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...

The succession in the Tizra Formation shows an excellent exposure of a small open marine platform where alternating microbial boundstones (buildups) and oolitic/bioclastic grainstone (shoals) packstone facies tempestites occur repetitively for sort interval only 0.55 Myr, scenario unknown geological record. relatively extent allows detailed study ecological variations, to determine controlling ...

Ooids are one of the common constituents of ancient carbonate rocks, yet the role that microbial communities may or may not play in their formation remains unresolved. To search for evidence of microbial activity in modern and Holocene ooids, samples collected from intertidal waters, beaches and outcrops in the Bahamas and in Shark Bay in Western Australia were examined for their contents of li...

The sediment along the shorelines of Great Salt Lake (GSL), Utah is dominated by ooids, concentrically-coated carbonate sand grains. Two characteristics differentiate GSL ooids from typical modern marine ooids: well-developed radial aragonite microfabrics and ubiquitous occurrence a Mg-silicate phase. have formed basis conceptual models applied to understand formation fabrics in ancient but Mg-...

The concentric layers of ooids from the modern environment are mostly aragonite and those ancient calcite Mg-calcite. Dolomitic rare usually formed via replacement or calcite. Here, dolomitic were found in Pliocene Shizigou Formation Qaidam Basin, Northern Tibet Plateau. This paper focuses on whether is a primary precipitate. Optical microscope scanning electron observation, combined with X-ray...

the jajarm karst bauxite deposit is located about 175 km southwest of bojnourd. the deposit has been developed as a stratiform horizon along the contact of triassic dolomites and the jurassic shales and sandstone. in this study, the textural elements of the jajarm bauxites are classified into matrix and separated textures based on morphological and genetic criteria. pelitomorphic and microgranu...