Permian-Triassic Research Articles

RECONSTRUCTION OF THE SUBSIDENCE DYNAMICS AND PALAEOTEMPERATURE REGIME OF THE NORTHERN MARGIN OF THE SIBERIAN PLATFORM

The formation mechanisms of sedimentary basins are considered as a response of deep processes in the mantle, therefore they carry important information about the geodynamics and thermal regime of the lithosphere. For different sectors of the northern margin of the Siberian Platform, the dynamics of sedimentation and subsidence was reconstructed. The analysis of subsidence curves shows that during the Late Paleozoic the sedimentary infill formed in the foreland basin environment. In the Late Permian–Early Triassic time, in the central and western sectors, the subsidence was accelerating due to the development of a thick trap complex; after the Permian and Triassic boundary the subsidence slowed down. During the period of trap magmatism, an anomalously high subsidence rate up to 4.8 km/Ma in the central and up to 0.5–1.1 km/Ma in the eastern and western parts was reconstructed. The high rate and short duration of accumulation of volcanogenic sediments can be explained by an episode of short-term extension under the influence of a plume, followed by a long period of thermal subsidence. Numerical modelling of the temperature regime near mafic intrusive bodies was carried out, which showed that when determining the paleoheat flow, the influence of trap intrusions can be traced up to 400–500 m from the contacts. Estimates of the paleoheat flow for the Permian–Triassic stage of tectonic evolution of the eastern sector were obtained. It was calibrated using the PetroMod software package, based on laboratory measurements of modern values of vitrinite reflectance for rock samples from wells, modern temperature and heat flow in the sedimentary cover. It was determined that trap magmatism occurred at temperatures increased to 100 mW/m2, while the mantle component of the heat flow reached 38–72 mW/m2; it is several times higher as compared to modern one. The obtained paleoheat flow estimates for the Late Permian–Early Triassic stage appear to correspond to anomalously high values of modern continental rifts.

Jurassic Bryozoans of the Family Eleidae (Melicerititida, Stenolaemata)

Additional analysis of the skeletal morphology of bryozoans of the family Eleidae d’Orbigny, 1852 (Melicerititida, Stenolaemata) and three of its species from the Middle Jurassic (Middle Callovian) of the Moscow Region – Elea lyapini Viskova, 2011, E. troshkovensis Viskova, 2011 и E. taylori Viskova, 2011was conducted. It confirmed that these species belong to the family Eleidae. The morphology of these bryozoans is considered as the result of reconstruction of the principal plan of construction of the cylindrical autozooid of the Tubuliporida bryozoans. It took place to the first after Permian-Triassic extinction the radiation of bryozoans that occurred in time of the vast Callovian transgression.

Alternative climatic steady states near the Permian-Triassic Boundary.

Due to spatial scarcity and uncertainties in sediment data, initial and boundary conditions in deep-time climate simulations are not well constrained. On the other hand, depending on these conditions, feedback mechanisms in the climate system compete and balance differently. This opens up the possibility to obtain multiple steady states in numerical experiments. Here, we use the MIT general circulation model to explore the existence of such alternative steady states around the Permian-Triassic Boundary (PTB). We construct the corresponding bifurcation diagram, taking into account processes on a timescale of thousands of years, in order to identify the stability range of the steady states and tipping points as the atmospheric CO2 content is varied. We find three alternative steady states with a difference in global mean surface air temperature of about 10°C. We also examine how these climatic steady states are modified when feedbacks operating on comparable or longer time scales are included, namely vegetation dynamics and air-sea carbon exchanges. Our findings on multistability provide a useful framework for explaining the climatic variations observed in the Early Triassic geological record, as well as some discrepancies between numerical simulations in the literature and geological data at PTB and its aftermath.

Cryptic degassing and protracted greenhouse climates after flood basalt events

AbstractLarge igneous provinces erupt highly reactive, predominantly basaltic lavas onto Earth’s surface, which should boost the weathering flux leading to long-term CO2 drawdown and cooling following cessation of volcanism. However, throughout Earth’s geological history, the aftermaths of multiple Phanerozoic large igneous provinces are marked by unexpectedly protracted climatic warming and delayed biotic recovery lasting millions of years beyond the most voluminous phases of extrusive volcanism. Here we conduct geodynamic modelling of mantle melting and thermomechanical modelling of magma transport to show that rheologic feedbacks in the crust can throttle eruption rates despite continued melt generation and CO2 supply. Our results demonstrate how the mantle-derived flux of CO2 to the atmosphere during large igneous provinces can decouple from rates of surface volcanism, representing an important flux driving long-term climate. Climate–biogeochemical modelling spanning intervals with temporally calibrated palaeoclimate data further shows how accounting for this non-eruptive cryptic CO2 can help reconcile the life cycle of large igneous provinces with climate disruption and recovery during the Permian–Triassic, Mid-Miocene and other critical moments in Earth’s climate history. These findings underscore the key role that outgassing from intrusive magmas plays in modulating our planet’s surface environment.

The biogeographic history of the allokotosaurian archosauromorphs in the Triassic of Pangaea

ABSTRACT Allokotosauria (Trilophosauridae + Azendohsauridae) is a clade of Early – Late Triassic quadruped, sprawling archosauromorphs with diverse dietary habits, known from Madagascar, India, Morocco, North America, and Europe. We conducted the first quantitative biogeographic analysis of the clade to reconstruct its ancestral areas and dispersal events. The results estimated the India + Tanzania area as ancestral for Allokotosauria. Eastern North America was reconstructed as the ancestral area of Trilophosauridae, implying an Early Triassic Southern to Northern Hemisphere dispersal. Subsequently, trilophosaurids were restricted to the Northern Hemisphere, and at least two dispersal events from Europe to western North America are estimated during the early Anisian and probably during the early Carnian, respectively. Azendohsauridae retained the ancestral area of India + Tanzania during much of its evolutionary history. Two dispersal events to western and eastern North America, respectively, are reconstructed during the Carnian – early Norian, likely during or in the aftermath of the Carnian Pluvial Episode (CPE). This pattern mirrors that of early dinosaurs, which were restricted to the Southern Hemisphere with dispersals to the Northern Hemisphere not recorded until the end of the CPE. This study informs about biogeographic patterns involved in the biotic recovery after the end-Permian mass extinction and the early evolutionary radiation of Archosauromorpha.

Characterization of genome-wide phylogenetic conflict uncovers evolutionary modes of carnivorous fungi.

Mass extinction has often paved the way for rapid evolutionary radiation, resulting in the emergence of diverse taxa within specific lineages. The emergence and diversification of carnivorous nematode-trapping fungi (NTF) in Ascomycota have been linked to the Permian-Triassic (PT) extinction, but the processes underlying NTF radiation remain unclear. We conducted phylogenomic analyses using 23 genomes that represent three NTF lineages, each employing distinct nematode traps-mechanical traps (Drechslerella spp.), three-dimensional (3D) adhesive traps (Arthrobotrys spp.), and two-dimensional (2D) adhesive traps (Dactylellina spp.), and the genome of one non-NTF species as the outgroup. These analyses revealed multiple mechanisms that likely contributed to the tempo of the NTF evolution and rapid radiation. The species tree of NTFs based on 2,944 single-copy orthologous genes suggested that Drechslerella emerged earlier than Arthrobotrys and Dactylellina. Extensive genome-wide phylogenetic discordance was observed, mainly due to incomplete lineage sorting (ILS) between lineages. Two modes of non-vertical evolution (introgression and horizontal gene transfer) also contributed to phylogenetic discordance. The ILS genes that are associated with hyphal growth and trap morphogenesis (e.g., those associated with the cell membrane system and polarized cell division) exhibited signs of positive selection.IMPORTANCEBy conducting a comprehensive phylogenomic analysis of 23 genomes across three NTF lineages, the research reveals how diverse evolutionary mechanisms, including ILS and non-vertical evolution (introgression and horizontal gene transfer), contribute to the swift diversification of NTFs. These findings highlight the complex evolutionary dynamics that drive the rapid radiation of NTFs, providing valuable insights into the processes underlying their diversity and adaptation.

Lithium isotopes track changes in continental weathering regimes across the end-Permian mass extinction in Southwest China

It has been assumed there was a massive amount of volcanic CO2 injection into the Permian-Triassic atmosphere and ocean systems, leading to rapid climatic warming and expansion of marine anoxia. However, it remains intriguing how Earth recovered from such a CO2-driven hyperthermal condition. One potential mechanism involves the negative feedback between continental silicate weathering and atmospheric CO2, which could have helped maintain habitability across the end-Permian mass extinction (EPME) interval. This process can be examined using lithium isotopes (δ7Li), which reflect the balance of physical erosion and chemical weathering, and chemical weathering indices such as the Chemical Index of Alteration (CIA), which indicates the chemical alteration of parent materials during weathering. In this study, we analyze siliciclastic sedimentary rocks from the Lopingian to Lower Triassic depositional sequences in the HK-1 drill core at the Lengqinggou section, a terrestrial coastal depositional environment in Southwest China, to reconstruct changes in continental chemical weathering intensity across the EPME. We observed a significant ∼4 ‰ positive shift in δ7Li, accompanied by a marked decrease in Li content from 26 ppm to 6 ppm. Our corrected CIA data (CIAcorr) also exhibits a considerable decrease from 94 to 59 across the EPME. The new δ7Li and CIAcorr data from the terrestrial section indicate a decrease in overall chemical weathering intensity in Southwest China, alongside an increase in physical erosion rates, suggesting a shift from a transport-limited to a kinetically limited weathering regime across the EPME. These changes in the continental weathering regime appear to be linked to active volcanic activity near the South China Block, which led to massive deforestation and the collapse of soil systems. Dramatic reductions in chemical weathering intensity may result in inefficient atmospheric CO2 consumption through silicate weathering if other climatic and tectonic conditions remain constant, potentially contribute to maintaining high global surface temperatures and prolonged marine anoxia into the Early Triassic.

Absolute Geomagnetic Paleointensity at the Permian–Triassic Boundary: the Problem of the Mesozoic Dipole Low

Absolute Geomagnetic Paleointensity at the Permian–Triassic Boundary: the Problem of the Mesozoic Dipole Low

Palygorskite Mineralization in the Induan Sediments of the Moscow Syneclise as an Effect of Regional and Global Paleogeographic Changes at the Permian–Triassic Boundary

Palygorskite Mineralization in the Induan Sediments of the Moscow Syneclise as an Effect of Regional and Global Paleogeographic Changes at the Permian–Triassic Boundary

Re‐Evaluating Water Column Reoxygenation During the End Permian Mass Extinction

AbstractOcean anoxia is considered a key driver of the end‐Permian mass extinction (EPME). However, it is much debated whether there was an ocean reoxygenation phase during, and in the aftermath, of the EPME. Evidence for ocean reoxygenation is often inferred from the absence of framboidal pyrite in some boundary marine sediments (termed the “framboid gap”). To reconstruct ocean redox evolution across the EPME, we investigated the carbon isotopic, sedimentological, and redox records of the Ruichang and Ehtan sections in South China. These documents two negative δ13Ccarb excursions and the development of anoxia associated with deepening leading up to the Permian‐Triassic boundary. Above the level at which most siliceous organisms became extinct, pyrite framboid and iron proxies indicate that water column redox conditions were predominantly oxygenated but sporadically anoxic/ferruginous [non‐sulfidic, free Fe(II) in the water] at Ruichang, while ferruginous conditions were more widely developed at Ehtan. These contrasting redox states are characteristic of a dynamic ocean redox landscape in the extinction interval. The “framboid gap” is seen in strata deposited under both oxic and ferruginous conditions, suggesting that the availability of decomposable organic matter for sulfate reduction additionally controlled framboid genesis. Our data confirm that oxygenated conditions were developed in some deep water basins during the EPME.

Temporal scaling of carbon emission accumulations and rates of the Meso-Cenozoic hyperthermal events: implication to the Anthropocene global warming

Anthropocene global warming is largely associated with fossil fuel carbon emissions. Temporal scaling provides a way to place current carbon emissions on a geological scale. The scaling of carbon emissions at the onset of hyperthermal events suggests that we might anticipate higher carbon emission rates over longer time scales than what we currently observe in the Anthropocene. However, this inference is uncertain due to limited data concerning the accumulations and time intervals of carbon emissions of Meso-Cenozoic hyperthermal events. While on the long-time hyperthermal-event scales of several to hundreds of kiloyears, modern carbon accumulations and emission rates are 9 times greater than those of the hyperthermal-event emissions. The present-day carbon release can be effectively compared to the onset of hyperthermal events through temporal scaling. If current carbon emission trends persist, we may reach the carbon emission thresholds for hyperthermal events in one to three hundred years, getting an intensified hydrological cycle, enhanced continental weathering and ocean acidification. And if the situation gets worse, we may reach the upper limit of the carbon emission threshold for hyperthermal events (e.g., Permian-Triassic Boundary event, PTB) with a biotic mass extinction over four to thirteen hundred years. This study offers new insights into current carbon emissions from a temporal scale perspective, enhancing our understanding of contemporary climate change.

Heterogeneity dynamics: influencing rock type responses to overburden pressure, Permian–Triassic of the Persian Gulf

This study considers the impact of reservoir pressures on rock type variations within the Permian–Triassic formations in the Persian Gulf. Lithological composition, textures, visible porosity, pore types, and cementations of 328.85 m of carbonate rocks from Kangan and Dalan formations were determined using a polarizing microscope. Porosity, permeability, and rock types were analyzed under ambient and reservoir pressures. Findings showed limestone’s frequent rock type changes under reservoir pressure via the Winland method, while dolomite samples showed significant alterations using the flow zone indicator method. Grainstones predominated overall, persisting even amidst pressure-induced rock type shifts, indicating texture’s minimal influence. Pore throat size of low porosity samples rapidly decreased under reservoir pressure, leading to substantial rock type changes. Fewer alterations were observed based on permeability-to-porosity ratio via the flow zone indicator method. Additionally, low permeability samples exhibited varied rock types under the Winland method, while flow zone indicator method transitions mainly occurred within specific permeability ranges. In essence, this study offers a detailed understanding of pressure’s intricate interplay with rock types and properties in Persian Gulf carbonate reservoirs.

Variability of Middle Triassic vermicular limestone ichnofabrics: the Anisian Hisban Formation in Jordan

The strongly bioturbated Middle Triassic (Anisian) limestones, referred to as vermicular limestone, are the dominant lithology of the Hisban Formation in Jordan. This limestone exhibits the monotonous Oravaichnium– Planolites ichnofabrics, which are known and common in the northern Peri-Tethys and the Germanic Basin. The most abundant and widespread trace fossil here is Oravaichnium carinatum, which is produced by bivalves. Specimens of O. carinatum from the Hisban Formation are typically strongly elongated in the vertical axis and have a smooth surface, whereas specimens from the Germanic Basin mainly have a pear-shaped cross-section. Nevertheless, both morphologies and transitional morphotypes between these ichnospecies are present in both areas. The difficulty in distinguishing between Oravaichnium and Planolites causes the intense bioturbation by bivalves to be underestimated. The wide occurrence of the Oravaichnium ichnofabric in the northern and southern Peri-Tethys suggests that small burrowing bivalves played a significant role in the colonization and infaunalization during the long-term recovery of the benthos after the Permian–Triassic crisis. They experienced intense development during the Middle Triassic, when they were responsible for extensive bioturbation.

Hydrothermal activity near the Permian–Triassic transition in the south‐western Ordos Basin, China: Evidence from carbonate cementation in Upper Permian sandstones

ABSTRACTCarbonate cementation in the Upper Permian sandstones informs the timing and temperature of hydrothermal activity in the south‐western Ordos Basin. This study presents a detailed examination of these hydrothermally influenced carbonate cements, constraining their age, carbonate diagenesis and relationship with regional geodynamic evolution. Sedimentological analyses demonstrate the development of deltaic plain and front sand bodies in the study area, which resulted in interbeds of volcanic matrix‐rich sandstones with matrix‐free sandstones. Petrography and electron microprobe analysis reveal four carbonate mineral growth phases of matrix‐free sandstones in the following sequence; scarce pure siderite, scarce Mg‐rich siderite, abundant blocky calcite and moderately abundant grain‐replacing calcite. The fluid inclusion data show anomalies of homogenization temperature of blocky carbonate cements during early diagenesis, over a wide range of ca 148 to 228°C. In addition, blocky carbonate cements show low δ13C (−5.9 to −13.1‰ Vienna PeeDee Belemnite) and δ18O (clustered tightly from −12.4 to −14.6‰ Vienna PeeDee Belemnite) values, interpreted to result from elevated temperatures during cementation, associated with activation of basement faults and concomitant hydrothermal fluid intrusion triggered by oceanic crust subduction in the south‐west margin of the Ordos Basin. Using in situ calcite U–Pb geochronology, the timing of hydrothermal activity was constrained to ca 247.0 ± 11 to 248.2 ± 4.7 Ma. This work provides a case study for applying intergranular calcite U–Pb dating to determine the absolute timing of fluid flow in sedimentary basins, offering tremendous potential to capture snapshots of various diagenetic evolution stages in sediments. The proposed diagenetic model can also provide new insights and understanding regarding hydrothermally influenced sediments. More importantly, hydrothermal activity may have commenced earlier than previously thought. The North Qinling Orogen uplift and associated Mianlue oceanic crust subduction may have begun at the Permian–Triassic transition with a protracted hydrothermal event in the south‐western Ordos Basin.

The Bica São Tomé fossil site, Paraná Basin, Rio Grande do Sul, Brazil: A unique window to the dawn of the Mesozoic Era

The Early Triassic is pivotal for understanding the recovery and diversification of post-extinction biotas, marking the initial emergence or early diversification of many modern life forms. This phase holds dual significance as it establishes the groundwork for contemporary biodiversity evolution and provides crucial insights into managing present ecological challenges. Focused efforts on the Sanga do Cabral Formation in the Paraná Basin unveil a critical opportunity for studying Early Triassic vertebrates in South America, offering a unique perspective on Western Gondwana's biotic recovery after the End-Permian Mass Extinction. Here, we review the geology and fossil record of the most important fossiliferous outcrop of the Sanga do Cabral Formation, the Bica São Tomé Fossil Site. Prospections at the outcrop have already recovered over two hundred specimens, including holotypes and representative materials of important Early Triassic taxa. Our review aims to demonstrate the relevance of the site and highlight strategies for its preservation. The site includes an unusual representation of archosauromorphs, although its content is dominated by procolophonids. Among the known localities of the Sanga do Cabral Formation, the Bica São Tomé Fossil Site stands out for the unique presence of well-preserved specimens in articulation, such as the nearly complete skeleton of the archosauromorph Teyujagua paradoxa. Even so, most of the record is dominated by fragmentary and reworked specimens. The Bica São Tomé site stands as a beacon for understanding Lower Triassic ecosystems in Latin America, presenting an unparalleled opportunity for Mesozoic exploration in Brazil. The Sanga do Cabral Formation, with its wealth of fossil evidence, promises to enrich our understanding of the Early Triassic period and its significance in shaping modern biodiversity.

Mega El Niño instigated the end-Permian mass extinction.

The ultimate driver of the end-Permian mass extinction is a topic of much debate. Here, we used a multiproxy and paleoclimate modeling approach to establish a unifying theory elucidating the heightened susceptibility of the Pangean world to the prolonged and intensified El Niño events leading to an extinction state. As atmospheric partial pressure of carbon dioxide doubled from about 410 to about 860 ppm (parts per million) in the latest Permian, the meridional overturning circulation collapsed, the Hadley cell contracted, and El Niños intensified. The resultant deforestation, reef demise, and plankton crisis marked the start of a cascading environmental disaster. Reduced carbon sequestration initiated positive feedback, producing a warmer hothouse and, consequently, stronger El Niños. The compounding effects of elevated climate variability and mean state warming led to catastrophic but diachronous terrestrial and marine losses.

Astronomical timescale across the middle Permian–Early Triassic unconformities in the northwestern Junggar Basin: Implications for the origin of the unconformities

The middle Permian–Early Triassic terrestrial successions in the Junggar Basin record an important tectonic transformation stage characterized by the development of unconformities. These unconformities control billion-ton-scale hydrocarbon reservoirs in the northwestern Junggar Basin; however, their age, duration and underlying causes remain uncertain in the absence of an accurate Permian‒Triassic timescale. This study performed a comprehensive cyclostratigraphic analysis utilizing natural gamma ray data from 14 wells to determine the age and duration of the unconformities spanning from the middle Permian Lower Wuerhe (P2w) Formation to the lower Triassic Baikouquan (T1b) Formation while also revealing their potential origins. Our results suggest that astronomically forced climate changes were recorded in the western Junggar Basin during the Permian‒Triassic period. By applying astronomical tuning through sedimentation rates across each well, 14 time-domain series were generated. Using two previously reported maximum sedimentary ages from detrital zircon U–Pb dating, a 38.2-million-year long astronomical timescale was constructed, encompassing the period from the middle Permian Xiazijie Formation to the lower Triassic Baikouquan Formation. This analysis constrains the duration of unconformities between the P2w and T1b formations to ∼7–23 Myr. By integrating the duration, order, and implications of these unconformities with previously reported evidence, we conclude that the unconformity between the middle Permian and upper Permian was driven primarily by tectonic inversion resulting from intensified regional tectonic activity. In contrast, the unconformity between the upper Permian and Lower Triassic likely arose from uplift and erosion induced by compressive stresses associated with tectonic activity, which contributed to the formation of unconformities and stratigraphic discontinuities. This work provides a crucial reference for further studies aimed at integrating detailed sedimentological analyses with high-resolution geochronological data to further elucidate the timing and effects of these tectonic events on sedimentary facies and basin development.

The Cretaceous world: plate tectonics, palaeogeography and palaeoclimate

The tectonics, geography and climate of the Cretaceous world were very different from the modern world. At the start of the Cretaceous, the supercontinent of Pangaea had just begun to break apart and only a few small ocean basins separated Laurasia, West Gondwana and East Gondwana. Unlike the modern world, there were no significant continent–continent collisions during the Cretaceous, and the continents were low-lying and easily flooded. The transition from a Pangaea-like configuration to a more dispersed continental arrangement had important effects on the global sea level and climate. During the Early Cretaceous, as the continents rifted apart, the new continental rifts were transformed into young ocean basins. The oceanic lithosphere in these young ocean basins was thermally elevated, which boosted sea level. Sea level, on average, was c. 70 m higher than that of the present day. Sea level was highest during the mid-Cretaceous (90–80 Ma), with a subsidiary peak occurring c. 120 Myr ago (early Aptian). Overall, the Cretaceous was much warmer than the present-day climate (>10°C warmer). These very warm times produced oceanic anoxic events (OAEs), and the high temperatures in equatorial regions sometimes made terrestrial and shallow-marine ecosystems uninhabitable (temperatures >40°C). This is unlike anything we have seen in the last 35 Myr and may presage the eventual results of man-made global warming. This mostly stable, hot climate regime endured for nearly 80 Myr before dramatically terminating with the Chicxulub bolide impact 66 Myr ago. Temperatures plummeted to icehouse levels in the ‘impact winter’ as a result of sunlight-absorbing dust and aerosols being thrown into the atmosphere. As a consequence of the collapse of the food chain, c. 75% of all species were wiped out. The effect of this extinction event on global ecosystems was second only to the great Permo-Triassic Extinction.

Repeated pulses of volcanism drove the end-Permian terrestrial crisis in northwest China

The Permo-Triassic mass extinction was linked to catastrophic environmental changes and large igneous province (LIP) volcanism. In addition to the widespread marine losses, the Permo–Triassic event was the most severe terrestrial ecological crisis in Earth’s history and the only known mass extinction among insects, but the cause of extinction on land remains unclear. In this study, high-resolution Hg concentration records and multiple-archive S-isotope analyses of sediments from the Junggar Basin (China) provide evidence of repeated pulses of volcanic-S (acid rain) and increased Hg loading culminating in a crisis of terrestrial biota in the Junggar Basin coeval with the interval of LIP emplacement. Minor S-isotope analyses are, however, inconsistent with total ozone layer collapse. Our data suggest that LIP volcanism repeatedly stressed end-Permian terrestrial environments in the ~300 kyr preceding the marine extinction locally via S-driven acidification and deposition of Hg, and globally via pulsed addition of CO2.

Jarosite formation in Permian-Triassic strata at Xiakou (South China): Implications for jarosite precipitation from H2S upwelling on Mars

Abstract The source of sulfuric acid and associated aqueous alteration of ancient martian sedimentary rocks remain under debate in the context of divergent models of jarosite formation. Here, we report the formation of sulfates, including jarosite in K-bentonites within shallow-water facies of the Permian-Triassic (P-T) transition at Xiakou in South China. In these strata, jarosite is dispersed in the clay matrix or forms aggregates in pore spaces, has a euhedral morphology, and coexists with variably 34S-depleted paragenetic gypsum and bassanite (δ34S = –37.23‰ to +3.20‰ VCDT). Subaqueous alteration of volcanic tuffs concurrently with oxidation of upwelled, biogenically sourced H2S is the process of jarosite formation in the Xiakou K-bentonites. This mechanism of jarosite precipitation and stability over geological time challenges the long-held view of acidic, water-limited conditions leading to iron(III) sulfate precipitation and would be consistent with possible microbial or nanobial life on early Mars.