Fault, which separates the Southwestern Fiordland Block from deeper crustal levels, kyanite-grade Paleozoic rocks are intruded by the voluminous 121 Ma Supper Cove Orthogneiss and are dominated by Cretaceous deformation and metamorphism (at 6-8 kbar and 600-650°C). The Supper Cove Orthogneiss is similar in geochemical composition to the Western Fiordland Orthogneiss, but was metamorphosed at lower pressures and could, therefore, represent higher levels of the Western Fiordland Orthogneiss complex. The Western Fiordland Orthogneiss, the Supper Cove Orthogneiss and the intruded Paleozoic cover experienced rapid cooling to temperatures around 300°C as result of rapid exhumation. 40Ar-39Ar mica ages of 107 Main the Western Fiordland Orthogneiss and 40 Ar-39 Ar hornblende and mica ages of 100 Ma and 90 Ma, respectively, in the Supper Cove Orthogneiss and kyanite-grade Paleozoic cover, indicate that the deeper level Western Fiordland Orthogneiss cooled more rapidly than the higher level Supper Cove Orthogneiss. This could indicate that the Western Fiordland Orthogneiss was exhumed from beneath the Supper Cove Orthogneiss along an extensional detachment zone, thereby bringing the two orthogneisses at a similar crustal level. This is consistent with the observation that, following the rapid cooling, both areas remained at similar temperatures until final exhumation and cooling in the late Tertiary, as indicated by K-feldspar age spectra. A similar model has been proposed for the thermal event in the Southwestern Fiordland Block: middle to lower crustal rocks were exhumed from beneath the Southwestern Fiordland Block, bringing hot lower crustal rocks at shallower levels and increasing the heatflow. The relatively small temperature difference between the Southwestern Fiordland Block and the mid to lower crustal Cretaceous orthogneisses following mid Cretaceous rapid cooling confirms that lower crustal rocks were brought within 5 km of the Southwestern Fiordland Block. These observations may indicate that several detachment zones were active at the same time at various levels in the crust. The continental extension resulted in the break-up of the Gondwana margin. K-feldspar 40 Ar-39 Ar age spectra from the Southwestern Fiordland Block and Central Fiordland Belt indicate slow cooling at rates of 1 °-2°0Ma from about 100 Ma to at least 50 Ma, when temperatures dropped to below ca 200°C. This is consistent with 60- 80 Ma zircon fission track ages. A minor deformation event around 50 Ma is indicated by resetting of the argon isotopic system in K-feldspars from the Western Fiordland Orthogneiss and Supper Cove Orthogneiss and by increased cooling rates indicated by Kfeldspar 40Ar-39 Ar age spectra from the Southwestern Fiordland Block. This is thought to be related to Eocene plate reconfiguration in the southwest Pacific. The initiation of the final exhumation and cooling is well constrained by Kfeldspar 40Ar-39 Ar age spectra from the Western Fiordland Orthogneiss and Supper Cove Orthogneiss, which show a sudden increase in cooling rate from <1 °C/Ma to -13°0Ma around 15 Ma. Final exhumation was probably the result of the start of compression across the precursor of the Alpine Fault and possibly of subduction of the Australian plate under southern Fiordland. Consistent ca 7 Ma apatite fission track ages across southern Fiordland indicate that the brittle Dusky Fault and other equivalent faults were mainly active between 15 and 7 Ma, during which the Western Fiordland Orthogneiss and Supper Cove Orthogneiss were brought up to the same crustal level as the Southwestern Fiordland Block

Fjernmålingsbasert kartlegging og overvåking av tidevannssonen

Source at https://www.miljodirektoratet.no/publikasjoner/2021/mai-2021/satellite-based-national-intertidal-zone-mapping-of-continental-norway-with-sentinel-12/The report describes updated methods that were originally developed in Haarpaintner & Davids (2020) to map the intertidal zone, in terms of atmospheric exposure, type and areal extent, based on radar and optical high resolution (10m) satellite imagery from Sentinel-1A/B (C-band synthetic aperture radar, C-SAR) and Sentinel-2A/B (multi-spectral instruments) of the European Copernicus Program. It further presents the application of the method to create products covering the whole Norwegian coast, and describes some limitations and error sources. The project resulted in a first version of national products of the intertidal zone area, type and its atmospheric exposure

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Mapping of abandoned mine tailings and acid mine drainage using in situ hyperspectral measurements and WorldView-3 satellite imagery. (20/2018)

publishedVersio

Sluttrapport: Fjernmålingsbasert kartlegging og overvåking av tidevannssonen.

The report describes developed methods and results based on radar and optical high resolution (10-20m) satellite imagery from Sentinel-1 C-band synthetic aperture radars (C-SAR) S1A and S1B and Sentinel-2 MultiSpectral Instruments (MSI) S2A and S2B from the European Copernicus Program to map the intertidal zone in Trondheimsfjorden, Norway, with the aim to extend it nationally.Miljødirektorate

Ground displacements on Aitik tailings dams using SAR Interferometry. (21/2018)

As part of the REmote SEnsing supporting surveillance and operation of Mines (RESEM) project, we performed a preliminary study about the use of Synthetic Aperture Radar Interferometry (InSAR) for documenting ground displacements on tailings dams (Aitik copper mine, Sweden). The Stacking and SBAS methods have been applied to map the spatial distribution of the ground displacements based on 2015–2017 TerraSAR-X and Sentinel-1 satellite data, as well as to retrieve time series between May and November 2017. The 2D InSAR method has been used to combine results from ascending and descending SAR geometries. The report summarized described the main findings of the InSAR analysis and discuss the potential and limitations of the technique for applications in in the mining sector.publishedVersio

Detecting contamination-induced tree stress within the Chernobyl exclusion zone

The radioactive contamination from the 1986 accident at the Chernobyl Nuclear Power Plant (CNPP) caused significant change in the abundance and distribution of tree species in the exclusion zone. Some 400 ha of Scots pine (Pinus sylvestris) were killed from high levels of contamination and these areas have since been recolonised by silver birch (Betula pendula). Much work has shown that changes in leaf pigments (chlorophyll a and b, carotenoids) and biomass as a result of water and nutrient deficiencies and other environmental influences can be detected through spectral reflectance characteristics of leaves. This paper presents the results of a reconnaissance study showing that spectral reflectance measurements can also be used to detect the effect of radionuclide contamination on the vegetation in the Chernobyl exclusion zone. Through laboratory and in situ spectroradiometry of silver birch and Scots pine, we demonstrate that the chlorophyll red edge and the Three Channel Vegetation Index (TCHVI) correlate well with specific activities of 90Sr and 137Cs in leaves, &gamma;-dose rates and 137Cs inventories in soil. The results show that remote sensing has the potential of providing a valuable monitoring technique for assessing the ecological impact of radionuclide contamination

Satellite Based Intertidal-Zone Mapping from Sentinel-1&2

The report describes developed methods and results based on radar and optical high resolution (10-20m) satellite imagery from Sentinel-1 C-band synthetic aperture radars (C-SAR) S1A and S1B and Sentinel-2 MultiSpectral Instruments (MSI) S2A and S2B from the European Copernicus Program to map the intertidal zone in Trondheimsfjorden, Norway, with the aim to extend it nationally

Mapping Atmospheric Exposure of the Intertidal Zone with Sentinel-1 CSAR in Northern Norway

The intertidal zone (ITZ) is a highly dynamic and diverse coastal ecosystem under pressure that provides important eco-services. Being periodically under water makes it challenging to monitor, and the only possibility to map it in all tidal stages is by using dense time series of observations. At high latitudes, the Sentinel-1 (S1) constellation of the European Copernicus Program consistently provides radar imagery at fixed times on a near-daily basis, independently of cloud cover and sunlight. As tides have a period of 12 h 25.2 min, 1–2 year long S1 time series are therefore able to sample the whole tidal range and, thus, map the percentage of atmospheric exposure of the ITZ, which is an important environmental parameter. Tidal reference levels of mean high/low water at spring, mean and neap tide correspond each to specific percentiles of tidal heights and inversely correspond to atmospheric exposure. The presented method maps atmospheric exposure on the basis of purely statistical analyses of Sentinel-1 time series without the need for any tidal gauge data, by extracting water lines via simple thresholding of radar backscatter percentiles images. The individual thresholds for the second, fifth, 25th, 50th, 75th, 95th, and 98th percentile image were determined by fitting the threshold contour lines to in situ water line GPS tracks collected at corresponding tidal reference levels at five locations around Tromsø in Northern Norway. They inversely correspond to atmospheric exposures of 98%, 95%, 75%, 50%, 25%, 5%, and 2%, respectively. The method was applied to the whole Tromsø Municipality resulting in an ITZ atmospheric exposure map. The validation shows that the mean low water lines at neap, mid, and spring tide were mapped with accuracies of 93%, 84%, and 64%, respectively. The overall approach should be applicable worldwide