Proposal. Palaeoreconstruction of the ca. 2.5 Ga Batatal


reservoir: multiple geochemical research.

As Batatal Fm. is the first deep-sea section of sedimentary rocks in Minas Supergroup after Archean greenstone belt formation (Rio Das Velhas Supergroup) on the São Francisco Craton after crust reworking during Jequié Orogeny 2.7-2.5 Ga it means Batatal Fm represents the first appearance of broad (?) water masses on the São Francisco continent. Question about existence of oceans as we know it now in Archean – Palaeproterozoic time is hot debated. I propose the project about palaeoreconstruction of water masses during Batatal Fm. black shales using multiple geochemical methods: S, C, O isotopic composition, and the main redox sensitive elements (Fe, Mo, Re, U, etc). 

Age of the Batatal Fm. constraints geochronological data from lower and upper records: U-Pb 2580±7 Ma age of detrital zircon from the upper Moeda Formation quartzite and 2420±19 Ma (Pb-Pb) the Gandarela Fm. Closely age-related sections from Western Australian (Mt. Mc Shale and Mt. Sylvia Fm.) and South African (Upper Nauga and Klein Naute Fm.) cratons are well-studied and represent records formed at the same time as Batatal Fm. The similarity among these records not only composition (black shale and carbonates) but overlying BIF (banded-iron formations): Brockman in Australia, Kuruman in Africa and Cauê in Brazil. Comparison of above black shale containng formations helps us to understand spatial geochemistry of water reservoirs in time near Archean-Palaeproterozoic boundary (ca. 2580 – 2460 Ma).