The K – T boundary represents one of the most dramatic turnovers in the fossil record for various calcareous nanoplankton that formed the calcium deposits that gave the Cretaceous its name.

The Cretaceous – Paleogene extinction event, which in the oceans dramatically affected organisms with calcareous skeletons, appears to have had relatively little impact on diatom evolution.

The arrangement of coccolithophores are as spherical cells about 5 – 100 micrometres across, enclosed by calcareous plates, coccoliths, about 2 – 25 micrometres across.

It is typically found over calcareous substrates such as limestone, growing on limestone slopes and in moist valley soils, at elevations of 120 – 600 m.

Not all reefs in the past were formed by corals: those in the Early Cambrian ( 542 – 513 Ma ) resulted from calcareous algae and archaeocyathids ( small animals with conical shape, probably related to sponges ) and in the Late Cretaceous ( 100 – 65 Ma ), when there also existed reefs formed by a group of bivalves called rudists ; one of the valves formed the main conical structure and the other, much smaller valve acted as a cap.

It typically grows in calcareous grassland, and reaches 70 – 120 cm tall.

the hills area of " les garrigues " ( at south of the village ) is composed of soil dating from the Cretaceous – Paleocene ( calcareous sandstone, calcareous lacustrine clay, colorful, white and ocher sands and some ferruginous ) and from the Miocene ( molasses limestone, sand and marl ).

This vertical cliff was composed of the calcareous reefs of the Cathedral Formation, which probably formed shortly before the deposition of the Burgess Shale.

The underlying rock is limestone so the majority of the park is calcareous grassland, probably created about 1000 years ago by clearing of oak forest, hosting a range of wild flower species and associated animals such as butterflies.

As small organisms with hard, calcareous shells have trouble growing at extreme depths because of the high solubility of calcium carbonate in the pressurized water, scientists theorize that the preponderance of soft-shelled organisms in the Challenger Deep may have resulted from the typical biosphere present when the Challenger Deep was shallower than it is now.

Although their shell may be so fine as to be transparent, it is nevertheless calcareous ; their shells are bilaterally symmetric and can vary widely in shape: coiled, needle-like, triangular, globulous.

Marine annelid worms in the family Serpulidae create shells made of calcareous tubes cemented onto other surfaces.

In 2011, researchers suggested that " extant marine invertebrates face the same synergistic effects of multiple stressors " that occurred during the end-Permian extinction, and that genera " with poorly buffered respiratory physiology and calcareous shells ", such as corals, were particularly vulnerable.

They are worm-like, lacking shells or distinct muscular feet ; they instead have scales and calcareous spines called sclerites, for movement.

The most common and often-found macrofossils are the very hard calcareous shells of articulate brachiopods ( that is, the everyday " lampshells ") and of mollusks ( such as the omnipresent clams, snails, mussels and oysters ).

How did it continue to produce eggs with calcareous shells on a calcium poor diet on a soil entirely lacking in limestone?

* Trypanites are elongated cylindrical borings in calcareous substrates such as shells, carbonate hardgrounds and limestones.

The machair forms a different kind of calcareous grassland, where fertile low-lying plains are formed on ground that is calcium-rich due to shell sand ( pulverised sea shells ).

When they died, the microscopic calcium carbonate plates, which formed their shells settled downward through the ocean water and accumulated on the ocean bottom to form a thick layer of calcareous ooze, which eventually became the Chalk Group.

Near the continental margins sediment is terrigenous, meaning derived from the land, unlike deep sea sediments which are made of tiny shells of marine organisms, usually calcareous and siliceous, or it can be made of volcanic ash and terrigenous sediments transported by turbidity currents.

Echinoderms have a mesodermal skeleton composed of calcareous plates or ossicles.

Their phylogenetic affiliation has been subject to changing interpretations, yet the consensus is growing that the archaeocyath was indeed a kind of sponge ,< ref name =" Rowland2001ArchaeocyathaPhylogeneticInterpretations "> Scuba divers have discovered living calcareous sponges, including one species that -- like the archaeocyathans -- is without spicules, thus morphologically similar to the archaeocyaths.

However it is uncertain which group of sponges is closest to Eumetazoa, as both calcareous sponges and a subgroup of demosponges called Homoscleromorpha have been nominated by different researchers.

The best-known haptophytes are coccolithophores, which have an exoskeleton of calcareous plates called coccoliths.

The precipitation being assisted with mosses and other vegetable structures, thus leaving cavities in the calcareous sinter after they have decayed.

Other algal groups, such as the red algae and green algae, have a number of calcareous members.

Some forms have a calcareous spicule that may be preserved as a fossil.

Much of the Hoosic and Housatonic River Valleys have underlying bedrock limestone and marble which contribute to calcareous wetlands, unique to Massachusetts.

Baby leopard geckos will have an “ egg tooth ,” a calcareous tip at the end of its snout to help break their egg shell.

The majority of prosobranchs have an operculum, a corneous or calcareous plate situated on the dorsal surface of the foot.

Species in this superfamily have a calcareous, bilaterally symmetrical conical or globular shell.

These outcrops are composed of basalt flows of 4 million years, although there have been discoveries of calcareous fossiliferous sediments of 4-6 million years.

Large, nearly idiomorphic crystals are sometimes found in argillaceous rocks ( altered calcareous shales ) that have suffered thermal metamorphism.

They are defined as mineral soils which contain no calcareous material anywhere within the soil, have less than 10 % weatherable minerals in the extreme top layer of soil, and have less than 35 % base saturation throughout the soil.

In the Upper Silurian series, the Leintwardine beds outcrop in the area and these consist of a calcareous sandstone which would have been suitable for making querns of a finer grade than could be obtained from Millstone grit, which was commonly used.

Querns of this calcareous sandstone have been found at Viroconium.

Granite and gneiss, in this condition of being undifferentiated, tend to have an acidi pH level ; whereas calcareous rock tends to be more basic.

Dinaric calcareous Silver Fir forests have an open structure which is environmentally sensible.

Near-shore areas along the northern margin have extensive areas of glacial till which forms a calcareous well-drained loam.

The UK cover of lowland calcareous grassland has suffered a sharp decline in extent since the middle of the 20th century.

The species is often found in wet calcareous habitats with low fertility, low canopy cover, and high plant diversity.

Although it is strongly associated with land that has had a long continuity of woodland or shrub cover, and only rarely occurs in extensive areas of secondary woodland, it is nevertheless able to colonise new deciduous woods on dry, calcareous soils at an annual rate of a metre or more.