526 MINERALS/Carbonates Figure Lithified carbonates (A) Articulated bivalves embedded in a packstone matrix; Ironshore Formation, Pleistocene, Grand Cayman (B) Well preserved patch reef formed of Porites; Ironshore Formation, Pleistocene, Grand Cayman (C) Limestone with fossil mouldic porosity (after corals); Pleistocene, Barbados (D) Thin section photomicrograph, showing grainstone formed of bioclasts embedded in spar calcite cement; Brac Formation, Oligocene, Cayman Brac Field of view covers $6 Â mm (E) Finely crystalline dolostone with cavities lined with dolomite cement (white) and filled with calcite cement (stained red by Alizarin Red S solution); Cayman Formation, Oligocene, Cayman Brac Field of view covers $1 Â mm (F) Sucrosic dolomite formed of euhedral dolomite crystals that have a dirty core surrounded by a clear rim; note ghost structures of skeletal fragments in cores, inherited from precursor limestone; Brac Formation, Oligocene, Cayman Brac Field of view $1.5 Â mm precipitated following their deposition (Figure 3D) Cementation may take place while the sediments are still in their original depositional setting (e.g., hardgrounds, reefs) or millions of years later, after the sediments have been buried Classification Numerous classification schemes have been proposed for carbonate sediments and sedimentary rocks The Folk and Dunham classification schemes, which