Evolving Earth最新文献

The Arabian Sea hosts a perennial and intense oxygen minimum zone (OMZ) at 150–1200 m depths with O₂ concentrations <0.5 ml/l. It is generally believed that the oxygen-depleted conditions at mid-water depths result from high rate of O₂ consumption due to monsoon-driven productivity generating a high organic matter flux, combined with slow renewal of thermocline waters in the region. With global warming and increasing hypoxia, there is growing interest to better understand the various factors controlling oxygen conditions in the thermocline waters and the impact on the nutrient cycling and climate. In this contribution, we provide an overview of new advances in understanding the basin-wide changes of the OMZ, and highlight new perspectives on the relative roles of ocean and atmospheric circulations in modulating the OMZ intensity through the late glacial-Holocene period. Comprehension of the existing and new proxy records (δ¹⁵N, aragonite preservation, δ¹³C of benthic foraminifera) from the productive western and oligotrophic eastern and north-eastern Arabian Sea provides insights into the regional heterogeneity in basin-wide changes of the OMZ, denitrification and carbonate (aragonite) lysocline, and their links to the seasonal monsoon variability and reorganisation of thermocline circulation. We also highlight the limitations of the existing proxy data to address the important questions of how circulation and chemical properties of intermediate/deep water masses contributing to the Arabian Sea thermocline waters changed in the past. Hence, more detailed proxy data are required to characterise sources of water masses, past changes in their pathways and vertical extents in the Arabian Sea, which are crucial to better constrain the temporal evolution of thermocline ventilation basin-wide.

The global energy transition has dramatically increased the demand for raw materials, including lithium. The largest global reserves of lithium are situated in the salt flats of the Atacama Desert in Chile and the current boom is expected to result in an increase in production. Local communities and environmental NGOs fear a destabilisation of the vulnerable ecosystem of the salt flat. However, the mining companies present scientific studies that refute such claims. In this interdisciplinary research paper, this contradiction in the impact debate is further analysed and interpreted through a literature study and interviews with representatives of different stakeholders on location. What is observed is an unbalanced and possibly incomplete field of knowledge production, with a different role of the involved stakeholders. The state takes a passive position when it comes to monitor compliance of existing environmental legislation and lets the initiative for area and impact studies to the other stakeholders. This leaves the companies in a dominant position with their historical access to research equipment, technological knowhow and data. The communities lack the capacity to match the position of the companies and seem hesitant towards interacting with external researchers. In order to resolve this impasse and understand the long-term effect of large-scale lithium mining in the region, what is urgently needed is more independent research, ideally with a more proactive role of the state.

The end-Permian mass extinction event resulted in devastated continental biomes, desolated land, and toxic waters. Anoxia led to widespread extinctions in marine ecosystems, affecting most oceanic clades. In this paper, the palynofacies of the marine Kockatea Shale, Western Australia, was studied in drill cores Hovea-3 and Redback-2, with the aim of linking changes in the marine and continental realms across the Permian–Triassic boundary interval in Australia. We show that the post-extinction ‘Dead Zone’ of the Frazer Beach Member of the Sydney Basin, eastern Australia, whose base is dated to 252.10 ± 0.06 Ma, directly correlates to the lower part of the Kockatea Shale in the Perth Basin, the so-called Inertinitic Interval. We demonstrate that the extinction of Permian Glossopteris forests observed in the Perth Basin had an immediate impact on the marine faunas due to the massive buildup of organic matter, leading to euxinia in the photic zone and ultimately pushing the marine faunas to an ecological extinction. The last lingering occurrence of marine invertebrates of Permian aspect occur in layers that may tentatively mark the Permian–Triassic boundary, positioned just below the appearance of Triassic floras of the Kraeuselisporites saeptatus Zone (equivalent to the Lunatisporites pellucidus Zone). A striking feature at the base of the Early Triassic Sapropelic Interval of the Hovea Member is the sudden and synchronous appearances of anomalously abundant acritarchs and lycophyte spores, alongside the mass occurrence of the bivalve Claraia, allowing correlation with the rise of the eastern Australian post-extinction pioneer floras in the Early Triassic. This demonstrates a significant lag time between the recovery of the terrestrial versus the marine pioneer biota in high-latitude Gondwana, with a significant delay for the faunal recovery.

The discipline of micropalaeontology, fundamental in Geology, has witnessed substantial technological advancements in recent decades, aided by the exploitation of Artificial Intelligence (AI) systems to facilitate microfossil identification. This perspective paper explores the transformative role of AI in micropalaeontology, particularly in species identification, and its potential to help with the interpretation of microfossil assemblages. While it is argued that AI cannot fully replicate the expertise of a micropalaeontologist, an abundance of scientific studies shows the promising success of AI becoming adept at accurately identifying microfossil species.

We report fossil mammal burrows from backshore beach facies in the Camacho Formation of southern Uruguay, of Late Miocene (Huayquerian SALMA) age. The presence of desiccation cracks and rhizoliths indicate the occurrence of relatively extended periods of subaerial exposure and the incipient development of vegetation. The analysis of the burrows' spatial extent, size, and structure reveals the existence of exceptionally well-preserved and intercrossing tunnel systems. We show the existence of different size classes of burrows, which indicate that at least four different taxa were responsible for their construction. Considering the inferred body masses of the trace makers obtained from allometric relationships and the body masses of taxa recovered for the Camacho Formation, the burrows may have been produced by a combination of the following mammals: one of several rodents, notoungulates, cingulates, folivorans, and a carnivoran. The fossil association represents an exceptional case of a community of ecosystem engineers in the Late Miocene of southeastern South America.

Digital well-logs registering the mineral properties of a drilled section provide information directly referring to its layering. Returns analyses of such logs can be used to generate an inventory of the layer thicknesses defined by the sampled variable. This reveals that layer thickness relationships have fractal-like power-law attributes, with negative exponents around 1.7, independent of the scale, age, facies and rates of accumulation of the analysed sections. Further research may show this to be a universal property of the stratigraphic record. Also, global average rates of accumulation of a wide range of facies prove to decline, power-law fashion, as the time-span of the estimate increases. Hence the stratigraphic record's layer-limiting hiatuses appear fractal-like in their temporal scaling. These related lines of evidence combine to suggest that the record is neither naturally hierarchical, nor inherently cyclic; and the corollary of an established universal stratal power-law would be that accumulation rarely occurs other than in circumstances leading to this condition.

In this study, we examine how metazoan biodiversity has accumulated from the late Precambrian until the Silurian at various scales of taxonomic organization using compilations of the First Appearance Data (FAD) of global marine Metazoa from the datasets available in the Paleobiology Database (PBDB) and primary literature. The results indicate that all animal phyla appear during the late Precambrian and the earlier parts of the Cambrian, which corresponds to the usual concept of the Cambrian Explosion. However, at lower taxonomic ranks, a significant increase of first appearances is observed during the Ordovician, corresponding to an Ordovician Explosion of animal orders, families and genera. The cumulative counts of metazoan FADs at these lower taxonomic ranks reveal a gradual and long-term increase of diversity, reflecting a single large-scale radiation that started in the late Precambrian and lasted at least until the Silurian. This scenario corroborates recent studies that point towards a single long-term radiation during the early Palaeozoic, without clearly distinguishable global diversity explosions during discrete intervals.

The principles of ecosystem and community assembly developed by modern ecologists should be, in principle, applicable to the evolutionary assembly of terrestrial ecosystems during the Paleozoic. There are three broad, general, not time-specific Assembly Rules that have been described by ecologists: dispersal constraints (i.e., can a species reach a given location?), environmental constraints (i.e., if it can reach the location, can a species survive under the prevailing physical conditions there?), and biotic constraints (i.e, once on site, can a species co-exist with or compete successfully against occupants, if any?). These three constraints are, in fact, filters, and function to mediate the process of evolution, selection acting only as a passive arbiter of variation. A paleontological perspective adds consideration of irreducible historical contingency that invisibly, unless explicitly considered, affects the detailed manifestation of the other three; this also can be and has been accessed to some degree via considerations of phylogeny. An explicitly ecological perspective provides a framework to conceptualize the development of early ecosystems via the evolutionary addition of plant-based architectural complexity and the addition of the fungal, arthropod, and vertebrate components. For long-term patterns, such as the increase in structural complexity of vegetation through the Devonian and Carboniferous, assembly rules help to explain long lag times between the origin of innovations and their rise to widespread prominence. For individual paleocommunities, they help to resolve questions of biodiversity - whether the taxonomic record of an assemblage is oversplit or overlumped, for example. That evolution takes place within the framework of ecology is undisputed. But what exactly is that framework? At the most basic level, it is assembly rules.

The late Miocene was a critical time in the development of the North American Great Plains marked by paleoclimate-driven biotic change, including faunal turnovers and the spread of C₄ dominated grasslands. The large volume of sediment shed from the Rocky Mountain region during this time preserves a record of these transitions, which can be informed by previously undescribed paleosol and trace fossil properties from the Ogallala Formation of the central High Plains. The purpose of this paper is to reconstruct paleoenvironments, paleoclimate, and paleoecology from outcrops of the Ogallala Formation in western Kansas by integrating paleopedology, ichnology, and stable isotope geochemistry. Eleven lithofacies are recognized in the study area, mostly massive to crudely stratified, fine-to coarse-grained sandstone and pebbly gravel with stratigraphically uncommon fine-grained lithofacies restricted to thinly bedded intervals or lens-shaped geometries within the sand-dominated strata. These host five pedotypes: 1) calcic Vertisols developed on overbank fines, 2) Entisols developed on braid bar gravels, 3) Entisols developed on volcaniclastic sediment lenses, 4) calcic Inceptisols developed on coarse sandy channel fills, and 5) calcareous Mollisols developed on fine sandy bedforms and channel fills. We recognize ten ichnogenera within paleosols, including burrows attributed to ants, bees, beetles or hemipterans, vinegarroon-like arthropods, fossorial reptiles, seed caching mammals, and large carnivorous mammals. Organic carbon stable isotopes indicate that the flora consisted entirely of C₃ plants, and paleosols and trace-fossil evidence suggest a tree-limited savanna environment with patches of unvegetated soil. Paleoclimate proxies from paleosol and trace fossil properties indicate mean annual air temperatures between 8 °C and 20 °C with seasonal differences of up to 14 °C between mean monthly temperatures of the warmest and coolest months. Mean annual precipitation was likely between 250 mm and 460 mm with a seasonal difference of up to 250 mm between mean monthly precipitation of the driest and wettest months. While hymenopteran tracemakers were active, soil surface temperatures reached at least 30 °C and moisture content was between 10% and 20%. With timing of deposition constrained biostratigraphically to the Barstovian through Hemphillian, our paleoclimate interpretations are most consistent with the period of relative climate stability after Middle Miocene Climate Transition cooling and before Late Miocene Cooling (∼13.8 Ma–7 Ma). The trace-fossil assemblage reveals previously unknown biodiversity among soil arthropods, as well as important trophic connections between the belowground and aboveground components of the terrestrial food web.

Frenelopsis Schenk (family Cheirolepidiaceae†) was among the most widespread conifer genera and a dominant element of wetland ecosystems in low to mid-palaeolatitudes in the the Northern Hemisphere. It was also one of the more important peat-forming shrubs and trees generating extensive deposits of Cretaceous lignite. The genus became extinct at the end of the Cretaceous. Studies of the presence/absence and diversity of Frenelopsis allow us to analyse its evolutionary history, biogeography, and the consider the possible causes of its extinction. During the Early Cretaceous, the genus diversified, triggered by the rise of short-lived species and the constraint of endemism. The maximum diversity and species richness were attained in Barremian and Aptian times while the maximum number of global occurrences is documented during the Albian. In the Late Cretaceous, Frenelopsis species richness declined and the genus became progressively more restricted to the Tethyan archipelago in the context of the rise to dominance of angiosperms. In the Maastrichtian, the last representatives of Frenelopsis survived in the coastal wetlands of Iberia as a relictual plant. In northeast Iberia (present-day Pyrenees) the last occurrences from this genus are early to middle Maastrichtian in age and show an intriguing contrast between the abundance of vegetative remains and the lack of Classopollis pollen grains. These data suggest that at the end of its lineage, the plant was reproducing only vegetatively and that male sterility may have contributed to extinction.