Evidence in pre-2.2 Ga paleosols for the early evolution of atmospheric oxygen and terrestrial biota: comment and reply

Article Abstract:

Interpretations of paleosol records reveal that pre 2.2 Ga paleosols were highly oxidized with minimal or zero iron loss because they were formed under an oxic atmosphere or were positively affected by algal mats which contributed to iron remobilization. Critics, however, dispute such a hypothesis because aluminum is always reduced during iron depletion as suggested by high Ti/Al ratios. Aluminum loss was not demonstrated during the iron-reduced late Archean and early Proterozoic paleosols.

Analysis, Environmental aspects, Oxidation-reduction reaction, Oxidation-reduction reactions, Soils, Iron (Metal), Soil chemistry, Weathering, Paleopedology

---

Carbonation and decarbonation of eclogites: the role of garnet

Article Abstract:

The possibility that garnet responds with carbon dioxide was explored to examine the carbonation of clinopyroxene through the reaction dolomite + 2 coesite = diopside + 2 CO2. The location of the reaction 3 magnesite + kyanite + 2 coesite = pyrope + 3 CO2 between 5 and 11 GPa in multi-anvil apparatus was identified. The carbonation of eclogitic rocks with increasing pressure reacts with clinopyroxene at the temperatures ...1200 degrees centigrade.

Carbonates, Garnet

---

Further comments on using carbon isotopes in paleosols to estimate the CO2 content of the palaeo-atmosphere

Article Abstract:

An analysis describing the application of carbon isotopes in palaeosols for measuring atmospheric carbon dioxide is presented. Earlier research proposed the use of calcretes and principles of physical chemistry for atmospheric analysis. However, such methods present problems for analyzing ancient atmospheres. It is also shown that the validity of the diffusion-reaction model requires geochemical and palaeopedological knowledge.

Evaluation, Isotopes, Atmospheric research

Similar abstracts:

• Abstracts: Stratigraphic evidence for the Siberia-Laurentia connection and Early Cambrian rifting: comments and reply. Influence of changes in climate, sea level, and depositional systems on the fossil record of the Neoproterozoic-Early Cambrian metazoan radiation, Australia
• Abstracts: Extensional collapse of the northern Taiwan mountain belt: comment and reply. Fracture-controlled magma conduits in an obliquely convergent continental magmatic arc: comment and reply
• Abstracts: Taconian orogeny in the New England Applachians: collision between Laurentia and the Shelburn Falls arc: comment and reply
• Abstracts: Discussion on garnet provenance studies, juxtaposition of Laurentian marginal terranes and timing of the grampian orogeny in Scotland
• Abstracts: An improved procedure for testing the effects of key innovations on rate of speciation. Body size and consumer-resource dynamics

This website is not affiliated with document authors or copyright owners. This page is provided for informational purposes only. Unintentional errors are possible.