Middle Eocene Climatic Optimum's Ocean Productivity Spiked Because of Increased Eolian Iron Fertilization

Environmental magnetic implications of magnetofossil occurrence during the Middle Eocene Climatic Optimum (MECO) in pelagic sediments from the equatorial Indian Ocean

Authors:

Savian et al

Abstract:

Magnetic properties of pelagic marine sediments that record the Middle Eocene Climatic Optimum (MECO) at ~ 40 Ma provide information about major environmental changes. The main variations observed during this transient warming event reflect a bacterial magnetofossil signal, but the cause of the linkage between bacterial production and climate remains unclear. We present an environmental magnetic study of middle Eocene deep-sea sediments from the northern edge of Madingley Rise (Ocean Drilling Program Hole 711A, equatorial Indian Ocean) to investigate the origin of the increased magnetic mineral concentration concomitant with subchron C18n.2n, which corresponds to the MECO interval in ODP Hole 711A. This magnetic mineral peak also coincides with a change in lithofacies from calcareous nannofossils to radiolarian ooze, and a slight increase in clay concentration. Magnetite is the main magnetic mineral in the MECO sediments, which occurs as magnetically non-interacting single domain biogenic particles. The increased magnetic mineral concentration across the MECO event is likely to have been caused by increased eolian iron fertilization. This is interpreted to have given rise to increased surface ocean productivity, where increased delivery of iron and nutrients to the seafloor enhanced magnetotactic bacterial populations during the MECO event.

Are Iron Isotopes From Archean Deposits Biosignatures?

Does a Heavy Fe-Isotope Composition of Akilia Quartz-Amphibole-Pyroxene Rocks Necessitate a BIF Origin?

Authors:

Whitehouse et al

Abstract:

The age and origin of the quartz-amphibole-pyroxene (qap) gneiss from the island of Akilia, southern West Greenland, have been the subject of intense debate since the light C-isotope composition of graphite inclusions in apatite was interpreted to indicate the presence of Earth's earliest biological activity. Although this claim for biogenic relicts has been vigorously challenged, the possibility that the rocks might represent some of Earth's earliest water-lain sediments and, hence, a suitable repository for life remains an open question. While some workers have suggested that the entire sequence represents an originally mafic-ultramafic igneous precursor subsequently modified by metasomatism, quartz injection, high-grade metamorphism, and extreme ductile deformation, others maintain that at least a small part of the sequence retains geochemical characteristics indicative of a chemical sedimentary origin. Fractionated Fe isotopes with δ56Fe values similar to those observed in Isua BIF have been reported from high-SiO2 units of qap and used to support a chemical sedimentary protolith for the qap unit. Here, we present new Fe isotope data from all lithologic variants in the qap gneiss on Akilia, including layers of undisputed ultramafic igneous origin. Since the latter require introduction of fractionated Fe into at least part of the qap unit, we argue that Fe isotopes must therefore be treated with considerable caution when used to infer BIF for part or all of the qap protolith.

Kabuno Bay's Iron Oxidizing Bacteria Give Clues to Earth's Archean and Proterozoic Oceans

An isolated, iron-rich bay in the heart of East Africa is offering scientists a rare glimpse back into Earth's primitive marine environment, and supports theories that tiny microbes created some of the world's largest ore deposits billions of years ago.

According to University of British Columbia (UBC) research published this week in Scientific Reports, 30 per cent of the microbes in the Democratic Republic of the Congo's Kabuno Bay grow by a type of photosynthesis that oxidizes (rusts) iron rather than converting water into oxygen like plants and algae.

"Kabuno Bay is a time machine back to the Earth's early history when iron-rich ocean chemistry prevailed," said Marc Llirós of the University of Namur, first author of the paper.

"The bay is giving us real-world insight into how ancient varieties of photosynthesis may have supported Earth's early life prior to the evolution of the oxygen producing photosynthesis that supports life today," said UBC geomicrobiologist Sean Crowe, senior author of the study.

While iron-respiring bacteria were discovered in 1993, the new Scientific Reports study provides evidence that microorganisms could have been directly involved in depositing the Earth's oldest iron formations.

Before 2.3 billion years ago, there was little oxygen in the atmosphere but plenty of dissolved iron and many organisms like bacteria derived energy by metabolizing the metal. Many researchers believe iron-metabolizing microbes might have turned plentiful dissolved iron into minerals, which then settled out of seawater and deposited along the ocean floor.

link.

Implications of Quartez Embedded Biogenic Iron-Rich Filaments From Ediacaran NeoProterozoic China

Biogenic Iron-Rich Filaments in the Quartz Veins in the Uppermost Ediacaran Qigebulake Formation, Aksu Area, Northwestern Tarim Basin, China: Implications for Iron Oxidizers in Subseafloor Hydrothermal Systems

Authors:

Zhou et al

Abstract:

Fe-(oxyhydr)oxide-encrusted filamentous microstructures produced by microorganisms have been widely reported in various modern and ancient extreme environments; however, the iron-dependent microorganisms preserved in hydrothermal quartz veins have not been explored in detail because of limited materials available. In this study, abundant well-preserved filamentous microstructures were observed in the hydrothermal quartz veins of the uppermost dolostones of the terminal-Ediacaran Qigebulake Formation in the Aksu area, northwestern Tarim Basin, China. These filamentous microstructures were permineralized by goethite and hematite as revealed by Raman spectroscopy and completely entombed in chalcedony and quartz cements. Microscopically, they are characterized by biogenic filamentous morphologies (commonly 20–200 μm in length and 1–5 μm in diameter) and structures (curved, tubular sheath-like, segmented, and mat-like filaments), similar to the Fe-oxidizing bacteria (FeOB) living in modern and ancient hydrothermal vent fields. A previous study revealed that quartz-barite vein swarms were subseafloor channels of low-temperature, silica-rich, diffusive hydrothermal vents in the earliest Cambrian, which contributed silica to the deposition of the overlying bedded chert of the Yurtus Formation. In this context, this study suggests that the putative filamentous FeOB preserved in the quartz veins might have thrived in the low-temperature, silica- and Fe(II)-rich hydrothermal vent channels in subseafloor mixing zones and were rapidly fossilized by subsequent higher-temperature, silica-rich hydrothermal fluids in response to waning and waxing fluctuations of diffuse hydrothermal venting. In view of the occurrence in a relatively stable passive continental margin shelf environment in Tarim Block, the silica-rich submarine hydrothermal vent system may represent a new and important geological niche favorable for FeOB colonization, which is different from their traditional habitats reported in hydrothermal vent systems at oceanic spreading centers or volcanic seamounts. Thus, these newly recognized microfossils offer a new clue to explore the biological signatures and habitat diversity of microorganisms on Earth and beyond.

The Role of Iron Silicate Nanoparticles in pre Great Oxidation Event PaleoOceans

Precipitation of iron silicate nanoparticles in early Precambrian oceans marks Earth's first iron age

Authors:

Rasmussen et al

Abstract:

The early ocean was characterized by anoxic, iron-rich (ferruginous) conditions before the rise of atmospheric oxygen ∼2.45 b.y. ago. A proxy for ferruginous conditions in the ancient ocean is the deposition of banded iron formations (BIFs), which are iron- and silica-rich chemical sediments whose constituents were largely derived from seawater. Although experiments simulating ancient ocean chemistry support the rapid growth of iron-silicate phases, the main iron precipitates are hypothesized to have been ferric oxyhydroxides. The paradox between the prevailing reducing conditions and the deposition of oxidized iron phases is explained by biologically mediated oxidation in the water column. New high-resolution microscopy of BIFs and shales throughout the 2.63–2.45 b.y. old Hamersley Group, Australia, reveals the presence of vast quantities of nanometer-sized iron-silicate particles in laminated chert. The nanoparticles are finely disseminated in early diagenetic chert and locally define sedimentary lamination, indicating that they represent relicts of the original sediments. By inference from experimental studies simulating the composition of the early Precambrian ocean, we suggest that the nanoparticles precipitated from anoxic seawater enriched in silica and dissolved iron, and were silicified upon deposition. The prevalence of iron-silicate nanoparticles implies that they were pervasive background precipitates in ferruginous, silica-enriched oceans, forming the primary sediments of BIFs during periods of enhanced submarine mafic volcanism. Our results imply that silicate precipitation was a major sink of seawater iron and silica before the Great Oxidation Event and, because of the reactivity of nanoparticle surfaces, may also have influenced the transport and geochemical cycling of trace metals and nutrients. Our hypothesis that the basic building blocks of BIFs were predominantly iron-silicate muds rather than iron oxides and/or hydroxides may lead to new insights into seawater chemistry on the early Earth and the role of biology in the deposition of BIFs.

Hunting for Iron From the South Pole-Aitken Basin Impactor

Surveying the South Pole-Aitken basin magnetic anomaly for remnant impactor metallic iron

Authors:

Cahill et al

Abstract:

The Moon has areas of magnetized crust (“magnetic anomalies”), the origins of which are poorly constrained. A magnetic anomaly near the northern rim of South Pole-Aitken (SPA) basin was recently postulated to originate from remnant metallic iron emplaced by the SPA basin-forming impactor. Here, we remotely examine the regolith of this SPA magnetic anomaly with a combination of Clementine and Lunar Prospector derived iron maps for any evidence of enhanced metallic iron content. We find that these data sets do not definitively detect the hypothesized remnant metallic iron within the upper tens of centimeters of the lunar regolith.

Mothers who do NOT Take Iron Supplements are 5x at Risk for Having Autistic Child, Older Mothers More

Mothers of children with autism are significantly less likely to report taking iron supplements before and during their pregnancies than the mothers of children who are developing normally, a study by researchers with the UC Davis MIND Institute has found.

Low iron intake was associated with a five-fold greater risk of autism in the child if the mother was 35 or older at the time of the child's birth or if she suffered from metabolic conditions such as obesity hypertension or diabetes.

The research is the first to examine the relationship between maternal iron intake and having a child with autism spectrum disorder, the authors said. The study, "Maternal intake of supplemental iron and risk for autism spectrum disorders," is published online today in the American Journal of Epidemiology.

"The association between lower maternal iron intake and increased ASD risk was strongest during breastfeeding, after adjustment for folic acid intake," said Rebecca J. Schmidt, assistant professor in the Department of Public Health Sciences and a researcher affiliated with the MIND Institute.

The authors of the current study in 2011 were the first to report associations between supplemental folic acid and reduced risk for autism spectrum disorder, a finding later replicated in larger scale investigations.

"Further, the risk associated with low maternal iron intake was much greater when the mother was also older and had metabolic conditions during her pregnancy."

link.

*cough*older mothers*cough*

Evidence of a River Delta From Statherian PaleoProterozoic Australia

Riverine mixing and fluvial iron formation: A new type of Precambrian biochemical sediment

Authors:

Pufahl et al

Abstract:

Precambrian iron formations are biochemical sediments that record ocean chemistry and circulation on the early Earth. The appearance of large, economically important continental margin iron formation reflects the creation of extensive continental shelves and oxygenation of the ocean-atmosphere system near the end of the Archean. Exhalative iron formation contains a record of hydrothermal vent chemistry through time. We introduce here fluvial iron formation, a new type of Fe-rich microbial-biochemical sediment that formed by mixing river discharge and seawater in coastal environments. The Paleoproterozoic Chiall Formation (ca. 1.8 Ga), Earaheedy Basin, Western Australia, contains laminated and granular hematitic iron formation in delta channel deposits. Where mixing occurred in adjacent peritidal settings, laminated iron formation and hematitic oncoids formed. Because fluvial iron formations precipitated at the interface between terrestrial and marine realms, the locus of known Fe precipitation processes is shifted landward into paleoestuarine settings and reflects Fe derived from both terrestrial weathering and coastal upwelling, providing a new window into ocean-atmosphere evolution.