Earth Events Research Articles

La luna nelle tradizioni di Lama dei Peligni

Lama dei Peligni is a village in Abruzzo (province of Chieti) that has undergone various economic and socio-cultural transformations. In this work, after brief general considerations concerning the geography, general mythology and traditions of the moon, we proceed to the listing of all the traditions, anecdotes, proverbs and beliefs concerning the moon in the context for the purpose to preserve their memory and then to analyze and interpret their functions and symbolic meanings. The set of facts collected document that the moon had a great importance in the traditions of the context of investigation since it touches many spheres of human action. In the current situation it feeds: the beliefs according to which besides the tides it would influence other earthly events; the magical thought that has not completely dissolved; the romance of poets, singers and simple lovers who entrust their dreams and love messages to her; various traditions and beliefs recovered and inserted into the mechanisms that ensure the show and collective escape.

Chemically Oscillating Reactions during the Diagenetic Formation of Ediacaran Siliceous and Carbonate Botryoids

Chemically oscillating reactions are abiotic reactions that produce characteristic, periodic patterns during the oxidation of carboxylic acids. They have been proposed to occur during the early diagenesis of sediments that contain organic matter and to partly explain the patterns of some enigmatic spheroids in malachite, phosphorite, jasper chert, and stromatolitic chert from the rock record. In this work, circularly concentric self-similar patterns are shown to form in new chemically oscillating reaction experiments with variable mixtures of carboxylic acids and colloidal silica. This is carried out to best simulate in vitro the diagenetic formation of botryoidal quartz and carbonate in two Ediacaran-age geological formations deposited after the Marinoan–Nantuo snowball Earth event in South China. Experiments performed with alkaline colloidal silica (pH of 12) show that this compound directly participates in pattern formation, whereas those with humic acid particles did not. These experiments are particularly noteworthy since they show that pattern formation is not inhibited by strong pH gradients, since the classical Belousov–Zhabotinsky reaction occurs in solution with a pH around 2. Our documentation of hundreds of classical Belousov–Zhabotinsky experiments yields a number of self-similar patterns akin to those in concretionary structures after the Marinoan–Nantuo snowball Earth event. Morphological, compositional, and size dimensional comparisons are thus established between patterns from these experiments and in botryoidal quartz and carbonate from the Doushantuo and Denying formations. Selected specimens exhibit circularly concentric layers and disseminations of organic matter in quartz and carbonate, which also occurs in association with sub-micron-size pyrite and sub-millimetre iron oxides within these patterns. X-ray absorption near edge structure (XANES) analyses of organic matter extracted from dolomite concretions in slightly younger, early Cambrian Niutitang Formation reveal the presence of carboxylic and N-bearing molecular functional groups. Such mineral assemblages, patterns, and compositions collectively suggest that diagenetic redox reactions take place during the abiotic decay of biomass, and that they involve Fe, sulphate, and organic matter, similarly to the pattern-forming experiments. It is concluded that chemically oscillating reactions are at least partly responsible for the formation of diagenetic siliceous spheroids and concretionary carbonate, which can relate to various other persistent problems in Earth and planetary sciences.

Evolution and dispersal of snakes across the Cretaceous-Paleogene mass extinction

Mass extinctions have repeatedly shaped global biodiversity. The Cretaceous-Paleogene (K-Pg) mass extinction caused the demise of numerous vertebrate groups, and its aftermath saw the rapid diversification of surviving mammals, birds, frogs, and teleost fishes. However, the effects of the K-Pg extinction on the evolution of snakes—a major clade of predators comprising over 3,700 living species—remains poorly understood. Here, we combine an extensive molecular dataset with phylogenetically and stratigraphically constrained fossil calibrations to infer an evolutionary timescale for Serpentes. We reveal a potential diversification among crown snakes associated with the K-Pg mass extinction, led by the successful colonisation of Asia by the major extant clade Afrophidia. Vertebral morphometrics suggest increasing morphological specialisation among marine snakes through the Paleogene. The dispersal patterns of snakes following the K-Pg underscore the importance of this mass extinction event in shaping Earth’s extant vertebrate faunas.

Cyclostratigraphy of the Cryogenian Fiq Formation, Oman and its implications for the age of the Marinoan glaciation

Cyclostratigraphy is a powerful tool in chronostratigraphic studies, and has shown its potential in Precambrian time. The Cryogenian Period is one of the most dynamic and intriguing intervals in Earth history and it is a witness to the most extreme climate changes on the planet, known as two Snowball Earth events. However, a robust chronostratigraphic framework is still lacking especially for the younger Marinoan Snowball Earth event, hampering the stratigraphic correlation and comparison among geographically separated records, as well as the understanding of the initiation and termination of this global-scale glaciation. The Cryogenian Fiq Formation in Oman is thought to be Marinoan-equivalent. The duration of the nonglacial units in the Fiq Formation could provide a conservative age constraint on the previously not well-determined onset age of the Marinoan glaciation. In this work, a cyclostratigraphic study has been conducted on three drill cores of the Fiq Formation. The multi-taper method (MTM) spectral analysis, the correlation coefficient (COCO), and the evolutionary correlation coefficient (eCOCO) analyses were performed on the high-resolution gamma-ray (GR) data from the three cores. A hierarchy of Milankovitch cycles (eccentricities, obliquities, and precessions) has been identified, which was used to estimate the optimal sedimentary accumulate rates and the duration of the Fiq Formation in each core. Based on the cyclostratigraphic results, the time scale of the Fiq Formation is at least ~6 Myr. Integrating the radiometric ages and the cyclostratigraphic data from other continents, the onset age of the Marinoan glaciation is suggested to be 650–641 Ma. This new result helps improve the chronostratigraphic framework for the Cryogenian Period and also provides critical temporal constraints for the geological and numerical models that explore the possible mechanisms for the Snowball Earth events.

Worlding Excavation Practices

Abstract This paper seeks to do justice to the often complex, messy, and sometimes ambiguous meaning making practices of archaeological field work. Taking recent adoptions of assemblage theory and sensory studies in archaeology as an angle of arrival, I contribute here to discussions on self-reflective and interpretive archaeology. Drawing on empirical encounters with troweling and backfilling at the Ardnamurchan Transitions Project in western Scotland, I describe the production of archaeological knowledge in terms of storying: the coming into existence of an earthly archaeological world through sensory correspondences. I show how storying generates meaning and knowledge through correspondences of more proximate with more distant excavation practices and interplays between them. Furthermore, I propose that through storying, archaeological meaning making as well as knowledge production can be understood as worlding: the generation of sustained remembrances of earthly events with lively corresponding materials.

Reverse weathering may amplify post-Snowball atmospheric carbon dioxide levels

Snowball Earth glaciations are the most extreme climate perturbations recorded in Earth’s history. It has been argued that the termination of these events was characterized by a single rapid transition from near-global ice coverage to an ice-free greenhouse climate state. Notably, this deviates with more extended transition periods of ice sheet waxing and waning typical of Phanerozoic glaciations. Using a coupled mineralogical and Mg and Li isotopic approach, we explore the role that authigenic clay formation within the seafloor may have played on Earth’s climate during deglaciation of the Marinoan Snowball Earth event. Marine authigenic clay formation—a process referred to as reverse weathering—recycles carbon within the ocean–atmosphere system and acts to elevate atmospheric CO2 levels. The results indicate a shift towards more extensive reverse weathering within the uppermost portion of the glaciogenic Nantuo Formation in South China. Carbon cycle modeling indicates that widespread reverse weathering could have driven a protracted (millions of years) carbon dioxide drawdown following high carbon dioxide levels expected during deglaciation.

Habitable zones with an earth climate history model

A simulation of Earth's climate system through geological time was produced with a view to estimating the sun's continuously habitable zone (CHZ). The model consists of four boxes (air, land, ocean, and rock) and parameterizes the carbonate-silicate cycle as a five-step process, comprising volcanism, dissolution of airborne carbon dioxide in seawater, continental weathering, neritic deposition of carbonates on the sea floor, and seafloor weathering. Weathering, surface albedo, and planetary albedo are affected by the growth of continents over time, and by changes in cloud cover with planetary rotation rate. Radiative transfer is handled with a semigray method based on conditions on preindustrial Earth and present-day Mars. The model includes a process for recovering from Snowball Earth events, involving changing surface albedo due to volcanic soot deposition. The simulation produces a runaway greenhouse effect inside 0.982 AU and “limit cycling” between temperate and freezing temperatures outside 1.18 AU. Because continental weathering is less reactive to temperature than previously thought, the results indicate that Earth is more vulnerable to catastrophic climate runaways at the outer CHZ boundary than foreseen earlier. The narrow spacing ratio (R ​= ​1.20) implies that habitable planets will be less frequent than previously expected.

Phylogeny and Evolutionary History of Respiratory Complex I Proteins in Melainabacteria.

The evolution of oxygenic photosynthesis was one of the most transformative evolutionary events in Earth’s history, leading eventually to the oxygenation of Earth’s atmosphere and, consequently, the evolution of aerobic respiration. Previous work has shown that the terminal electron acceptors (complex IV) of aerobic respiration likely evolved after the evolution of oxygenic photosynthesis. However, complex I of the respiratory complex chain can be involved in anaerobic processes and, therefore, may have pre-dated the evolution of oxygenic photosynthesis. If so, aerobic respiration may have built upon respiratory chains that pre-date the rise of oxygen in Earth’s atmosphere. The Melainabacteria provide a unique opportunity to examine this hypothesis because they contain genes for aerobic respiration but likely diverged from the Cyanobacteria before the evolution of oxygenic photosynthesis. Here, we examine the phylogenies of translated complex I sequences from 44 recently published Melainabacteria metagenome assembled genomes and genomes from other Melainabacteria, Cyanobacteria, and other bacterial groups to examine the evolutionary history of complex I. We find that complex I appears to have been present in the common ancestor of Melainabacteria and Cyanobacteria, supporting the idea that aerobic respiration built upon respiratory chains that pre-date the evolution of oxygenic photosynthesis and the rise of oxygen.

Thinking beyond the data: When the sea went dark

AbstractFive mass extinction events in earth's history each resulted in major oceanic species loss. All of these appear to be associated with significant atmospheric aerosol loading and a reduction in sunlight intensity at the surface. Importantly for marine species, it is not only the intensity of the incident light, but also its colour that is important as, within the ocean, only light with wavelengths less than about 550 nm penetrate to significant depths. However, it is these shorter wavelengths that are preferentially absorbed by atmospheric aerosol, with this effect thereby amplifying any reduction of light within the sea. This was modelled for various aerosol loadings, and it is shown that the amount of light in the sea, required for photosynthesis and visual predation, is especially sensitive to the aerosol loading and type.

Metamorphic conditions and igneous activity in the Um Zariq area, East Sinai, Egypt: Mineralogical and petrological evidences for the transformation from collisional to an extensional regime in the Arabian-Nubian shield

The authors present new petrographic and mineralogical data for the Um Zariq Formation which belongs to Arabian–Nubian Shield metamorphic exposures in the Sinai Peninsula. The formation is believed to be a metasedimentary sequence whose protolith was deposited during the Sturtian Snowball Earth Event (SEE). Our new field data indicate the occurrence of metasomatised limestones/dolostones (calc-silicates) which is distinct from those reported from The Feiran-Solaf Metamorphic Complex. We highlight the presence of a lamprophyre body close to the Kid A-type granite; the Malhaq vogesite - a variety of hornblende-phyric lamprophyre with orthoclase feldspar-. Based on mineral assemblages, field observations and petrographic study, metapelites record an early greenschist/lower amphibolite facies regional metamorphism. Intrusion of the syn-collisional deformed granites (CA1) synchronised with the regional metamorphism at ca. 660±25 Ma. Both of the metamorphic events overprinted on the metapelites and calc-silicates. The contact metamorphism formed cordierite and andalusite in the metapelites and pyroxenes in the calc-silicates. Calc-silicates, on the other hand, record anisotropic fabrics, higher T metamorphic mineral assemblages with hornfelsic texture. The Um Zariq metapelites protoliths were deposited at a deeper stratigraphic level and thus, recorded the regional and contact metamorphism contrary to the shallower carbonates. The peak metamorphic conditions were followed by retrograde metamorphism marked by chlorite and prehnite from metapelites and prehnite, epidote and chlorite in calc-silicates. The Um Zariq igneous activity (Kid A-type Granite and the Malhaq Lamprophyre) marks the transformation from collisional to extensional regime in the Arabian–Nubian Shield at ca. 600 Ma.

Biting midges (Diptera: Ceratopogonidae) from the middle Eocene Anglesea amber (Australia) originated in a subpolar greenhouse earth

ABSTRACT Australian Anglesea amber, late middle Eocene in age, has been recently reported. It occurs in coal deposits formed in a meandering river system on an Austral subpolar coastal plain during a late Greenhouse Earth event, and contains well-preserved bioinclusions of plants, arthropods and microorganisms. Six specimens of biting midges have been recovered and two species are herein described: Meunierohelea anglesensis sp. nov. and Culicoides paleopestis sp. nov. These represent the second and third arthropod species described in Australian amber. The discovery of a new fossil species of the genus Meunierohelea is especially significant, since the only extant species is known from northern Australian tropical rainforests. Additionally, a partial specimen belongs to the Monohelea complex. Interestingly, a male and a female of C. paleopestis sp. nov. occur very close to each other, most likely trapped by the resin during mating, allowing the description of the sexual dimorphism of this species. The species of the genus Culicoides much have fed on the blood of Australian vertebrates during the Eocene, possibly transmitting diseases. These new data extend the knowledge about biting midges during the Eocene, a key time for understanding the global expansion of the Ceratopogonidae into subpolar latitudes.

Influence of Dust on the Initiation of Neoproterozoic Snowball Earth Events

AbstractIt has been demonstrated previously that atmospheric dust loading during the Precambrian could have been an order of magnitude higher than in the present day and could have cooled the global climate by more than 10 °C. Here, using the fully coupled atmosphere-ocean general circulation model CESM1.2.2, we determine whether such dust loading could have facilitated the formation of Neoproterozoic snowball Earth events. Our results indicate global dust emission decreases as atmospheric CO2 concentration (pCO2) decreases due to increasing snow coverage, but atmospheric dust loading does not change or even increases due to decreasing precipitation and strengthening June-July-August (JJA) Hadley circulation. The latter lifts more dust particles to high altitude and thus increases the lifetime of these particles. As the climate becomes colder and the surface albedo higher, the cooling effect of dust becomes weaker; when the global mean surface temperature is approximately -13 °C, dust has negligible cooling effect. The threshold pCO2 at which Earth enters a snowball state is between 280 to 140 ppmv when there is no dust, and is similar when there is relatively light dust loading (~4.4 times present-day value). However, the threshold pCO2 decreases dramatically to between 70 to 35 ppmv when there is heavy dust loading (~33 times present-day value), due to the decrease in planetary albedo which increases the energy input into the climate system. Therefore, dust makes it more difficult for Earth to enter a snowball state.

Influence of Dust on the Initiation of Neoproterozoic Snowball Earth Events

Influence of Dust on the Initiation of Neoproterozoic Snowball Earth Events

First palaeointensity data from the cryogenian and their potential implications for inner core nucleation age

SUMMARY The timing of inner core nucleation is a hugely significant event in Earth's evolution and has been the subject of intense debate. Some of the most recent theoretical estimates for the age of nucleation fall throughout the Neoproterozoic era; much younger than previously thought. A young inner core requires faster recent core cooling rates and a likely hotter early core; knowledge of its age would be invaluable in understanding Earth's thermal history and total energy budget. Predictions generated by numerical dynamo models need to be tested against such data, but records are currently much too sparse to constrain the event to a precise period of time. Here, we present results from 720 Ma dolerite dykes (and one sill) from the Franklin Large Igneous Province, which fall within a crucial 300 Myr gap in palaeointensity records. This study uses three independent techniques on whole rocks from 11 sites spread across High Arctic Canada and Greenland to produce virtual dipole moments ranging from 5 to 20 ZAm2 (mean 11 ZAm2); almost one order of magnitude lower than the present-day field. These weak-field results agree with recent ultralow palaeointensity data obtained from Ediacaran rocks formed ∼150 Myr later and may support that the dynamo was on the brink of collapse in the Neoproterozoic prior to a young inner core formation date.

Combined Lithophile‐Siderophile Isotopic Constraints on Hadean Processes Preserved in Ocean Island Basalt Sources

AbstractDetection of Hadean isotopic signatures within modern ocean island basalts (OIB) has greatly influenced understanding of Earth's earliest history and long‐term dynamics. However, a relationship between two isotopic tools for studying early Earth processes, the short‐lived 146Sm‐142Nd and 182Hf‐182W systems, has not been established in this context. The differing chemical behavior of these two isotopic systems means that they are complementary tracers of a range of proposed early Earth events, including core formation, magma ocean processes, and late accretion. There is a negative trend between 142Nd/144Nd and 182W/184W ratios among Réunion OIB that is extended by Deccan continental flood basalts. This finding is contrary to expectations if both systems were affected by silicate differentiation during the lifetime of 182Hf. The observed isotopic compositions are attributed to interaction between magma ocean remnants and Earth's core, coupled with later assimilation of recycled Hadean mafic crust. The effects of this scenario on the long‐lived 143Nd‐176Hf isotopic systematics mirror classical models invoking mixing of recycled trace‐element enriched (sedimentary) and depleted (igneous) domains in OIB mantle sources.If the core provides a detectible contribution to the tungsten element budget of the silicate Earth, this represents a critical component to planetary‐scale tungsten mass balance. A basic model is explored that reconciles the W abundance and isotopic composition of the bulk silicate Earth resulting from both late accretion and core‐mantle interaction. The veracity of core‐mantle interaction as proposed here would have many implications for long‐term thermochemical cycling.

Cryptic terrestrial fungus-like fossils of the early Ediacaran Period

The colonization of land by fungi had a significant impact on the terrestrial ecosystem and biogeochemical cycles on Earth surface systems. Although fungi may have diverged ~1500–900 million years ago (Ma) or even as early as 2400 Ma, it is uncertain when fungi first colonized the land. Here we report pyritized fungus-like microfossils preserved in the basal Ediacaran Doushantuo Formation (~635 Ma) in South China. These micro-organisms colonized and were preserved in cryptic karstic cavities formed via meteoric water dissolution related to deglacial isostatic rebound after the terminal Cryogenian snowball Earth event. They are interpreted as eukaryotes and probable fungi, thus providing direct fossil evidence for the colonization of land by fungi and offering a key constraint on fungal terrestrialization.

Mg isotope evidence for restriction events within the Paleotethys ocean around the Permian-Triassic transition

The Permian–Triassic transition witnessed the largest mass extinction event in Earth's history, multiple mechanisms have been proposed to explain the cause of this catastrophe, however, relatively less attention has been paid to the paleogeography and major element chemistry of seawater and its possible link to mass extinction during this interval. Syndepositional massive marine dolostones could record the Mg isotope signature of contemporaneous seawater that hold clues of ancient Mg cycling. In this study, we investigated Mg isotopes of dolomite from three widely spaced carbonate sections in the Paleotethys to trace oceanic Mg cycling during this critical period. The latest Permian dolostones from all studied sections have similar δ26Mg values around −2.1±0.1‰. However, a remarkable and consistent increase in δ26Mgdolomite across the extinction interval occurred in both eastern and western margins of the Paleotethys. The results suggest that δ26Mg of seawater in Paleotethys fluctuated by 0.4‰ within ∼750 kyr across the Permian-Triassic transition. Modeling reveals that the high rate of change in δ26Mgseawater required an extremely short residence time for seawater Mg. This is attributed to dramatically intensified dolomitization in a restricted oceanic environment, with Mg isotope evidence revealing that the Paleotethys Ocean experienced transient restriction events, in association with radical changes in the major cation composition of seawater, around the end-Permian mass extinction event (EPME).

Remarkable Migration of the Solar System from the Innermost Galactic Disk; a Wander, a Wobble, and a Climate Catastrophe on the Earth

Abstract Recent knowledge of Galactic dynamics suggests that stars radially move on the disk when they encounter transient spiral arms that are naturally generated during the process of disk formation. We argue that the large movement of the solar system from the innermost disk over its lifetime is inferred from an elemental abundance pattern of the Sun to those of solar twins within the Galactic chemical evolutionary framework. The implied metal-rich environment at the Sun’s birthplace and its formation time are supported by measured silicon isotopic ratios in presolar silicon carbide grains. We perform numerical simulations of the dynamical evolution of disk stars in a Milky Way–like galaxy to identify the lifetime trajectory of the solar system. We find that a solar system born in the proximity of the Galactic bulge could travel to the current locus by the effect of radial migration induced by several major encounters with spiral arms. The frequent feature we identify is the repeated passages of stars inside the same spiral arm owing to the wobble of stars traveling in and out of the spiral arms. We predict that such episodes are evidenced in the Earth’s geological history as snowball Earth and that their occurrence times are within our predictions. In particular, the stellar motion that vertically oscillates during passages through spiral arms occasionally leads to a split into two discrete passage episodes with an interval of several tens of megayears, implying two relevant snowball Earth events that occurred in rapid succession (∼720 and 650 million years ago).

Um Zariq formation, southeast sinai, Egypt: A new record of the Sturtian Snowball Earth event in the Arabian Nubian Shield

Despite the vast extent of the Arabian Nubian Shield (ANS) and its growth during the renowned Neoproterzoic dramatic climatic changes (Snowball Earth Events), only few records of snowball events are identified among its rocks. Here we present geological and geochemical evidence that the northern part of the Arabian Nubian Shield (Um Zariq Formation (UZF), southeast Sinai, Egypt) witnessed global snowball event(s). The UZF was deposited in a convergent plate margin during Cryogenian and comprises metapelitic schists and cap-carbonates on top. The whole succession underwent amphibolite facies metamorphism around 660 Ma ago. In the upper most part of the metapelitic schists, intercalations of conglomeritic, poorly sorted components and large pebbles show many features comparable to metamorphosed diamictites and dropstones. The arsenic (As) contents of metapelites are 1–3 orders of magnitude higher than average phyllites. The high As contents and the presence, cap carbonates, diamictites and dropstones at UZF point toward deposition under glacial -postglacial conditions apparently during the Sturtian (717-660 Ma) snowball event.

Vase-shaped microfossils from the late Ediacaran Dengying Formation of Ningqiang, South China: taxonomy, preservation and biological affinity

The origin and early evolution of protists are shroud in misty. The oldest evidence of heterotrophic protists may be the vase-shaped microfossils (found in Early Neoproterozoic sedimentary rocks around the world (c. 780–720 Ma). Here we explore the taxonomy, preservational types and biological affinity of three-dimensionally preserved vase-shaped microfossils (VSMs) from the Gaojiashan biota of the Dengying Formation, Ningqiang, China. Five species and two genera are recognized, namely Protolagena limbata, P. gaojiashanensis, P. papillata, Sicylagena formosa and S. latistoma. SEM-EDS-BSE data provide sound evidence of calcareous and agglutinated tests of these VSMs. In addition, Found in siltstone beds and clastic dolomite, sedimentological data suggest these VSMs inhabited a series of preservational types including calcification, silicification, phosphatization and pyritization. The fossiliferous strata have recently been dated with U-Pb age of 548 ± 8 Ma, which indicates they are not coeval with diverse vase-shaped microfossil assemblages described in other regions worldwide, but provides supportive evidence for the early diversification of possible protozoa foraminifera clades follow on the Gaskiers Snowball Earth event (c. 590–580 Ma).