Old View: Carbonates precipitate due to evaporation or temperature change. New View (e.g., PNAS, 2023): Extracellular Polymeric Substances (EPS) from cyanobacteria and sulfate-reducing bacteria directly template nucleation. 80% of Phanerozoic limestones show microbial "fingerprints" in their clumped isotopes.
This new PDF (48 pages, 12 figures, 3 tables) departs from traditional carbonate sedimentology texts by integrating recent advances: origin of carbonate sedimentary rocks pdf new
| Environment | Dominant Origin | Key New Insight | |-------------|----------------|------------------| | Tidal flats | Microbial mats, cryptalgal laminites | Widespread in Precambrian; modern rare due to grazing metazoans | | Lagoons | Fine-grained muds (fecal pellets, whitings) | High organic matter drives early dolomite | | Reefs | Skeletal (corals, sponges, algae) | Microbialite framework in deep time (reefs were microbial before Triassic) | | Slope & basinal | Pelagic ooze (coccoliths, forams), turbidites | Carbonate factories operate in deep time (e.g., Devonian globular calcimicrobes) | | Lacustrine | Abiotic, bio-induced (charophytes, cyanobacteria) | New importance for paleoclimate (Mg/Ca ratio as aridity proxy) | Old View: Carbonates precipitate due to evaporation or