Basaltic micrometeorites from the Novaya Zemlya glacier

Abstract– A large number of micrometeorites (MMs) was recovered from glacier deposits located at the north‐eastern passive margin of the Novaya Zemlya glacier sheet. Melted, scoriaceous, and unmelted micrometeorites (UMMs) are present. Unmelted micrometeorites are dominated mostly by chondritic matter, but also a few achondritic MMs are present. Here we report the discovery of four UMMs that, according to their texture, mineralogy, and chemistry, are identified as basaltic breccias. Mineral chemistry and Fe/Mn ratios of two basaltic micrometeorites indicate a possible relationship with eucrites and/or mesosiderites, whereas two others seem to have parents, which appear not to be present in our meteorite collections. The basaltic breccia UMMs constitute 0.5% of the total population of the Novaya Zemlya MM suite. This content should be lowered to 0.25% because the Novaya Zemlya MM collection appears to be biased with carbonaceous UMMs being underrepresented.     

Geochemistry and geochronology of the Proterozoic magmatic rocks of the Ulkan trough: New data

A model of the formation of the Ulkan trough was specified on the basis of new geochemical and geochronological data. The volcanics of the Ulkan Group exhibit geochemical features typical of the rocks of two modern geodynamic settings: suprasubduction and within-plate ones. The combination of the components derived from the different-depth sources in the magmatic chambers explains the formation of the volcanics with mixed geochemical signatures. The age of the granitoids of three phases of the Ulkan Massif is determined within the range of 1730–1925 Ga. The granites of the first and third phases have positive ɛNd(T) of + 3.5 and + 0.7, respectively. The granites of the first phase of the Ulkan Complex were likely derived from the Paleoproterozoic juvenile crust with an age of 1.84–1.95 Ga. The effusive rocks of the Ulkan Group were presumably formed in a geodynamic setting of a Cordilleran-type transform continental margin. Judging from the model T_Nd(DM) age, these geodynamic conditions operated >1.84 Ga ago.     

WSO-UV progress and expectations

The World Space Observatory Ultraviolet (WSO-UV) is the space mission that will grant access to the ultraviolet (UV) range in the post Hubble epoch. WSO-UV is equipped with instrumentation for imaging and spectroscopy and it is fully devoted to UV astronomy. In this article, we outline the WSO-UV mission model and present the current status of the project.     

Lochkovian (earliest Devonian) transgressions and regressions along the “Tethyan” margin of Gondwana: A review of lithostratigraphical data

Global sea-level rise and consequent regional transgressions are hypothesized at the beginning of the Devonian. A brief review of lithostratigraphical data available from three regions of the “Tethyan” margin of Gondwana, namely Northern Africa, Arabia, and the Tethys Himalaya, suggests that all of them were characterized by a regressive setting in the Lochkovian. In contrast, data from some terranes of the Greater Galatian Superterrane provide evidence of early Lochkovian transgression. The regressive setting documented on the 'Tethyan' margin of Gondwana differs from the transgressive–regressive cycles of Euramerica and the norm of global sea-level rise followed by a highstand. Only regional tectonic processes including those linked with dynamic topography could explain these differences. These processes may have been associated with syn-rift uplift preceding the opening of the Palaeo-Tethys Ocean, mantle uplift at the supercontinent margin, or the Eo-Variscan orogenic phase.     

Mode enslavement in a two-layer stellar dynamo

We consider a conventional stellar  α²ω  -dynamo with dynamo generators localized in two spherical shells separated by a passive layer. The signs of the α-effect as well as rotational shear in the dynamo active layers can be chosen to give dynamo waves that propagate in opposite directions (poleward and equatorward) if the layers are considered separately in the framework of the Parker migratory dynamo. In a sequence of numerical experiments we show that the variety of dynamo-generated magnetic configurations in the system under discussion is quite rich. We identify the possibility of almost independent dynamo waves existing in the two layers as well as enslavement of one layer by the other, and of activity waves generated by a joint action of the two layers. We suggest some qualitative explanations of the behaviour and discuss also the limited nature of these explanations. This variety of phenomena suggests previously underexploited freedoms to understand how predictions of dynamo theory may accommodate the observed solar and stellar activity phenomenology.     

Solar Activity Record from Archeomagnetic Data

Each of the available solar activity (SA) proxy data (historical notes, radio nuclides ¹⁴C and ¹⁰Be production) are contaminated by their specific noise factors. So, any additional proxy with its independent noise factors will essentially increase the accuracy of composite SA restorations. It is proposed here that archaeomagnetic measurements 95% confidence interval (α₉₅) may serve as new proxy for the SA estimation in the past. This proxy is compared with other available proxies during the years 1500–2000.     

Correction to: Accelerated reproduction of 2-D periodic waves

Ocean Dynamics - A Correction to this paper has been published: https://doi.org/ https://doi.org/10.1007/s10236-021-01450-3     

Crystal structures and phase transitions in Sr2InTaO6 perovskite

The preparation and crystal structure of the double perovskite oxide Sr₂InTaO₆ are reported. This oxide has a monoclinic structure in space group P2₁/n at room temperature, where In and Ta display a rock-salt type ordering with a = 5.73356(10), b = 5.74052(10), c = 8.10905(14) Å and β = 90.022(6)°. Variable temperature neutron diffraction measurements demonstrate this displays the sequence of phase transitions $ P2_{1} /n\mathop{\longrightarrow}\limits^{{605\,^\circ {\text{C}}}}I2/m\mathop{\longrightarrow}\limits^{{705\,^\circ {\text{C}}}}I4/m\mathop{\longrightarrow}\limits^{{930\,^\circ {\text{C}}}}Fm\bar{3}m $ as a consequence of the sequential loss of tilting of the corner shared octahedra upon heating. The evolution of Sr₂InTaO₆ crystal structure upon heating is analysed and described in terms of symmetry-adapted distortion modes. The GM4+ and X3+, that are responsible for anti-phase and in-phase tilting, respectively, are highly temperature dependent, with the GM4+ mode having the largest amplitude at room temperature.     

Were Late Cretaceous extinctions of gastropods selective by generic longevity?

Many gastropod taxa went extinct during the Late Cretaceous.The stratigraphic ranges of 268 genera permit to establish the longevity of extinction victims for each stage of this epoch."Young" taxa (originated within 3 epochs before the extinction) prevailed among victims of the extinctions in all stages.The proportion of "old" taxa(originated before the Cretaceous) that went extinct was the highest in the Cenomanian,and it was the lowest in the Coniacian and the Maastrichtian.It appears that the end-Cretaceous mass extinction affected chiefly "young" taxa.However,the comparison with the earlier time intervals suggests that this pattern of selectivity by generic longevity was not specific for the noted catastrophe,but,in contrast,it was typical for the entire Late Cretaceous.The latest Cenomanian environmental perturbation(OAE2) caused a stronger extinction of "old" taxa,and thus,this biotic crisis was less selective by generic longevity.This hypothesis,however,is not proven by the statistical test.