SIMS analyses of the oldest known assemblage of microfossils document their taxon-correlated carbon isotope compositions.

Preservation and detection of microstructural and taxonomic correlations in the carbon isotopic compositions of individual Precambrian microfossils

Here we present techniques for, and new data from, in situ carbon isotope (dC) analysis of Precambrian permineralized microscopic fossils with a reproducibility of 1–2& using secondary ion mass spectrometry (SIMS). Individual microfossils, selected for their excellent preservation, were analyzed in petrographic thin sections of stromatolitic cherts from the Proterozoic Gunflint ( 1880 Ma), Bitt...

C. Reproducibility of standards for carbon- and nitrogen isotope SIMS analyses C.1 Reproducibility of standards for carbon isotope SIMS analyses C.2 Reproducibility of standards for nitrogen isotope SIMS analyses

A Laurentian record of the earliest fossil eukaryotes

The oldest evidence of eukaryotes in the fossil record comes from a recurrent assemblage of morphologically differentiated late Paleoproterozoic to early Mesoproterozoic microfossils. Although widely distributed, the principal constituents of this Tappania-DictyosphaeraValeria assemblage have not hitherto been recognized on Laurentia. We have recovered all three taxa from a shallow-water shale ...

Urgonian Type Microfossils of the Dariyan Formation, from Southwest of Iran (Northeast of Shiraz)

The Lower Cretaceous Carbonate deposits of the Dariyan Formation of the HighZagros Belt are mainly composed of thick to medium bedded limestone. These depositscontain abundant and diversified benthic foraminifera which have been recovered fromcarbonate rocks. A rich assemblage of microfossils with characteristic: Palorbitolinalenticularis (Blumenbach), Mesorbitolina subconcava (Leymerie), Mesor...

Microfossils Preserved in Highly Metamorphosed Rocks: a New Window into the Early Biosphere

Circular graphite discs, among abundant irregular graphite particles, have been extracted from ArcheanPaleoproterozoic amphibolite grade metamorphic rocks in the Wutaishan area of North China. Raman spectroscopic analysis indicates that these graphite discs experienced maximum metamorphic temperature of 513 ± 50 °C. The discs bear morphological features related to metamorphism, but they are als...