Romer's Gap Plugged: 5 new Tetrapods From Tournaisian Mississippian Carboniferous Scotland

Phylogenetic and environmental context of a Tournaisian tetrapod fauna

Authors:

Clack et al

Abstract:

The end-Devonian to mid-Mississippian time interval has long been known for its depauperate palaeontological record, especially for tetrapods. This interval encapsulates the time of increasing terrestriality among tetrapods, but only two Tournaisian localities previously produced tetrapod fossils. Here we describe five new Tournaisian tetrapods (Perittodus apsconditus, Koilops herma, Ossirarus kierani, Diploradus austiumensis and Aytonerpeton microps) from two localities in their environmental context. A phylogenetic analysis retrieved three taxa as stem tetrapods, interspersed among Devonian and Carboniferous forms, and two as stem amphibians, suggesting a deep split among crown tetrapods. We also illustrate new tetrapod specimens from these and additional localities in the Scottish Borders region. The new taxa and specimens suggest that tetrapod diversification was well established by the Tournaisian. Sedimentary evidence indicates that the tetrapod fossils are usually associated with sandy siltstones overlying wetland palaeosols. Tetrapods were probably living on vegetated surfaces that were subsequently flooded. We show that atmospheric oxygen levels were stable across the Devonian/Carboniferous boundary, and did not inhibit the evolution of terrestriality. This wealth of tetrapods from Tournaisian localities highlights the potential for discoveries elsewhere.

pop sci write up.

Evidence of Terrestrial Life From Archean Paleosols

Archean coastal-plain paleosols and life on land

Authors:

Retallack et al

Abstract:

Coastal-plain paleosols in the 3.0 Ga Farrel Quartzite of Western Australia have organic surface (A horizon) and sulfate-rich subsurface (By) horizons, like soils of the Atacama Desert of Chile, Dry Valleys of Antarctica, and 3.7 Ga paleosols of Mars. Farrel Quartzite paleosols include previously described microfossils, permineralized by silica in a way comparable with the Devonian Rhynie Chert, a well known permineralized Histosol. Five microfossil morphotypes in the Farrel Quartzite include a variety of spheroidal cells (Archaeosphaeroides) as well as distinctive large spindles (new genus provisionally assigned to cf. Eopoikilofusa). Previously published cell-specific carbon isotopic analyses of the Farrel Quartzite microfossils, and unusually abundant sulfate considering a likely anoxic atmosphere, allow interpretation of these morphotypes as a terrestrial community of actinobacteria, purple sulfur bacteria, and methanogenic Archaea.

Evidence of Bacteria Producing Soil at the PaleoArchean/MesoArchean Boundary

Biogenic overgrowth on detrital pyrite in ca. 3.2 Ga Archean paleosols

Authors:

Sabhan et al

Abstract:

Regionally traceable paleosols in the lower Moodies Group of the Barberton greenstone belt (ca. 3.22 Ga, northeastern South Africa and Swaziland) contain locally abundant silicified nodules, originally composed of pedogenic carbonates and sulfates, interbedded with heavy-mineral laminae dominated by pyrite. Pyrite grains show rounded detrital cores and secondary idiomorphic rims with trace element concentrations and δ34S ratios clearly different from those of the cores. While cores have low Co and Ni concentrations and high Co/Ni ratios, rims show as much as 5.5 wt% of these elements and low Co/Ni ratios, reflecting the weathering of nearby ultramafic rocks. In-situ sulfur isotope analyses of pyrite cores show δ34SVCDT (Vienna Canyon Diablo troilite) values between +5‰ and –5‰, while the rims show δ34VCDT values between –20‰ and –24.5‰, suggesting biogenic fractionation of sulfur. The close spatial association and microtextural evidence for nearly contemporaneous formation of the pedogenic sulfate nodules and the secondary pyrite rims suggests microbial processing of sulfur in the paleosols, which provided reduced and 34S-depleted sulfur for the growth of authigenic pyrite. This indicates that vadose-zone soil-forming processes in the Archean involved not only physical and chemical modification of moist, unconsolidated sediment in a terrestrial environment but also already included its microbiological modification.

Tournaisian Mississipian Tetrapods of Scotland Lived in a Seasonal Mosaic Tropical Forest

The terrestrial landscapes of tetrapod evolution in earliest Carboniferous seasonal wetlands of SE Scotland

Authors:

Kearsey et al

Abstract:

The Lower Mississippian (Tournaisian) Ballagan Formation in SE Scotland yields tetrapod fossils that provide fresh insights into the critical period when these animals first moved onto land. The key to understanding the palaeoenvironments where they lived is a detailed analysis of the sedimentary architecture of this formation, one of the thickest and most completely documented examples of a coastal floodplain and marginal marine succession from this important transitional time anywhere in the world. Palaeosols are abundant, providing a unique insight into the early Carboniferous habitats and climate.

More than 200 separate palaeosols are described from three sections through the formation. The palaeosols range in thickness from 0.02 to 1.85 m and are diverse: most are Entisols and Inceptisols (63%), indicating relatively brief periods of soil development. Gleyed Inseptisols and Vertisols are less common (37%). Vertisols are the thickest palaeosols (up to 185 cm) in the Ballagan Formation and have common vertic cracks. Roots are abundant through all the palaeosols, from shallow mats and thin hair-like traces to sporadic thicker root traces typical of arborescent lycopods.

Geochemical, isotope and clay mineralogical analyses of the palaeosols indicate a range in soil alkalinity and amount of water logging. Estimates of mean annual rainfall from palaeosol compositions are 1000–1500 mm per year. The high mean annual rainfall and variable soil alkalinities contrast markedly with dry periods that developed deep penetrating cracks and evaporite deposits. It is concluded that during the early Carboniferous, this region experienced a sharply contrasting seasonal climate and that the floodplain hosted a mosaic of closely juxtaposed but distinct habitats in which the tetrapods lived. The diversification of coastal floodplain environments identified here may link to the evolution and movement of tetrapods into the terrestrial realm.

Review of the Supposed Ediacaran Paleosols

Field and laboratory tests for recognition of Ediacaran paleosols

Author:

Rettallack

Abstract:

Not a single paleosol had been described from rocks of Ediacaran age until 2011, but 354 Ediacaran paleosols have been described by 20 different authors since then. Some of these newly recognized paleosols have proven controversial, so this paper reviews 20 distinct tests to determine whether a particular Ediacaran bed could be a paleosol, or not. One problem has been that Ediacaran paleosols are not precisely like modern soils because they lack root traces, a diagnostic feature of Silurian and geologically younger paleosols. The principal problem for recognition of some Ediacaran paleosols is the occurrence in them of megafossils assumed to have been marine, although most of these fossils remain problematic for both biological and ecological affinities. Not all the tests discussed here are diagnostic of paleosols, some are ranked permissive or persuasive. Permissive conditions for paleosols include ripple marks, hummocky bedding, pyritic limestones, acritarchs or thalloid fossils, low strontium isotopic ratios, high δ26Mg ratios, and red color. Persuasive tests include loessites, tsunamites, desert playa minerals, low boron content, high δ10B isotopic ratios, high carbon/sulfur ratios, and very low total/reactive iron ratios. Diagnostic tests include matrix-supported lapilli or crystal tuff parent materials, ice wedges and other cryoturbation, sepic birefringence fabrics, evaporitic sand crystals, and negative geochemical strain and mass transfer, and highly correlated δ13C and δ18O. Like other geological periods, the Ediacaran is known from a variety of marine and non-marine paleoenvironments

The Paleoclimate and Enviroment of Early Cretaceous Sichuan Basin, China

Lower Cretaceous paleosols and paleoclimate in Sichuan Basin, China

Authors:

Li et al

Abstract:

Abundant Lower Cretaceous (Berriasian–Hauterivian) paleosols have been recognized in the Sichuan Basin, along with the preserved pedogenetic features, e.g., soil horizons, soil structure, root traces and pedogenic nodules. Chemical, geochemical and mineralogical analyses were used to examine the paleosols. These paleosols were classified as Entisols, Inceptisols, Aridisols and Alfisols in terms of the modern soil taxonomic system. Early Cretaceous paleoprecipitation and paleotemperature in the Sichuan Basin were estimated from the degree of chemical weathering for non-calcareous paleosols, and from the depth to the calcic horizon and stable oxygen isotopic composition of pedogenic carbonates in calcareous paleosols, respectively. A temperate semi-arid climate generally prevailed in the Sichuan Basin as a part of the South China Block (SCB) and was controlled by subtropical high-pressure and a rain-shadow effect because the humid air masses from the Paleo-Pacific were impeded by the highlands of the South China Block. Further, several intervals of sub-humid paleoclimate occurred due to strengthened monsoonal circulation in the Early Cretaceous. Using the paleosol barometer, the paleoatmospheric CO2 levels of the Early Cretaceous are estimated to range from ∼120 to ∼520 ppmv, with a mean of 305 ppmv. Regional temperature is generally coupled with atmospheric CO2 concentration and is roughly consistent with the sea level fluctuation.

Ethiopia's Paleoclimate Became Humid, Wetter and Possibly Monsoonal During the Carnian/Norian Triassic

Paleoclimatic records of Late Triassic paleosols from Central Ethiopia

Author:

Dawit

Abstract:

The present study documents the major paleosols types within the Lower Adigrat Sandstone in the Blue Nile Basin of central Ethiopia, with the aim of unraveling the paleoclimatic signatures embedded in them. The paleosols developed within an 80-m-thick siliciclastic succession deposited in a mixed tide- and wave-dominated incised valley estuary during the Late Triassic.

Based on down-profile variations in pedogenic features, three major paleosol types (i.e., types I, II and III) were identified. Type I paleosols dominate the lower part of the section and are interpreted as moderately well-drained argillic Vertisols. The dominant pedogenic process was shrinking and swelling of expandable clays (i.e., smectite) through repeated wetting and drying cycles. The morphologies and the mineralogy of the paleosols provide persuasive evidence for pedogenesis under semi-arid subtropical climatic conditions with pronounced wet-dry seasonality, highly fluctuating soil moisture regime, and deep groundwater table. The presence of a calcic Bk horizon deep in the profiles is consistent with elevated soil moisture deficits and low to moderate mean annual precipitation (MAP). Type II paleosols, interpreted to represent vertic Gleysols, are more common in the middle part of the section. The pervasive gleying reflects poor soil drainage and a shallow groundwater table where the soil is waterlogged most of the year. These paleosols suggest a humid tropical climate characterized by alternating wet-dry seasonality but with more wet months per year. The top of the unit is dominated by type III paleosols that represent gleyed Oxisols, reflecting a more humid equatorial climate marked by wet seasons, elevated annual soil moisture content, and a high water table. The presence of plinthite/laterite is in agreement with a wet equatorial climate characterized by extensive chemical weathering and long periods of landscape stability.

The observed vertical progression in the major paleosol types from Vertsols to Gleysols and Oxisols implies a systematic change in the number of wet months, most probably in response to regional tectonics and long-term climate change. Because the number of wet months is, in part, related to latitude and monsoonal climates, the upward stratigraphic trend in paleosol orders is interpreted to signal the northward or equatorward migration of the Blue Nile Basin and central Ethiopia within Pangea from dry subtropical low-latitudes in the early Late Triassic (Carnian‐Norian) toward the humid, wet equatorial, possibly monsoonal, paleoclimatic zone in the Late Triassic (Norian‐Rhaetian).

The Evolution of Devonian Trees Impact on Soils, Climate and Weather

Investigating Devonian trees as geo-engineers of past climates: linking palaeosols to palaeobotany and experimental geobiology

Authors:

Morris et al

Abstract:

We present the rationale for a cross-disciplinary investigation addressing the ‘Devonian plant hypothesis’ which proposes that the evolutionary appearance of trees with deep, complex rooting systems represents one of the major biotic feedbacks on geochemical carbon cycling during the Phanerozoic. According to this hypothesis, trees have dramatically enhanced mineral weathering driving an increased flux of Ca2+ to the oceans and, ultimately, a 90% decline in atmospheric CO2 levels through the Palaeozoic. Furthermore, experimental studies indicate a key role for arbuscular mycorrhizal fungi in soil–plant processes and especially in unlocking the limiting nutrient phosphorus in soil via Ca-phosphate dissolution mineral weathering. This suggests co-evolution of roots and symbiotic fungi since the Early Devonian could well have triggered positive feedbacks on weathering rates whereby root–fungal P release supports higher biomass forested ecosystems. Long-standing areas of uncertainty in this paradigm include the following: (1) limited fossil record documenting the origin and timeline of the evolution of tree-sized plants through the Devonian; and (2) the effects of the evolutionary advance of trees and their in situ rooting structures on palaeosol geochemistry. We are addressing these issues by integrating palaeobotanical studies with geochemical and mineralogical analyses of palaeosol sequences at selected sites across eastern North America with a particular focus on drill cores from Middle Devonian forests in Greene County, New York State.

Alluvial response to the Paleocene–Eocene Thermal Maximum

Alluvial response to the Paleocene–Eocene Thermal Maximum climatic event, Polecat Bench, Wyoming (U.S.A.)

Authors:

Kraus et al

Abstract:

The stratigraphic interval spanning the Paleocene–Eocene Thermal Maximum in the northern Bighorn Basin, Wyoming shows changes in the alluvial record that can be tied to a high resolution climate record. The complexity and stratigraphic spacing of paleosols change through the study section. Comparison to the climate record, reconstructed from paleosols, indicates the changes correspond to Paleocene–Eocene Thermal Maximum climatic fluctuations. In particular, the middle of the section contains thick, welded paleosols and thin avulsion deposits that link to times of well-drained floodplains and lower mean annual precipitation. Stratigraphic intervals below and above the main part of the Paleocene–Eocene Thermal Maximum interval correspond to times of less well drained floodplains and higher mean annual precipitation. These strata contain thinner paleosols and thick avulsion deposits.

Differences in paleosol complexity and spacing suggest that sediment flux to the depositional site varied in response to precipitation fluctuations associated with the Paleocene–Eocene Thermal Maximum. Welded paleosols and thin avulsion deposits indicate reduced floodplain accretion during deposition of the middle of the Paleocene–Eocene Thermal Maximum. Intervals with widely spaced paleosols indicate more rapid accretion. We hypothesize that drier episodes associated with warming caused reduced vegetation in source areas and promoted erosion and increased sediment yield. Because precipitation was reduced, much of that sediment was stored in upstream reaches of the fluvial system rather than moving to the depositional basin. Welded paleosols formed because of diminished sediment supply to the basin. With a return to wetter conditions during the recovery phase of the Paleocene–Eocene Thermal Maximum, upstream water flux increased, stored sediment moved to the basin, and vertically spaced, thinner paleosols developed. The results demonstrate how vertical sections of alluvial paleosols can provide information on how climate fluctuated through time and how the fluvial system responded to climate change.

Ubiquitous Basaltic-derived Paleosols From Neo Archean Australia

Ubiquitous occurrence of basaltic-derived paleosols in the Late Archean Fortescue Group, Western Australia

Authors:

Teitler et al

Abstract:

The 2.76 Ga old Mount Roe Basalt paleosols (MR#1 and MR#2), recognized near the base of the 2.76–2.69 Ga Fortescue Group in Western Australia, represent some of the oldest definite examples of Archean paleoweathering profiles. The loss of Fe and the absence of pedogenic carbonates in these reference paleosols have been considered as strong evidence for low oxygen and moderate carbon dioxide in the Late Archean atmosphere, respectively. However, the robustness of such interpretations suffers both from the scarcity of paleosol exposures and the superposition of post-weathering alteration over primary soil profiles. Here we report new exposures of the MR#1 paleosol as well as a number of new basalt-derived paleosol occurrences distributed in the Mount Roe Basalt and the 2.73 Ga old Kylena Formations of the Fortescue Group. We show that all these paleosols, including MR#1 and MR#2, were strongly affected by post-weathering reductive alteration. Nevertheless, we discovered early lithologic units, locally preserved within the hydrothermally altered paleosols, which feature distinct chemical and mineralogic compositions. These include: (i) 13C-depleted carbonaceous-rich, diaspore–pyrophyllite boudins likely inherited from the hydrolysis and bauxitization of the parent basalt and (ii) green hard core material, mostly composed of Fe–sericite associated with authigenic sphene and containing early relics of sulfate-bearing iron-rich smectite or berthierine. We argue that smectite relics may constitute a part of the primary pedogenic mineral assemblage, while berthierine and sphene formed during diagenesis through the circulation of reductive fluids. Because the depletion of iron observed in the Fortescue paleosols is not solely due to pedogenesis, but also to post-weathering alteration, particular care has to be taken when bulk chemical profiles of iron in such paleosols are used as atmospheric paleobarometer. Recognition of the regional-scale, syn-depositional alteration of the Fortescue subaerial basalts over the north Pilbara suggests the onset of intense continental weathering associated with the uplift and emergence of the Pilbara craton during continental break-up and rifting. Such a regional onset of continental weathering may have provided large amounts of nutrients to nearby marine and/or lacustrine systems, favoring the development of microbial life in shallow waters.

More Evidence Against the Snowball Earth From Cryogenian NeoProterozoic Hallett Cove, South Australia?

Periglacial paleosols and Cryogenian paleoclimate near Adelaide, South Australia

Authors:

Retallack et al

Abstract:

Late Cryogenian deformation of the Reynella Siltstone near Hallett Cove, South Australia has been interpreted as shallow marine methane seeps, which were furthermore proposed to have played a role in deglaciation from “Snowball Earth”. Re-examination and new analyses of these same outcrops confirms an earlier interpretation of this intrastratal deformation as periglacial paleosols, which are evidence that even at maximum extent, late Cryogenian glaciers did not cover all continental lowlands, let alone the world ocean. Known Miocene and Pliocene methane seeps of California examined for this study are very different in their gray color, rounded nodules and clayey host rock, compared with red, highly deformed, and silty to pebbly Reynella Siltstone of Hallett Cove. Stable isotopic composition of nodular carbonate in the Reynella Siltstone fails to show extreme carbon isotopic depletion or the meteoric oxygen lines characteristic of known methane seeps and sphaerosideritic waterlogged paleosols, but instead shows covariance of carbon and oxygen isotopic composition comparable with that in pedogenic and subaerial carbonate of well drained soils. Mass balance geochemical analyses show modest weathering compatible with sand wedge structures and evaporitic pseudomorphs indicative of arid and frigid paleoclimate. Outcrops of Reynella Siltstone near Hallett Cove represent frigid low latitude floodplains, not submarine methane seeps nor global glaciation.

Predicting Future Precipitation Based on Past Paleoclimate

Precipitation reconstructions are essential for predicting impacts of future climate change and preparing for potential changes in terrestrial environmental conditions, such as shifting amounts of regional rainfall, which in turn impact water resource availability and crop growth patterns. Reliable proxy records of paleoprecipitation, especially from past warm periods, are a valuable tool for assessing and modeling future soil and plant moisture and local water availability. However, current terrestrial proxies are limited in their applications, and as a result, a wide range of paleoenvironments are underrepresented in the geologic record.

In their GSA Bulletin study, published online ahead of print on 3 Feb. 2015, Ethan G. Hyland and colleagues present a new relationship between the magnetic properties of soils and precipitation, and use this new proxy to describe changes in paleoprecipitation during past periods of major climate change. This work doubles the potential range of terrestrial paleoclimate applications, and has great potential for robustly describing hydrologic conditions in the deep past. Improvements in our understanding of these conditions can lead to more accurate predictions of water availability and ecosystem stability in a warmer world.

Because soil formation occurs in most terrestrial ecosystems and is controlled strongly by climatic factors, paleosol-based proxies provide an important archive of terrestrial climate. These records are ideal because they are applicable to significantly longer time scales than records from ice cores, and they give greater spatial fidelity and temporal coverage than records from sources such as lake cores or botanical (pollen) records.

Understanding precipitation in the present and during past episodes of climate change is important for determining and preparing for impacts of changes in the hydrological cycle on global environmental systems in the future. Soil magnetic properties, specifically the ratio of pedogenic goethite to hematite in modern soils, can be related quantitatively to modern precipitation regimes worldwide via a robust linear regression model. This newly derived relationship serves as a precipitation proxy that is applicable to a wide range of soil types and climatic regimes worldwide, and the resulting climo-function has been successfully applied to paleosols in order to estimate paleoprecipitation during the early Eocene climatic optimum, an interval of rapid global climate change.

link.

paper link.

Evidence of Tectonic Uplift From Siderian/Rhyacian PaleoProterozoic China

Palaeopedogenesis of red palaeosols in Yunnan Plateau, southwestern China: Pedogenical, geochemical and mineralogical evidences and palaeoenvironmental implication

Authors:

Lu et al

Abstract:

Red palaeosol, as an important archive of ancient pedoenvironments, effectively reflects the palaeoenvironmental change and tectonic uplift history of the plateau. Four red palaeosol profiles were collected at 2200 to 2400 m elevations from the Yunnan Plateau (YP) to investigate the pedogenic features, chemical weathering process and mineral assemblages of soils. Pedological, geochemical and mineralogical techniques were used to understand the palaeopedogenic, palaeoenvironmental change and landscape evolution of the Plateau. Pedologically, the red palaeosols were characterized by the dark red color (a hue of 5YR or redder), strong acidity (pH < 5.4), and high free iron oxide (> 50 g kg− 1) and clay (> 50%) contents. The red palaeosols were enriched with Fe2O3, Al2O3, and TiO2 with very low contents of CaO, MgO, Na2O, and K2O and slightly low contents of Si2O and MnO. Chemical weathering indices, such as CIA (CIA = [Al2O3 / (Al2O3 + CaO + Na2O + K2O)] × 100), Sa (Sa = SiO2 / Al2O3), Saf (Saf = SiO2 / Al2O3 + Fe2O3), and A–CN–K diagram (Al2O3–CaO + Na2O–K2O), indicated that the red palaeosols had experienced strong chemical weathering processes. Scanning electron microscopy analyses revealed that quartz grains of the red palaeosols were characterized by a number of deep dissolution pits and cracks on their surfaces. The clay minerals of the red palaeosols were composed of kaolinite, gibbsite, hematite, and vermiculite in the order of abundance. Pedogenical, geochemical and clay mineralogical evidences revealed that the red palaeosols were developed by palaeopedogenic processes under tropical climatic environments. The presence of highly weathered soils at an altitude of 2200–2400 m indicated the influence of tectonic uplift on the soil vertical distribution. It is estimated that the red palaeosols had uplifted about 1600–2000 m since their initial formation. Palaeopedogenesis of red palaeosols provides new insight into the palaeoclimatic and palaeoenvironmental reconstruct and tectonic movement of YP.

Early Tetrapods Lived in Shallow Tideless Lagoons in Eifelian Devonian Poland

Palaeonvironments of the Eifelian dolomites with earliest tetrapod trackways (Holy Cross Mountains, Poland)

Authors:

Narkiewicz et al

Abstract:

The Eifelian dolomites in the Zachełmie Quarry (Holy Cross Mountains, Poland) contain trackways and tracks of tetrapods 390-391 Ma old, and thus the oldest known so far. The environments of the trackway-bearing beds have been investigated using sedimentological, palaeontological, geochemical and palaeomagnetic methods. The reconstructed tetrapod habitats comprised shallow-water lagoons separated from an open marine basin by sparsely vegetated islands and spits. The lagoonal waters were well-aerated and a few-meters deep at most, undergoing periodic desiccation. The dolomitic sediments, primarily of microbial origin, formed in tropical waters of slightly modified marine composition. Oxygen isotope data obtained from the dolomicrites suggest water temperatures around 30 °C. The seasonal semi-arid to subhumid climate, deduced from paleosol characteristics, was probably of a tropical monsoonal type. The degree of restriction of the lagoonal system evolved from relatively open, evaporation-dominated towards increasingly closed, fresh-water influenced.

The detailed observations of the footprint-bearing beds, as well as the characteristics of the tracks, indicate that they were formed mostly under subaqueous conditions, by wading, walking on the bottom or swimming animals. Lack of tidal indicators in the restricted Zachełmie lagoons argues against previous concept that tidal flats served as a food source for the early tetrapods. Nor is a hypothesis of flooded woodlands confirmed as a habitat promoting the “fish-to-tetrapod” transition. We propose that functional limbs emerged among aqueous animals that acquired their locomotional capabilities in a shallow lagoonal water before attempting longer excursions on land.

What Miocene Neogene Antarctic Paleosols can be Applied to Studying Mars

Mineralogy, chemistry and biological contingents of an early-middle Miocene Antarctic paleosol and its relevance as a Martian analogue

Authors:

Mahaney et al

Abstract:

Fossil mesofauna and bacteria recovered from a paleosol in a moraine situated adjacent to the inland ice, Antarctica, and dating to the earliest glacial event in the Antarctic Dry Valleys opens several questions. The most important relates to understanding of the mineralogy and chemistry of the weathered substrate habitat in which Coleoptera apparently thrived at some point in the Early/Middle Miocene and perhaps earlier. Here, Coleoptera remains are only located in one of six horizons in a paleosol formed in moraine deposited during the alpine glacial event ( greater than 15 Ma). A tendency for quartz to decrease upward in the section may be a detrital effect or a product of dissolution in the early stage of profile morphogenesis when climate was presumably milder and the depositing glacier of temperate type. Discontinuous distributions of smectite, laumontite, and hexahydrite may have provided nutrients and water to mesofauna and bacteria during the early stage of biotic colonization of the profile. Because the mesofauna were members of burrowing Coleoptera species, future work should assess the degree to which the organisms occupied other sites in the Dry Valleys in the past. Whereas there is no reasonable expectations of finding Coleoptera/insect remains on Mars, the chemistry and mineralogy of the paleosol is within a life expectancy window for the presence of microorganisms, principally bacteria and fungi. Thus, parameters discussed here within this Antarctic paleosol could provide an analogue to identifying similar fossil or life-bearing weathered regolith on Mars.

Paleosol Evidence of Ediacaran NeoProterozoic Gaskiers and/or Fauquier Glaciations From PaleoContinent

Petrology, mineralogy and geochemical climofunctions of the Neoproterozoic Baltic paleosol

Authors:

Liivamägi et al

Abstract:

The Oxisolic Baltic paleosol is a well preserved Neoproterozoic weathering sequence located in the Russian Platform of the East-European Craton, former Baltica continent. The Baltic paleosol is developed on different hostrock types ranging from amphibolites and metagabbros to gneissic rocks and is characterized by up to several meters of thick weathered uppermost residuum composed of kaolinite (greater than 60%), Fe-oxyhydroxides and residual quartz. The mineral index of alteration (MIA) and molecular weathering indices (CIA, CIA-K, PIA) all indicate strong and deep weathering most likely under warm and humid climate. Geochemical climofunctions, although not directly applicable to the Precambrian Baltic paleosol, agree with this interpretation suggesting high mean annual temperatures (greater than 17 °C) and precipitation (1300-1800 mm yr−1) similar to modern day tropical conditions. The age of the weathering is between 560-600 Ma. During that time interval the Baltica continent was not drifting at tropical latitudes, but it is plausible that the Baltic paleosol was formed as a consequence of increased weathering rates during greenhouse event(s) possibly related to the termination of the Ediacaran Gaskiers and/or Fauquier glaciations, or in the relation to the Shuram-Wonoka isotope excursion. The Baltic paleosol is most likely one of the few well preserved examples of paleosol formation in the latest Neoproterozoic because it developed in a tectonically stable interior of the Baltica paleocontinent while physical denudation prevailed on other continental blocks due to the build-up of Gondwana that erased weathering profiles from the geological record.

Paleosol Analysis Shows Tithonian Jurassic PaleoClimate of North America was Very Varied

The climate 150 million years ago of a large swath of the western United States was more complex than previously known, according to new research from Southern Methodist University, Dallas.

It's been thought that the climate during the Jurassic was fairly dry in New Mexico, then gradually transitioned to a wetter climate northward to Montana.

But based on new evidence, the theory of a gradual transition from a dry climate to a wetter one during the Jurassic doesn't tell the whole story, says SMU paleontologist Timothy S. Myers, lead author on the study.

Geochemical analysis of ancient soils, called paleosols, revealed an unexpected and mysterious abrupt transition from dry to wet even though some of the samples came from two nearby locales, Myers said.

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Late Noachian Gale Crater Alternated Between Very Cold and West Martian Climates

Paleosols and paleoenvironments of early Mars

Author:

Retallack

Abstract:

Fluviolacustrine sediments filling Gale Crater on Mars show two levels of former exposure and weathering that provide new insights into late Noachian (3.7 ± 0.3 Ga) paleoenvironments of Mars. Diagnostic features of the two successive paleosols in the Sheepbed member include complex cracking patterns of surface dilation (peds and cutans), a clayey surface (A horizon), deep sand-filled cracks with vertical lamination (sand wedges), and replacive sulfate nodules aggregated into distinct bands (gypsic By horizon) above bedded sandy layers (sedimentary C horizon). Shallow gypsic horizon, periglacial sand wedges, and limited chemical weathering are evidence of a hyperarid frigid paleoclimate, and this alternated with wetter conditions for the lacustrine parent materials in Gale Crater during the late Noachian. Depletion of phosphorus, vesicular structure, and replacive gypsic horizons of these Martian paleosols are features of habitable microbial earth soils on Earth, and encourage further search for definitive evidence of early life on Mars.

Late Triassic to Jurassic Paleoclimate Data From Western-Central Mediterranean Alpine Mountains Were Tropical Rain Forest

Palaeoclimatic conditions and palaeoweathering processes on Mesozoic continental redbeds from Western-Central Mediterranean Alpine Chains

Authors:

Perri et al

Abstract:

Chemical and mineralogical analyses of the Triassic to lowermost Jurassic mudstones from continental redbeds outcropping in the Internal Domains of the Betic-Rifian and Calabria-Peloritani chains have been used to infer the relationships between palaeoclimatic conditions and palaeoweathering processes during rifting of a continental crust block that finally detached from adjoining western Tethyan realms to form an independent microplate (Mesomediterranean Microplate) from Jurassic to lower Miocene time. The studied mudstone samples come from Middle Triassic and Upper Triassic beds of the Saladilla Formation (both in the Betic Cordillera and in the Rif), whereas the Calabria-Peloritani Arc studied mudstones come from Upper Triassic to lowermost Jurassic beds (both in the Sila and Longi Taormina Units). Major and trace element concentrations, based on the mass-balance calculation relative to the upper continental crust, show negative values both in Gibraltar and Calabria-Peloritani Arcs, implying that mudstone formation in the Early Mesozoic involved moderate to intense continental palaeoweathering of the crust. In particular, CaO, Na2O, MgO, Sr, Ba, Fe2O3, MnO and transition metal elements (V, Cr, Co and Ni) are more depleted in the Triassic to Upper Jurassic samples of the Calabria-Peloritani samples than in the Middle to Upper Triassic Betic-Rifian samples, and suggest an increase of continental palaeoweathering in the Mediterranean region from the Triassic to the Jurassic. In addition enrichment in SiO2, TiO2, Al2O3, K2O and incompatible elements in the Calabria-Peloritani Arc mudstones indicates sediment recycling effects that gradually increase from the Triassic to Jurassic time. The hinterland palaeoweathering and sediment recycling effects have been mathematically distinguished using principal component analysis (PC1 is a measure of palaeoweathering rate mainly due to humidity (positive values) against aridity (negative values), whereas PC2 corresponds to the extent of sediment recycling). The results strongly indicate that humidity had increased from the Triassic to the Jurassic and that the depositional environments in Calabria-Peloritani Arc were probably more suitable for sediment recycling. These seasonal climate alternations corresponding to an increase in palaeoclimatic humidity that favored palaeoweathering conditions and recycling processes. These results are also confirmed by the mineralogical data, which show a higher abundance of kaolinite, typical of warm-humid conditions, in the Calabria-Peloritani mudstones than in those of the Betic Cordillera and the Rif. Furthermore, the comparison among geochemical weathering index values of the studied samples and of recent soils from different climatic zones likely suggests a tropical rainforest climate in the studied area during the Triassic to the lowermost Jurassic.

Paleosols Indicate Atmospheric Oxygen During MesoArchean Archean, 700 Million Years Earlier

Oxygen appeared in the atmosphere up to 700 million years earlier than we previously thought, according to research published today in the journal Nature, raising new questions about the evolution of early life.

Researchers from the University of Copenhagen and University of British Columbia examined the chemical composition of three-billion-year-old soils from South Africa – the oldest soils on Earth – and found evidence for low concentrations of atmospheric oxygen. Previous research indicated that oxygen began accumulating in the atmosphere only about 2.3 billion years ago during a dynamic period in Earth's history referred to as the Great Oxygenation Event.

"We've always known that oxygen production by photosynthesis led to the eventual oxygenation of the atmosphere and the evolution of aerobic life," says Sean Crowe, co-lead author of the study and an assistant professor in the Departments of Microbiology and Immunology, and Earth, Ocean and Atmospheric Sciences at UBC.

"This study now suggests that the process began very early in Earth's history, supporting a much greater antiquity for oxygen producing photosynthesis and aerobic life," says Crowe, who conducted the research while a post-doctoral fellow at Nordic Center for Earth Evolution at the University of Southern Denmark in partnership with the centre's director Donald Canfield.

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