The Ediacaran period coincides with the emergence of ancestral animal lineages and cyanobacteria capable of thriving in nutrient deficient oceans which together with photosynthetic eukaryotic dominance, culminated in the rapid oxygenation of the Ediacaran atmosphere. However, ecological evidence for the colonization of the Ediacaran terrestrial biosphere by photosynthetic communities and their contribution

In east‐central Brazil, the Ediacaran‐Cambrian Bambuí Basin has the potential to provide a record of unique geochemical responses of Earth's ocean and atmosphere evolution during this key time interval. From this perspective, we studied an interval of the upper Bambuí Basin using sedimentologic, stratigraphic, and chemostratigraphic tools. The lower Cambrian Jaíba Member of the uppermost Serra da Saudade

Achromatium is a long known uncultured giant gammaproteobacterium forming intracellular CaCO3 that impacts C and S geochemical cycles functioning in some anoxic sediments and at oxic‐anoxic boundaries. While intracellular CaCO3 granules have first been described as Ca oxalate then colloidal CaCO3 more than one century ago, they have often been referred to as crystalline solids and more specifically

It is established that green algae and land plants progressively colonized freshwater and terrestrial habitats throughout the Paleozoic Era, but little is known about the ecology of Paleozoic saline lakes. Here, we report lipid biomarker and petrographic evidence for the occurrence of a green alga as a major primary producer in a late Paleozoic alkaline lake (Fengcheng Formation; 309–292 Ma). A persistently

Animal evolution transformed microbial mat development. Canonically inferred negative effects include grazing, disturbance and competition for space. In contrast, ancient examples of cooperation between microbial mats and invertebrates have rarely been reported. Late Cambrian (~485 million years) Cryptozoön is widely regarded as the first stromatolite to have received a taxonomic name and has been

The vertical distribution of subseafloor archaeal communities is thought to be primarily controlled by in situ conditions in sediments such as the availability of electron acceptors and donors, although sharp community shifts have also been observed at lithological boundaries suggesting that at least a subset of vertically stratified Archaea form a long‐term genetic record of coinciding environmental

The subsurface is Earth's largest reservoir of biomass. Micro‐organisms are the dominant lifeforms in this habitat, but the nature of their in situ activities remains largely unresolved. At the Deep Mine Microbial Observatory (DeMMO) located in the Sanford Underground Research Facility (SURF) in Lead, South Dakota (USA), we performed in situ electrochemical incubations designed to assess the potential

Nitrogen is an essential element to life and exerts a strong control on global biological productivity. The rise and spread of nitrogen‐utilizing microbial metabolisms profoundly shaped the biosphere on the early Earth. Here, we reconciled gene and species trees to identify birth and horizontal gene transfer events for key nitrogen‐cycling genes, dated with a time‐calibrated tree of life, in order

The Khatyspyt Lagerstätte (~544 Ma, Russia) provides a valuable window into late Ediacaran Avalon‐type ecosystems with rangeomorphs, arboreomorphs, and mega‐algae. Here, we tackle the geobiology of this Lagerstätte by the combined analysis of paleontological features, sedimentary facies, and lipid biomarkers. The Khatyspyt Formation was deposited in carbonate ramp environments. Organic matter (0.12–2

A Jurassic negative carbon isotope excursion (CIE), co‐evolved with Toarcian Oceanic Anoxic Event (OAE) at ~183 Ma, is suggested to be linked to a global carbon‐cycle perturbation and is well documented for Toarcian terrestrial fossil woods and marine sediments around the globe. A theoretically coupled δ13Ccarb‐δ13Corg pattern due to such dubbed global carbon‐cycle event from the negative CIE in Dotternhausen

Microbial mats from alkaline hot springs in the Yellowstone National Park are ideal natural laboratories to study photosynthetic life under extreme conditions, as well as the nuanced interactions of oxygenic and anoxygenic phototrophs. They represent distinctive examples of chlorophototroph (i.e., chlorophyll or bacteriochlorophyll‐based phototroph) diversity, and several novel phototrophs have been

With annual precipitation less than 20 mm and extreme UV intensity, the Atacama Desert in northern Chile has long been utilized as an analogue for recent Mars. In these hyperarid environments, water and biomass are extremely limited, and thus, it becomes difficult to generate a full picture of biogeochemical phosphate‐water dynamics. To address this problem, we sampled soils from five Atacama study

In the geological record, fossil phosphatic stromatolites date back to the Great Oxidation Event in the Paleoproterozoic, but living phosphatic stromatolites have not been described previously. Here, we report on cyanobacterial stromatolites in a supratidal freshwater environment at Cape Recife, South African southern coast, precipitating Ca carbonate alternating with episodes of Ca phosphate deposition

Shallow‐water hydrothermal plumes concomitantly host both photosynthetic and chemoautotrophic organisms in a single biotope. Yet, rate measurements to quantify the contributions of different autotrophic activity types are scarce. Herein, we measured the light and dark dissolved inorganic carbon (DIC) uptake rates in the plume water of the Kueishantao hydrothermal field using the 13C‐labeling approach

The siliciclastic ~1 Ga‐old strata of the Torridon Group, Scotland, contain some of the most exquisitely preserved three‐dimensional organic‐walled microfossils (OWMs) of the Precambrian. A very diverse microfossil assemblage is hosted in a dominantly phosphatic and clay mineral matrix, within the Diabaig and the Cailleach Head (CH) Formations. In this study, we report on several microfossil taxa within

Rhizoliths, that is, roots fossilized by secondary carbonates, have been known for ages and are increasingly used for paleoenvironmental reconstructions. However, knowledge about their formation mechanisms remains limited. This study reports the mineralogical and chemical characterization of rhizoliths at different stages of mineralization and fossilization in the Late Pleistocene loess–paleosol sequence

Coccolithophores are a key functional phytoplankton group and produce minute calcite plates (coccoliths) in the sunlit layer of the pelagic ocean. Coccoliths significantly contribute to the sediment record since the Triassic and their geometry have been subject to palaeoceanographic and biological studies to retrieve information on past environmental conditions. Here, we present a comprehensive analysis

All life requires energy to drive metabolic reactions such as growth and cell maintenance; therefore, fluctuations in energy availability can alter microbial activity. There is a gap in our knowledge concerning how energy availability affects the growth of extreme chemolithoautotrophs. Toward this end, we investigated the growth of thermoacidophile Acidianus ambivalens during sulfur oxidation under

It has been argued that skeletal Mg/Ca ratio in echinoderms is mostly governed by Mg2+ and Ca2+ concentrations in the ambient seawater. Accordingly, well‐preserved fossil echinoderms were used to reconstruct Phanerozoic seawater Mg2+/Ca2+ ratio. However, Mg/Ca ratio in echinoderm skeleton can be affected by a number of environmental and physiological factors, the effects of which are still poorly understood

The South Oman Salt Basin (SOSB) has been studied extensively for knowledge concerning the habitat of the enigmatic Ediacaran–Cambrian oils that are produced from that region. Geological, geochemical, geophysical, and geochronological investigations have all contributed to improved understanding of the range of late Neoproterozoic depositional environments recorded there. Of particular interest has

Throughout most of the sedimentary record, the marine carbon cycle is interpreted as being in isotopic steady state. This is most commonly inferred via isotopic reconstructions, where two export fluxes (organic carbon and carbonate) are offset by a constant isotopic fractionation of ~25 (termed ). Sedimentary deposits immediately overlying the Marinoan snowball Earth diamictites, however, stray from

Microtextures of titanite (CaTiSiO5) in exceptionally preserved Archean pillow lavas have been proposed as the earliest examples of microbial ichnofossils. An origin from microbial tunneling of seafloor volcanic glass that is subsequently chloritized and the tunnels infilled by titanite has been argued to record the activities of subseafloor microbes. We investigate the evidence in pillow lavas of

Fibrous‐radiating carbonate spherulites spatially associated with poorly crystalline Mg‐Si substances have formed within conical microbialites in modern hypersaline lakes on Rottnest Island, Western Australia. Two spherulitic fabrics can be distinguished based on compositional and textural differences. The oldest (lowermost) fabric comprises variably intergrown aragonitic spherulites 100–500 μm wide

Neutrophilic, microaerobic Fe(II)‐oxidizing bacteria (FeOB) from marine and freshwater environments are known to generate twisted ribbon‐like organo‐mineral stalks. These structures, which are extracellularly precipitated, are susceptible to chemical influences in the environment once synthesized. In this paper, we characterize the minerals associated with freshwater FeOB stalks in order to evaluate

The shallow marine and subaerial sedimentary and hydrothermal rocks of the ~3.48 billion‐year‐old Dresser Formation are host to some of Earth's oldest stromatolites and microbial remains. This study reports on texturally distinctive, spherulitic barite micro‐mineralization that occur in association with primary, autochthonous organic matter within exceptionally preserved, strongly sulfidized stromatolite

The chemical composition of fossil soft tissues is a potentially powerful and yet underutilized tool for elucidating the affinity of problematic fossil organisms. In some cases, it has proven difficult to assign a problematic fossil even to the invertebrates or vertebrates (more generally chordates) based on often incompletely preserved morphology alone, and chemical composition may help to resolve

Metal sulfide minerals, including mercury sulfides (HgS), are widespread in hydrothermal vent systems where sulfur‐oxidizing microbes are prevalent. Questions remain as to the impact of mineral composition and structure on sulfur‐oxidizing microbial populations at deep‐sea hydrothermal vents, including the possible role of microbial activity in remobilizing elemental Hg from HgS. In the present study

Digitate siliceous hot spring deposits are a form of biomediated sinter that is relatively common in the Taupo Volcanic Zone (TVZ), New Zealand, and elsewhere on Earth. Such deposits have gained prominence recently because of their morphological similarity to opaline silica rocks of likely hot spring origin found by the Spirit rover on Mars and the consequent implications for potential biosignatures

Sulfate minerals are rare in the Archean rock record and largely restricted to the occurrence of barite (BaSO4). The origin of this barite remains controversially debated. The mass‐independent fractionation of sulfur isotopes in these and other Archean sedimentary rocks suggests that photolysis of volcanic aerosols in an oxygen‐poor atmosphere played an important role in their formation. Here, we report

Morphologically complex trace fossils, recording the infaunal activities of bilaterian animals, are common in Phanerozoic successions but rare in the Ediacaran fossil record. Here, we describe a trace fossil assemblage from the lower Dunfee Member of the Deep Spring Formation at Mount Dunfee (Nevada, USA), over 500 m below the Ediacaran–Cambrian boundary. Although millimetric in scale and largely not

Deep subsurface biofilms are estimated to host the majority of prokaryotic life on Earth, yet fundamental aspects of their ecology remain unknown. An inherent difficulty in studying subsurface biofilms is that of sample acquisition. While samples from marine and terrestrial deep subsurface fluids have revealed abundant and diverse microbial life, limited work has described the corresponding biofilms

The discovery of mid‐Proterozoic (1.8–0.8 billion years ago, Ga) indigenous biomarkers is a challenge, since biologically informative molecules of such antiquity are commonly destroyed by metamorphism or overprinted by drilling fluids and other anthropogenic petroleum products. Previously, the oldest clearly indigenous biomarkers were reported from the 1.64 Ga Barney Creek Formation in the northern

Organic and inorganic stable isotopes of lacustrine carbonate sediments are commonly used in reconstructions of ancient terrestrial ecosystems and environments. Microbial activity and local hydrological inputs can alter porewater chemistry (e.g., pH, alkalinity) and isotopic composition (e.g., δ18Owater, δ13CDIC), which in turn has the potential to impact the stable isotopic compositions recorded and

Constraints on Precambrian ocean chemistry are dependent upon sediment geochemistry. However, diagenesis and metamorphism can destroy primary biosignatures, making it difficult to consider biology when interpreting geochemical data. Modern analogues for ancient ecosystems can be useful tools for identifying how sediment geochemistry records an active biosphere. The Middle Island Sinkhole (MIS) in Lake

Methane emissions from peat bogs are mitigated by methanotrophs, which live in symbiosis with peat moss (e.g. Sphagnum). Here, we investigate the influence of temperature and resultant changes in methane fluxes on Sphagnum and methanotroph‐related biomarkers, evaluating their potential as proxies in ancient bogs. A pulse‐chase experiment using 13C‐labelled methane in the field clearly showed label

Few topics in geobiology have been as extensively debated as the role of Earth's oxygenation in controlling when and why animals emerged and diversified. All currently described animals require oxygen for at least a portion of their life cycle. Therefore, the transition to an oxygenated planet was a prerequisite for the emergence of animals. Yet, our understanding of Earth's oxygenation and the environmental

Organic microfossils preserved in three dimensions in transparent mineral matrices such as cherts/quartzites, phosphates, or carbonates are best studied in petrographic thin sections. Moreover, microscale mass spectrometry techniques commonly require flat, polished surfaces to minimize analytical bias. However, contamination by epoxy resin in traditional petrographic sections is problematic for the

On the basis of phylogenetic studies and laboratory cultures, it has been proposed that the ability of microbes to metabolize iron has emerged prior to the Archaea/Bacteria split. However, no unambiguous geochemical data supporting this claim have been put forward in rocks older than 2.7–2.5 giga years (Gyr). In the present work, we report in situ Fe and S isotope composition of pyrite from 3.28‐ to

The rise of eukaryotes to ecological prominence represents one of the most dramatic shifts in the history of Earth's biosphere. However, there is an enigmatic temporal lag between the emergence of eukaryotic organisms in the fossil record and their much later ecological expansion. In parallel, there is evidence for a secular increase in the availability of the key macronutrient phosphorus (P) in Earth's

The nitrogenase metalloenzyme family, essential for supplying fixed nitrogen to the biosphere, is one of life's key biogeochemical innovations. The three forms of nitrogenase differ in their metal dependence, each binding either a FeMo‐, FeV‐, or FeFe‐cofactor where the reduction of dinitrogen takes place. The history of nitrogenase metal dependence has been of particular interest due to the possible

The incorporation of metal cofactors into protein active sites and/or active regions expanded the network of microbial metabolism during the Archean eon. The bioavailability of crucial metal cofactors is largely influenced by earth surface redox state, which impacted the timing of metabolic evolution. Vanadium (V) is a unique element in geo–bio‐coevolution due to its complex redox chemistry and specific

Cold‐water coral (CWC) mounds are build‐ups comprised of coral‐dominated intervals alternating with a mixed carbonate‐siliciclastic matrix. At some locations, CWC mounds are influenced by methane seepage, but the impact of methane on CWC mounds is poorly understood. To constrain the potential impact of methane on CWC mound growth, lipid biomarker investigations were combined with mineralogical and

Ediacaran sediments record an unusual global carbon cycle perturbation that has been linked to widespread oceanic oxygenation, the Shuram negative C isotope excursion (NCIE). However, proxy‐based estimates of global ocean redox conditions during this event have been limited largely due to proxy specificity (e.g., euxinic sediments for Mo and U isotopes). Modern global seawater documents a homogenous

An experimental decay methodology is developed for a cnidarian model organism to serve as a comparison to the many previous such studies on bilaterians. This allows an examination of inherent bias against the fossilisation of cnidarian tissue and their diagnostic characters, under what conditions these occur, and in what way. The decay sequence of Actinia equina was examined under a series of controlled

Ferruginous stromatolites occur associated with Middle Jurassic condensed deposits in several Tethyan and peri‐Tethyan areas. The studied ferruginous stromatolites occurring in the Middle Jurassic condensed deposits of Southern Carpathians (Romania) preserve morphological, geochemical, and mineralogical data that suggest microbial iron oxidation. Based on their macrofabrics and accretion patterns,

The identification of cellular life in the rock record is problematic, since microbial life forms, and particularly bacteria, lack sufficient morphologic complexity to be effectively distinguished from certain abiogenic features in rocks. Examples include organic pore‐fillings, hydrocarbon‐containing fluid inclusions, organic coatings on exfoliated crystals and biomimetic mineral aggregates (biomorphs)

Lipid biomarker assemblages preserved within the bitumen and kerogen phases of sedimentary rocks from the ca. 780–729 Ma Chuar and Visingsö Groups facilitate paleoenvironmental reconstructions and reveal fundamental aspects of emerging mid‐Neoproterozoic marine communities. The Chuar and Visingsö Groups were deposited offshore of two distinct paleocontinents (Laurentia and Baltica, respectively) during

We employ complementary field and laboratory‐based incubation techniques to explore the geochemical environment where siderite concretions are actively forming and growing, including solid‐phase analysis of the sediment, concretion, and associated pore fluid chemistry. These recently formed siderite concretions allow us to explore the geochemical processes that lead to the formation of this less common

Bacillus subtilis endospore‐mediated forsterite dissolution experiments were performed to assess the effects of cell surface reactivity on Mg isotope fractionation during chemical weathering. Endospores present a unique opportunity to study the isolated impact of cell surface reactivity because they exhibit extremely low metabolic activity. In abiotic control assays, 24Mg was preferentially released

Molecular nitrogen (N2) constitutes the majority of Earth's modern atmosphere, contributing ~0.79 bar of partial pressure (pN2). However, fluctuations in pN2 may have occurred on 107–109 year timescales in Earth's past, perhaps altering the isotopic composition of atmospheric nitrogen. Here, we explore an archive that may record the isotopic composition of atmospheric N2 in deep time: the foliage of

The early‐successional status of lichens in modern terrestrial ecosystems, together with the role lichen‐mediated weathering plays in the carbon cycle, have contributed to the long and widely held assumption that lichens occupied early terrestrial ecosystems prior to the evolution of vascular plants and drove global change during this time. Their poor preservation potential and the classification of

The Atacama Desert is the driest non‐polar desert on Earth, presenting precarious conditions for biological activity. In the arid coastal belt, life is restricted to areas with fog events that cause almost daily wet–dry cycles. In such an area, we discovered a hitherto unknown and unique ground covering biocenosis dominated by lichens, fungi, and algae attached to grit‐sized (~6 mm) quartz and granitoid

Carbonate microbialites in lakes can serve as valuable indicators of past environments, so long as the biogenicity and depositional setting of the microbialite can be accurately determined. Late Pleistocene to Early Holocene frondose draping tufa deposits from Winnemucca Dry Lake (Nevada, USA), a subbasin of pluvial Lake Lahontan, were examined in outcrop, petrographically, and geochemically to determine

Fayetteville Green Lake (FGL) is a recognized, extensively studied present‐day model of the stratified Proterozoic ocean. Nonetheless, biomass sedimentation in FGL remains hard to explain: while virtually all sediment pigments belong to photosynthetic sulfur bacteria from a chemocline, the isotopic carbon signature of the bulk organic matter suggests its epilimnetic phytoplankton origin. To explain