Bitumens extracted from 2.7 to 2.5 billion-year-old (Ga) shales of the Fortescue and Hamersley Groups in the Pilbara Craton, Western Australia, contain traces of molecular fossils. Based on a combination of molecular characteristics typical of many Precambrian bitumens, their consistently and unusually high thermal maturities, and their widespread distribution throughout the Hamersley Basin, th...

[1] During the Archean (3.8–2.5 billion years ago), the Sun was up to 25% less luminous than today, yet there is strong evidence that the Earth’s ocean surface was not completely frozen. The most obvious solutions to this ‘faint young Sun problem’ demand high concentrations of greenhouse gases such as carbon dioxide. Here we present the first comprehensive 3-dimensional simulations of the Arche...

Highly cracked and isomerized archaeal lipids and bacterial lipids, structurally changed by thermal stress, are present in solvent extracts of 2,707- to 2,685-million-year-old (Ma) metasedimentary rocks from Timmins, ON, Canada. These lipids appear in conventional gas chromatograms as unresolved complex mixtures and include cyclic and acyclic biphytanes, C36-C39 derivatives of the biphytanes, a...

Mass-independent fractionation of sulfur isotopes (reported as Δ(33)S) recorded in Archean sedimentary rocks helps to constrain the composition of Earth's early atmosphere and the timing of the rise of oxygen ~2.4 billion years ago. Although current hypotheses predict uniformly negative Δ(33)S for Archean seawater sulfate, this remains untested through the vast majority of Archean time. We appl...

Previous research has shown that methane may have been sustained at high concentrations in the Archean atmosphere, helping to offset lower insolation and solve the faint young sun problem. However, recent updates to the HITRAN (High-Resolution Transmission) line database have significantly increased the shortwave absorption by CH4 in comparison to older versions of the database (e.g. HITRAN 200...

The Slave craton in northern Canada is one of the world's smallest Archean cratons (surface exposure of 300,000 km), but makes up for this diminutive stature with excellent exposure and by hosting the oldest dated rocks on Earth (4.03 Ga, Stern and Bleeker 1998). It records continental accretion processes, albeit cryptically, and potentially offers the best opportunity worldwide to address the ...

Populations of sulfide inclusions in diamonds from the Orapa kimberlite pipe in the Kaapvaal-Zimbabwe craton, Botswana, preserve mass-independent sulfur isotope fractionations. The data indicate that material was transferred from the atmosphere to the mantle in the Archean. The data also imply that sulfur is not well mixed in the diamond source regions, allowing for reconstruction of the Archea...

Citation: Carlut J, Isambert A, Bouquerel H, Pecoits E, Philippot P, Vennin E, Ader M, Thomazo C, Buoncristiani J-F, Baton F, Muller E and Deldicque D (2015) Low temperature magnetic properties of the Late Archean Boolgeeda iron formation (Hamersley Group, Western Australia): environmental implications. Front. Earth Sci. 3:18. doi: 10.3389/feart.2015.00018 Low temperature magnetic properties of...

Komatiites from Alexo and Pyke Hill in the Archean Abitibi greenstone belt provide petrological evidence for an early Earth carbon and water cycle, ingassing in the cool Hadean and outgassing in the hot Archean. The komatiites have SiO2 contents that are lower than those expected of advanced volatile-free melting of mantle peridotite. The SiO2 misfit cannot be plausibly accounted for by variati...

Cratons form the cores of continents and were formed within a narrow window of time (2.5–3.2 Gy ago), the majority having remained stable ever since. Petrologic evidence suggests that the thick mantle roots underlying cratons were built by underthrusting of oceanic and arc lithosphere, but paradoxically this requires that the building blocks of cratons are weak even though cratons must have bee...