Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life.
Stromatolites or stromatoliths are layered sedimentary formations (microbialite) that are created mainly by photosynthetic microorganisms such as cyanobacteria, sulfate-reducing bacteria, and Pseudomonadota. These microorganisms produce adhesive compounds that cement sand and other rocky materials to form mineral "microbial mats". In turn, these mats build up layer by layer, growing gradually over time. A stromatolite may grow to a meter or more. Fossilized stromatolites provide important records of some of the most ancient life. Today the living forms are rare.
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. Many reefs result from natural, abiotic (non-living) processes such as deposition of sand or wave erosion planing down rock outcrops. However, reefs such as the coral reefs of tropical waters are formed by biotic (living) processes, dominated by corals and coralline algae. Artificial reefs such as shipwrecks and other man-made underwater structures may occur intentionally or as the result of an accident, and are sometimes designed to increase the physical complexity of featureless sand bottoms to attract a more diverse range of organisms. Reefs are often quite near to the surface, but not all definitions require this.
A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Tufa is a variety of limestone formed when carbonate minerals precipitate out of water in unheated rivers or lakes. Geothermally heated hot springs sometimes produce similar carbonate deposits, which are known as travertine. Tufa is sometimes referred to as (meteogene) travertine. It should not be confused with hot spring (thermogene) travertine. Tufa, which is calcareous, should also not be confused with tuff, a porous volcanic rock with a similar etymology that is sometimes also called "tufa".
Dovedale is a valley in the Peak District of England. The land is owned by the National Trust and attracts a million visitors annually. The valley was cut by the River Dove and runs for just over 3 miles (5 km) between Milldale in the north and a wooded ravine, near Thorpe Cloud and Bunster Hill, in the south. In the wooded ravine, a set of stepping stones cross the river and there are two caves known as the Dove Holes.
Calcareous is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime or being chalky. The term is used in a wide variety of scientific disciplines.
Parkhouse Hill is a small but distinctive hill in the Peak District National Park of the Hartington Middle Quarter civil parish, in the English county of Derbyshire. It lies on the north side of the River Dove, close to the border with Staffordshire.
Chrome Hill is a limestone reef knoll in Derbyshire, England, in the upper Dove valley beside the border with Staffordshire, within the civil parish of Hartington Middle Quarter. It is adjacent to Parkhouse Hill, another reef knoll. The walk over Chrome Hill and Parkhouse Hill is known as the Dragon's Back ridge.
Cracoe is a small village and civil parish in the Craven district of North Yorkshire, England. It is situated near to Rylstone and about 6 miles south-west of Grassington. Cracoe has an estimated population of 160 residents, measured at 178 in the 2011 census. Cracoe is a village which is also situated near Rylstone beneath Barden Fell and the twin skyline landmarks of Rylstone Cross and Cracoe Pinnacle in the Yorkshire Dales.
Clitheroe Castle is a ruined early medieval castle in Clitheroe in Lancashire, England. It was the caput of the Honour of Clitheroe, a vast estate stretching along the western side of the Pennines.
The Burgsvik Beds are a sequence of shallow marine limestones and sandstones found near the locality of Burgsvik in the southern part of Gotland, Sweden. The beds were deposited in the Upper Silurian period, around 420 million years ago, in warm, equatorial waters frequently ravaged by storms, in front of an advancing shoreline. The Burgsvik Formation comprises two members, the Burgsvik Sandstone and the Burgsvik Oolite.
The Geology of Yorkshire in northern England shows a very close relationship between the major topographical areas and the geological period in which their rocks were formed. The rocks of the Pennine chain of hills in the west are of Carboniferous origin whilst those of the central vale are Permo-Triassic. The North York Moors in the north-east of the county are Jurassic in age while the Yorkshire Wolds to the south east are Cretaceous chalk uplands. The plain of Holderness and the Humberhead levels both owe their present form to the Quaternary ice ages. The strata become gradually younger from west to east.
A microbial mat is a multi-layered sheet of microorganisms, mainly bacteria and archaea, or bacteria alone. Microbial mats grow at interfaces between different types of material, mostly on submerged or moist surfaces, but a few survive in deserts. A few are found as endosymbionts of animals.
Shallow water marine environment refers to the area between the shore and deeper water, such as a reef wall or a shelf break. This environment is characterized by oceanic, geological and biological conditions, as described below. The water in this environment is shallow and clear, allowing the formation of different sedimentary structures, carbonate rocks, coral reefs, and allowing certain organisms to survive and become fossils.
The geology of Lancashire in northwest England consists in the main of Carboniferous age rocks but with Triassic sandstones and mudstones at or near the surface of the lowlands bordering the Irish Sea though these are largely obscured by Quaternary deposits.
The Laborcita Formation is a geologic formation in the Sacramento Mountains of New Mexico. It preserves fossils dating back to the late Pennsylvanian to early Permian.
A Waulsortian mudmound is a calcareous geographical feature found in Early Carboniferous strata of Central Europe. It is a type of fossil-rich bioconstruction, formed by microbial activity in deep tropical waters during the mid-Dinantian. Mud mounds are a type of high-relief biologically-mediated seafloor deposit, similar to a reef. Unlike a true reef, a mud mound is composed almost entirely of uncemented mud-sized matrix grains, and the isolated fossils do not form a significant skeletal framework.
The Craven Basin is a sedimentary basin in northern England, having the shape of a southerly-tilted graben which was active during the Carboniferous period. It is one of a series of such basins which developed across northern England in this period separating upstanding blocks which were typically underlain by buoyant granites. The basin trends roughly east–west and is bounded by the Lake District block to the northwest, the Askrigg Block to the northeast and the Central Lancashire High to the south. One distinct section of the basin is a half graben which contains over 3km thickness of late Devonian to Courceyan strata and is referred to as the Bowland Sub-basin. These basins resulted from the crust of the region being subjected to a north–south lateral tension regime which began in the late Devonian and lasted through until the Visean.
The geology of the Peak District National Park in England is dominated by a thick succession of faulted and folded sedimentary rocks of Carboniferous age. The Peak District is often divided into a southerly White Peak where Carboniferous Limestone outcrops and a northerly Dark Peak where the overlying succession of sandstones and mudstones dominate the landscape. The scarp and dip slope landscape which characterises the Dark Peak also extends along the eastern and western margins of the park. Although older rocks are present at depth, the oldest rocks which are to be found at the surface in the national park are dolomitic limestones of the Woo Dale Limestone Formation seen where Woo Dale enters Wye Dale east of Buxton.
