The deaths in the Antarctic of Captains Robert Falcon Scott and Lawrence “Titus” Oates are the most examined in almost all exploration. However, one object, until today unknown, gives a clue to the real story of the last three days of the Terra Nova expedition leaders. This is the sextant that Captain Scott had with him throughout his career until his death, passed from Kathleen Scott to Peter Scott and thence to its current owner. The sextant, its history and the meaning of the relic are set out before the public for the first time.

In many technical and geomechanics applications, for example tire and ski design or avalanche prediction, the capability to model the mechanical behaviour of snow is of high importance. To this end, we propose in the present study to extend the 3-D H-model, a multi-scale constitutive law originally developed for granular materials, to densely packed snow. In the model, single ice grains are described by spherical particles bonded by brittle elasto-viscoplastic bridges. Snow is thus described explicitly through its ice skeleton microstructure. As a validation, confined compression test results from the litterature are used to assess the suitability of the model to correctly describe snow behaviour. Multiple parameter studies were conducted to demonstrate the capability of the model to capture the behaviour of different snow types over a significant range of temperatures and loading rates at small deformations. Notably, the initial bond radius emerges as an effective proxy for snow aging under isothermal conditions, with stress levels increasing directly with the initial bond radius. Additionally, low strain rates and elevated temperatures are shown to influence the viscous response of ice bonds, their failure rates and the overall stress within the snow material.

This study aims to synthesize nano-metakaolin (NMK) through mechanical activation and to investigate the physical, chemical and microstructural changes that occur to the initial raw material. The efficiency of the activation process is affected by various process parameters as well as the mineralogy of the original material. Two different kaolin qualities were subjected to mechanical activation through high-energy ball-milling (HEBM) under various conditions. The parameters investigated were the milling speed and time. The final properties of the NMK samples produced were examined using X-ray diffraction, Fourier-transform infrared spectroscopy, laser dynamic light scattering, thermogravimetry/differential thermal analysis, Brunauer–Emmett–Teller and scanning electron microscopy analysis. Additionally, the pozzolanic activity of the fully activated samples was evaluated using the Chapelle test. The percentage of impurities contained in the initial kaolin affected the transformation into metakaolin. The milling parameters also affected the activation, contributing mainly to the particle size of the final material. Finally, concerning the metakaolin microstructure, the material showed a tendency to form stacks and agglomerates of plates due to the development of powerful static forces.

Rubinite, a garnet with the ideal formula Ca3Ti3+2Si3O12, is an indicator of super-reduced conditions and has been found recently in refractory inclusions in a few CV3 chondrites. We discovered rubinite in phosphide-bearing breccia from the pyrometamorphic Hatrurim Complex, Negev Desert, Israel. Aggregates of phosphide and native iron are concentrated at the boundary of thermally altered sedimentary xenoliths encased in flamite–gehlenite paralava. Rubinite, with the average empirical formula (Ca2.97Mg0.02Fe2+0.01)Σ3.00(Ti3+1.10Al0.44Ti4+0.37Mg0.08Cr0.01)Σ2(Si2.71Al0.29)Σ3.00O12, was found in a small xenolith composed of hydrogrossular, tacharanite and calcite, and containing relics of high-temperature minerals such as pseudowollastonite, cuspidine, gehlenite, baghdadite, barringerite, murashkoite, osbornite, paqueite and oldhamite. For the first time, the structure of rubinite, with the composition (Ca2.99Mg0.01)Σ3(Ti3+0.78Al0.62Ti4+0.43Mg0.17)Σ2(Si2.74Al0.26)Σ3O12, has been refined. Its unit-cell parameter a = 12.0193(4) Å, is significantly smaller than that of the synthetic analogue of Ca3Ti2Si3O12, 12.1875 Å. In the rubinite Raman spectrum weak bands corresponding to the vibrations of Ti4+–O in the (TiO6)8– octahedra: 610 cm–1 ν1(TiO6)8– and 438 cm–1 ν4(TiO6)8– are present in addition to the bands related to Si–O and Al–O vibrations in the TO4 tetrahedra. Rubinite forms a thin reactive rim (<10 μm) on pseudowollastonite grains. It probably formed during a sharp increase in rock porosity in the course of natural clinkerisation of sedimentary xenoliths caused by the thermal impact of the paralava. The high porosity increased the effect of reductive gases on the rocks, which were by-products of pyrometamorphism. The brief appearance of super-reduced conditions defined the formation of the Ti3+-bearing minerals osbornite and rubinite. Paqueite, Ca3Ti4+(Ti4+Al2)Si2O14, which crystallised in a thin melting zone of xenolith at the boundary with the paralava, does not contain Ti3+.

The minerals of the kröhnkite, talmessite and fairfieldite groups plus dondoellite, general formula X2M2+(TO4)2(H2O)2 where X = Na, Ca; M2+ = Mg, Fe, Mn, Co, Ni, Zn, Cu; and T = S, P, As; have been consolidated into the IMA-approved kröhnkite supergroup. The cell dimensions and space-group symmetries of the minerals in these three groups and dondoellite are distinct but the structures of these minerals are strongly related as they have topologically identical structural units. Differences in structure between the different groups involve the disposition of adjacent [M2+(TO4)2(H2O)2] chains and the stereochemical details of the hydrogen bonds that link adjacent [M2+(TO4)2(H2O)2] chains. The ions that form the interstitial complex of a mineral and the structural unit must satisfy the principle of correspondence of Lewis acidity–basicity whereby stable structures will form where the Lewis acidity of the structural unit closely matches the Lewis basicity of the interstitial complex. For pentavalent T cations (P5+or As5+), the Lewis acidity of Ca2+ shows the closest match of all cations to the Lewis basicity of the structural unit. For hexavalent T cations (S6+), the Lewis acidity of Na+ shows the closest match of all cations to the Lewis basicity of the structural unit.

To investigate dislocation densities of deformed polycrystalline ice the modified Warren-Averbach and modified Williamson-Hall plots of X-ray line broadening have been applied to artificial ice with and without silica particles, which model microparticles in ice sheets. This also provides us with the dislocation velocity during creep. Creep tests were conducted at −20ºC and 2 MPa by altering the strains using the artificial ice. In the primary creep region the ice with microparticles is remarkably deformed, and the strain rate is suppressed because of high dislocation densities. At 10% strain the dislocation density shows the maximum value due to the continuous dislocation pile-ups in the silica-containing ice: the dislocation density in the pure ice remains almost constant within the maximum strain used in this study. As the strains continuously decrease, microparticles pin the grain boundaries, leading to small grain sizes. Such small grain sizes provide sinks for dislocation annihilations, resulting in decrease in the dislocation densities in the silica-containing ice.

Brine migration from sea ice into the overlying snowpack is relatively understudied yet can significantly modify thermodynamic and electromagnetic properties of the snow. In this study, we investigate the impact of snow properties on brine wicking and runoff by producing samples of four distinctly different snow types (soft wind slab, hard wind slab, faceted grains and melt-freeze clusters) and monitor changes in snow properties after adding brine. The results illustrate that snow grain type and density have a pronounced effect on the height of brine wicking and runoff, snow compaction rates and salt concentrations. In all samples, we observed separation of the initial brine-saturated slush layer into two sublayers with distinctly different properties: solid saline snow-ice at the bottom and less saline brine-wetted snow above it. The maximum height of brine wicking ranged from 6.5 cm in faceted snow to 8.9 cm in hard wind slab samples, which was equivalent of 40 to 50% of total samples’ height. The volume and timing of brine runoff varied between samples, occurring later and in smaller volumes in hard wind slab compared to soft wind slab and coarse-grained samples.

Radiocarbon (14C) dating of soil samples by accelerator mass spectrometry (AMS) has been proven useful for studying carbon (C) cycling in terrestrial ecosystems. However, this application has two primary difficulties in sample preparation: inhibition of graphite formation due to sulfur (S)-containing impurities and contamination of samples with modern C (MC). Herein, we evaluated these effects using three sample preparation methods (silver foil, silver wire, and Sulfix) by conducting AMS-14C measurements of a 14C-dead charred wood and S-rich soil samples. The preparation methods were all successful in graphite formation and AMS-14C measurement for soil samples with an organic S content <6.9 wt%. The methods showed different percent modern carbon (pMC) values from 0.16% to 0.64% for the 14C-dead sample. The results also revealed that across different methods, MC contamination can be significantly reduced by applying two-step procedure (combustion and subsequent reaction to remove S-containing impurities) during sample preparation. The three methods had a negligible influence on determining the 14C age for samples that were at least younger than 12,000 yr BP. As the 14C ages of the soil samples are typically younger than 12,000 yr BP, any method explored in this study can be employed for 14C dating with sufficient accuracy for application to C cycle studies.

Accurate modeling of firn densification is necessary for ice core interpretation and assessing the mass balance of glaciers and ice sheets. In this paper, we revisit the nonlinear-viscous firn rheology introduced by Gagliardini and Meyssonnier (1997) that allows multidimensional firn densification problems to be posed, subject to arbitrary stress and temperature fields. First, we extend the calibration of the coefficient functions that control firn compressibility and viscosity to five additional Greenlandic sites, showing that the original calibration is not universally valid. Next, we demonstrate that the transient collapse of a Greenlandic firn tunnel can be reproduced in a cross-section model, but that anomalous warm summer temperatures during 2012–14 reduce confidence in attempts to independently validate the rheology. Finally, we show that the rheology can explain the increased densification rate and varying bubble close-off depth observed across the shear margins of the Northeast Greenland Ice Stream. Although we suggest more work is needed to constrain the near-surface compressibility and viscosity functions of the rheology, our results strengthen the empirical grounding of the rheology for future use, such as modeling horizontal firn density variations over ice sheets for mass-loss estimates or estimating ice-gas age differences in ice cores subject to complex strain histories.

Phacopid trilobites are well documented during the Paleozoic. Nevertheless, while 2D quantitative analyses have advanced our understanding of the morphological relationships among trilobites, the quantification of their morphological traits in 3D remains rarely documented. Based on two sets of morphological data (head and tail), 2D versus 3D shape quantification approaches were used to explore shape allometries as well as to explore how the shape variations can be explained by the phylogenetic relationships among phacopid trilobite species for the first time. We demonstrate that (1) there are similar patterns of morphological variability across taxa in 3D and 2D; (2) there are rather congruent results between 3D and 2D to discriminate taxa; (3) 2D and 3D landmarks capture different levels of detail, and the third dimension in 3D is very important for making taxonomic distinctions at the genus level; (4) there is congruity between 2D and 3D datasets for allometric patterns with results showing similar allometric slopes among species exhibiting a glabellar length decrease during growth leading to wider cephala; (5) the phylomorphospaces show tree branches that do not intersect, suggesting possible phylogenetic constraints on morphospace occupation for each species and supporting the idea that the Austerops and Morocops groups are sister clades that experienced different modes of morphological evolution; and (6) the morphological descriptors in morphometric analyses in 2D and 3D throughout phacopid evolution are effective.

We present 35 AMS 14C dates from 26 horizons on a 30-cm gravity core from Shira Lake in the republic of Khakassia, Central Russia. The chronology of the core is determined by 210Pb/137Cs dating results and interpretation of elemental geochemistry with historic documents, covering deposition since ca. 1870 CE. This study assesses the old carbon influence (OCI) on organic carbon 14C by comparison with the 210Pb/137Cs dates, sources of carbon, and lake conditions interpreted from elemental proxies. These include elemental concentrations in 0.5N HCl leaches and Aqua Regia dissolution fractions, as well as organic C, N and C/N measurements. From these data we establish a succession of the following six zones: I) (1870∼1900 CE) relatively fresh lake with high lake level, low productivity and high surface runoff (wet conditions); II) (1900∼1940 CE) a “white zone” reflected by high carbonate and low magnetic signal formed in a saline, oxidizing and holomictic lake stage; III) (1940∼1963 CE) reduced carbonate with elevated organic C, N, C/N, Mo and magnetic signal, indicating a stratified and anaerobic lake; IV) (1963∼1994 CE) increased salinity and productivity with the highest observed magnetic signal and elevated heavy metal and Mo contents, implying enhanced anoxic conditions and human impact; V) (1994∼2003 CE) high C/N, organic and carbonate contents suggesting meromictic and anaerobic lake conditions; VI) (2003∼2020 CE) decreased carbonate content with increased organic C and N, and heavy metals showing a deteriorating lake environment under human impact.

Proper identification of behavioral patterns is an important prerequisite for the identification of any trace fossil and even more so for its interpretation. For the last 70 yr, the continually advancing state of ichnological knowledge has led to a gradual recognition of recurrent patterns of organismal behavior documented in the fossil record, which in turn gave rise to the ethological categories. “Mortichnia” was proposed for traces created during a death struggle of the tracemaker but has been reported only in a few cases. Fish mortichnia so far have only been reported in one specimen recovered from the Upper Jurassic Plattenkalk of Nusplingen (SW Germany). The category mortichnia is refined herein, but remains ambiguous. Eight newly discovered unique specimens of mortichnia from Upper Cretaceous marine sediments in central Lebanon (Haqil, En Nammoura) are preserved together with their tracemakers and described herein. In addition, 14 further incomplete specimens were collected where no tracemakers are present. However, morphology and close provenance allow them to be assigned to the same ichnotaxon.

The Lebanese mortichnia originate from fish that were subjected to significant environmental or individual stress leading to their deaths. During death convulsions, their bodies created sedimentary structures with a specific recurring morphology. The ichnogenus Pinnichnus n. igen. with ichnospecies P. haqilensis and P. emmae n. ispp. is proposed for these specimens.

The Ediacaran/Cambrian transition (ECT; ~575–500 Ma) captures the early diversification of animals, including the oldest crown-group taxa of most major animal phyla alive today. Key to understanding the drivers underneath the ECT macroevolutionary patterns are the interactions of animals with one another and their environment, and how these interactions scale up to global diversity patterns. Understanding the ecology of ECT organisms is enabled by the abundance of Lagerstätten over this time period, with a relatively large proportion of soft-bodied organisms preserved, often within the communities in which they lived. Here, we review our understanding of organismal, community, and macroecology of the ECT, and how these different scales of ecological analyses relate to the macroevolutionary diversification patterns we see over this 75 Myr time period. Across all ecological scales, we find clear trends, starting with stochastic ecosystem dynamics dominated by generalist taxa in the first Ediacaran communities, to more structured, niche-driven specialist dynamics by Cambrian Epoch 2. These trends are reflected in organism functional morphology, the complexity and strength of organisms’ interactions within their communities, and large-scale metacommunity, biogeographic, and biodiversity patterns. Yet there is often a time delay between the origination of a new type of ecological interaction and when it is observed to impact the ecosystem as a whole. As such, while many modern ecological innovations were in place by the end of the Cambrian, the knock-on effects and complexity of these interactions continued to build up throughout the Phanerozoic, leading to the complex biosphere we have today.

The conditions under which ice fractures and calves icebergs from Antarctic ice shelves are poorly understood due largely to a lack of relevant observations. Though previous studies have estimated the stresses at which ice fractures in the laboratory and through sparse observations, there remains significant uncertainty in the applicability of these results to naturally deforming glacier ice on larger scales. Here, we aim to better constrain the stresses under which ice fractures using remote sensing data by identifying large-scale fractures on Antarctic ice shelves, calculating the principal stresses from the observed strain rates and comparing the stresses of unfractured and fractured areas. Using the inferred stresses, we evaluate five common fracture criteria: Mohr–Coulomb, von Mises, strain energy, Drucker–Prager and Hayhurst. We find the tensile strength of ice ranges from 202 to 263 $\mathrm{kPa}$ assuming the viscous stress exponent n = 3, narrowing the range produced by previous observational studies. For n = 4, we find tensile strengths of 423–565 $\mathrm{kPa}$, bringing our inferences closer to alignment with laboratory experiments. Importantly, we show that crevassed and uncrevassed areas in the four largest ice shelves are distinct in principal stress space, suggesting our results apply to all ice shelves and the broader ice sheet.

The ubiquitous marine radiocarbon reservoir effect (MRE) constrains the construction of reliable chronologies for marine sediments and the further comparison of paleoclimate records. Different reference values were suggested from various archives. However, it remains unclear how climate and MREs interact. Here we studied two pre-bomb corals from the Hainan Island and Xisha Island in the northern South China Sea (SCS), to examine the relationship between MRE and regional climate change. We find that the MRE from east of Hainan Island is mainly modulated by the Southern Asian Summer Monsoon-induced precipitation (with 11.4% contributed to seawater), rather than wind induced upwelling. In contrast, in the relatively open seawater of Xisha Island, the MRE is dominated by the East Asian Winter Monsoon, with relatively more negative (lower) ΔR values associated with high wind speeds, implying horizontal transport of seawater. The average SCS ΔR value relative to the Marine20 curve is –161±39 14C years. Our finding highlights the essential role of monsoon in regulating the MRE in the northern SCS, in particularly the tight bond between east Asian winter monsoon and regional MRE.

Capillary suction across the soil–snow interface is a possible mechanism for the formation of wet basal snow layers, which are necessary for snow gliding and glide-snow avalanches. However, little is known about the conditions under which this process occurs. We investigated capillary suction across the soil–snow interface considering realistic snow and soil properties. Snow properties were determined from snow profiles and soil properties were determined from field measurements of liquid water content, matric potential, soil texture and bulk density for 40 alpine soils in Davos, Switzerland, as well as a field site in the region (Seewer Berg) with glide-snow avalanche activity. For the alpine soils investigated here, the results show that capillary flow from the soil to the snow is possible for realistic snow properties but requires a soil saturation of ∼90% or higher at the soil surface. When comparing the 90% saturation threshold to field measurements, the results suggest that capillary suction across the soil–snow interface is unlikely to contribute significantly to the formation of wet basal layers on Seewer Berg. These results are also relevant for soil and snow hydrology, where water transport across the soil–snow interface is important and understudied.

This paper presents the radiocarbon context of the megalithic monument El Amarejo 1, situated in the corridor of Almansa in the southern region of La Meseta in Spain. The monument was constructed using small and medium-sized masonry, comprising a short corridor and two separate chambers in which burials were carried out. The results of the 14C analyses of each of the 11 individuals documented indicate that the monument was in use between approximately 1900 and 1200 cal BC. Bayesian modeling of the radiocarbon dates allows for the proposition of hypotheses regarding the construction, utilisation dynamics, and abandonment of the monument. The combination of these new data with the analysis of the 14C dating of other burials from the Bronze Age of La Mancha reveals a complex and heterogeneous panorama. The evidence presented and analyzed in this paper suggests that burial practices associated with fortified settlements and their domestic areas shared space and time with the construction of megalithic monuments located near settlements.