Search Results (86)

The northern segment of the Great Xing’an Range, northeastern China, hosts a previously unrecognized near-E–W-trending rhyolite belt in the Tulihe area. We conducted systematic geochronological and geochemical investigations to constrain its formation age, petrogenesis, and regional tectonic significance. Field investigation, petrographic observation, and zircon laser ablation–inductively coupled plasma–mass spectrometry (LA-ICP-MS) U–Pb dating indicate that the rhyolite belt was formed during the Early Cretaceous, with emplacement ages directly determined from three samples ranging from 143.8 to 131.5 Ma. Geochemically, the rhyolites yielded high SiO₂ contents (74.44–75.88 wt.%), high total alkalis (K₂O + Na₂O = 8.50–8.99 wt.%), and low MgO contents (0.16–0.55 wt.%). They displayed strong enrichment in light rare earth elements and depletion in high field strength elements, weakly negative Eu anomalies, A/CNK ratios near unity, and relatively high Nb/Ta ratios. Trace element signatures and incompatible element abundances (Zr + Nb + Ce + Y = 193.2–338.3 × 10⁻⁶) are mostly consistent with highly fractionated I-type volcanic rocks, rather than S-type or M-type affinities. The geochemical data suggest that the rhyolites were mainly generated by partial melting of a medium- to high-K basaltic lower crust, with minor crustal assimilation and limited mantle input. Tectonically, Early Cretaceous magmatism in the northern Great Xing’an Range was governed by flat-slab subduction and subsequent rollback of the Paleo-Pacific (Izanagi) plate, while the local E–W-trending rhyolite belt was controlled by pre-existing faults, reflecting localized post-orogenic extension consistent with regional NE-trending volcanic belts. The northwest-to-southeast younging trend records asthenospheric upwelling and enhanced crust–mantle interaction induced by slab rollback. These results highlight the petrogenetic and tectonic evolution of medium- to high-K magmatism along the NE Asian continental margin and improve our understanding of Mesozoic volcanism in the Great Xing’an Range. Full article

The Hatu region in the Western Junggar, Xinjiang, is one of the most significant gold metallogenic concentration areas in China. Gold mineralization is primarily controlled by several parallel NE-trending strike-slip faults and Late Paleozoic granitic plutons, accompanied by multiple stages of hydrothermal activity. To enhance the objectivity and accuracy of mineral prospecting prediction, this study develops an integrated forecasting framework that combines multi-source remote sensing datasets with machine learning techniques. Alteration anomalies related to iron staining and hydroxyl-bearing minerals are extracted from ASTER data, alteration mineral mapping is performed using GF-5 hyperspectral imagery, and Landsat-9 data is used for structural interpretation to refine the regional metallogenic framework. On this basis, these multi-source remote sensing products are then integrated to delineate five prospective metallogenic areas (T1–T5). Subsequently, a Random Forest (RF) model optimized by the Grey Wolf Optimizer (GWO) algorithm is employed to quantitatively integrate key evidence layers, including alteration, structure, and geochemistry, for estimating mineralization probability. The results show that the GWO-RF model effectively concentrates anomalous areas and identifies two high-confidence targets, Y1 and Y2, both with mineralization probabilities exceeding 0.8. Among them, the Y1 target is associated with the Bieluagaxi pluton and exhibits strong montmorillonitization, chloritization, and iron-staining alteration, typical for magmatic–hydrothermal controlled mineralization. In contrast, the Y2 target is strictly controlled by the Anqi Fault and its subsidiary faults, primarily characterized by linear chloritization and iron-staining anomalies indicative of structure–hydrothermal mineralization. Field verification confirms the significant metallogenic potential of both Y1 and Y2, demonstrating the effectiveness of integrating multi-source remote sensing and machine learning for predicting orogenic gold systems. This approach not only deepens the understanding of the diverse gold mineralization processes in the Western Junggar but also provides a transferable methodology and case study for improving regional mineral exploration accuracy. Full article

In this study, an I-optimal design was used to select an optimal muña essential oil nanoemulsion (MEO-NE) for application in active starch-based films. Four independent variables were used to optimize the process: emulsifier concentration (X₁) (% w/w), sonication time (X₂) (min), essential oil concentration (X₃) (% w/w), and emulsifier type (X₄) (Tween 80 or sapote gum). Results revealed that MEO-NE containing 5.24% of MEO, 6% Tween^® 80, and 9 min of ultrasound treatment exhibited a small droplet size (Y₁) (48.6 nm), moderate ζ-potential (Y₂) (−15 mV), and DPPH inhibition (Y₃) (95.6%). Starch-based films were incorporated with optimized MEO-NE at 5% (F₁) and 10% (F₂) and compared with control films (F₀). F₁ and F₂ exhibited lower moisture content, water solubility, and water vapor permeability than F₀; however, their contact angles were higher. The addition of MEO-NE into the polymeric matrix increased the stiffness of F₁ and F₂; however, the elongation at yield was slightly lower than that of F₀, resulting in less stretchable composite films. All films were disintegrated by more than 90% after 5 days of burial under composting conditions. The incorporation of MEO-NE into composite films significantly enhanced their properties, suggesting their potential use as eco-friendly packaging. Full article

As a well-known World Cultural Heritage Site, the Historic Centre of Macao’s historical buildings possess a wealth of decorative patterns. These patterns contain cultural esthetics, geographical environment, cultural traditions, and other elements from specific historical periods, deeply reflecting the evolution of religious rituals and political and economic systems throughout history. Through long-term research, this article constructs a dataset of 11,807 images of local decorative patterns of historical buildings in Macau, and proposes a fine-grained image classification method using the ConvNeXt-L model. The ConvNeXt-L model is an efficient convolutional neural network that has demonstrated excellent performance in image classification tasks in fields such as medicine and architecture. Its outstanding advantages lie in limited training samples, diverse image features, and complex scenes. The most typical advantage of this model is its structural integration of key design concepts from a Transformer, which significantly enhances the feature extraction and generalization ability of samples. In response to the objective reality that the decorative patterns of historical buildings in Macau have rich levels of detail and a limited number of functional building categories, ConvNeXt-L maximizes its ability to recognize and classify patterns while ensuring computational efficiency. This provides a more ideal technical path for the classification of small-sample complex images. This article constructs a deep learning system based on the PyTorch 1.11 framework and compares ResNet50, EfficientNet-B7, ViT-B/16, Swin-B, RegNet-Y-16GF, and ConvNeXt series models. The results indicate a positive correlation between model performance and structural complexity, with ConvNeXt-L being the most ideal in terms of accuracy in decorative pattern classification, due to its fusion of convolution and attention mechanisms. This study not only provides a multidimensional exploration for the protection and revitalization of Macao’s historical and cultural heritage and enriches theoretical support and practical foundations but also provides new research paths and methodological support for artificial intelligence technology to assist in the planning and decision-making of historical urban areas. Full article

Background/Objectives: Diabetic retinopathy is a leading cause of vision impairment worldwide, and the development of reliable automated classification systems is crucial for early diagnosis and clinical decision-making. This study presents a comprehensive comparative evaluation of two state-of-the-art deep learning families for the task of classifying diabetic retinopathy using retinal fundus images. Methods: The models were trained and tested in both binary and multi-class settings. The experimental design involved partitioning the data into training (70%), validation (20%), and testing (10%) sets. Model performance was assessed using standard metrics, including precision, sensitivity, specificity, F1-score, and the area under the receiver operating characteristic curve. Results: In binary classification, the ResNeXt101-64x4d model and RegNetY32GT model demonstrated outstanding performance, each achieving high sensitivity and precision. For multi-class classification, ResNeXt101-32x8d exhibited strong performance in early stages, while RegNetY16GT showed better balance across all stages, particularly in advanced diabetic retinopathy cases. To enhance transparency, SHapley Additive exPlanations were employed to visualize the pixel-level contributions for each model’s predictions. Conclusions: The findings suggest that while ResNeXt models are effective in detecting early signs, RegNet models offer more consistent performance in distinguishing between multiple stages of diabetic retinopathy severity. This dual approach combining quantitative evaluation and model interpretability supports the development of more robust and clinically trustworthy decision support systems for diabetic retinopathy screening. Full article

The Zaghouan Fluorite Province (ZFP) encloses F-Ba(Pb-Zn) ores hosted within Jurassic carbonate series, in northeastern Tunisia. Critical breakthroughs on the Jebel Stah fluorite deposits, an MVT-style F-mineralization, have been made within the Lower Jurassic limestones along the Zaghouan Fault, which is a major target for mineralization. This study presents the first REE-Y analyses conducted by LA-ICP-MS on fluorites in Tunisia, and specifically on the fluorites of Jebel Stah deposit. This analytical technique provides highly accurate insights into the geochemical regime of mineralizing fluids and the related scavenging sources. Distinct geochemical characteristics between two fluorite generations (G1 and G2) were revealed. Fluorites (Fl2) from the early generation (G1) showed low ΣREE + Y (36.3 and 39.73 ppm, respectively). When normalized to chondrites, early fluorite G1 displayed a bell-shaped REE + Y pattern with a depletion in LREE relative to HREE and a slight MREE hump. Late fluorite (Fl3) generation (G2) displayed higher ΣREE + Y concentrations (77.43 ppm), but an almost similar REE pattern. Ce/Ce* ratios demonstrated strong negative Ce anomalies in all fluorites, while Eu/Eu* ratios indicated weak negative Eu anomalies. The positive Y anomaly observed in the REE + Y patterns of fluorites G1 and G2 suggests Y-Ho fractionation in the fluid system. Moreover, significant degrees of differentiation between terbium (Tb) and lanthanum (La) have been observed in all fluorite samples. The plot of fluorites from both fluorite generations on the Tb/La–Tb/Ca diagram gives evidence of the sedimentary hydrothermal origin of the ore-forming fluids in the Jebel Stah F-deposit. Sr isotopes show that the mineralizing fluids are radiogenic and deeply sourced basinal brines, whereas the small variation in ⁸⁷Sr/⁸⁶Sr ratios suggests a similar source for Sr in fluorites G1 and G2. These results allow us to conclude that the economic fluorite (G1) ore of Jebel Stah was deposited due to the interaction of the deeply sourced hydrothermal fluid with the carbonated host rocks (dolomitization, an increase in pH, and Ca activity), whereas the late fluorite (G2) is an accessory and could have resulted from the mixing of the hydrothermal fluid with shallow meteoric waters. Full article

This study aimed to identify single nucleotide polymorphism (SNP) loci within the coding sequence of the neuropeptide Y (NPY) gene and evaluate their association with egg production traits in Thai native chickens. The goal was to enhance productivity through selective breeding. A total of 117 chickens, including three Thai native breeds and commercial laying hens, were analyzed. The phenotypic traits measured included age at first egg production (AFEP), first egg weight (FEW), egg weight at 9 months (EW_9M) and 12 months (EW_12M) of egg production period, number of eggs at 9 months (NE_9M) and 12 months (NE_12M) of egg production period, number of eggs per month (EperM), and egg mass (EMs). The NPY gene was sequenced to examine the association between these traits and specific genotypes. The results showed that commercial laying hens (LC) significantly outperformed native breeds in overall egg production. Among the native breeds, Pradu Hang Dum (PH) demonstrated the earliest laying age and the highest cumulative egg production. Genetic diversity analysis revealed moderate heterozygosity levels (PIC = 0.22 to 0.50, He = 0.26 to 0.50). Specific SNP loci (SNP1, SNP2, SNP3, SNP4, SNP5, and SNP6) were found to be associated with key egg production traits, such as AFEP, FEW, EW_9M, EW_12M, NE_9M, NE_12M, EperM, and EMs. These findings highlight the potential of using genetic markers for improving egg production traits in Thai native chickens. By incorporating marker-assisted selection into breeding programs, this research supports the development of more efficient and sustainable poultry farming practices, particularly for local breeds. This study also underscores the importance of preserving genetic diversity while enhancing productivity, ensuring the long-term sustainability of native chicken populations. Full article

Copper accumulation in neurons induces oxidative stress, disrupts mitochondrial activity, and accelerates neuronal death, which is central to the pathophysiology of neurodegenerative diseases like Wilson disease. Standard treatments for copper toxicity, such as D-penicillamine, trientine, and chloroquine, are frequently associated with severe side effects, creating a need for safer therapeutic alternatives. To address this, we developed a curcumin-loaded nanoemulsion (CUR-NE) using the spontaneous emulsification technique, aimed at enhancing the bioavailability and therapeutic efficacy of curcumin. The optimized nanoemulsion displayed a particle size of 76.42 nm, a zeta potential of −20.4 mV, and a high encapsulation efficiency of 93.69%, with a stable and uniform structure. The in vitro tests on SH-SY5Y neuroblastoma cells demonstrated that CUR-NE effectively protected against copper-induced toxicity, promoting significant cellular uptake. Pharmacokinetic studies revealed that CUR-NE exhibited a longer half-life and extended circulation time compared to free curcumin. Additionally, pharmacodynamic evaluations, including biochemical assays and histopathological analysis, confirmed that CUR-NE provided superior neuroprotection in copper overload conditions. These results emphasize the ability of CUR-NE to augment the therapeutic effects of curcumin, presenting a novel approach for managing copper-induced neurodegeneration. The study highlights the effectiveness of nanoemulsion-based delivery platforms in improving chelation treatments for neurological diseases. Full article

A computational study of X-H···Y binary hydrogen-bonded complexes was undertaken to examine the red- and blue-shifting behavior of three model X-H proton donors interacting with a series of Lewis bases: Y = NH₃, NCLi, NCH, NCF, C₂H₂, BF, CO, N₂ and Ne. Two of these proton donors, FArH and F₃CH, have blue-shifting tendencies, while the third, FH, has red-shifting tendencies. A perturbation theory model for frequency shifts that was derived many years ago was employed to partition the predicted frequency shift into the sum of two components, one dependent on the second derivative of the interaction energy with respect to X-H displacement and the other dependent on the X-H bond length change in the binary complex. The predicted shifts were found to be in good agreement with standard ab initio computations, but they were obtained at much lower computational cost. The change in the infrared intensity of the X-H stretching frequency, expressed as a ratio of complex to monomer intensities, was also investigated, along with its relation to the X-H permanent dipole moment derivative and total induced dipole moment derivative with respect to X-H displacement, and used to rationalize the observed infrared intensity changes in the red- and blue-shifted X-H···Y complexes. Full article

The Waxing Mo polymetallic deposit is located in the central part of the Lesser Xing’an–Zhangguangcai Range (LXZR), NE China. The Mo (Cu) mineralization in the deposit is dominantly hosted by quartz veinlets and stockworks and is closely related to silicification and potassic alteration, while the W mineralization is most closely related to greisenization. Zircon samples from granodiorite, biotite monzogranite, granodiorite porphyry, and syenogranite in the Waxing deposit yielded U-Pb ages of 172.3 Ma, 172.8 Ma, 173.0 Ma, and 171.4 Ma, respectively. Six molybdenite samples from porphyry Mo ores yielded a Re-Os isochron age of 172.0 ± 1.1 Ma. The granitoids in the ore district are relatively high in total alkali (Na₂O + K₂O), are metaluminous to weakly peraluminous, and are classified as I-type granitoids. The zircon samples from all granitoids showed a relatively consistent Hf isotopic composition, as shown by positive ε_Hf(t) values (3.1–8.3) and young T_DM2 ages (0.69–1.25 Ga). These results, combined with the whole-rock geochemistry, suggest that the magma source of these rocks most likely derived from partial melting of a juvenile middle-lower continental crust, with a minor contribution from the mantle. These granitoids have compositional characteristics of adakites such as relatively high Sr contents (e.g., >400 ppm) and Sr/Y ratios (e.g., >33), as well as weak Eu anomalies (e.g., Eu/Eu* = 0.8–1.1), indicating extensive fractionation crystallization of a hydrous magma. The apatite geochemistry indicates that the ore-related magma in Waxing is F-rich and has a relatively low content of sulfur. The zircon geochemistry reveals that the granodiorite, biotite monzogranite, and granodiorite porphyry have relatively high oxygen fugacity (i.e., ΔFMQ = +1.1~1.3), whereas the fO₂ values of the granite porphyry and syenogranite are relatively low (i.e., ΔFMQ = +0.1~0.5). The whole-rock and mineral geochemistry suggest that the Mo mineralization in Waxing is probably genetically related to granitoids (i.e., granodiorite, biotite monzogranite, and granodiorite porphyry), with higher oxygen fugacity and a high water content, whereas the magmatic S concentration is not the key factor controlling the mineralization. A comparison of the geochemical compositions of ore-forming and barren stocks for porphyry Mo deposits in the LXZR showed that geochemical ratios, including Eu/Eu* (>0.8), 10,000*(Eu/Eu*)/Y (>600), Sr/Y (>33), and V/Sc (>8), could be effective indicators in discriminating fertile granitoids for porphyry Mo deposits from barren ones in the region. Full article

A protocol for the monazite (LREE,Y,Th,U,Si,Ca)PO₄ in situ Th-U-Pb dating by electron probe microanalyser (EPMA) involves a suitable reference monazite. Ages of several potential reference monazites were determined by TIMS-U-Pb isotope analysis. The EPMA protocol is based on calibration with REE-orthophosphates and a homogeneous Th-rich reference monazite at beam conditions of 20 kV, 50 nA, and 5 µm for best possible matrix matches and avoidance of dead time bias. EPMA measurement of samples and repeated analysis of the reference monazite are performed at beam conditions of 20 kV, 100 nA, and 5 µm. Analysis of Pb and U on a PETL crystal requires YLg-on-PbMa and ThMz-on-UMb interference corrections. Offline re-calibration of the Th calibration on the Th-rich reference monazite, to match its nominal age, is an essential part of the protocol. EPMA-Th-U-Pb data are checked in ThO₂*-PbO coordinates for matching isochrones along regressions forced through zero. Error calculations of monazite age populations are performed by weighted average routines. Depending on the number of analyses and spread in ThO₂*-PbO coordinates, minimum errors <10 Ma are possible and realistic for Paleozoic monazite ages. A test of the protocol was performed on two garnet metapelite samples from the Paleozoic metamorphic Zone of Erbendorf-Vohenstrauß (NE-Bavaria, western Bohemian Massif). Full article

The Kunduleng granite hosts one of several significant uranium anomalies within the southern Great Xing’an Range, NE China. Whole-rock geochemistry and mineral chemistry data, along with the zircon U-Pb-Hf isotope have been used to constrain the petrogenesis of this granitic intrusion and the origin of the uranium anomaly. Microscopically, quartz, alkali-feldspar, and plagioclase are the essential mineral constituents of the granite, with minor biotite, while monazite, apatite, xenotime, and zircon are accessory minerals. Geochemically, the silica- and alkali-rich granites show a highly fractionated character with “seagull-shaped” REE patterns and significant negative anomalies of Ba and Sr, along with low Zr/Hf and Nb/Ta ratios. The granite has positive zircon ε_Hf(t) values ranging from +12.7 to +14.5 and crustal model ages (T_DM2) of 259–376 Ma, indicating a Paleozoic juvenile crustal source. Uraninite and brannerite are the main radioactive minerals responsible for the uranium anomaly within the Kunduleng granite. Uraninite presents well-developed cubic crystals and occurs as tiny inclusions in quartz and K-feldspar with magmatic characteristics (e.g., elevated ThO₂, Y₂O₃, and REE₂O₃ contents and low CaO, FeO, and SiO₂ concentrations). The calculated U-Th-Pb chemical ages (135.4 Ma) are contemporaneous with the U-Pb zircon age (135.4–135.6 Ma) of the granite, indicating a magmatic genesis for uraninite. The granites are highly differentiated, and extreme magmatic fractionation might be the main mechanism for the initial uranium enrichment. Brannerite is relatively less abundant and typically forms crusts on ilmenite and rutile or it cements them, representing the local redistribution and accumulation of uranium. Full article

Fe-Mn carbonate is the dominant mineral in the Erdaokan Ag deposit, which represents the first large independent silver deposit during the Late Triassic Period in the Duobaoshan Cu-Mo-Au mineralization concentrated area of Heilongjiang Province, NE China. The Fe-Mn carbonates in the deposit frequently co-exist with Ag minerals. Thus, the presence of Fe-Mn carbonates plays a crucial role in the ore-formation process, making their analysis essential for obtaining valuable metallogenic information about the Erdaokan deposit. Through microexamination, SEM and EDS analysis, a clear relationship between Fe-Mn carbonate minerals and Ag minerals was established. Furthermore, electron probe microanalysis, LA-ICP-MS, and Sr-Nd isotope tests were conducted to analyze Fe-Mn carbonates for significant metallogenic insights. The distribution pattern of trace elements and rare-earth elements in Fe-Mn carbonates is similar, characterized by Zr depletion (below 0.131 ppm), enrichment of light rare-earth elements, a noticeable deficit of Eu (δEu = 0.06–0.63), and an average Y/Ho value of 34.29, indicating the involvement of upper mantle-derived deep magma in the formation of ore-forming materials. The samples had a Sm-Nd isochron age of 233.7 ± 1.2 Ma, suggesting that the Erdaokan Ag deposit was formed during the Late Triassic Period. This study highlights the significance of Fe-Mn carbonate as a valuable mineral indicator for regional silver prospecting purposes, and confirms the Late Triassic Period as another important metallogenic stage in the Duobaoshan Cu-Mo-Au mineralization concentrated area. Full article

The Igla Ahmr region in the Central Eastern Desert (CED) of Egypt comprises mainly syenogranites and alkali feldspar granites, with a few tonalite xenoliths. The mineral potential maps were presented in order to convert the concentrations of total rare earth elements (REEs) and associated elements such as Zr, Nb, Ga, Y, Sc, Ta, Mo, U, and Th into mappable exploration criteria based on the line density, five alteration indices, random forest (RF) machine learning, and the weighted sum model (WSM). According to petrography and geochemical analysis, random forest (RF) gives the best result and represents new locations for rare metal mineralization compared with the WSM. The studied tonalites resemble I-type granites and were crystallized from mantle-derived magmas that were contaminated by crustal materials via assimilation, while the alkali feldspar granites and syenogranites are peraluminous A-type granites. The tonalites are the old phase and are considered a transitional stage from I-type to A-type, whereas the A-type granites have evolved from the I-type ones. Their calculated zircon saturation temperature T_Zr ranges from 717 °C to 820 °C at pressure < 4 kbar and depth < 14 km in relatively oxidized conditions. The A-type granites have high SiO₂ (71.46–77.22 wt.%), high total alkali (up to 9 wt.%), Zr (up to 482 ppm), FeOt/(FeOt + MgO) ratios > 0.86, A/CNK ratios > 1, Al₂O₃ + CaO < 15 wt.%, and high ΣREEs (230 ppm), but low CaO and MgO and negative Eu anomalies (Eu/Eu* = 0.24–0.43). These chemical features resemble those of post-collisional rare metal A-type granites in the Arabian-Nubian Shield (ANS). The parent magma of these A-type granites was possibly derived from the partial melting of the I-type tonalitic protolith during lithospheric delamination, followed by severe fractional crystallization in the upper crust in the post-collisional setting. Their rare metal-bearing minerals, including zircon, apatite, titanite, and rutile, are of magmatic origin, while allanite, xenotime, parisite, and betafite are hydrothermal in origin. The rare metal mineralization in the Igla Ahmr granites is possibly attributed to: (1) essential components of both parental peraluminous melts and magmatic-emanated fluids that have caused metasomatism, leading to rare metal enrichment in the Igla Ahmr granites during the interaction between rocks and fluids, and (2) structural control of rare metals by the major NW–SE structures (Najd trend) and conjugate N–S and NE–SW faults, which all are channels for hydrothermal fluids that in turn have led to hydrothermal alteration. This explains why rare metal mineralization in granites is affected by hydrothermal alteration, including silicification, phyllic alteration, sericitization, kaolinitization, and chloritization. Full article

We analyzed mineralogical characteristics, and major as well as rare earth element concentrations, from a cryptotephra layer in sediments of the infilled maar of Auel (Eifel, Germany). The results of detailed geochemical analyses of clinopyroxenes and their glassy rims from the Auel cryptotephra layer showed that they are similar to those from the thick Campanian Ignimbrite tephra occurrence in a loess section at Urluia (Romania). Both tephras show idiomorphic green clinopyroxenes and formation of distorted grains up to millimeter scale. The cryptotephra in the Auel core has a modelled age of around 39,940 yr b2k in the ELSA-20 chronology, almost identical to the latest ⁴⁰Ar/³⁹Ar dates for the Campanian Ignimbrite/Y-5 (CI/Y-5) eruption. These observations suggest that parts of the CI/Y-5 ash cloud were transported also northwestward into Central Europe, whereas the main branch of the CI/Y-5 ash plume was transported from southern Italy towards the NE, E, and SE. Based on pollen analyses, we conclude there was no direct effect on vegetation from the CI/Y-5 fallout in the Eifel area. Trees, shrubs, and grasses remained at pre-tephra-airfall levels for roughly 240 years, but changed around 39,700 yr b2k when thermophilic woody plants (e.g., Alnus and Carpinus) disappeared and Artemisia spread. This change in vegetation was well after the Laschamp geomagnetic excursion and also after the GI9 interstadial and quite probably represents the onset of the Heinrich Event 4 (H4) cold spell, when climatic conditions over the North Atlantic, and apparently also in Central Europe, deteriorated sharply. Full article