A | B | C | D | E | F | G | I | J | K | L | M | N | O | P | Q | R | S | T | U | V | W
  • Describes a limestone composed of more or less worn fragments of shells or pieces of older limestone. The particles are generally sand-sized.
  • Said of a rock containing as much as 50% of calcium carbonate (CaCO3), but also composed of something else (synonym: limy).
  • The heating of calcite or limestone to its temperature of dissociation so that it loses its carbon dioxide; also applied to the heating of gypsum to drive off its water of crystallization to make plaster of paris.
  • A common rock-forming mineral consisting of CaCO3; it may be white, colorless, or pale shades of gray, yellow, and blue; it has perfect rhombohedral cleavage, appears vitreous, and has a hardness of 3 on the Mohs' scale; it effervesces (fizzes) readily in cold dilute hydrochloric acid. It is the principal constituent of limestone.
  • The earliest period of the Paleozoic, thought to have covered the span of time between 543 and 490 million years ago; also, the corresponding system of rocks. It is named after Cambria, the Roman name for Wales, where rocks of this age were first studied.
  • A cavity in the earth large enough for a human to enter. Caves can form as a result of physical and chemical weathering of rock. Physical weathering usually produces shelter-type caves that extend into the rock for only a few feet. Chemical weathering of rock can produce caves (solution channels along fractures and bedding planes) that extend for many miles into the rock.
  • An era of geologic time, from the beginning of the Tertiary period to the present. (Some authors do not include the Quaternary, considering it a separate era.) It is characterized paleontologically by the evolution and abundance of mammals, advanced mollusks, and birds; paleobotanically, by angiosperms. The Cenozoic is considered to have begun about 65 million years ago.
  • Silicon dioxide (SiO2); a compact, massive rock composed of minute particles of quartz and/or chalcedony; it is similar to flint but lighter in color.
  • The Chesterian Series, the uppermost series of the Mississippian System, is named for Chester, Randolph County, where it is well exposed in the bluffs of the Mississippi River. The Chesterian Series consists of limestone-shale formations alternating with sandstone-shale formations. It extends from the major unconformity at the base of the Pennsylvanian System (sub-Absaroka unconformity) down to the base of the Shetlerville Member of the Renault Formation, which is the top of the Valmeyeran Series. Many of the Chesterian limestones and shales are abundantly fossiliferous. The sandstones are much less fossiliferous, but can contain some plant fossils. Coals, a few inches thick at most, occur in some of the Chesterian sandstones. Many of the limestones contain abundant crinoidal fragments, and the series is characterized by the presence of Talarocrinus which distinguishes it from the underlying Valmeyeran containing Platycrinites penicillus. Blastoids and the corkscrew bryozoan, Archimedes, are common and characteristic.
  • Chitin: A resistant organic compound with the same basic carbohydrate structure as cellulose, but nitrogenous because some hydroxyl groups are replaced by ascetamide groups. It is a common constituent of various invertebrate skeletons such as insect exoskeletons and foraminiferal inner test, and also occurs in hyphae and spores of fungi.
  • Said of rocks composed of particles of other rocks or minerals, including broken organic hard parts as well as rock substances of any sort, transported and deposited by wind, water, ice, or gravity.
  • A low, roughly concave topographic feature in a landscape. Rain falling within the boundaries of the depression would be channeled toward its lowest part (usually near its center).
  • The difference in altitude between the crest of a dome or anticline and the lowest structural or elevation contour that completely surrounds it.
  • A graphic representation, in the form of one or more vertical column(s), of the vertical succession and stratigraphic relations of rock units in a region.
  • (a) A hard, compact mass or aggregate of mineral matter, normally subspherical, but commonly oblate, disk-shaped, or irregular with odd or fantastic outlines; formed by precipitation from aqueous solution about a nucleus or center, such as a leaf, shell, bone, or fossil, in the pores of a sedimentary or fragmental volcanic rock, and usually of a composition widely different from that of the rock in which it is found and from which it is rather sharply separated. It represents a concentration of some minor constituent of the enclosing rock or cementing material, such as silica (chert), calcite, delimite, iron oxide, pyrite, or gypsum, and it ranges in size from a small pellet-like object to a great spheroidal body as much as 3 m in diameter. Most concretions were formed during diagenesis, and many (especially in limestone and shale) shortly after sediment deposition. (b) A collective term applied loosely to various primary and secondary mineral segregations of diverse origin, including irregular nodules, spherulities, crystalline aggregates, geodes, septaria, and related bodies.
  • Said of strata deposited one upon another without interruption in accumulation of sediment; beds parallel.
  • The final period of the Mesozoic era (after the Jurassic and before the Tertiary period of the Cenozoic era), thought to have covered the span of time between 144 and 65 million years ago; also, the corresponding system of rocks. It is named after the Latin word for chalk (creta) because of the English chalk beds of this age.
  • A conglomerate is a rock consisting of individual rounded fragments within a finer-grained groundmass of rock that have become cemented together.