Paläobiogeographie des Korallenooliths (Mittleres Oxfordium - Unteres Kimmeridgium): Tethyale Faunen- und Florenelement auf höherer Paläobreite

An overview is given here on the palaeobiogeography of the Korallenoolith Formation (middle Oxfordian to early Kimmeridgian) in NW Germany (Lower Saxony Basin). Based on microfacies observations, abundant faunal and floral elements of the tropical tethyan realm are recognized in shallow-marine calcareous sediments of the Korallenoolith Formation. Foraminiferal fauna is both highly diverse and abundant and mostly of mediterranean character. Also, there is a small flora recorded, which includes heavily calcified red algae, aragonitic green algae, and cayeuxiid algae. They display restricted diversity when compared to those of shallow-marine tropical tethyan seas. Chaetetids and diceratids are locally abundant. Lithocodium aggregatum and Bacinella irregularis have been observed in Late Jurassic palaeolatitudes north of the Tethys for the first time. Corals are present in numerous genera and species. Their occurrence is restricted to a few horizons of the Korallenoolith Formation where they build patch reefs, coral biostroms and coral meadows. The overall character of the coral-thrombolite-reefs (florigemma-Bank Member) is very similar to those of the Tethys. The presence of these marine tethyan taxa assigned the position of the Lower Saxony Basin during middle Oxfordian to early Kimmeridgian palaeobiogeographically into the submediterranean province and reflects northward migration of tropical tethyan fauna and flora which reach in the Lower Saxony Basin their northern limit. These biota seem to be biogeo-graphically transitional between communities present in England and the Tethys.Der derzeitige Kenntnisstand zur Paläobiogeographie des Mitteloxfordium- bis Unterkimmeridgium-zeitlichen Korallenooliths (Niedersächsisches Becken, NW-Deutschland) wird zusammengefaßt. Bis vor wenigen Jahren zeichneten sich noch enge Beziehung zu dem borealen englischen Oberjura ab, da tethyale bzw. mediterrane Faunen- und Florenelemente entweder zu fehlen oder nur artenarm aufzutreten schienen. Vor allem mit Hilfe mikrofazielle Arbeitsansätze konnten erstmals zahlreiche „Tethys-Zeiger“ - insbesondere komplex-gebaute Sandschaler und Milioliden, Grünalgen, Lithocodium aggregatum, Bacinella irregularis und Chaetetiden - erstmals für das Niedersächsichen Becken in der Korallenoolith- Fazies nachgewiesen werden. Insgesamt zeigen Fauna und untergeordnet auch Flora (Kalkalgen) des Korallenooliths signifikante Ähnlichkeiten mit einer solchen aus Schelfplattformbereichen der Tethys. Die postulierte sukzessive Verarmung von tethyalen Vertretern (z.B. Riffkorallen oder Nerineen) in Richtung Norden und ihre Verbreitungsgrenzen werden kritisch diskutiert. Ihre angebliche Seltenheit oder das früher vermutete Fehlen läßt sich rückblickend am besten mit dem kursorischen Bearbeitungsstand des Korallenooliths erklären. Die Ergebnisse sprechen für eine enge Bindung des Niedersächsischen Beckens während der Sedimentation des Korallenooliths an den mediterranen Raum, die durch Vorstöße tethyaler Faunen- und Florenelemente belegt sind. Tethyale Elemente rücken somit auch in Ablagerungsräume auf höherer Paläobreite vor, wenn günstige fazielle Gegebenheiten vorliegen

Entwicklung der Faziesverteilung eines Riffkomplexes im Korallenoolith (Oberjura) des Osterwaldes (Niedersachsen)

The Hainholz quarry in the Osterwald hills of NW-Germany is the most impressive outcrop in the Lower Saxony Basin exposing Late Jurassic (Korallenoolith, Oxfordian) coral buildups. The Korallenoolith deposits in the quarry commence with a oolitic sequence about 20 m thick which is limited by a distinctive hardground at its top. This sequence is overlain by the so called “Obere Korallenbank”-Member about 13 m in thickness which is mainly build up by coral reef complexes. Throughout a lateral extend of about 400 m exposed in the quarry, the Obere Korallenbank Member shows numerous pillar-shaped reefal build ups which are flanked by a reefal debris limestone. The coral fauna of the in situ reefal bioconstructions comprises not less than 37 taxa most of which have been described from the Lower Saxony Basin for the first time. Probably, the pillar-shaped reefs formed a small positive relief of only a few dm against the debris deposits during deposition. The interreef debris limestones in the lower and middle part of the Obere Korallenbank Member show three intercalated biostromal coral layers. In the upper part of the member, the interreef facies is represented by a mikritic peloidal limestone rich in sponge remains and, unusual in such a depositional environment, ammonites (Dichotomo-sphinctes bifurcatoides, D. sp.). Additionaly, at the top of of the peloidal limestone a layer enriched in nerineids and other gastropods limits the reefal constructions of the Obere Korallenbank Member against the overlying “humeralis-Oolith” sequence. On the basis of the facies development of this depositional sequence the reef formation in relation to sealevel changes is discussed.Der Steinbruch am Hainholz (Rohstoffbetriebe Eldagsen, Werk Wülfinghausen) im Osterwald (NW-Deutschland) bietet den eindrucksvollsten Einblick in die oberjurazeitlichen (Korallenoolith, Oxfordium) Korallenvorkommen des Niedersächsischen Beckens. Er erschließt den gesamten Korallenoolith, der hier mit einer nicht weiter gliederbaren, etwa 20 m mächtigen Kalkoolith-Folge einsetzt. Sie wird von einem markanten Hartgrund abgeschlossen, auf den im stratigraphischen Niveau der sogenannten „Oberen Korallenbank“ ein insgesamt 13 m mächtiger Korallenriffkomplex folgt. Der auf ca. 400 m Lateralerstreckung erschlossene Riffkomplex besteht aus zahlreichen stotzenartigen Riffkörpern. Die Korallenfauna dieser in situ-Biokonstruktionen, die sich vermutlich nur wenige m über den Sedimentspiegel erhoben, umfaßt mindestens 37 Taxa, von denen ein Großteil erstmals im NW-deutschen Oberjura belegt ist. Einen wesentlichen Bestandteil der Korallenstotzen bildet Mikrobialith, der wie die Korallen intensiv angebohrt ist. Im unteren Teil des Riff-Horizontes werden die Riffkörper von einem im bewegten Flachwasser abgelagerten Riffschuttkalkstein flankiert, der wiederholt von (drei) bankartigen, im Steinbruchbereich durchhaltenden Korallenlagen unterbrochen wird. Von anderen NW-deutschen Lokalitäten sind solche Riffschuttkalke nicht bekannt. Im Hangenden des Riffschuttkalksteins folgt ein rhaxenrei-cher, mikritischer Peloidkalkstein mit für den Korallenoolith ungewöhnlich zahlreichen Ammonitenresten (Dichotomos-phinctes sp., D. bifurcatoides). Sein Top ist durch einen Anreicherungshorizont von Nerineen und Kleingastropoden gekennzeichnet, der das Ende des Riffwachstums markiert und zum humeralis-OoYnh überleitet. Aus der faziellen Abfolge vom Liegenden bis in das Hangende der Oberen Korallenbank wird neben einer Interpretation der steuerndem Faktoren der Riffentwicklung und -Zerstörung die Entwicklungsgeschichte des Meeresspiegels abgeleitet

Possible Pleistocene hominin tracks from South Africa’s west coast

Two probable tracks have been identified on the ceiling of a small overhang in the Pleistocene Langebaan Formation on South Africa’s west coast. They may have been made by a hominin trackmaker. They appear to have been registered at walking speed on a level, sandy dune substrate. Three tracks, attributed to Homo sapiens, were previously identified near Langebaan in 1995, and were popularly labelled ‘Eve’s Footprints’. The new identification of possible hominin tracks near Langebaan is the second from South Africa’s west coast. This discovery adds to the sparse but growing global record of possible hominin tracks preserved in aeolianites. Significance:• Two probable fossil tracks have been identified on the ceiling of an overhang near Langebaan.• The tracks may have been made by a human walking on a level dune surface during the Pleistocene.• This discovery is the second of its kind on the west coast, and complements the 1995 identification near Langebaan of Pleistocene fossil tracks attributed to humans

A new mechanism for mtDNA pathogenesis: impairment of post-transcriptional maturation leads to severe depletion of mitochondrial tRNA(Ser(UCN)) caused by T7512C and G7497A point mutations

We have studied the consequences of two homoplasmic, pathogenic point mutations (T7512C and G7497A) in the tRNA(Ser(UCN)) gene of mitochondrial (mt) DNA using osteosarcoma cybrids. We identified a severe reduction of tRNA(Ser(UCN)) to levels below 10% of controls for both mutations, resulting in a 40% reduction in mitochondrial protein synthesis rate and in a respiratory chain deficiency resembling that in the patients muscle. Aminoacylation was apparently unaffected. On non-denaturating northern blots we detected an altered electrophoretic mobility for G7497A containing tRNA molecules suggesting a structural impact of this mutation, which was confirmed by structural probing. By comparing in vitro transcribed molecules with native RNA in such gels, we also identified tRNA(Ser(UCN)) being present in two isoforms in vivo, probably corresponding to the nascent, unmodified transcripts co-migrating with the in vitro transcripts and a second, faster moving isoform corresponding to the mature tRNA. In cybrids containing either mutations the unmodified isoforms were severely reduced. We hypothesize that both mutations lead to an impairment of post-transcriptional modification processes, ultimately leading to a preponderance of degradation by nucleases over maturation by modifying enzymes, resulting in severely reduced tRNA(Ser(UCN)) steady state levels. We infer that an increased degradation rate, caused by disturbance of tRNA maturation and, in the case of the G7497A mutant, alteration of tRNA structure, is a new pathogenic mechanism of mt tRNA point mutations

Molecular dysfunction associated with the human mitochondrial 3302A>G mutation in the MTTL1 (mt-tRNA(Leu(UUR))) gene

The gene encoding mt-tRNA(Leu(UUR)), MT-TL1, is a hotspot for pathogenic mtDNA mutations. Amongst the first to be described was the 3302A>G transition which resulted in a substantial accumulation in patient muscle of RNA19, an unprocessed RNA intermediate including mt-16S rRNA, mt-tRNA(Leu(UUR)) and MTND1. We have now been able to further assess the molecular aetiology associated with 3302A>G in transmitochondrial cybrids. Increased steady-state levels of RNA19 was confirmed, although not to the levels previously reported in muscle. This data was consistent with an increase in RNA19 stability. The mutation resulted in decreased mt-tRNA(Leu(UUR)) levels, but its stability was unchanged, consistent with a defect in RNA19 processing responsible for low tRNA levels. A partial defect in aminoacylation was also identified, potentially caused by an alteration in tRNA structure. These deficiencies lead to a severe defect in respiration in the transmitochondrial cybrids, consistent with the profound mitochondrial disorder originally associated with this mutation

Antiskyrmions and their electrical footprint in crystalline mesoscale structures of Mn1.4PtSn

Skyrmionic materials hold the potential for future information technologies, such as racetrack memories. Key to that advancement are systems that exhibit high tunability and scalability, with stored information being easy to read and write by means of all-electrical techniques. Topological magnetic excitations such as skyrmions and antiskyrmions, give rise to a characteristic topological Hall effect. However, the electrical detection of antiskyrmions, in both thin films and bulk samples has been challenging to date. Here, we apply magneto-optical microscopy combined with electrical transport to explore the antiskyrmion phase as it emerges in crystalline mesoscale structures of the Heusler magnet Mn1.4PtSn. We reveal the Hall signature of antiskyrmions in line with our theoretical model, comprising anomalous and topological components. We examine its dependence on the vertical device thickness, field orientation, and temperature. Our atomistic simulations and experimental anisotropy studies demonstrate the link between antiskyrmions and a complex magnetism that consists of competing ferromagnetic, antiferromagnetic, and chiral exchange interactions, not captured by micromagnetic simulations