Gunther Kletetschka

The Australasian tektite strewn field, the largest known on Earth, extends ~13,000 km from Southeast Asia to Antarctica. Previous studies have relied largely on bulk geochemical analyses, which cannot resolve particle-scale processes associated with impact-plume formation and ejecta transport. Here we report, to our knowledge, the first integrated microparticle- and nanoparticle-scale investigation of tektites across the Australasian strewn field. We document quenched micrometer-scale spherules and metallic particles attached to or embedded within freshly fractured interior glass, including specimens whose exterior surfaces were removed before crushing. Electron microscopy was combined with single-particle inductively coupled plasma time-of-flight mass spectrometry (SP-ICP-TOF-MS) to characterize more than 175,000 individual nanoparticles, including over 10,000 containing platinum-group elements (PGEs), from seven regions spanning >7,000 km. The metallic particles and spherules include Fe-, Ni-, and Cu-rich metals, oxides, sulfides, and aluminosilicate phases. Some spherules are vesicular or compound, and, to our knowledge, discrete Ni-Cu-rich metallic particles have not previously been documented within Australasian tektite glass. Quartz grains exhibiting progressive melting and vesicular SiO₂-rich domains are consistent with intense heating and possible silica volatilization at ~1900–2200 °C. PGE-bearing nanoparticle mass distributions and inter-element relationships are broadly similar among regions, while bulk multi-element patterns also show strong compositional coherence, suggesting that these characteristics were established before long-range transport. In contrast, recovered nanoparticle abundance and summed PGE mass vary geographically and generally decline toward distal parts of the strewn field, although Thailand and central Australia depart from a simple monotonic distance trend. Several non-PGE metal nanoparticle populations show distinct regional distributions, indicating that different elements were not transported or retained uniformly across the strewn field. Single-particle Ir/Fe and Pt/Fe ratios differ markedly from average crustal reference values and overlap broad ranges reported for cometary particles, refractory metal nuggets, micrometeorites, and iron meteorites. These overlaps are consistent with, but do not prove, incorporation of extraterrestrial metal and are not diagnostic of a specific impactor class. Hydrocode simulations indicate that multi-kilometer-scale impactors can generate high-velocity, strongly downrange ejecta under shallow-impact conditions, consistent with the first-order transport requirements of the Australasian strewn field.

Hydrothermal systems in volcanic calderas are critical in signalling volcanic unrest, forming ore deposits, and sustaining chemosynthetic microorganisms. Analysis of a ~3500-year sequence of sediments collected from the Santorini caldera, Greece, during International Ocean Discovery Program (IODP) Expedition 398 reveals the behaviour of a prolonged paleo-hydrothermal system. Sediment geochemical and metagenomic data record vigorous hydrothermal activity and metal fluxes for ~1100 years, within a 2270-year window between two major eruptions. Sediment hydrothermally-derived trace metals are significantly enriched over background (~200-fold for As and Hg, and 10–50-fold for Mn, Sb, Mo, and V), with long-term metal fluxes (9 t yr ⁻¹ As, 2.5 t yr ⁻¹ Cu, 7 kg yr ⁻¹ Ag) comparable to fluxes from present-day geothermal fields in the Taupo Volcanic Zone. Metagenomic analysis identifies elevated metal resistance genes—signals of microbial adaptation to heightened hydrothermal stressors. Here we integrate geological and genomic evidence to decipher the paleoenvironmental and biogeochemical history of the past hydrothermal system at Santorini caldera.

The temporal relationship between the Laacher See eruption (LSE), the Younger Dryas Boundary (YDB) layer, and the abrupt onset of Younger Dryas (YD) climate change has long been debated. The Körslättamossen fen in southernmost Sweden provides the first robustly dated Scandinavian record demonstrating that these events are clearly separated stratigraphically and temporally. The Laacher See Tephra (LST) layer at 288.5 cm (~13,006 cal BP) lies 6–10 cm below a discrete PGE-rich horizon (282–279 cm) marking YDB deposition, interpreted here as a 3-cm-thick impact fallout layer. This interval has an onset Bayesian-modeled age of 12,861 ± 54 cal BP, ~150 years after the eruption, indicating that the LST and YDB deposition represent separate events. Within this fallout layer, Fe–Si microspherules with dendritic quench textures peak at 282–281 cm, while maximum PGE-bearing nanoparticle mass occurs at 280–279 cm, consistent with delayed settling of submicron particles. LA-ICP-MS reveals Si-rich microspherules containing PGE-bearing microdomains but negligible Ni, Co, and Cr. These compositions indicate that the microspherules are dominated by terrestrial target material rather than meteoritic metal, while the associated PGE-rich microdomains and nanoparticle populations record a minor but detectable extraterrestrial component. Single-particle ICP-TOF-MS detects a sharp Pt anomaly with Pt-dominant elemental ratios (e.g., high Pt relative to Fe and Ir), consistent with the platinum enrichment reported in the YDB in the GISP2 ice core. Immediately above the fallout layer, a dark, organic-rich horizon records the abrupt hydroclimatic shift to cooler, wetter YD conditions. These observations document three stratigraphically distinct horizons: the LSE, a separate YDB fallout layer, and the near-synchronous onset of YD climate change, providing a well-constrained European stratigraphic framework for evaluating mechanisms proposed for the YD onset.

Human evolution presents a multiscale problem of information transmission spanning intracerebral neural processing on millisecond timescales, interpersonal learning within small-scale social units over individual lifetimes, and cumulative cultural accumulation across hundreds of millennia. The "Homo informatio" schema identifies these as three coupled levels whose interaction drove the emergence of the human cognitive-cultural niche. We provide a conceptual-formal synthesis and argue that the coupled, multiscale, and perspectivally structured temporal dynamics of this system raise a relevant problem of temporal representation that existing single-axis formalisms handle with inconsistencies. Active inference and the Zone of Bounded Surprisal provide the computational vocabulary for describing information transmission at each level, but their standard one-dimensional temporal formulation does not naturally capture the geometric structure of cross-scale coupling or the perspectival distortions inherent in both the archaeological record and human temporal cognition. Drawing on a mathematical system for three-dimensional time, we propose, provisionally, that a three-dimensional temporal formalism, with orthogonal axes representing the characteristic dynamics of intracerebral, interpersonal, and evolutionary-scale information transmission, may offer one candidate architecture for representing these dimensionally related processes. A minimal dynamical system with explicit coupling terms and a projection operator onto single-axis clock-time is introduced. The information-theoretic result of Ortega and Tishby, that perceived duration corresponds to the change in an agent's predictive memory state, is reinterpreted here as a vector quantity in this three-dimensional temporal space, providing a formal link between time-perspectivism and multiscale information processing. A measure of temporal integrated information, structurally related to but distinct from integrated information theory, is proposed as a formalization of cross-scale coupling strength. The system is connected to the Baldwin effect, working memory expansion, white matter maturation, and the non-linear tempo of the archaeological record. Conditions for empirical support, limitation, and falsification are stated explicitly.

This study investigates the feasibility of using a low-cost, rapidly deployable UAV-based system for gamma radiation monitoring. A UAV equipped with a GammaRAE II R dosimeter was used to conduct radiation surveys at the Třebsko site, Czech Republic. The system mapped spatial variations in gamma radiation and identified hotspots, showing strong correlation with previous high-resolution surveys of the area. Data analysis, conducted using open-source software, included altitude corrections, spatial interpolation, and statistical techniques to visualize radiation distribution patterns. Peak gamma dose rate values reached 1.276 μSv/h (altitude-normalized), with 11 locations showing statistically significant elevation (Z-score >3). While the system’s sensitivity is lower than professional-grade equipment, it demonstrated sufficient accuracy for preliminary surveys and rapid assessments. This approach, combining consumer-grade technology with open-source tools, provides a practical solution for environmental monitoring, emergency response, and educational applications, particularly valuable in resource-limited or time-sensitive scenarios. The results validate the potential of affordable radiation monitoring systems as complementary tools to traditional high-cost methods.

The temporal relationship between the Laacher See eruption (LSE), the Younger Dryas Boundary (YDB) layer, and the abrupt onset of Younger Dryas (YD) climate change has long been debated. The Körslättamossen fen in southernmost Sweden provides the first robustly dated Scandinavian record demonstrating that these events are clearly separated stratigraphically and temporally. The Laacher See Tephra (LST) layer at 288.5 cm (~13,006 cal BP) lies 6–10 cm below a discrete PGE-rich horizon (282–279 cm) marking YDB deposition, interpreted here as a 3-cm-thick impact fallout layer. This interval has an onset Bayesian-modeled age of 12,861 ± 54 cal BP, ~150 years after the eruption, indicating that the LST and YDB deposition represent separate events. Within this fallout layer, Fe–Si microspherules with dendritic quench textures peak at 282–281 cm, while maximum PGE-bearing nanoparticle mass occurs at 280–279 cm, consistent with delayed settling of submicron particles. LA-ICP-MS reveals Si-rich microspherules containing PGE-bearing microdomains but negligible Ni, Co, and Cr. These compositions indicate that the microspherules are dominated by terrestrial target material rather than meteoritic metal, while the associated PGE-rich microdomains and nanoparticle populations record a minor but detectable extraterrestrial component. Single-particle ICP-TOF-MS detects a sharp Pt anomaly with Pt-dominant elemental ratios (e.g., high Pt relative to Fe and Ir), consistent with the platinum enrichment reported in the YDB in the GISP2 ice core. Immediately above the fallout layer, a dark, organic-rich horizon records the abrupt hydroclimatic shift to cooler, wetter YD conditions. These observations document three stratigraphically distinct horizons: the LSE, a separate YDB fallout layer, and the near-synchronous onset of YD climate change, providing a well-constrained European stratigraphic framework for evaluating mechanisms proposed for the YD onset.

In this paper, we propose a six-dimensional para-Hermitian manifold in which each spatial dimension carries an intrinsic temporal mode via split-complex coordinates with signature (3,3). The geometry is restricted to Minkowski space on the four-dimensional submanifold defined by synchronized temporal modes, with no rescaling of the speed of light required. A single action is analyzed in two complementary dynamical limits. In the phase-locked sector, Kaluza–Klein reduction recovers four-dimensional Einstein gravity, with Newton’s constant determined by the ratio of the six-dimensional gravitational coupling to the transverse fiber volume. In the phase-fluctuating sector, the non-relativistic limit of the bulk Klein–Gordon equation for the misalignment doublet leads to the Schrödinger equation, with Planck’s constant identified as the canonical normalization of the diagonal Goldstone field. The Born rule probability measure coincides with the geometric [Formula: see text] norm on the misalignment plane, as a consistency condition associated with that Goldstone mode, which serves as a Page–Wootters relational clock specified by the geometry. The Wheeler–DeWitt frozen-time problem is thereby reformulated in relational terms. A single new mass scale separates the quantum and classical regimes; the conservative model-independent lower bound from LHC non-observation of new scalar states places this scale at a few TeV.

Here, we present a multidisciplinary investigation of a late-Pleistocene Greenland ice-margin sequence near Kangerlussuaq that spans the Bølling-Allerød, Younger Dryas, and early Holocene. This study investigates the cause of the Younger Dryas (YD) cooling event (~12,800 years ago) and its possible relationship to a cosmic impact. The Kangerlussuaq interval was previously identified using visible dust stratigraphy, oxygen-isotope measurements, and a peak in nanocarbon particles interpreted as nanodiamonds. We expand that record using bulk ICP-MS, single-particle ICP-time-of-flight mass spectrometry (SP-ICP-TOF-MS), microscopy, mineralogical observations, and hydrocode modeling. The Kangerlussuaq sequence preserves a dark, dust-rich YD interval bounded by clearer Holocene and Bølling-Allerød ice. Stable δ ¹⁸ O values and dust-related geochemical changes support correlation of this interval with the YD cooling episode, although the ice-margin setting introduces uncertainties related to compression, ablation, meltwater infiltration, and multi-season sample alignment. Within this framework, the Greenland record resolves three superimposed signals. First, bulk geochemistry and nanoparticle mineral-phase associations document a sustained YD-scale reorganization of atmospheric dust provenance and transport, consistent with colder, drier, and windier conditions and enhanced mineral-dust flux throughout much of the ~1,200–1,300-year YD interval. Second, a narrow proxy-rich horizon at the YDB layer (~5.5 m along the sloping ice) contains peak abundances of multiple particulate proxies, including nanocarbon particles previously interpreted as nanodiamonds, quartz grains with shocked planar microstructures, meltglass, glass-filled lithic aggregates, Fe- and Si-rich spherules, carbon-rich spherules, glasslike carbon, charcoal, and soot. Third, nanoparticle concentrations begin to rise at the YDB layer (~5.5 m), marking the onset of enrichment, but reach their maximum immediately above, at ~5.2 m. SP-ICP-TOF-MS identifies this overlying interval as the peak in nanoparticle-scale terrestrial and siderophile components, including Nb, Ta, U, As, Pb, Sb, PGEs, Ni, Co, and Re. Elemental behavior across the nanoparticle dataset can be grouped into three principal populations: climate-driven terrestrial mineral dust, high-temperature plume-derived possible ET condensates, and lower-temperature terrestrial plume derivatives. This offset between the boundary layer and the nanoparticle maximum is a key observation: concentrations are lowest within the YDB layer, increase at the boundary, and peak in the overlying sample, indicating temporally structured deposition involving initial boundary-layer input followed by delayed fallout or redistribution of fine particles. This delay is supported by independent evidence from the GISP2 ice core of a platinum anomaly coincident with the onset of Younger Dryas climate change, including a delayed peak over ~21 years, supporting non-instantaneous deposition of impact-related material and suggesting a temporal link to YD climate change. The PGE-bearing nanoparticle population provides the strongest geochemical evidence for a non-crustal contribution. At ~5.2 m, PGE sum, Ir, Pt, Os, Pd, Ni, Co, and Re are enriched relative to the YDB layer; these elements are strongly enriched in extraterrestrial (ET) materials relative to crustal abundances, suggesting a non-terrestrial source. Ratio-ratio diagrams and PGE fractionation versus Ir/Fe comparisons indicate that the YDB nanoparticle population is compositionally distinct from Greenland background dust and typical terrestrial reservoirs. The Greenland YDB value of (Os+Ir+Ru)/(Rh+Pd+Pt) is sub-chondritic, while Ir/Fe is highly elevated, consistent with a heterogeneous mixture containing a refractory PGE-rich component, possibly from ET refractory metal nuggets (RMNs), together with more volatile PGE-bearing material. This signature does not match any single impactor class (e.g., bulk chondrite, iron meteorite, or achondrite), but is consistent with a mixed, fractionated nanoparticle population superimposed on background cosmic dust influx. Hydrocode modeling demonstrates that a high-velocity impact or airburst interacting with an ice-sheet target can plausibly generate high pressures, elevated temperatures, shocked quartz, melt products, spherules, and widespread nanoparticle dispersal; however, this modeling is intended to illustrate a viable mechanism for proxy formation and does not imply that such an impact occurred at the Greenland site. Instead, these results are consistent with broader Younger Dryas Impact Hypothesis scenarios involving regionally or globally distributed impact and airburst phenomena. The combined proxy assemblage is difficult to explain by volcanism, biomass burning, authigenesis, anthropogenic contamination, or climate-driven dust deposition alone. No single proxy is uniquely diagnostic of impact; rather, the interpretation rests on the stratigraphic co-occurrence of multiple high-temperature, shocked, carbonaceous, siderophile-enriched, and PGE-bearing materials within the YD onset interval. Together, the Greenland record is consistent with a short-duration, high-energy airburst or impact-related depositional episode superimposed on and possibly a major trigger of the broader climatic transition into the Younger Dryas.