Biogenous ooze is

marine sediment Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles either have their origins in soil and Rock (geology), rocks and have been Sediment transport, ...

that accumulates on the

seafloor The seabed (also known as the seafloor, sea floor, ocean floor, and ocean bottom) is the bottom of the ocean. All floors of the ocean are known as seabeds. The structure of the seabed of the global ocean is governed by plate tectonics. Most of ...

and is a byproduct of the death and sink of the skeletal remains of marine organisms.

Formation and composition

Biogenous ooze consists of

organic compound Some chemical authorities define an organic compound as a chemical compound that contains a carbon–hydrogen or carbon–carbon bond; others consider an organic compound to be any chemical compound that contains carbon. For example, carbon-co ...

s, usually in the form of

microorganism A microorganism, or microbe, is an organism of microscopic scale, microscopic size, which may exist in its unicellular organism, single-celled form or as a Colony (biology)#Microbial colonies, colony of cells. The possible existence of unseen ...

tests Test(s), testing, or TEST may refer to: * Test (assessment), an educational assessment intended to measure the respondents' knowledge or other abilities Arts and entertainment * ''Test'' (2013 film), an American film * ''Test'' (2014 film) ...

that fall from closer to the

ocean surface The sea surface microlayer (SML) is the boundary interface between the atmosphere and ocean, covering about 70% of Earth's surface. With an operationally defined thickness between 1 and , the SML has physicochemical and biological properties tha ...

to the ocean floor after death. For marine sediment to receive this classification, it must be composed of more than 30% skeletal material which also includes teeth and shells.

Types of biogenous sediments

The two primary types of ooze are siliceous, which is composed primarily of

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

(), and

calcareous Calcareous () is an adjective meaning "mostly or partly composed of calcium carbonate", in other words, containing lime (mineral), lime or being chalky. The term is used in a wide variety of Science, scientific disciplines. In zoology ''Calcare ...

carbonate A carbonate is a salt of carbonic acid, (), characterized by the presence of the carbonate ion, a polyatomic ion with the formula . The word "carbonate" may also refer to a carbonate ester, an organic compound containing the carbonate group ...

, which is mostly

calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ...

(). In an area in which biogenous is the dominant sediment type, the composition of microorganisms in that location determines to which category it is classified. The primary types of microorganisms used to classify ooze are

radiolarian The Radiolaria, also called Radiozoa, are unicellular eukaryotes of diameter 0.1–0.2 mm that produce intricate mineral skeletons, typically with a central capsule dividing the cell into the inner and outer portions of endoplasm and ecto ...

s and

diatom A diatom (Neo-Latin ''diatoma'') is any member of a large group comprising several Genus, genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of Earth's B ...

s (siliceous), and

coccolithophore Coccolithophores, or coccolithophorids, are single-celled organisms which are part of the phytoplankton, the autotrophic (self-feeding) component of the plankton community. They form a group of about 200 species, and belong either to the kingdom ...

s and

foraminifera Foraminifera ( ; Latin for "hole bearers"; informally called "forams") are unicellular organism, single-celled organisms, members of a phylum or class (biology), class of Rhizarian protists characterized by streaming granular Ectoplasm (cell bio ...

(calcareous). The presence of these organisms can lead to sub-classifications based upon their dominance.

Siliceous

Along some areas of

terrigenous sediment In oceanography, terrigenous sediments are those derived from the erosion of rocks on land; that is, they are derived from ''terrestrial'' (as opposed to marine) environments. Consisting of sand, mud, and silt carried to sea by rivers, their c ...

are

siliceous ooze Siliceous ooze is a type of biogenic pelagic sediment located on the Abyssal, deep ocean floor. Siliceous oozes are the least common of the deep sea sediments, and make up approximately 15% of the ocean floor. Oozes are defined as sediments which ...

. This is due to siliceous ooze being more abundant in areas of cooler, more nutrient rich water. The nutrients allow for the abundant growth of microorganisms, and silica dissolves slower in cooler water, allowing adequate time for deposition. Radiolarians and diatoms are the primary plankton used to classify siliceous ooze. Radiolaria is a part of a diverse group of plankton with transparent skeletons and come in a variety of shapes. They range in size from . They are most abundant in regions near the equator as well as subpolar regions. Diatoms are single-celled siliceous algae that are a major part of phytoplankton. They come in pinnate and centric shapes and range in size from . Siliceous oozes lean towards dissolution in warmer waters with lower pressures, meaning they are best preserved in deep ocean.

Calcareous

Calcareous sediments are more common in the

deep ocean The deep sea is broadly defined as the ocean depth where light begins to fade, at an approximate depth of or the point of transition from continental shelves to continental slopes. Conditions within the deep sea are a combination of low tempe ...

, comprising about half of its surface area. However, the deepest parts of the ocean are dominated by

abyssal The abyssal zone or abyssopelagic zone is a layer of the pelagic zone of the ocean. The word ''abyss'' comes from the Greek word (), meaning "bottomless". At depths of , this zone remains in perpetual darkness. It covers 83% of the total area o ...

clay instead. Calcareous debris are mostly composed of forminiferal ooze and make about almost 50% of sediments on the seafloor. Calcareous oozes also have a terrigenous fraction made up of quartz and clay minerals. This is because

calcareous ooze 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. In zoology ''Calcareous'' is used as an adje ...

is limited by the calcite compensation depth (CCD). The CCD refers to the depth at which the rate of supply of calcareous deposits equal the rate of dissolution and varies around the world and is based upon temperature. The CCD occurs at approximately 4000-5000 meters deep because

dissolves faster in cooler water, so as water temperature decreases with depth, its deposition rate also decreases. The temperature dependence also means that calcareous ooze is more likely to be present in warmer waters, which also leads to its dominance in shallow areas surrounding

tropical The tropics are the regions of Earth surrounding the equator, where the sun may shine directly overhead. This contrasts with the temperate or polar regions of Earth, where the Sun can never be directly overhead. This is because of Earth's ax ...

and

subtropical The subtropical zones or subtropics are geographical zone, geographical and Köppen climate classification, climate zones immediately to the Northern Hemisphere, north and Southern Hemisphere, south of the tropics. Geographically part of the Ge ...

islands that do not have much terrigenous sediment runoff. Another important depth is the lysocline, also known as the depth where well preserved calcareous grain are separated from poorly preserved ones. The lysocline occurs at approximately deep. Calcareous grains above the lysocline are able to accumulate without threat of dissolution.

Distribution

Despite the common association between shallow water and high productivity, biogenous ooze is not as common around

continental shelves A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island ...

. This is due to the transport of

s by methods such as rivers and wind from the continents. The terrigenous sediment buries most accumulated organic material, preventing enough biological material from being present for it to be classified as biogenous. Distribution of biogenous sediments is determined by three factors: # Distance from continents and land masses, the closer these sediments are to land masses the higher the likelihood of being diluted by terrigenous materials # Water depth, which affects the likelihood of preservation of the sediments # Ocean fertility, which helps dictate productivity in surface oceans Accumulation rate of biogenous ooze is about 1cm per 1000 years.

Determination of climate history

In the fields of

paleoceanography Paleoceanography is the study of the history of the oceans in the geologic past with regard to circulation, chemistry, biology, geology and patterns of sedimentation and biological productivity. Paleoceanographic studies using environment model ...

and

paleoclimatology Paleoclimatology ( British spelling, palaeoclimatology) is the scientific study of climates predating the invention of meteorological instruments, when no direct measurement data were available. As instrumental records only span a tiny part of ...

, biogenous ooze and other pelagic sediments can be collected form the seafloor and used to reconstruct Earth's climate for the last 100 million years. Reconstruction can be done through analysis of biogeography, stable isotopes along with important oxygen and carbon isotopes.

References

{{reflist Oceanography Sediments Sedimentary rocks