Pondering the Precambrian #39

Proterozoic:

NeoProterozoic:

Global microfossil changes across the Ediacaran/Cambrian are characterized.

A new method of characterizing oxygen availability across the Ediacaran/Cambrian boundary has been found.

The lack of attention to taphonomy can mislead about the late Ediacaran fossils.

Data from Argentina covers the Ediacaran's oxygenation event.

Simulations of Ernettia suggest it was a filter feeder and fed better in groups.

Has there been a case of lateral gene transfer detected in bilaterians?

Ancient paralogies suggest jellyfish are a sister group to all other metazoans.

Green algae transitioned to macroscopic growth multiple times, but only as recently as the NeoProterozoic.

There is evidence of strange magmatism in the Sahara from the Ediacaran 580 million years ago.

An astronomical time scale for the middle/upper Doushantuo Formation has been established.

Braided rivers were not the rule prior to the evolution of plant life despite previous thought.

The Paleo Hunan Ocean was completely closed by 830 million years ago during the Tonian.

Evidence of two carbon excursions are detected in Tonian deposits in Namibia.

MesoProterozoic:

A new model suggests a sluggish, tepid mesoproterozoic ecosystem.

A very large igneous magmatic province has been found in South Africa from Stenian of South Africa.  These provinces are associated with mass extinctions like the Permian and Triassic/Jurassic.

An impact has been found in Scotland dating from the Mesoproterozoic.

Was anaerobic photosynthesis the reason for the delayed rise in oxygen in Earth's atmosphere?

PaleoProterozoic:

Iron stones were laid down by iron oxidizing bacteria during the Statherian.

There is evidence of deep subduction from North China from the Paleoproterozoic.

There is also evidence of a significant back arc continental collision during the Orosirian in the North China Craton.

There is evidence, according to Retallack, of macroscopic terrestrial life from the Orosirian.

The shape of the Dhala Crater in India from the Rhyacian is reconstructed.

Paleoproterozoic dolomites shed some light on the evolution of marine chemistry.

Archean:

The early Earth's oceans may not have been as hot as originally thought.

Compared to later granites, Archean granites had relatively unstable compositions.

Archean sulfur isotopes from Australia's Fraser Zone have unexplained ratios and amounts.

Did the subduction of the oceanic basins take place during the mesoarchean?

Could continents have existed from the dawn of the Archean, during the Eoarchean?

Eoarchean hydrothermal vent boron deposits give some insight to the origin of life.

Origin of Life:

Peptides can form without amino acids.

Could microscopic bubbles (interfaces) have helped kickstart life?

Pondering the Precambrian #10

NeoProterozoic:

The Ediacaran's Palaeopascichnus linearis appears to be the oldest macroscopic organism.

Exceptinal preservation of biomarkers was found in Ediacaran deposits from the Eastern European Craton.

The paleoenvironmental change gets examined leading up to the Gaskiers Glaciation in the Ediacaran.

The interglacial timeframe in the Cryogenian appears to should anoxic marine waters in South China.

The end of the Cryogenian Sturtian Glaciation according to new dating techniques supports a global and rapid deglaciation consistent with the snowball earth scenario.

At the dawn of the Sturtian glaciation during the Cryogenian, solar activity left no sign of any change.

Stromatoveris appears to be a survivor from the Ediacaran into the Cambrian.

Mesoproterozoic:

During the Stenian, the marine ecosystems were dominated by bacteria.

There is evidence of increased, but still limited biological productivity from the Ectasian/Calymmian boundary in Canada.

Paleoproterozoic:

There is evidence in from an Orosirian lake in Russia, that methanotrophic and autophototrophic biomes lived in the same body of water.

Orosirian micrometer fossils were identified using laser ablation mass spectrometry.

Researchers attempted to model the GOE atmosphere and had an interesting result regarding methane.

Evidence from the Boolgeeda Iron Formation in Australia suggests shallow water oxygenation took place while the iron banded formations were being deposited.

The Kaapvaal Craton shows evidence of subduction at the Archean/PaleoProterozoic Boundary.

Archean:

Shallow waters in South Africa just prior to the Great Oxygenation Event were still anoxic.

The disappearance of certain sulfur compounds appears to make a good proxy for the rise of oxygen in the Archean atmosphere.

There seems to have been intermittent surface ocean oxygenation prior to the Great Oxygenation Event during the NeoArchean.

There is evidence of continental collisions and subduction from the MesoArchean.

There is evidence of bacterial mats inhabiting terrestrial environments during the late PaleoArchean.

There is also evidence of bacterial speciation from the PaleoArchean deposits of Pilbara, Australia.

The Strelley Pool micro fossils from the PaleoArchean appear to be biological.

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.

Plants may Have Evolved From TERRESTRIAL Algae 100s of Millions of Years Earlier Than Previously Thought

Plant biologists agree that it all began with green algae. At some point in our planet's history, the common ancestor of trees, ferns, and flowers developed an alternating life cycle--presumably allowing their offspring to float inland and conquer Earth. But on December 16 in Trends in Plant Science, Danish scientists argue that some green algae had been hanging out on land hundreds of millions of years before this adaptation and that land plants actually evolved from terrestrial, not aquatic, algae.

Botanists have suspected this possibility since 1980, but supporters have lacked proof. Now, Carlsberg Laboratory's Jesper Harholt and University of Copenhagen's Øjvind Moestrup and Peter Ulvskov present genetic and morphological evidence that corroborates the theory. Notably, traits that land plants use to survive on land today are well conserved in some species of green algae.

The collaboration began while Harholt and Ulvskov were studying the evolution of the plant cell wall, long considered to be a key adaptation for a terrestrial lifestyle, as it provides body support for plants growing under the influence of gravity.

"We realized that algae have a cell wall that's similarly complex to terrestrial plant cell walls, which seemed peculiar because ancient algae were supposedly growing in water," says Harholt, Science Manager at the Carlsberg Laboratory. "We then started looking for other traits that would support the idea that algae were actually on land before they turned into land plants."

link.

The Terrestrial Biota Prior to the Evolution of Plants

The terrestrial biota prior to the origin of land plants (embryophytes): a review of the evidence

Authors:

Wellman et al

Abstract:

It is often assumed that life originated and diversified in the oceans prior to colonizing the land. However, environmental constraints in chemical evolution models point towards critical steps leading to the origin of life as having occurred in subaerial settings. The earliest fossil record does not include finds from terrestrial deposits, so much of our understanding about the presence of a terrestrial microbial cover prior to the Proterozoic is based on inference and geochemical proxies that indicate biospheric carbon cycling during the Archaean. Our assessment is that by 2.7 Ga, microbial ecosystems in terrestrial settings were driven by oxygen-generating, photosynthetic cyanobacteria. Studies of modern organisms indicate that both the origin and primary diversification of the eukaryotes could have occurred in terrestrial settings, shortly after 2.0 Ga, but there is no direct fossil evidence of terrestrial eukaryotes until about 1.1 Ga. At this time, it appears that the diversity of life in non-marine habitats exceeded that found in marine settings where sulphidic seas may have impaired eukaryotic physiology and retarded evolution. Geochemical proxies indicate the establishment of an extensive soil-forming microbial cover by 850 Ma, and it is possible that a rise in atmospheric oxygen at this time was due to the evolutionary expansion of green algae into terrestrial habitats. Direct fossil evidence of the earliest terrestrial biotas in the Phanerozoic consists of problematical palynomorphs from the Cambro-Ordovician of Laurentia. These indicate that the evolution of the first land plants (embryophytes) during the Middle Ordovician took place within a landscape that included aeroterrestrial algae which were actively adapting to selection in subaerial settings.

Trilobites Invaded Tidal Flats During the Early Cambrian

Trilobites in early Cambrian tidal flats and the landward expansion of the Cambrian explosion

Authors:

Mángano et al

Abstract:

The timing of the early invasion of the continents, the routes to the land, and the environmental breadth of the Cambrian explosion are important topics because they are at the core of our understanding of early evolutionary breakthroughs. Illuminating some aspects of these problems are trilobite trace fossils in tidal-flat deposits from the lower Cambrian Rome Formation in the southern Appalachian Mountains of Tennessee (USA). Morphologic details and size range of the trace fossils suggest production by olenellid trilobites, which occur as body fossils in the same unit. The occurrence of this ichnofauna, together with physical structures indicative of periodic subaerial exposure (desiccation cracks) and deposition within the intertidal zone (flat-topped ripples), shows that trilobites forayed into the upper intertidal zone during the Cambrian. Our finding supports the migration of subtidal organisms into marginal-marine, intertidal settings at the dawn of the Phanerozoic, suggesting that trilobites contributed to the establishment of the intertidal ecosystem during the Cambrian. The sequence of events involved in the colonization of early Paleozoic tidal flats is consistent with the idea that most terrestrial taxa originated from marine rather than freshwater ancestors, and that direct routes to the land from marginal-marine ecosystems were involved in the colonization of continental environments early in the Phanerozoic.

This is How the Terrestrial World's Biosphere Will End

Swansong Biospheres II: The final signs of life on terrestrial planets near the end of their habitable lifetimes

Authors:

O'Malley-James et al

Abstract:

The biosignatures of life on Earth do not remain static, but change considerably over the planet's habitable lifetime. Earth's future biosphere, much like that of the early Earth, will consist of predominantly unicellular microorganisms due to the increased hostility of environmental conditions caused by the Sun as it enters the late stage of its main sequence evolution. Building on previous work, the productivity of the biosphere is evaluated during different stages of biosphere decline between 1 Gyr and 2.8 Gyr from present. A simple atmosphere-biosphere interaction model is used to estimate the atmospheric biomarker gas abundances at each stage and to assess the likelihood of remotely detecting the presence of life in low-productivity, microbial biospheres, putting an upper limit on the lifetime of Earth's remotely detectable biosignatures. Other potential biosignatures such as leaf reflectance and cloud cover are discussed.

pop sci write up.

Terrestrial Ecosystems to Radically Reorganize Under All Climate Change Scenarios

Over 80% of the world's ice-free land is at risk of profound ecosystem transformation by 2100, a new study reveals. "Essentially, we would be leaving the world as we know it," says Sebastian Ostberg of the Potsdam Institute for Climate Impact Research, Germany. Ostberg and collaborators studied the critical impacts of climate change on landscapes and have now published their results in Earth System Dynamics, an open access journal of the European Geosciences Union (EGU).

The researchers state in the article that "nearly no area of the world is free" from the risk of climate change transforming landscapes substantially, unless mitigation limits warming to around 2 degrees Celsius above preindustrial levels.

Ecosystem changes could include boreal forests being transformed into temperate savannas, trees growing in the freezing Arctic tundra or even a dieback of some of the world's rainforests. Such profound transformations of land ecosystems have the potential to affect food and water security, and hence impact human well-being just like sea level rise and direct damage from extreme weather events.

The new Earth System Dynamics study indicates that up to 86% of the remaining natural land ecosystems worldwide could be at risk of major change in a business-as-usual scenario (see note). This assumes that the global mean temperature will be 4 to 5 degrees warmer at the end of this century than in pre-industrial times – given many countries' reluctance to commit to binding emissions cuts, such warming is not out of the question by 2100.

"The research shows there is a large difference in the risk of major ecosystem change depending on whether humankind continues with business as usual or if we opt for effective climate change mitigation," Ostberg points out.

But even if the warming is limited to 2 degrees, some 20% of land ecosystems – particularly those at high altitudes and high latitudes – are at risk of moderate or major transformation, the team reveals.

The researchers studied over 150 climate scenarios, looking at ecosystem changes in nearly 20 different climate models for various degrees of global warming. "Our study is the most comprehensive and internally consistent analysis of the risk of major ecosystem change from climate change at the global scale," says Wolfgang Lucht, also an author of the study and co-chair of the research domain Earth System Analysis at the Potsdam Institute for Climate Impact Research.

link.

How to Terraform Mars: Start with Antarctic Lichen

Adaptation of an Antarctic lichen to Martian niche conditions can occur within 34 days

Authors:

1. Jean-Pierre de Vera (a)
2. Dirk Schulze-Makuch (b)
3. Afshin Khan (b)
4. Andreas Lorek (a)
5. Alexander Koncz (a)
6. Diedrich Möhlmann (a)
7. Tilman Spohn (a)

Affiliations:

a. German Aerospace Centre, Institute of Planetary Research, D-12489 Berlin, Germany

b. School of Earth and Environmental Sciences, Washington State University, USA

Abstract:

Stresses occurring on the Martian surface were simulated in a Mars Simulation Chamber (MSC) and included high UV fluxes (Zarnecki and Catling, 2002), low temperatures, low water activity, high atmospheric CO2 concentrations, and an atmospheric pressure of about 800 Pa (Kasting, 1991 and Head et al., 2003). The lichen Pleopsidium chlorophanum is an extremophile that lives in very cold, dry, high-altitude habitats, which are Earth‘s best approximation of the Martian surface. Samples with P. chlorophanum were exposed uninterruptedly to simulated conditions of the unprotected Martian surface (i.e. 6344 kJm−2) and protected niche conditions (269 kJm−2) for 34 days. Under unprotected Martian surface conditions the fungal symbiont decreases its metabolic activity and it was unclear if the algal symbiont of the lichen was still actively photosynthesizing. However, under “protected site“ conditions, the entire lichen not only survived and remained photosynthetically active, it even adapted physiologically by increasing its photosynthetic activity over the 34 days.

So do you think NASA is wasting money being overly paranoid?

Or perhaps we ought to just get on with it and terraform Mars how we can?

Terrestrial Bacterial Mats During PaleoProterozoic 200 Million Years After Onset of Great Oxidation Event

Evidence for 2.0 Ga continental microbial mats in a paleodesert setting

Authors:

1. Edward L. Simpson (a)
2. Elizabeth Heness (a)
3. Adam Bumby (b)
4. Patrick G. Eriksson (b)
5. Kenneth A. Eriksson (c)
6. Hannah L. Hilbert-Wolf (d)
7. Sarah Linnevelt (b)
8. H. Fitzgerald Malenda (a)
9. Tshepiso Modungwa (b)
10. O.J. Okafor (b)

Affiliations:

a. Department of Physical Sciences, Kutztown University of Pennsylvania, Kutztown PA 19530, USA

b. Department of Geology, University of Pretoria, Pretoria 0002, South Africa

c. Department of Geosciences, Virginia Tech, Blacksburg,VA 24061, USA

d. School of Earth and Environmental Sciences, James Cook University, Townsville, Qld 4811, Australia

Abstract:

Early evolved microbial communities characterized the initial biological invasion of Precambrian continental landscapes. In modern arid settings, microbial mats and biological soil crusts are well-developed and stabilize sediment. The Paleoproterozoic Makgabeng Formation in South Africa is one of the oldest and best preserved, dryland systems on Earth. Six types of microbial mat-related structures are now recognized within these depositional systems. This paper presents three newly discovered structures that include tufted microbial mat, biological soil crusts, and gas-escape features, in addition to three previously documented structures that include roll up features, sand cracks, and wrinkled features. These discoveries demonstrate that microbial communities were well-established and inhabited diverse continental settings by 2.0 Ga, approximately 200 million years after the onset of the Great Oxidation Event.

Terrestrial Planets, Migrating Jovians and Mars

TERRESTRIAL PLANET FORMATION DURING THE MIGRATION AND RESONANCE CROSSINGS OF THE GIANT PLANETS

Authors:

1. Patryk Sofia Lykawka (a)
2. Takashi Ito (b)

Affiliations:

a. Astronomy Group, Faculty of Social and Natural Sciences, Kinki University, Shinkamikosaka 228-3, Higashiosaka-shi, Osaka 577-0813, Japan

b. National Astronomical Observatory of Japan, Osawa 2-21-1, Mitaka, Tokyo 181-8588, Japan

Abstract:

The newly formed giant planets may have migrated and crossed a number of mutual mean motion resonances (MMRs) when smaller objects (embryos) were accreting to form the terrestrial planets in the planetesimal disk. We investigated the effects of the planetesimal-driven migration of Jupiter and Saturn, and the influence of their mutual 1:2 MMR crossing on terrestrial planet formation for the first time, by performing N-body simulations. These simulations considered distinct timescales of MMR crossing and planet migration. In total, 68 high-resolution simulation runs using 2000 disk planetesimals were performed, which was a significant improvement on previously published results. Even when the effects of the 1:2 MMR crossing and planet migration were included in the system, Venus and Earth analogs (considering both orbits and masses) successfully formed in several runs. In addition, we found that the orbits of planetesimals beyond a ~ 1.5-2 AU were dynamically depleted by the strengthened sweeping secular resonances associated with Jupiter's and Saturn's more eccentric orbits (relative to the present day) during planet migration. However, this depletion did not prevent the formation of massive Mars analogs (planets with more than 1.5 times Mars's mass). Although late MMR crossings (at t less than 30 Myr) could remove such planets, Mars-like small mass planets survived on overly excited orbits (high e and/or i), or were completely lost in these systems. We conclude that the orbital migration and crossing of the mutual 1:2 MMR of Jupiter and Saturn are unlikely to provide suitable orbital conditions for the formation of solar system terrestrial planets. This suggests that to explain Mars's small mass and the absence of other planets between Mars and Jupiter, the outer asteroid belt must have suffered a severe depletion due to interactions with Jupiter/Saturn, or by an alternative mechanism (e.g., rogue super-Earths).

3D Video Reconstruction of Retallack's Problematic "Terrestrial" Fossils

 

The original post about Retallack's latest controversial fossil is here.  This video is from the supplements.

Diskagma buttonii: Evidence of Paleoproterozoic Terrestrial Life?

Problematic urn-shaped fossils from a Paleoproterozoic (2.2 Ga) paleosol in South Africa

Authors:

1. Gregory J. Retallack (a)
2. Evelyn S. Krull (b)
3. Glenn D. Thackray (c)
4. Dula Parkinson (d)

Affiliations:

a. Department of Geological Sciences, University of Oregon, Eugene, Oregon

b. C.S.I.R.O. Land and Water, Waite Campus, Glen Osmond, South Australia 5064

c. Department of Geosciences, Idaho State University, Pocatello, Idaho 83209

d. Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, California 94720

Abstract:

Small (0.3-1.8 mm long), locally abundant, urn-shaped fossils within surface horizons of a paleosol in the 2.2 Ga Hekpoort Formation near Waterval Onder, South Africa, are here described and named Diskagma buttonii Retallack gen. et sp. nov. The fossils are from fresh rock of a deep highway cutting, and have been metamorphosed to upper greenschist facies like their matrix. Despite metamorphic alteration, total organic carbon of the samples was 0.04% and its isotopic composition (δ13C) was–25.6 ± 0.08 ‰ (two standard deviations) versus Vienna Pee Dee belemnite standard. Organic outlines of the fossils are also accentuated by recystallized berthierine and opaque oxides. The fossils are locally clumped within surface swales of a Vertisol paleosol, identified from characteristic penecontemporaneous deformation (clastic dikes between swales of mukkara structure) and from pronounced geochemical differentiation (phosphorus and copper strain-corrected mass-depletion characteristic of an oxidized biologically active soil). This paleosol's chemical composition is evidence of temperate humid climate (mean annual temperature 11.3 ± 4.4 °C, and mean annual precipitation 1489 ± 182 mm). Associated paleosols indicate atmospheric CO2 of 6640 +12880/-4293 ppm (0.6%) and 0.9-5% atmospheric O2. The best preserved examples of Diskagma are shaped like an urn with a flared rim, and closed below the flare. Observation of hundreds of specimens in thin section reveals substantial variation in growth (elongation) and decay (shredding and deflation). They had a hollow ellipsoidal interior that is unusually devoid of opaque debris, unlike the matrix. Diskagma is superficially comparable with lichens such as Cladonia (Ascomycota) and Geosiphon (Glomeromycota). Definitive reproductive structures remain unknown. They predate the oldest other likely fossil eukaryotes (1.9 Ga) and fungi (1.5 Ga), and current molecular clock estimates for eukaryotes (1.6 Ga) and fungi (1.1 Ga). Lichenized actinobacteria are plausible prokaryotic alternatives permitted by molecular clocks. Although biological affinities of Diskagma are uncertain, these fossils reveal the general appearance of Paleoproterozoic life on land.

I gotta add that I am skeptical.  Not that there is life, but...lichens?  That early?  The paper even notes there are problems with the timing...