9.2 CARBONATES
399
Fig. 9.1. Sketches of some of the principal types of carbonate grain. For full descriptions see text. Photomicrographs of recent and ancient examples are shown in plates Plates 6 and 7, respectively.
many types, as briefly described here. First are the detrital grains, which are of two
types. They include rock fragments, or lithodasts. These are grains of noncarbonate
material which originated outside the depositional basin. Quartz grains are a typical
example of lithoclasts and, as they increase in abundance, limestones grade into sandy
limestones and thence to calcareous sandstones. The second type of detrital grains are
intraclasts. These are fragments of reworked carbonate rock which originated within the
depositional basin (Plate 6B). Early cementation followed by penecontemporaneous
erosion is a common feature of carbonate rocks, and is responsible for the generation
399
Fig. 9.1. Sketches of some of the principal types of carbonate grain. For full descriptions see text. Photomicrographs of recent and ancient examples are shown in plates Plates 6 and 7, respectively.
many types, as briefly described here. First are the detrital grains, which are of two
types. They include rock fragments, or lithodasts. These are grains of noncarbonate
material which originated outside the depositional basin. Quartz grains are a typical
example of lithoclasts and, as they increase in abundance, limestones grade into sandy
limestones and thence to calcareous sandstones. The second type of detrital grains are
intraclasts. These are fragments of reworked carbonate rock which originated within the
depositional basin (Plate 6B). Early cementation followed by penecontemporaneous
erosion is a common feature of carbonate rocks, and is responsible for the generation