Causes and Mechanisms of Remagnetisation in Palaeozoic Sedimentary Rocks - a Multidisciplinary Approach

The present work combines palaeomagnetic and rock magnetic methods with clay mineralogy, isotope geochemistry of clay minerals and trace element geochemistry of Fe-oxide leachates to study remagnetised sedimentary rocks from Palaeozoic outcrops in Middle and Eastern Europe. Three areas were selected (NE Rhenish Massif, Barrandian and Holy Cross Mountains), where the causes of Late Palaeozoic remagnetisations are yet unclear. The results yield important implications for the processes and mechanisms responsible for the remagnetisations in the areas studied. NE Rhenish Massif: A Late Carboniferous remagnetisation (component B) is identified in Late Palaeozoic carbonate and clastic rocks from the NE Rhenish Massif. Three individual incremental regional fold tests across the area show a unique and distinctive variation in timing of remagnetisation relative to the age of folding. The remagnetisation is postfolding in the South and of synfolding origin in the North of the area. Consequently, the timing and the duration of the remagnetisation event is constrained by the age of folding, which varies throughout the area and reflects a northward migration of the deformation front during 325 Ma to 300 Ma. Comparison of the resulting palaeolatitude of the NE Rhenish Massif with the palaeolatitudinal drift history for the region yields an estimate for the age of remagnetisation of ca. 315 - 300 Ma, which is in good agreement with the age of deformation. The concordance of the magnetic palaeoinclinations obtained from the entire area indicates that the rocks were remagnetised during a relatively short period of only a few My. The thermal stability of the remanence up to 550°C the comparably low palaeotemperatures in the studied region and the short duration of the remagnetisation event favour a chemical remagnetisation process. Rock magnetic experiments reveal a complex magnetomineralogy of the remagnetised Palaeozoic sediments from the NE Rhenish Massif. The dominant carrier of the Carboniferous magnetisation component is magnetite, but pyrrhotite and hematite accompany magnetite as carrier of the NRM in some grey carbonates and red sandstones or red nodular limestones, respectively. The hysteresis ratios, magnetic viscosity and low temperature behaviour of the carbonate rocks give strong evidence for the presence of very fine grained (superparamagnetic) magnetic minerals. This material is also thought to be responsible for similar rock magnetic properties of siliciclastic rocks. This interpretation, however, is not unique for the siliciclastic rocks, due to the predominance of detrital MD magnetite and the high amount of paramagnetic material. The hysteresis ratios from medium to coarse grained rocks and reef carbonates fall in or close to the fields of MD magnetite and remagnetised carbonates, respectively. The fine grained clastic rocks (siltstones) and limestone turbidites have intermediate hysteresis properties. This implies the presence of very fine grained magnetic material in all lithologies of the NE Rhenish Massif, which is indicative for authigenic growth of magnetic minerals and formation of a CRM. However, the magnetic fingerprint of SP grains gets increasingly disguised with increasing amount of detrital MD magnetite in clastic rocks. K-Ar dating of <0.2µm clay fractions indicates two diagenetic events in the NE Rhenish Massif. The observation of K-Ar isochrons rules out contamination from detrital sources and preferential loss of radiogenic ^40Ar from authigenic illites. Middle Devonian clastic rocks are characterised by an illitisation event at 336 +/- 6.2 Ma, which is probably connected to a major magmatic event at ca. 340 - 330 Ma in the Mid-German Crystalline Rise. The second period of illite formation at 312 +/- 10 Ma is coeval to the northward migration of deformation through the Rhenish Massif and is only recorded by Upper Devonian and Lower Carboniferous rocks. This indicates that the metamorphic conditions were not sufficient to recrystallise the earlier illite generation in the more deeply buried Middle Devonian rocks. The age of the younger illitisation event is not significantly different from the age of the pervasive, syntectonic remagnetisation. However, the remagnetisation event was not restricted to the upper part of the fold and thrust belt and also affected the Middle Devonian strata. A characteristic enrichment in MREE is observed in Fe-oxide leachates, which is more pronounced in the Middle Devonian clastic rocks and which is correlated to the amount of Ba in the leachates. This indicates, that Ba was mobilised during the older diagenetic event and probably originates from synsedimentary (SEDEX), baryte-bearing deposits. The younger illite generation is characterised by lower Gd/La ratios in leachates, which are thought to reflect the formation of Fe-oxides and apatite with flat NASC normalised REE patterns. Consequently, the REE patterns of leachates indicate the interference of two mineralisations of different ages. Furthermore, the REE patterns from different samples show a variation of Eu and Ce, which indicates varying redox conditions in the lithologies studied. This is taken as evidence against a pervasive migration of orogenic fluids on a regional scale as a cause of remagnetisation in the NE Rhenish Massif. While a temporal relationship between clay diagenesis and remagnetisation is observed in Upper Devonian and Lower Carboniferous rocks, the remagnetisation is not related to clay diagenesis in Middle Devonian rocks. Here, the transformation of smectite to illite cannot account for the growth of authigenic magnetic minerals, which must have been triggered by a different mechanism. Since the ages of remagnetisation and main deformation are generally similar, this mechanism could be related to localised pressure solution and changing pore fluid pressure due to tectonic stress. However, this raises the question, why the remagnetisation occurred during different stages of folding in the northern and southern parts of the NE Rhenish Massif. Barrandian: In the Barrandian, Czech Republic, a remagnetisation is identified, which is predominantly carried by magnetite. Fold test analysis and comparison of the resulting palaeolatitude with the palaeomagnetic reference frame yields ambiguous results. Based on palaeomagnetic evidence, the remagnetisation event could have occurred during the late stage of the Variscan deformation in the Late Devonian or the remagnetisation could be postfolding in origin and of Late Carboniferous age. The apparent K-Ar ages of <0.2µm fractions indicate a diagenetic event around 390 - 365 Ma. This age interval is almost identical with the age of deformation in the Barrandian and the illite diagenesis is likely to be related to the deformation. The REE patterns of Fe-oxide leachates show a distinct enrichment in MREE, which is generally correlated to the Ba-content. SEM studies indicate oxidation of framboidal pyrite to magnetite in grey Late Silurian limestones and the formation of Fe-oxides in red Devonian limestones. Magnetite pseudoframboids and authigenic illite form a characteristic parageneses. Since oxidation of framboidal pyrite is a possible mechanism of remagnetisation, the K-Ar ages of illite are thought to constrain the remagnetisation to be Late Devonian in age. The SEM studies also indicate, that authigenesis of magnetic minerals in red Devonian limestones is related to dissolution of baryte. Holy Cross Mountains: The palaeomagnetic results from Late Devonian limestones from the Holy Cross Mountains, Poland, reveal a complex (re-)magnetisation history. Two remagnetisations are identified, which are postfolding in origin and were acquired in Late Paleozoic (component A) and Mesozoic (component C) times. A third component of magnetisation (B) yields synfolding results during fold test analysis. Although remagnetisations A and B are likely to be Late Palaeozoic in age, the exact timing of remanence acquisition remains unclear. Components A and B are carried by magnetite and SEM studies indicate the oxidation of framboidal pyrite to magnetite. The Triassic remagnetisation (C) resides in hematite, which is observed as secondary coatings of spherical pore spaces. The apparent K-Ar ages and isotopic compositions of <0.2µm fractions indicate a mixture of different generations of sheet silicates. These results can be explained by the presence of a illite generation younger than ca. 290 Ma years, which is contaminated by different amounts of detrital material (muscovite) or an older authigenic illite generation. However, diffusive loss of ^{40}Ar from the illite crystal lattice subsequent to illite formation cannot be ruled out. Further studies are needed to better understand the diagenetic history of the Late Devonian limestones in the Holy Cross Mountains. Remagnetisation processes: The results of this study imply, that the processes and mechanism responsible for the remagnetisations in the areas studied are rather complex. The regional migration of orogenic-type fluids, which is thought to be responsible for widespread remagnetisations in Palaeozoic rocks of the Hercynian realm of North America (Stamatakos et al., 1996 and references therein), can be excluded for the NE Rhenish Massif and is not supported by the observations made in rocks from the Barrandian and the Holy Cross Mountains. Chemical changes associated with the smectite/illite transition could be responsible for the remagnetisation of Late Devonian and early Carboniferous rocks from the NE Rhenish Massif. In limestones from the Barrandian and the Holy Cross Mountains, the observation of pseudoframboidal magnetite indicates the oxidation of pyrite to magnetite as a possible remagnetisation mechanism. This process requires the presence of a fluid phase, which could originate from pore fluids or local migration of fluids on fractures and faults. In the Middle Devonian sequences of the NE Rhenish Massif the illite generation and the remagnetisation are not contemporaneous and oxidation of pyrite was not observed. Here, the remagnetisation must be related to a different mechanism. It can be speculated, that the remagnetisation mechanism in the Middle Devonian sequences could be related to pressure solution and changing pore fluid pressure during deformation. The Mesozoic remagnetisations in the NE Rhenish Massif and the Holy Cross Mountains are carried by hematite and are either related to hematite bearing mineralisation events during phases of uplift in the Mesozoic or caused by oxidising fluids percolating from the weathering surface and penetrating zones of enhanced permeability

Räumliche Anordnung von Suppressiven Myeloiden Zellen und Zytotoxischen T Zellen im Dickdarmkrebs

Recent advances in digital computational pathology opened the possibility to analyze the spatial characterization of tumor immune cell infiltration patterns with measurements beyond the classical cell density. These include the location of cells, the distance between cells and the spatial overlap of dense immune cell occupied areas. By leveraging that methodology the focus of the current study was in understanding the influence of suppressive myeloid cells on the cytotoxic T cell location and their function within the tumor immune microenvironment (TiME) of primary Colorectal Cancer (CRC) tumors. Therefore, a cohort of 74 treatment-naïve CRC patient samples was analyzed with multiplexed immunohistochemistry assays to identify monocytic (CD11b+CD14+), granulocytic (CD11b+CD15+) and immunosuppressive (ARG1+) myeloid cells, together with proliferating and non-proliferating cytotoxic T cells (CD8+Ki67+/-). With the HALO Software (IndicaLabs) respective cell objects were detected and through slide registration cell coordinates were extracted and used for subsequent spatial statistics. Spatial features derived from distance and spatial overlap analysis were correlated with integrated gene expression data to define immune cell functions related to T cell activation or exhaustion and myeloid cell derived pro-inflammation or immunosuppression. Results show very heterogeneous distribution patterns of both T cells and myeloid cells, emphasizing the importance of a more comprehensive characterization of TiME. Inter-cell distance analysis revealed the spatial relation of myeloid cells to T cells, which either co-localize in the tumor stroma or spatially separate from myeloid cells by infiltration into the tumor epithelium. The extend of Myeloid-T cell spatial overlap, on the contrary, shows strong expression of immunosuppressive genes suggesting a local inhibition of T cell response. Furthermore, introduced spatial analysis allowed characterization of CRC tumors irrespective of their mismatch repair (MMR) status or consensus molecular subgroup (CMS) classification. All these aspects highlight the importance of better understanding the influencing factors that shape the TiME, in order to improve the potential development of new immunotherapy strategies.Jüngste Fortschritte in der digitalen Pathologie eröffnen die Möglichkeit, die räumliche Anordnung von infiltrierenden Immunzellen in der Tumorregion zu charakterisieren. Dies übertrifft die sonst nur übliche Berechnung der Zelldichte. Im Detail kann die Lage der Zellen, die Distanz zwischen den Zellen und die räumliche Überlappung von Bereichen im Gewebe bestimmt werden, die dicht mit Immunzellen besetzt sind. Der Schwerpunkt der Arbeit lag darin, den Einfluss supprimierender myeloider Zellen zu studieren, den diese auf die Lage und Funktion der zytotoxischen T-Zellen in der Tumor-Immun-Mikroumgebung von primären Dickdarmtumoren ausüben. Eine Kohorte von 74 unbehandelten Dickdarmtumor-Patientenproben wurde mit Mulitplex Immunohistochemie Assays analysiert, um monozytische (CD11b+CD14+), granulozytische (CD11b+CD15+) und immunsuppressive (ARG1+) myeloide Zellen, und auch proliferierende and nicht-proliferierende zytotoxische T-Zellen (CD8+Ki67+/-) auf den Gewebsschnitten zu identifizieren. Unter Verwendung der HALO-Software (IndicaLabs) wurden entsprechende Zellobjekte detektiert und durch Registrierung der einzelnen digitalisierten Gewebsbilder konnten Koordinaten der Zellen extrahiert und für anschließende geometrische Analysen verwendet werden. Abgeleitete Merkmale aus der Distanz- und der räumlichen Überlappungsanalyse wurden dann mit integrierten Genexpressionsdaten korreliert, um diese mit Immunzellfunktionen in Verbindung zu bringen. Bevorzugt wurden Gene, die mit der Aktivierung und Erschöpfung von T-Zellen oder der von myeloiden Zellen abgeleiteten Entzündung und Immunsuppression zusammenhängen, gesucht. Die Ergebnisse zeigen ein sehr heterogenes Verteilungsmuster von T-Zellen und myeloiden Zellen, was vor allem die Notwendigkeit einer umfassenderen Charakterisierung der Tumor-Immun-Mikroumgebung in Dickdarmtumoren unterstreicht. Die Berechnung der Zell-Zell-Distanz ermöglicht zunächst die Beschreibung der räumlichen Beziehung von myeloiden Zellen zu T-Zellen, die entweder im Tumorstroma mit myeloiden Zellen co-lokalisieren oder sich durch Infiltration in das Tumorepithel räumlich von myeloiden Zellen trennen. Im Vergleich dazu zeigen Tumore mit hoher räumlicher Überlappungsrate von Bereichen mit dicht besiedelten myeloiden und T-Zellen eine erhöhte Expression von immunsuppressiven Genen, was widerrum auf eine lokale Inhibierung der T-Zell-Antwort hinweist. Außerdem konnten durch diese Art der räumliche Analyse die Darmtumor-Patientenproben unabhängig von ihrem MMR-Status (Mismatch Repair) oder ihrer CMS-Klassifizierung (Consensus Molecular Subgtype) stratifiziert werden. All die genannten Aspekte sollten dazu anregen, ein besseres Verständnis dafür zu erlangen, wie die Tumor-Immun-Mikroumgebung im Detail aufgebaut ist und welche weiteren Faktoren einen großen Einfluss auf deren Formierung nehmen. Dies würde die potenzielle Entwicklung neuer Strategien für die Immuntherapie verbessern

Las técnicas de enseñanzas y el desarrollo de habilidades en los procesos de soldadura SMAW en los estudiantes de construcciones metálicas de la Facultad de Educación UNJFSC-2023

Objetivo: es un estudio con el fin de adquirir la licenciatura para Educación en la materia de Construcciones metálicas en la UNJFSC, Huacho. El método utilizado está presente en la indagación Básica, de magnitud descriptiva, correlacional y la hipótesis propuesta es: “Las técnicas de enseñanza se relacionan con el desarrollo de habilidades en los procesos de soldadura SMAW en los estudiantes de Construcciones Metálicas de la Facultad de Educación de la UNJFSC- 2023”. En el procedimiento dirigido a la indagación, la población es de 102 estudiantes y el muestreo de 18. La herramienta primordial utilizada para este trabajo será la ficha de observación, aplicada para ambas variantes. El producto manifiesta la existente asociación en intensidad buena para las técnicas de enseñanza y el desarrollo en habilidades por el procesos soldadura SMAW en los estudiantes pertenecientes a Construcciones Metálicas-Educación de la UNJFSC- 202

Integrated stratigraphy and 40Ar/39Ar chronology of the Early to Middle Miocene Upper Freshwater Molasse in eastern Bavaria (Germany)

A detailed integrated stratigraphic study was carried out on middle Miocene fluvial successions of the Upper Freshwater Molasse (OSM) from the North Alpine Foreland Basin, in eastern Bavaria, Germany. The biostratigraphic investigations yielded six new localities thereby refining the OSM biostratigraphy for units C to E (sensu; Heissig, Actes du Congres BiochroM'1997) and further improving biostratigraphic correlations between the different sections throughout eastern Bavaria. Radioisotopic ages of 14.55 ± 0.19 and 14.88 ± 0.11 Ma have been obtained for glass shards from the main bentonite horizon and the Ries impactite: two important stratigraphic marker beds used for confirming our magnetostratigraphic calibration to the Astronomical Tuned Neogene Time Scale (ATNTS04; Lourens et al. in Geologic Time Scale 2004, Cambridge University Press, 2004). Paleomagnetic analysis was performed using alternating field (AF) and thermal (TH) demagnetization methods. The AF method revealed both normal and reverse polarities but proofs to yield unreliable ChRM directions for the Puttenhausen section. Using the biostratigraphic information and radioisotopic ages, the magnetostratigraphic records of the different sections are tentatively correlated to the Astronomical Tuned Neogene Time Scale (ATNTS04; Lourens et al. in Geologic Time Scale 2004, Cambridge University Press, 2004). This correlation implies that the main bentonite horizon coincides to chron C5ADn, which is corroborated by its radioisotopic age of 14.55 Ma, whereas the new fossil locality Furth 460, belonging to OSM unit E, probably correlates to chron C5Bn.1r. The latter correlation agrees well with the Swiss Molasse locality Frohberg. Correlations of the older sections are not straightforward. The Brock horizon, which comprises limestone ejecta from the Ries impact, possibly correlates to C5ADr (14.581 ± 14.784 Ma), implying that, although within error, the radioisotopic age of 14.88 ± 0.11 Ma is somewhat too old. The fossil localities in Puttenhausen, belonging to the older part of OSM unit C, probably coincide with chron C5Cn.2n or older, which is older than the correlations established for the Swiss Molasse. © Springer-Verlag 2007

Influence of palaeoweathering on trace metal concentrations and environmental proxies in black shales

The mineralogical and chemical compositions of Lower Carboniferous (Tournaisian) marine black shale from the Kowala quarry, the Holy Cross Mountains, Poland, were investigated. This study focuses on disturbances in palaeoenvironmental proxies caused by palaeoweathering, which progressively changed the major and trace element abundances. Palaeomagnetic investigations reveal that the Devonian – Carboniferous succession was weathered during the Permian-Triassic by the infiltration of oxidizing fluids related to karstification following post-Variscan exhumation. The weathering process led to vermiculitization of chlorite, partial dissolution of calcite and replacement of pyrite by hematite and goethite. Moreover, the concentrations of some trace metals, including Co, Cu, Pb, Mo, Ni, As and U, significantly decreased. Consequently, some elemental abundance ratios that are used as environmental proxies, including U/Th, Ni/Co and V/Cr, were altered. Elements that are bound to iron sulphides (e.g., Mo) appear to be especially prone to mobilization by even a lightly weathered black shale. The documented weathering, including changes in elemental concentrations, can potentially create misinterpretations of the original palaeoenvironmental conditions. In addition, the palaeoweathering of the studied samples appears to have substantially changed the carbon, oxygen, nitrogen and molybdenum stable isotope values. The nitrogen and molybdenum stable isotope ratios, in particular, appear to be most sensitive to the effects of weathering and therefore are good indicators of (palaeo)weathering processes. The major cause of these changes is the decay of organic matter and pyrite. For the organic carbon stable isotopes ratios, the main factor that controlls this process appears to be the preferential degradation of labile organic matter. A combination of the total organic carbon (TOC), total sulphur (TS) content, Mo concentration and stable isotope compositions seems to be the most useful for identify (palaeo)weathering. Our results suggest that reductions in TS and Mo in tandem with diminished Mo stable isotope values in the absence of obvious changes to the TOC content provide the most compelling evidence of (palaeo)weathering