Breccia

Breccia ( /ˈbrɛtʃiə/ or /ˈbrɛʃiə/) is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments. Breccia ( /ˈbrɛtʃiə/ or /ˈbrɛʃiə/) is a rock composed of broken fragments of minerals or rock cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments. The word has its origins in the Italian language, in which it means either 'loose gravel' or 'stone made by cemented gravel'. A breccia may have a variety of different origins, as indicated by the named types including sedimentary breccia, tectonic breccia, igneous breccia, impact breccia, and hydrothermal breccia. Sedimentary breccia is a type of clastic sedimentary rock which is made of angular to subangular, randomly oriented clasts of other sedimentary rocks. A conglomerate, by contrast, is a sedimentary rock composed of rounded fragments or clasts of pre-existing rocks. Both breccia and conglomerate are composed of fragments averaging greater than 2 millimetres (0.079 in) in size. The angular shape of the fragments indicates that the material has not been transported far from its source. Sedimentary breccia consists of angular, poorly sorted, immature fragments of rocks in a finer grained groundmass which are produced by mass wasting. It is lithified colluvium or scree. Thick sequences of sedimentary (colluvial) breccia are generally formed next to fault scarps in grabens. Breccia may occur along a buried stream channel where it indicates accumulation along a juvenile or rapidly flowing stream. Sedimentary breccia may be formed by submarine debris flows. Turbidites occur as fine-grained peripheral deposits to sedimentary breccia flows. In a karst terrain, a collapse breccia may form due to collapse of rock into a sinkhole or in cave development. Fault breccia results from the grinding action of two fault blocks as they slide past each other. Subsequent cementation of these broken fragments may occur by means of the introduction of mineral matter in groundwater.