In recent years, a rapidly expanding database, especially in sensitive high-resolution ion microprobe (SHRIMP) geochronology, has led to signifi cant advances in understanding of the Precambrian tectonic evolution of the Grenville Province, including its Adirondack outlier, and the Mesoproterozoic inliers of the Appalachians. Based upon this information, we review the geochronology and tectonic...

Tintinnids are very common in all marine water and even fresh water. The oldest fossils of Tintinnids are not only appeared in Neoproterozoic Era, but also in Mesoproterozoic Calymmian. Eight species of six genera Tintinnids of Mesoproterozoic Calymmian, from Huangmailing Phosphoric Ore in Hubei Province of Central China, are illustrated in this paper. They are the oldest ancestor of Tintinnids...

Ooids are common carbonate particles that are traditionally considered as abiogenically formed by physical and chemical processes in highly agitated environments. Recent studies point to the importance of microbial activities in ooid formation, but more case studies are required to confirm and clarify the roles of microbes and their organomineralization processes. Here we report an integrated p...

Figure 1. Regional geologic map of northeastern Minnesota showing the location of Gunflint Trail (modified from Jirsa and Miller, 2005). Field trip area lies near the northwestern end of the trail at the junction of Neoarchean, Paleoproterozoic, and Mesoproterozoic terranes.

Thick, unmetamorphosed successions of siliciclastic and carbonate rocks in eastern and western Siberia preserve a record of Middle Riphean to Early Upper Riphean sedimentary environments and geochemistry. Consistent with data from other continents, our studies in the Uchur–Maya region in southeastern Siberia and the Turukhansk Uplift in northwestern Siberia suggest a first-order shift in C from...

In rocks of late Paleoproterozoic and Mesoproterozoic age (ca. 1700-1000 million years ago), probable eukaryotic microfossils are widespread and well preserved, but assemblage and global diversities are low and turnover is slow. Near the Mesoproterozoic-Neoproterozoic boundary (1000 million years ago), red, green, and chromophytic algae diversified; molecular phylogenies suggest that this was p...

doi: 10.7185/geochemlet.1725 The Poll a’Mhuilt Member of the Stoer Group (Torridonian Supergroup) in Scotland has been heralded as a rare window into the ecology of Mesoproterozoic terrestrial environments. Its unusually high molybdenum concentrations and large sulphur isotope fractionations have been used as evidence to suggest that lakes 1.2 billion years ago were better oxygenated and enrich...

Agić, H. 2015. Palaeobiology and diversification of Proterozoic-Cambrian photosynthetic eukaryotes. Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 1308. 47 pp. Uppsala: Acta Universitatis Upsaliensis. ISBN 978-91-554-9389-9. One of the most important events in the history of life is the evolution of the complex, eukaryotic cell. The eukaryote...

The environmental expression of sulfur compound disproportionation has been placed between 640 and 1050 million years ago (Ma) and linked to increases in atmospheric oxygen. These arguments have their basis in temporal changes in the magnitude of 34S/32S fractionations between sulfate and sulfide. Here, we present a Proterozoic seawater sulfate isotope record that includes the less abundant sul...