Pyritic stromatolites from the Paleoarchean Dresser Formation, Pilbara Craton: Resolving biogenicity and hydrothermally influenced ecosystem dynamics.

This study investigates the paleobiological significance of pyritic stromatolites from the 3.48 billion-year-old Dresser Formation, Pilbara Craton. By combining paleoenvironmental analyses with observations from well-preserved stromatolites in newly obtained drill cores, the research reveals stratiform and columnar to domal pyritic structures with wavy to wrinkly laminations and crest thickening, hosted within facies variably influenced by syn-depositional hydrothermal activity. The columnar and domal stromatolites occur in strata with clearly distinguishable primary depositional textures. Mineralogical variability and fine-scale interference textures between the microbialites and the enclosing sediment highlight interplays between microbial and depositional processes. The stromatolites consist of organomineralization - nanoporous pyrite and microspherulitic barite - hosting significant thermally mature organic matter (OM). This includes filamentous organic microstructures encased within nanoporous pyrite, resembling the extracellular polymeric substance (EPS) of microbes. These findings imply biogenicity and support the activity of microbial life in a volcano-sedimentary environment with hydrothermal activity and evaporative cycles. Coupled changes in stromatolite morphology and host facies suggest growth in diverse niches, from dynamic, hydrothermally influenced shallow-water environments to restricted brine pools strongly enriched in SO 4 2 - $$ {\mathrm{SO}}_4^{2-} $$ from seawater and hydrothermal activity. These observations, along with S stable isotope data indicating influence by S metabolisms, and accumulations of biologically significant metals and metalloids (Ni and As) within the microbialites, help constrain microbial processes. Columnar to domal stromatolites in dynamic, hydrothermally influenced shallow water deposits likely formed by microbial communities dominated by phototrophs. Stratiform pyritic structures within barite-rich strata may reflect the prevalence of chemotrophs near hydrothermal venting, where hydrothermal activity and microbial processes influenced barite precipitation. Rapid pyrite precipitation, a putative taphonomic process for preserving microbial remnants, is attributed to microbial sulfate reduction and reduced S sourced from hydrothermal activity. In conclusion, this research underscores the biogenicity of the Dresser stromatolites and advances our understanding of microbial ecosystems in Earth's early history.

Long-Term Efficacy and Safety of Modified Canaloplasty Versus Trabeculectomy in Open-Angle Glaucoma.

BACKGROUND: To evaluate the long-term efficacy and safety of modified canaloplasty versus trabeculectomy in open-angle glaucoma. METHODS: In total, 210 subjects with open-angle glaucoma were included. 70 were treated with Mitomycin C-augmented modified canaloplasty with enhanced subconjunctival filtration and 140 with Mitomycin C-augmented trabeculectomy. Cases were matched 1:2 by sex and age. RESULTS: In canaloplasty and trabeculectomy groups, 61.4% and 57.9% of participants were female. Mean age was 60.0 ± 13.9 and 63.0 ± 12.2 years, median follow-up time was 4.6 [IQR 4.3, 5.05] years and 5.8 [IQR 5.4, 6.3]. Strict success was achieved in 20.0% and 56.4%, complete success in 24.3% and 66.4%, and qualified success in 34.3% and 73.6% (each p < 0.001). Kaplan-Meier survival analysis showed a better survival probability for trabeculectomy than for canaloplasty (p < 0.001) and Cox regression analysis revealed an HR of 6.03 (95%-CI 3.66, 9.93, p < 0.001) after canaloplasty. Trabeculectomy showed superiority in terms of IOP decrease (9.2 ± 7.9 mmHg vs. 13.7 ± 10.4 mmHg, p = 0.002), use of AGM (50.0% vs. 10.7%, p < 0.001), and the number of revision surgeries (41.4% vs. 21.4%, p = 0.004). Occurrence of complications was similar in both groups (14.5% vs. 7.5%, p = 0.19). CONCLUSIONS: Trabeculectomy showed superiority in efficacy and equality in safety compared to modified canaloplasty.

Biogeochemistry of Recently Fossilized Siliceous Hot Spring Sinters from Yellowstone, USA.

Active hot springs are dynamic geobiologically active environments. Heat- and element-enriched fluids form hot spring sinter deposits that are inhabited by microbial and macroscopic eukaryotic communities, but it is unclear how variable heat, fluid circulation, and mineralization within hot spring systems affect the preservation of organic matter in sinters. We present geological, petrographic, and organic geochemical data from fossilized hot spring sinters (<13 Ka) from three distinct hot spring fields of Yellowstone National Park. The aims of this study were to examine the preservation of hydrocarbons and discern whether the hydrocarbons in these samples were derived from in situ communities or transported by hydrothermal fluids. Organic geochemistry reveals the presence of n-alkanes, methylalkanes, hopanes, and other terpanes, and the distribution of methylheptadecanes is compared to published observations of community composition in extant hot springs with similar geochemistry. Unexpectedly, hopanes have a thermally mature signal, and Raman spectroscopy confirms that the kerogen in some samples has nearly reached the oil window, despite never having been buried. Our results suggest that organic matter maturation occurred through below-surface processes in the hotter, deeper parts of the hydrothermal system and that this exogenous material was then transported and emplaced within the sinter.

Taphonomy of microorganisms and microbial microtextures at sulfidic hydrothermal vents: A case study from the Roman Ruins black smokers, Eastern Manus Basin.

Biological activity at deep-sea hydrothermal chimneys is driven by chemotrophic microorganisms that metabolize chemicals from the venting high-temperature fluids. Understanding taphonomy and microbial microtextures in such environments is a necessity for micropaleontological and palaeoecological research. This study examines fossilized microorganisms and related microtextures in a recent black smoker from the Roman Ruins hydrothermal vent site, Eastern Manus Basin offshore of Papua New Guinea. Whereas the center of the examined sulfide chimney is dominated by high-temperature mineralogy (chalcopyrite and dendritic sphalerite), filamentous and coccoidal biomorphs occur in an outer, warm zone of mixing between hydrothermal fluids and seawater, which is indicated by their occurrence within colloform and botryoidal pyrite of barite-pyrite coprecipitates. Both morphotypes can be interpreted as thermophilic microorganisms based on their occurrence in a high-temperature habitat. Their separate (non-commensal) occurrence hints at sensitivities to microenvironmental conditions, which is expectable for strong temperature, pH, and redox gradients at the walls of deep-sea hydrothermal chimneys. Whereas both morphotypes experienced mild thermal overprint, taphonomic differences exist: (i) spaces left by cells in filamentous fossils are predominately filled by silica, whereas inter/extracellular features (crosswalls/septae and outer sheaths) are pyritized; (ii) coccoidal fossils show both silica- and pyrite-infilled interiors, and generally better preservation of cell walls. These different manifestations presumably relate to an interplay between microenvironmental and biological factors, potentially contrasting metabolisms, and differences in cell wall chemistries of distinct bacteria and/or archaea. A further hypothesis is that the coccoidal features represent biofilm-forming organisms, whose organic matter derivates contributed to the formation of intimately associated wavy and wrinkly carbonaceous laminations that are at least locally distinguishable from the texture of the surrounding pyrite. Hence, the presented data provide evidence that microtextures of microbiota from hydrothermal systems can have a similar significance for palaeobiological research as those from sedimentary environments.

Biogenicity of Spicular Geyserite from Te Kopia, New Zealand: Integrated Petrography, High-Resolution Hyperspectral and Elemental Analysis.

Hyperspectral and micro X-ray fluorescence (µXRF) imagery were used to derive maps of mineralogy and elemental chemistry from a sample of a siliceous hot spring deposit, or sinter, collected from a landslide breccia deposit at the base of the Paeroa fault, which bounds the eastern Taupo Rift at Te Kopia, Taupo Volcanic Zone, New Zealand. The sample is of a known biogenic sinter layer from a paleo-vent area of a recently extinct alkali chloride hot spring. The aim of the study was to distinguish it from other horizons derived from nonbiogenic sources, which is of relevance to early and extraterrestrial life research, specifically to help assess the potential reliability of morphology as an indicator of biology in the geological record. In particular, the distribution of opal, a common mineral in hot springs deposits that is known to preserve microbial features, and the relative abundances of Al-OH clay and water (OH and H2O) were mapped from hyperspectral imagery and element distributions defined by µXRF element mapping. Layers within the sinter sample composed of spicular geyserite-a type of micro-columnar stromatolite-showed contrasting mineralogy and water content in comparison with interspicular clastic sediment. Whereas clay was found to be concentrated in the interspicular sediment, high water contents characterized the spicules. µXRF imagery also showed differences in the composition of the two components of the spicule-bearing layers, with interspicular sediment being enriched in K, Ti, Fe, and Rb relative to the spicules, which are enriched in Ga. The contrasting nature of the mapped components highlights the detailed upward-branching nature of the spicules, identical to those found in living microstromatolites. These discriminants show that the spicular component can be discerned from the geological background through hyperspectral and µXRF mapping and used to define morphological features that may survive burial diagenesis and metamorphism as a biosignature in deep time rocks.

Elements for the Origin of Life on Land: A Deep-Time Perspective from the Pilbara Craton of Western Australia.

For decades, deep sea hydrothermal vents have been a preferred setting for the Origin of Life, but "The Water Problem" as relates to polymerization of organic molecules, together with a propensity to dilute critical prebiotic elements as well as a number of other crucial factors, suggests that a terrestrial hot spring field with the capacity for wet-dry cycling and element concentration may represent a more likely candidate. Here, we investigate a 3.5 billion-year-old, anoxic hot spring setting from the Pilbara Craton (Australia) and show that its hydrothermal veins and compositionally varied pools and springs concentrated all of the essential elements required for prebiotic chemistry (including B, Zn, Mn, and K, in addition to C, H, N, O, P, and S). Temporal variability (seasonal to decadal), together with the known propensity of hot springs for wet-dry cycling and information exchange, would lead to innovation pools with peaks of fitness for developing molecules. An inference from the chemical complexity of the Pilbara analogue is that life could perhaps get started quickly on planets with volcanoes, silicate rocks, an exposed land surface, and water, ingredients that should form the backbone in the search for life in the Universe.

Formation of micro-spherulitic barite in association with organic matter within sulfidized stromatolites of the 3.48 billion-year-old Dresser Formation, Pilbara Craton.

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 samples obtained from drill cores. Spherulitic barite micro-mineralization within the sulfidized stromatolites generally forms submicron-scale aggregates that show gradations from hollow to densely crystallized, irregular to partially radiating crystalline interiors. Several barite micro-spherulites show thin outer shells. Within stromatolites, barite micro-spherulites are intimately associated with petrographically earliest dolomite and nano-porous pyrite enriched in organic matter, the latter of which is a possible biosignature assemblage that hosts microbial remains. Barite spherulites are also observed within layered barite in proximity to stromatolite layers, where they are overgrown by compositionally distinct (Sr-rich), coarsely crystalline barite that may have been sourced from hydrothermal veins at depth. Micro-spherulitic barite, such as reported here, is not known from hydrothermal systems that exceed the upper temperature limit for life. Rather, barite with near-identical morphology and micro-texture is known from zones of high bio-productivity under low-temperature conditions in the modern oceans, where microbial activity and/or organic matter of degrading biomass controls the formation of spherulitic aggregates. Hence, the presence of micro-spherulitic barite in the organic matter-bearing Dresser Formation sulfidized stromatolites lend further support for a biogenic origin of these unusual, exceptionally well-preserved, and very ancient microbialites.