Banded Iron Formations (BIFs) and Associated Sediments Do Not Reflect the Physical and Chemical Properties of Early Precambrian Seas

Abstract

Ring-in-ring structures in Australian Early Precambrian banded iron formation (BIF) were identified as bubbling mud wavelets, which lithified during temporary exposure, contradicting the alleged BIF deep ocean origin. Least altered BIFs consist of alternating chert laminae with, and without iron oxides (or carbonates). They were precipitated during on-and-off periods of ferrous iron oxidation controlled by microbial oxygenic photosynthetic activity during solar illumination, which stopped during darkness as characterizing the Polar Regions, thus forming genuine annual varves. This polar environment is further corroborated by the magnetite-hematite-magnetite microcrystal layers in the iron-rich laminae reflecting mid-spring-summer-autumn changes in solar radiation, and by diamictite at the end of the sequence deposited from melting glaciers when the continental plate shifted to lower latitudes. BIF sequences in various countries comprise evaporates. They attest to intensive evaporation of the warm hydrothermal solution in restricted shallow lakes under the freezing dry climate up to silica (geyserite) precipitation referred to chert. The existence of oceans, midocean-ridges and island arcs during the Early Precambrian results from the misinterpreted oceanic origin of BIFs and the Phanerozoic occurrences of the associated mafic-ultramafic basalt flows (Greenstone Belt).

Life on Earth Originated Where Later Microbial Oxygenic Photosynthesis Precipitated Banded Iron Formation, Suppressing Life Diversification for 1.4 Ga

“…These were compared to circular bubbling mud wavelets (Figure 2) forming today at the exposed surface of mud pools in the volcanic terrain of Rotorua, northern New Zealand [11,17]. Both extant and fossil examples have a complete central bubble about 3 cm in diameter surrounded by elevated rings of sediment nearly 1 cm wide with a slit between them.…”

“…Stromatolitelike structures could have precipitated non-biologically just as layered travertine structures from hot water [17,40]. Accordingly, the 3.8 -1.9-Ga-old BIFs accumulated in huge, shallow lakes of hydrothermal water in tectonically subsiding volcanic terrains situated on continental plates shifting over the globe on molten lava, passing through the Polar Regions [11,17]. These paleoecological and paleogeographical depositional settings are herein extended to pre-3.8 Ga times, prior to the origin of oxygenic photosynthetic cyanobacteria [41], or another biological oxidation process [42] when chemoautotrophic prokaryotes and other microbial forms (e.g.…”

“…The polar position of the aforementioned lakes during the precipitation of the varved BIF [11,17] comprised physical and chemical settings, which would have facilitated the earlier creation and preservation of life-forms. Hydrothermal solutions entered these lakes from numerous fumaroles scattered over the whole bottom [30] as attested to by the homogeneity of the chemical precipitates over most of the huge lakes.…”

“…Some of the deep-ocean vents ("Lost City systems") yield unique geochemical settings of a high alkalinity (pH 9 -11) and high concentrations of dissolved H 2 , CH 4 and other low-molecular-mass hydrocarbons, but almost no dissolved CO 2 where lifeforms could have emerged [9,10]. However, the occurrence of such inter-plate spreading centers during the Archean-Paleoproterozoic eons seems questionable, as is the existence of oceans in their Phanerozoic configuration [11]. The present-day deep-sea vents are scattered habitats of micro-and macro-faunal assemblages living confined to the sites of peculating mineral-rich hydrothermal water, suggesting that an ecological (chemical) hindrance prevents them from acclimatizing to the ambient ocean water.…”

“…These hazardous constraints render low the hypothetical "intrastellar panspermia", which is herein rejected by the identification on the early Earth of environments comprising most suitable physical and chemical conditions for the origin of life according to the latest biochemical scenarios. These archaic environments are the recently reconstructed depositional basins of the Early Precambrian (3.8 -1.9 Ga) banded iron formation (BIF) based on the least altered varved BIF in Western Australia and South Africa [11,17].…”