1. Cool-Water Carbonates

2. Iceberg rainout Muddy limestone Dropstone Polar carbonates associated with ice sheets and icebergs Lower Permian, Tasmania

3. Classical carbonate environments are tropical Contain abundant abiotic precipitates (ooids, micrite, etc.) Contain abundant aragonitic biota of photosynthetic organisms Termed “Photozoan”

4. Carbonates can also form in cool water where siliciclastic influx is limited Lack abiotic precipitates and contain calcitic biota of heterotrophic animals (rare photosynthetic) Termed “Heterozoan”

5. HETEROZOANPHOTOZOAN Cool-waterTropicalSubtropical Bryozoan (Cenozoic) Ooid Peloid Green Algae Larger Foraminifera Bryozoan (Paleozoic) Colonial Scleractinian Coral (Mz-Cz) Colonial Rugose Coral (Pz) Small Foraminifera Brachiopod (Pz) Mollusc (Mz-Cz) Micrite Abiotic Minimal control Hypercalcified Colonial Sponges Some control Solitary Coral Strong control Barnacle (Cenozoic) Red Algae Physiology and temperature- sensitivity of carbonate allochems

6. Temperature is not the only control on photozoan/heterozoan carbonates Nutrients: heterozoan assemblage replaces photozoan in eutrophic settings Photozoan organisms gain energy from sunlight, but cannot compete with faster-growing heterotrophic animals as nutrient levels rise

7. Cool-water carbonates lack early cement because aragonitic grains are not present (which normally dissolve and raise saturation during early diagenesis, leading to cement formation) Mechanical grain compaction and suturing (pressure solution)