Fossil Plants Research Articles

Pollen signal of modern vegetation registered in surface soil samples along an elevation gradient from Iztaccíhuatl volcano, central Mexico

AbstractCharacterising the vegetation-pollen signal is a crucial task for enhancing the interpretation of fossil pollen records. This study analyses 28 surface soil samples collected in the surroundings of Iztaccíhuatl volcano, between 2,650 and 4,024 m asl. Pollen zones and ordination analysis were assessed to establish a qualitative connection between the pollen signal and the distribution of plant communities along the elevation gradient. The results show: (i) the predominant pollen type in the pollen assemblage is Pinus; (ii) pollen grains of Quercus and Alnus are present along the elevation gradient, even at high elevations where the parental plants are not typically found; (iii) samples taken between 2,650 and 3,338 m asl., where fir forests dominate, exhibit higher values of Abies pollen compared to samples above 3,405 m asl.; (iv) the locally-dispersed pollen of the hemiparasite Arceuthobium results key in identifying the presence of pine forests; and (v) pollen taxa such as Apiaceae, Eryngium, Valerianaceae, and Caryophyllaceae are linked to higher elevations, specifically where the plant communities of Pinus hartwegii and alpine grassland occur. The study suggests that the pollen signal along the elevation gradient is useful to characterise the main plant communities of the study site (fir forest, pine forest and alpine grassland). Additionally, the percentage variations of Abies in the pollen signal below 3,600 m asl. show the reduction of fir forest communities resulting from recent human activities in the area.

A new species of Neocalamites from the Upper Buntsandstein (Anisian) of Üdingen (Rur Eifel, Germany)

Well preserved Early-Middle Triassic plant fossils from Northwest Europe are relatively rare due to the environmental conditions within the Germanic basin during this time period. The only sphenophyte species commonly described in the floras that are found in the area, is Equisetites mougeotii. However, only stems without leaf sheaths were ever reported. Here, we describe sphenophyte stems with free standing leaves from the Upper Buntsandstein of Üdingen, Germany, which we attribute to the genus Neocalamites based on this characteristic and the difference, mainly in stem size, of the Üdingen material to E. mougeotii. Most of the material consists of internodal, infertile stems that are unbranched and vary in width. A few of these stems are three-dimensionally preserved. Due to the difference of the material to the other, rarely present, Neocalamites species reported from the Anisian of Western Europe, we propose the plant fossils from Üdingen to be a new species called Neocalamites vanderburghii n.sp.

Shaolinia: A Fossil Link between Conifers and Angiosperms.

The flowering plants (angiosperms) are the dominant and defining group of the Earth ecosystems today. However, from which group and by what way flowers, especially their gynoecia (the key characteristic organs of angiosperms), are derived have been key questions in botany, and have remained unanswered despite botanists' efforts over centuries. Such an embarrassing situation can be attributed to the lack of plants with partially enclosed ovules, which are supposed fill a position between gymnosperms and angiosperms. Here, we report a fossil plant that has apparent coniferous vegetative and reproductive characters but has a single seed partially wrapped by the subtending bract. Such a morphology suggests that a carpel of some angiosperms is equivalent to a lateral appendage (a bract plus its axillary seed) of this fossil. Such a non-traditional interpretation of the homology of angiosperm carpels is compatible with various new progresses made in botany and is in line with Tomlinson's recent hypothesis. Together with other fossil evidence reported recently, it appears that gynoecia in angiosperms are derived in multiple ways.

Latitudinal gradients in the phylogenetic assembly of angiosperms in Asia during the Holocene

Spatio-temporal assessment of phylogenetic diversity gradients during the Holocene (past 12,000 years) provides an opportunity for a deeper understanding of the dynamics of species co-occurrence patterns under environmental fluctuations. Using two robust metrics of phylogenetic dispersion (PD) and 99 fossil pollen sequences containing 6557 samples/assemblages, we analyse spatio-temporal variation in PD of angiosperms and its relationship with Holocene climate in central Asia. Overall, PD throughout the Holocene decreases linearly with increasing latitude, except for a rise in mean nearest taxon distance from ca. 25 to 35° N. This indicates that phylogenetically divergent taxa decrease progressively with increasing latitude, leaving more phylogenetically closely related taxa in the assemblages, thereby increasing phylogenetic relatedness among the co-occurring taxa. The latitudinal gradient of PD has not been consistent during the Holocene, and this temporal variation is concordant with the Holocene climate dynamics. In general, profound temporal changes in the latitudinal PD toward higher latitudes implies that the major environmental changes during the Holocene have driven considerable spatio-temporal changes in the phylogenetic assembly of high-latitude angiosperm assemblages. Our results suggest that environmental filtering and the tendency of taxa and lineages to retain ancestral ecological features and geographic distributions (phylogenetic niche conservatism) are the main mechanisms underlying the phylogenetic assembly of angiosperms along the climate-latitudinal gradient. Ongoing environmental changes may pose future profound phylogenetic changes in high-latitude plant assemblages, which are adapted to harsh environmental conditions, and therefore are phylogenetically less dispersed (more conservative or clustered).

Fossil pollen data can reconstruct robust spatial patterns of biodiversity in the past

Fossil pollen data are valuable for understanding past spatio-temporal variations in plant diversity. However, deducing robust patterns of fossil pollen-assemblage properties is challenging due to factors related to pollen production, dispersal, and fossilisation; sediment sampling; and nomenclature and taxonomy of the fossil pollen grains reflecting the vegetation that produced them. If the composition pattern of the most recent fossil pollen assemblage concords with those in modern or surface pollen assemblages from the same location(s), the pattern can be regarded as robust.Using recent (50–500 years) fossil pollen and surface pollen assemblages of angiosperms compiled from the same geographic area of Central Asia, we analyse spatial patterns in compositional turnover and phylogenetic dispersion. These are widely used to quantify different aspects of plant diversity.Despite differences in the data regarding spatial coverage, number of pollen records, and number of pollen taxa, the spatial pattern in the modern and fossil pollen-assemblage properties across climate zones is broadly similar. Especially, the latitudinal patterns of pollen-assemblage properties are strikingly similar between both data types. However, the degree of concordance varies according to the diversity metric being analysed, and the magnitudes of the metric may differ between both data types. When the data are compiled, processed, and standardised following consistent criteria and analysed using appropriate metrics and methods, spatial patterns in pollen-assemblage properties of fossil pollen data are as robust as those in surface pollen data (∼modern vegetation). Therefore, regional patterns of compositional turnover and phylogenetic dispersion can be confidently inferred from older fossil assemblages through the Holocene.

Effect of cobalt on Microstructure and toughness properties of 9Cr-1.8W-0.4Ni-xCo weld metal

In this research, microstructural characterization and mechanical properties of 9%Cr, 0.4%Ni (including W and Mo) steel weld metal with alloyed cobalt were investigated. Due to their strong creep resistance, oxidation resistance, and low thermal expansion, 9%Cr steels are used in nuclear power plants, petrochemical industries, and fossil fuel-powered power plants that operate in high temperature conditions. In this context, weld metals comprising 0.5 %, 1 % and 1.5 % cobalt and cobalt-free weld metal were produced by SMAW (shielded metal arc welding) technique. Microstructure of the weld metals were characterized with optical microscope (OM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). Also, XRD analysis was performed on the bulk samples and precipitated carbide/nitride phases extracted from the weld metals. In addition, differential scanning calorimetry (DSC) was used to determine the phase transformations. Thermo-Calc modeling study was also performed. Hardness, tensile and Charpy-V impact tests were carried out to determine the mechanical properties. The hardness did not change significantly when cobalt up to 1.5 % in the weld metal. However, with the increase of cobalt, the yield and tensile strength increased without affecting the elongation value too much. In the Charpy impact tests performed at different temperatures (−40 °C, −20 °C, +20 °C, +40 °C, +60 °C), the amount of cobalt increased toughness, especially at +40 and + 60oC temperatures. Ductile brittle transformation temperature (DBTT) of the weld metal with 1.5 % Co decreased from 29 °C to 15 °C compared to cobalt free weld metal. It is thought that this may be caused by the further separation of C, Cr and W from the matrix through forming precipitate by the cobalt effect. Besides the mechanical properties, microstructure was also affected by adding Co with inhibition of delta ferrite formation which decrease the toughness. Curie temperature increased with increasing cobalt content detected by DSC.

Studi Penurunan Emisi GRK dan Analisa Ekonomi Pada Pembangkit Listrik Tenaga Surya (PLTS) Apung Tembesi 46 MWP

Based on data from the Ministry of Energy and Mineral Resources, Indonesia has abundant potential for solar power development, even with relatively low irradiation times. The implementation of solar power plants can directly mitigate the negative impact of carbon emissions caused by fossil power plants, especially coal-fired power plants. This study is aimed to calculate the carbon emission reduction from the construction of FPVPP Tembesi Batam and conduct economic analysis of FPVPP construction by considering Net Present Value (NPV), and Payback Period (PBP), and Internal Rate of Return (IRR) for PLN Batam located in Tembesi Batam Islands Indonesia. This Tembesi solar power plant will be the largest solar power plant in Batam Island which is intended to replace the role of fossil power plants. The study also analyzes the financial impact of carbon credits and renewable energy certificates that PLN Batam will obtain if it fully implements the Tembesi solar power plant. Based on the results of our study, the total carbon emission reduction due to the use of FPVPP when compared to Batam's electricity carbon emission is 67,278,560-ton CO2 in a year. The use of FPVPP in Tembesi, Batam affects the savings of primary energy payments each year and from the economic analysis using the NPV, PBP, and IRR methods, the results show that the feasibility of investing in the construction of FPVPP in Tembesi, Batam is considered feasible and profitable for PT PLN (Persero), the environment, and the scope of the Indonesian state.

Analisis dan Desain Floating PV System di Beberapa Waduk Batam untuk Optimalisasi Bauran Energi Terbarukan

The climate crisis caused by the use of fossil fuels is prompting countries around the world to shift to renewable energy. Indonesia has substantial solar energy potential, but this must be balanced with land conservation efforts. PT PLN Batam, a subsidiary of PT PLN (Persero), shares the responsibility of meeting the national renewable energy mix target of 23% by 2025. Adding new power plants requires a large area, which is a significant challenge in the development of both fossil and renewable energy plants in Batam. The floating PV system is an alternative solution to this problem. This study aims to design a floating solar power generation system at Tembesi and Mukakuning Reservoirs, focusing on solar energy potential, energy production, and system design. The results indicate that solar irradiation at both locations reaches 1,650 kWh/m² with an average horizontal PSH of 4.52 hours/day and net PSH Modules of 4.32 hours/day. Energy production in Year-1 is 55.83 GWh with a performance ratio of 81.65%, resulting in annual energy production of 1,345 kWh/kWp. The floating PV system design at Tembesi and Mukakuning Reservoirs consists of 10 islands, each with 19 array boxes and 20 strings per array box, comprising 28 PV modules per string. A total of 106,400 PV modules with a capacity of 390 Wp each is utilized. The system employs 3,125 kVA PV inverters, 7,500 kVA MV transformers, and 35 MVA HV transformers to ensure high efficiency and reliability. The system design also considers environmental durability, including resistance to corrosion and water level fluctuations. Recommendations include optimizing the design based on seasonal variations and implementing effective monitoring and maintenance systems.

New records for the Middle Siwalik flora of eastern Nepal and their climatic significance

The Siwalik plant fossils are important in understanding the climate change caused by the uplift of the Himalaya. The plant fossil assemblages are abundantly known from Nepal's central and western Siwalik sediments. However, they are poorly known from the Siwalik of the eastern region from where the modern Indian Summer Monsoon (ISM) enters Nepal. That is why fossils of this region are important in understanding the evolutionary history of ISM in Nepal. In the present communication, we report four new fossil leaf impressions/ compressions, namely Thelypteridaceophyllum tertiarum Joshi and Mehrotra of the family Thelypteridaceae, Calophyllum suraikholaensis Awasthi and Prasad of the Calophyllaceae, Albizia siwalica Prasad of the family Fabaceae, and Daphnogene makumensis Mehrotra, Dilcher et Lott of the family Lauraceae from the well-dated Middle Siwalik (∼9.5 Ma) sediments of eastern Nepal. The aforementioned and previous fossil records suggest that seasonal or monsoonal rainfall was present during the deposition of the sediments.

Paleoclimatic implications of a vascular plant from the lowermost Itararé Group

Plant fossils serve as critical proxies for interpreting past climates and environments, offering insights into the history of biosphere and climatic conditions. Here we describe a large tracheophyte cast, as well as the sedimentological settings in which it is preserved, expanding the paleobotanical database of the Itararé Group and contributing to the understanding of the LPIA in the Paraná Basin. This fossil occurs in Ponta Grossa, Paraná state, Brazil, within sedimentary levels interpreted as glacially dominated and deposited during the Late Paleozoic Ice Age (LPIA). The plant macrofossil is preserved as a cast, and the log is vertically oriented with a slight inclination in relation to the bedding plane. Taphonomic data indicate an allochthonous preservation, suggesting that the log was transported from inland areas to a plain before final burial. The identification of the tracheophyte cast within these glacial beds suggests that even in a dominantly glacial context, there were periods of episodic climatic amelioration. This finding implies that the climatic conditions during the Mississippian were not uniformly harsh, allowing the growth of vegetation as represented by the reported tracheophyta.

Insect herbivory on ferns from a midland Atlantic Rainforest locality, southern Brazil: implications for interpreting fossil plant–insect interaction

ABSTRACT This work contains the results of fern–arthropod interactions from a midland Atlantic Rainforest locality and addresses the taphonomic, morphological and ecological implications of insect damage on ferns to interpret them on fossil plant assemblages. Six functional feeding groups – margin feeding, hole feeding, surface feeding, piercing and sucking, mining and galling – are present on the three fern species inhabiting the understory of an Araucaria Forest in the Atlantic Forest biome, southern Brazil. We recognised 19 damage types (DTs), including 14 arthropod-induced DTs, three of which are newly proposed herein. Five of the DTs found were first recorded on ferns. Of the DTs found, the proportion of guilds such as mining and galling shows a significant similarity with those of an upland locality. Products of arachnids and insect behaviour on ferns made up 25% of all fern–arthropod interactions in the midland locality, which included dead bodies and byproducts from processes of arthropod life cycle, which are unlikely to be preserved in the fossil record. This rate of arthropod products consists of significant evidence of interactions to unveil deep-time relationships between arthropods and plants. Lastly, leaf damage on living ferns is more frequent than those occurring in fossil plant assemblages.

First Findings of Fossil Pollen of Ancestor Forms of Cathaya Conifers, a Modern Relic, and a Climate Indicator in the Paleogene and Neogene of West Siberia (Kulunda)

First Findings of Fossil Pollen of Ancestor Forms of Cathaya Conifers, a Modern Relic, and a Climate Indicator in the Paleogene and Neogene of West Siberia (Kulunda)

Paleoenvironmental records from the analysis of Barreiras Formation soils and organic matter dating (12C, 13C, 14C)

The Barreiras Formation possesses soils with horizons and subsurface layers cemented by Si, Al and Fe and commonly enriched with organometallic compounds, which show current and past podzolization processes. The study of these horizons and cemented layers can assist in understanding pedogenesis and paleoenvironmental evolution. Three soil profiles were selected along a toposequence for which morphological and micromorphological descriptions were made and samples of organic matter from spodic horizons and cemented layers were dated using carbon isotopes (12C, 13C, 14C), with the aim of obtaining records of paleoenvironmental conditions and understanding the genetic chronology of the soils. The results were interpreted considering three premises: (i) podzols develop under predominantly humid climatic conditions; (ii) organic matter enclosed in cemented horizons is fossilized and provides data regarding the chronological record of cementation time; and (iii) analysis of fossil plant organic residues using the 13C/12C ratio (δ13C) provides an indication of paleo-vegetal coverage. The results indicate that there were two distinct podzolization events in the study area under humid climatic conditions because the area was dominated by tree vegetation according to δ13C, which ranged from −27.2 %o to −25.3 %o. The first, and oldest, podzolization event, related to the range of 17,530–14,970 years BP, reached all three soil profiles, while the second, younger, event started around 6430 years BP, and is registered only in the upper part of the cemented layer of the P-10 profile located at the top of the slope. Combining the results of organic matter dating with morphological and micromorphological analyses of the profiles leads to the conclusion that the P-10 profile is developing on a cemented bedrock and the P-13 and P-15 profiles are developing on two bedrocks — superficial horizons arising from colluviums coming from the top of the slope and subsurface horizons developing from cemented material.

Plant-insect interactions in the mid-Cretaceous paleotropical El Chango Lagerstätte (Cintalapa Fm., Mexico)—patterns of herbivory during the Angiosperm Terrestrial Revolution

Plants and insects are two of the more diverse and abundant organisms in terrestrial ecosystems. The fossil record of plant-insect interactions offers crucial insights into the coevolutionary dynamics between these groups, shedding light on the intricate relationships that have shaped terrestrial ecosystems. The study of fossil interactions is especially relevant in mid-Cretaceous ecosystems, a time of dramatic changes in the composition of floras and, consequently, in plant-insect relationships. Here, we describe the first suite of plant-insect interactions from the mid-Cretaceous of Mexico. We studied 554 plant fossils from the El Chango Lagerstätte (Cintalapa Formation, Chiapas, Mexico), including vegetative (leaves) and reproductive structures (fruits and seeds). The flora was dominated by gymnosperms (89.3%) followed by angiosperms (10.7%); other groups, such as pteridophytes and bryophytes, were absent. In total, 5.4% of the plant specimens hosted some damage. Angiosperms (all broad-leafed forms), despite being much less common than gymnosperms, expressed more evidence of damage by herbivores (35.6% of specimens damaged). In contrast, the narrow-leafed gymnosperms, the dominant group in the flora, hosted a much lower proportion of herbivory damage (1.8% of specimens damaged). The diversity of damage types (DTs) was relatively low: 14 DTs were identified, corresponding to seven FFGs, including margin feeding, hole feeding, surface feeding, piercing and sucking, oviposition, galling, and mining. Comparison with the other mid-Cretaceous plant-insect assemblages reveals a similar richness of DTs for angiosperms but a lower richness and diversity of DTs on gymnosperms from El Chango. These results indicate preferential herbivory on angiosperms (rather than on the available gymnosperms in the assemblage) by terrestrial arthropods during a period of major changes in the structure of terrestrial ecosystems. However, it is challenging to resolve whether this apparent preference is because insects particularly targeted angiosperms or if the herbivores simply targeted broad leaves in general, since most of the available gymnosperms from El Chango are scale-leafed forms.

A new approach to counting fossil and modern pollen grains: The orderly count

Palynology, the study of pollen and spores, plays a crucial role in various scientific disciplines, including earth sciences (paleovegetation and paleoclimatology), botany, allergy, archaeology, forensic sciencs and cosmetics. This study delves into the critical question in fossil pollen analysis studies: the minimum count of pollen grains required for accurate estimation of vegetation composition. Various statistical methods have been proposed over the years to address this question. Our research introduces an alternative technique, the orderly count, tailored to the nature of palynological analysis. We apply this method to diverse sediment catchments, including peat bogs, marine and lake sediments, from different geographical locations. Additionally, we revisit the reliability coefficients and propose adjustments for more accurate results. Our findings suggest that relying on statistical methods without considering the specific characteristics of palynological data may lead to low reliability. We advocate for the integration of dissimilarity criteria and the orderly count in sample size assessments for enhanced accuracy in palynological analyses. Our study emphasizes the importance of choosing appropriate methodologies aligned with the unique aspects of palynology to ensure robust and reliable results.

Heterogeneous occurrence of evergreen broad-leaved forests in East Asia: Evidence from plant fossils

Evergreen broad-leaved forests (EBLFs) are widely distributed in East Asia and play a vital role in ecosystem stability. The occurrence of these forests in East Asia has been a subject of debate across various disciplines. In this study, we explored the occurrence of East Asian EBLFs from a palaeobotanical perspective. By collecting plant fossils from four regions in East Asia, we have established the evolutionary history of EBLFs. Through floral similarity analysis and paleoclimatic reconstruction, we have revealed a diverse spatio-temporal pattern for the occurrence of EBLFs in East Asia. The earliest occurrence of EBLFs in southern China can be traced back to the middle Eocene, followed by southwestern China during the late Eocene–early Oligocene. Subsequently, EBLFs emerged in Japan during the early Oligocene and eventually appeared in central-eastern China around the Miocene. Paleoclimate simulation results suggest that the precipitation of wettest quarter (PWetQ, mm) exceeding 600 mm is crucial for the occurrence of EBLFs. Furthermore, the heterogeneous occurrence of EBLFs in East Asia is closely associated with the evolution of the Asian Monsoon. This study provides new insights into the occurrence of EBLFs in East Asia.

Strategies for decarbonizing European district heating: Evaluation of their effectiveness in Sweden, France, Germany, and Poland

Decarbonizing the EU's district heating is crucial for meeting climate goals and securing a sustainable energy future. Currently, district heating suffers from inefficiency, high operating temperatures, significant distribution losses, and reliance on fossil fuels. Literature highlights strategies for reducing emissions, including integrating low-carbon heat sources, lowering supply temperatures, and employing efficient technologies like heat pumps and combined heat and power (CHP). However, the individual effectiveness of these strategies in reducing emissions within existing networks remains unassessed. This study addresses the gap by applying a comprehensive model that evaluates energy and emissions across the district heating supply chain, coupled with a derivative-based sensitivity analysis. We apply this methodology to the national-level district heating systems of Sweden, France, Germany, and Poland. Results indicate that the impact of decarbonization strategies on district heating emissions varies significantly by the system's characteristics, i.e., the energy mix in power and district heating supply and the presence of CHP plants. Primarily, incorporating more low-carbon heat sources emerges as the most effective method for emission reduction across nearly all examined countries. A 1 % increase in the share of low-carbon heat sources can potentially cut emissions by 0.8–1.3 kg CO2e per GJ of heat. In countries like Sweden and France, where the power generation already relies heavily on low-carbon resources, technologies which convert electricity to heat—such as heat pumps and electric boilers—rank as the second most effective approach. In contrast, for countries like Germany and Poland, with their moderate to low use of low-carbon power, reducing distribution losses and decreasing heat demand prove more effective, with emission reductions ranging between 0.8-1.3 and 0.7–1.2 kg CO2e per GJ in these countries, respectively. Additionally, cutting down power generation in fossil fuel-based CHP plants significantly reduces emissions in these regions. While green hydrogen and carbon capture and storage (CCS) also contribute to emission reductions, a 1 % increase in green hydrogen's share might decrease emissions by just 0.3–0.5 kg CO2e per GJ of heat, highlighting their lower effectiveness compared to the aforementioned strategies. These insights hold value for both district heating operators and for technology suppliers seeking decarbonization pathways. This is also true for policymakers focused on climate change mitigation, guiding the distribution of subsidies and R&D investments.

New record of Brachyoxylon wood from the Lower Cretaceous of Qingyuan, southeastern China and its palaeoclimatic implications

Early Cretaceous was a key period for the evolution of terrestrial ecosystems. In southeastern China, the late Early Cretaceous (Aptian–Albian) floras are relatively well known and characterized by diverse Cheirolepidiaceae, but the early Early Cretaceous floras in southeastern China are poorly known mainly because of the lack of plant fossils. Here we report petrified woods from a new early Early Cretaceous locality in Qingyuan, southern Zhejiang Province, southeastern China. The new fossil woods collected from the Xishantou Formation (earliest Berriasian, earliest Early Cretaceous) are assigned to Brachyoxylon zhejiangense Tian, Zhu, and Wang based on the anatomy of the secondary xylem. The new material of Brachyoxylon zhejiangense from Qingyuan lacks distinct growth rings or resin canals and has mixed type pitting on the radial walls of the tracheids, araucarioid cross-field pitting, and uniseriate rays. It is the earliest record of Brachyoxylon in southeastern China. Brachyoxylon zhejiangense has been regarded as the wood of the extinct conifer family Cheirolepidiceae and grew in arid to semi-arid environments. Evidence also suggests Cheirolepidiaceae played an important role in the vegetation of southeastern China throughout the Early Cretaceous.

Significance of lignin and fungal markers in the Devonian (407 Ma) Rhynie Chert.

The Rhynie Chert (Lower Devonian, Scotland) hosts a remarkably well-preserved early terrestrial ecosystem. Organisms including plants, fungi, arthropods, and bacteria were rapidly silicified due to inundation by silica-rich hot spring fluids. Exceptional molecular preservation has been noted by many authors, including some of the oldest evidence of lignin in the fossil record. The evolution of lignin was a critical factor in the diversification of land plants, providing structural support and defense against herbivores and microbes. However, the timing of the evolution of lignin decay processes remains unclear. Studies placing this event near the end of the Carboniferous are contradicted by evidence for fungal pathogenesis in Devonian plant fossils, including from the Rhynie Chert. We conducted organic geochemical analyses on a Rhynie Chert sample, including hydropyrolysis (HyPy) of kerogen and high-resolution mass spectrometric mapping of a thin section, to elucidate the relationship between lignin and the potential fungal marker perylene. HyPy of kerogen showed an increase in relative abundance of perylene supporting its entrapment within the silicate matrix of the chert. Lignin monomers were isolated through an alkaline oxidation process, showing a distribution dominated by H-type monomers. G- and S-type monomers were also detected, preserved by rapid silicification. Polycyclic aromatic hydrocarbons including perylene, a known marker for lignin-degrading fungi, were also concentrated in the kerogen and found to be localized within silicified plant fragments. Our results strongly link perylene in the Rhynie Chert to the activity of phytopathogenic fungi, demonstrating the importance of fungal degradation processes as far back as the Early Devonian.

Elevated temperature rusting characteristics of UNS 31254 weldments within the operational confines of fossil fuel-fired plants and municipal waste incinerator surroundings at 700 °C

ABSTRACT This study investigates the air oxidation and rusting traits of fully austenitic alloy 254 stainless steel samples at 700°C after pulse current gas tungsten arc welding (PCGTA) and CO2 laser beam welding (CO2 LBW), with or without molten salt, relevant to coal-fired plants and waste incinerator settings. Among the weldments studied, CO2 laser weldments demonstrate greater resilience to corrosive gas and salt amalgamation, as well as air oxidation, compared to gas tungsten arc weldments, possibly due to thermal disparities and microstructural differences inherent in the welding processes. Protective oxides enhance corrosion resistance in air-oxidised samples, while corrosive compounds like CrS, Cr2K2O7, etc., reduce corrosion resistance and promote spallation in salt-degraded material. A thermogravimetric approach was used to assess rusting effects, alongside microstructural analysis employing optical, Scanning electron microscopy/ Energy dispersive x-ray spectroscopy (SEM/EDS), and X-Ray diffraction analysis (XRD) techniques.