Bioclasts are skeletal fossil fragments of once living marine or land organisms that are found in sedimentary rocks laid down in a marine environment—especially limestone varieties around the globe. some of which take on distinct textures and coloration from their predominate bioclasts—that

geologists A geologist is a scientist who studies the solid, liquid, and gaseous matter that constitutes Earth and other terrestrial planets, as well as the processes that shape them. Geologists usually study geology, earth science, or geophysics, althou ...

, archaeologists and

paleontologists Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of foss ...

use to date a rock strata to a particular

geological era The geologic time scale, or geological time scale, (GTS) is a representation of time based on the rock record of Earth. It is a system of chronological dating that uses chronostratigraphy (the process of relating strata to time) and geochrono ...

. In geology bioclasts are used for such things

relative dating Relative dating is the science of determining the relative order of past events (i.e., the age of an object in comparison to another), without necessarily determining their absolute age (i.e., estimated age). In geology, rock or superficial dep ...

purposes can be whole fossils or broken fragments of organisms. Their preponderance can give a rough guide to life diversity in the historic biosphere, but absolute counts much depend on water conditions such as the depth of the deposition, local currents, as well as wave strength in large body of water such as lakes. They can be used to study the age of the formation environment of the rocks that bioclasts finds itself in. one of the major contributions of bioclasts is that they form in regions where organisms lived and eventually died, over time. This is important because with the right conditions (pressure and temperature) there is a high possibility for

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ...

potential. This is due to the fact that hydrocarbons will eventually form due to the rich organic matter that has died and enriches the sediments. A vast chunk of the fossil records during the

Metazoan Animals are multicellular, eukaryotic organisms in the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, and go through an ontogenetic stage in ...

era were all bioclasts of '' Cloudina'' shells.

Cloudina

The ''Cloudina'' shells make their shell beds when they are filled into depressions that occur between thermobolitic domes and occasionally form in troughs between low amplitude current ripples that occur in

grainstone Under the Dunham classification (Dunham, 1962) system of limestones, a grainstone is defined as a grain-supported carbonate rock that contains less than 1% mud-grade material. This definition has recently been clarified as ''a carbonate-dominated ...

facies. These organisms have the best potential

index fossil Biostratigraphy is the branch of stratigraphy which focuses on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.Hine, Robert. “Biostratigraphy.” ''Oxford Reference: Dictionary of Bio ...

in the Late Ediacaran era. It has been determined that these organisms used to grow from a basally closed funnel. It would be also possible to see dichotomous branching off their vertical edges. They were once found in areas where the difference in water depths and transport in oceans is the major factors controlling the regions richness in a certain species. The areas of higher richness are found in medium to very fine sand and muddy bottoms with the bioclasts being at the shallowest stations. Studies of bioclasts in the fossil record revealed three main ''Cloudina'' morphology types: *In most scenarios, the organisms' basal end has a hemispherical shape but it shows no signs of attachment scars or anchoring and support structures. Basal end can range from 1 to 1.5 mm in diameter and 0.2 to 2 mm in length. *Tubes with a point, closed basal base. The length of this point can range from 0.05 to more than 1 mm. Its maximum diameter lies between 0.25 and 0.3 mm. *The basal element seems to be crushed or flattened. This is somewhat like the point morphology but it is blunter. The maximum diameter of the blunt basal varies from 0.15 to 0.35 mm, while its max length is 0.6 mm. There are some regions in the world where it is capable to actually see shells (bioclasts) of once living organisms within a geological structure called

lenticular bedding Lenticular bedding is a sedimentary bedding pattern displaying alternating layers of mud and sand. Formed during periods of slack water, mud suspended in the water is deposited on top of small formations of sand once the water's velocity has rea ...

. These beds are considerably thin, being only a few centimeters thick which are densely packed, poorly sorted. The shells are also randomly oriented and are recrystallized. By these characteristics it shows that the fragments have not been reworked long term, and have instead been reworked shortly after the death of the organism and was eventually deposited close to where they once lived. An area where you are able to see ancient sediments and rocks that have bioclast components dominating their matrix is a valley that once connected the

Miocene The Miocene ( ) is the first epoch (geology), geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and mea ...

Sommières Basin in southern France to the Mediterranean Sea. At this location the sediments are made of carbonate grains that have formed in the temperate factories. These grains have a wide variety in composition; they can be

barnacles A barnacle is a type of arthropod constituting the subclass Cirripedia in the subphylum Crustacea, and is hence related to crabs and lobsters. Barnacles are exclusively marine, and tend to live in shallow and tidal waters, typically in eros ...

bryozoa Bryozoa (also known as the Polyzoa, Ectoprocta or commonly as moss animals) are a phylum of simple, aquatic invertebrate animals, nearly all living in sedentary colonies. Typically about long, they have a special feeding structure called a ...

ns,

coralline algae Coralline algae are red algae in the order Corallinales. They are characterized by a thallus that is hard because of calcareous deposits contained within the cell walls. The colors of these algae are most typically pink, or some other shade of ...

and echinoids among others. When bioclasts are in its rock formation, meaning that they have gone through all the stages that sediments go through to reach its final phase, a whole rock unit, it is accompanied and mixed with variable amount of terrigenous material, glauconite particles and also phosphate grains. Studies done with the help of

plane polarized light Polarization ( also polarisation) is a property applying to transverse waves that specifies the geometrical orientation of the oscillations. In a transverse wave, the direction of the oscillation is perpendicular to the direction of motion of th ...

of several different rock formations showing the kinds of bioclastic mixtures that were found in this basin. In one rock unit there were barnacles, bryozoans, echinoid calcarentite, while in other rocks bryozoan-mollusk calcarenite and coralline algae were found. All of the rocks and bioclasts studied in this region are from the middle to upper

Pliocene The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58 In limestone rocks there are different types of possible bioclasts, depending on the region, time and the climate during the formation stage. Skeletal fragments: this type of limestone texture can be found as whole micro-fossils, whole large fossils or broken up fragments of larger fossils. This is the most common texture. The kinds of skeletal particles present depend upon the age of the rock and the paleoenvironmental conditions from the time they were deposited. With these different types of fossils, certain ones will be more dominant in a certain rock compared to others.

Trilobite Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the ...

skeletal fragments, for example, are a characteristic of early Paleozoic rock units but are not found in Cenozoic rocks, which is dominated by foraminifers. The climates and wave conditions play a role on the formation of skeletal fragments by that organisms like branching forms of bryozoan are fragile and are not found in high wave energy environments. Found in limestone units that have been deposited under quite less active water conditions.

Ooid Ooids are small (commonly ≤2 mm in diameter), spheroidal, "coated" (layered) sedimentary grains, usually composed of calcium carbonate, but sometimes made up of iron- or phosphate-based minerals. Ooids usually form on the sea floor, mo ...

s are coated carbonate grains that have some sort of a nucleus-a bioclast (shell fragment) in this case. They form where strong bottom currents and rough water conditions are present and where saturation levels of bicarbonates are high.

Mont Saint-Michel sediment

Sediments from Mont Saint-Michel region in France are a mixture of heterometric bioclastic debris and shell debris. This material has been reworked over time by the waves and ocean currents from the regions tidal flats. The shells are in the shape of a plate, curved and angular. With these characteristics it is easy for the bioclasts (shells) to be lifted and moved by the flow of the water currents. Joint density is when an object like a rock is being jointed by more matrix components rather than bioclasts, this is higher in rocks with a lower percent of figured grains and lower in rocks with higher amounts of figured grains (bioclasts). In other words, the ratio of bioclast grains influences the joint density. In all the regions that were under study, the joint density decreased while the number of bioclasts increased. This appears to inhibit the formation of joins in all carbonate rock formations.

References

{{Reflist Biostratigraphy Fossils Petrology