Siliceous ooze

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A centric diatom, magnified x150 Centric diatom (3075277530).jpg
A centric diatom, magnified x150

Siliceous ooze is a type of biogenic pelagic sediment located on the deep ocean floor. Siliceous oozes are the least common of the deep sea sediments, and make up approximately 15% of the ocean floor. [1] Oozes are defined as sediments which contain at least 30% skeletal remains of pelagic microorganisms. [2] Siliceous oozes are largely composed of the silica based skeletons of microscopic marine organisms such as diatoms and radiolarians. Other components of siliceous oozes near continental margins may include terrestrially derived silica particles and sponge spicules. Siliceous oozes are composed of skeletons made from opal silica SiO2·nH2O, as opposed to calcareous oozes, which are made from skeletons of calcium carbonate (CaCO3 · nH2O) organisms (i.e. coccolithophores). Silica (Si) is a bioessential element and is efficiently recycled in the marine environment through the silica cycle. [3] Distance from land masses, water depth and ocean fertility are all factors that affect the opal silica content in seawater and the presence of siliceous oozes.

Contents

A radiolarian, 160x magnified Radiolarian - Podocyrtis ampla (29391267424).jpg
A radiolarian, 160x magnified

Formation

Biological uptake of marine silica

Siliceous marine organisms, such as diatoms and radiolarians, use silica to form skeletons through a process known as biomineralization. Diatoms and radiolarians have evolved to uptake silica in the form of silicic acid, Si(OH)4. Once an organism has sequestered Si(OH)4 molecules in its cytoplasm, the molecules are transported to silica deposition vesicles where they are transformed into opal silica (B-SiO2). Diatoms and radiolarians have specialized proteins called silicon transporters that prevent mineralization during the sequestration and transportation of silicic acid within the organism. [4]

The chemical formula for biological uptake of silicic acid is:

Opal silica saturation state

The opal silica saturation state increases with depth in the ocean due to dissolution of sinking opal particles produced in surface ocean waters, but still remains low enough that the reaction to form biogenic opal silica remains thermodynamically unfavorable. Despite the unfavorable conditions, organisms can use dissolved silicic acid to make opal silica shells through biologically controlled biomineralization. [4] The amount of opal silica that makes it to the seafloor is determined by the rates of sinking, dissolution, and water column depth. [5]

Export of silica to the deep ocean

The dissolution rate of sinking opal silica (B-SiO2) in the water column affects the formation of siliceous ooze on the ocean floor. The rate of dissolution of silica is dependent on the saturation state of opal silica in the water column and the dependent on re-packaging of opal silica particles within larger particles from the surface ocean. [3] Re-packaging is the formation (and sometimes re-formation) of solid organic matter (usually fecal pellets) around opal silica. The organic matter protects against the immediate dissolution of opal silica into silicic acid, which allows for increased sedimentation of the seafloor. The opal compensation depth, similar to the carbonate compensation depth, occurs at approximately 6000 meters. Below this depth, there is greater dissolution of opal silica into silicic acid than formation of opal silica from silicic acid. Only four percent of opal silica produced in the surface ocean will, on average, be deposited to the seafloor, while the remaining 96% is recycled in the water column. [3]

Accumulation rates

Siliceous oozes accumulate over long timescales. In the open ocean, siliceous ooze accumulates at a rate of approximately 0.01 mol Si m−2 yr−1. [6] The fastest accumulation rates of siliceous ooze occur in the deep waters of the Southern Ocean (0.1 mol Si m−2 yr−1) where biogenic silica production and export is greatest. [7]  The diatom and radiolarian skeletons that make up Southern Ocean oozes can take 20 to 50 years to sink to the sea floor. [6] Siliceous particles may sink faster if they are encased in the fecal pellets of larger organisms. [6]  Once deposited, silica continues to dissolve and cycle, delaying long term burial of particles until a depth of 10–20 cm in the sediment layer is reached. [6]

Marine chert formation

When opal silica accumulates faster than it dissolves, it is buried and can provide a diagenetic environment for marine chert formation. [8]  The processes leading to chert formation have been observed in the Southern Ocean, where siliceous ooze accumulation is the fastest. [8]  Chert formation however can take tens of millions of years. [7] Skeleton fragments from siliceous organisms are subject to recrystallization and cementation. [8] Chert is the main fate of buried siliceous ooze and permanently removes silica from the oceanic silica cycle.

Geographic locations

World map showing the distribution of pelagic sediments. Green: siliceous sediments. White: Sediments of the continental margin. Blue: glacial sediments. Orange: land-formed sediments. Brown: pelagic clay. Yellow: calcareous sediments. Marinesediments.jpg
World map showing the distribution of pelagic sediments. Green: siliceous sediments. White: Sediments of the continental margin. Blue: glacial sediments. Orange: land-formed sediments. Brown: pelagic clay. Yellow: calcareous sediments.

Siliceous oozes form in upwelling areas that provide valuable nutrients for the growth of siliceous organisms living in oceanic surface waters. [9] A notable example is in the Southern ocean where consistent upwelling of Indian, Pacific, and Antarctic circumpolar deep water have resulted in a contiguous siliceous ooze that stretches around the globe. [7] There is a band of siliceous ooze that is the result of enhanced equatorial upwelling in Pacific Ocean sediments below the North Equatorial Current. In the subpolar North Pacific, upwelling occurs along the eastern and western sides of the basin from the Alaska current and the Oyashio Current. Siliceous ooze is present along the seafloor in these subpolar regions. Ocean basin boundary currents, such as the Humboldt Current and the Somali Current are examples of other upwelling currents that favor the formation of siliceous ooze. [8]

Siliceous ooze is often categorized based upon its composition. Diatomaceous oozes are predominantly formed of diatom skeletons and are typically found along continental margins in higher latitudes. [9] Diatomaceous oozes are present in the Southern Ocean and the North Pacific Ocean. [9] [10] Radiolarian oozes are made mostly of radiolarian skeletons and are located mainly in tropical equatorial and subtropical regions. [10] Examples of radiolarian ooze are the oozes of the equatorial region, subtropical Pacific region and the subtropical basin of the Indian Ocean. A small surface area of deep sea sediment is covered by radiolarian ooze in the equatorial East Atlantic basin. [10]

Role in the oceanic silica cycle

Diatom bloom in the South Atlantic Ocean, off the coast of Argentina Phytoplankton bloom off Argentina - November 9, 2013.jpg
Diatom bloom in the South Atlantic Ocean, off the coast of Argentina

Deep seafloor deposition in the form of ooze is the largest long-term sink of the oceanic silica cycle (6.3 ± 3.6 Tmol Si year−1). [11] As noted above, this ooze is diagenetically transformed into lithospheric marine chert. This sink is roughly balanced by silicate weathering and river inputs of silicic acid into the ocean. [11] Biogenic silica production in the photic zone is estimated to be 240 ± 40 Tmol si year −1. [10]  Rapid dissolution in the surface removes roughly 135 Tmol opal Si year−1, converting it back to soluble silicic acid that can be used again for biomineralization. [11] The remaining opal silica is exported to the deep ocean in sinking particles. [11] In the deep ocean, another 26.2 Tmol Si Year−1 is dissolved before being deposited to the sediments as opal silica. [11]  At the sediment water interface, over 90% of the silica is recycled and upwelled for use again in the photic zone. [11] The residence time on a biological timescale is estimated to be about 400 years, with each molecule of silica recycled 25 times before sediment burial. [11]

Siliceous oozes and carbon sequestration

Diatoms are primary producers that convert carbon dioxide into organic carbon via photosynthesis, and export organic carbon from the surface ocean to the deep sea via the biological pump. [12] Diatoms can therefore be a significant sink for carbon dioxide in surface waters. Due to the relatively large size of diatoms (when compared to other phytoplankton), they are able to take up more total carbon dioxide. Additionally, diatoms do not release carbon dioxide into the environment during formation of their opal silicate shells. [12] Phytoplankton that build calcium-carbonate shells (i.e. coccolithophores) release carbon dioxide as a byproduct during shell formation, making them a less efficient sink for carbon dioxide. [13] The opal silicate skeletons enhance the sinking velocity of diatomaceous particles (i.e. carbon) from the surface ocean to the seafloor. [14]  

Iron fertilization experiments

Atmospheric carbon dioxide levels have been increasing exponentially since the Industrial Revolution [13] and researchers are exploring ways to mitigate atmospheric carbon dioxide levels by increasing the uptake of carbon dioxide in the surface ocean via photosynthesis. [14] An increase in the uptake of carbon dioxide in the surface waters may lead to more carbon sequestration in the deep sea through the biological pump. The bloom dynamics of diatoms, their ballasting by opal silica, and various nutrient requirements have made diatoms a focus for carbon sequestration experiments.

Iron fertilization projects like the SERIES iron-enrichment experiments have introduced iron into ocean basins to test if this increases the rate of carbon dioxide uptake by diatoms and ultimately sinking it to the deep ocean. [13] Iron is a limiting nutrient for diatom photosynthesis in high-nutrient, low-chlorophyll areas of the ocean, thus increasing the amount of available iron can lead to a subsequent increase in photosynthesis, sometimes resulting in a diatom bloom. This increase removes more carbon dioxide from the atmosphere.  Although more carbon dioxide is being taken up, the carbon sequestration rate in deep sea sediments is generally low. Most of the carbon dioxide taken up during the process of photosynthesis is recycled within the surface layer several times before making it to the deep ocean to be sequestered. [13]

Paleo-oozes

Sediment cores, like these from the South Atlantic, allow paleoceanographers to handle and study paleo-oozes PS2492-2 0-1298 sediment-core hg.jpg
Sediment cores, like these from the South Atlantic, allow paleoceanographers to handle and study paleo-oozes

Before siliceous organisms

During the Precambrian, oceanic silica concentrations were an order of magnitude higher than in modern oceans. The evolution of biosilicification is thought to have emerged during this time period. [15] Siliceous oozes formed once silica-sequestering organisms such as radiolarians and diatoms began to flourish in the surface waters. [15]

Evolution of siliceous organisms

Radiolaria

Fossil evidence suggests that radiolarians first emerged during the late Cambrian as free-floating shallow water organisms. [16] They did not become prominent in the fossil record until the Ordovician. [16] Radiolarites evolved in upwelling regions in areas of high primary productivity and are the oldest known organisms capable of shell secretion. [17] The remains of radiolarians are preserved in chert; a byproduct of siliceous ooze transformation. [18] Major speciation events of radiolarians occurred during the Mesozoic. [19] Many of those species are now extinct in the modern ocean. [16] Scientists hypothesize that competition with diatoms for dissolved silica during the Cenozoic is the likely cause for the mass extinction of most radiolarian species.

Diatoms

The oldest well-preserved diatom fossils have been dated to the beginning of the Jurassic period. However, the molecular record suggests diatoms evolved at least 250 million years ago during the Triassic. [20] As new species of diatoms evolved and spread, oceanic silica levels began to decrease. [19] Today, there are an estimated 100,000 species of diatoms, most of which are microscopic (2-200 μm). [19] Some early diatoms were larger, and could be between 0.2 and 22mm in diameter. [17]

The earliest diatoms were radial centrics, and lived in shallow water close to shore. [19] These early diatoms were adapted to live on the benthos, as their outer shells were heavy and prevented them from free-floating. [19] Free-floating diatoms, known as bipolar and multipolar centrics, began evolving approximately 100 million years ago during the Cretaceous. [19] Fossil diatoms are preserved in diatomite (also known as diatomaceous earth), which is one of the by-products of the transformation from ooze to rock formation. [19] As diatomaceous particles began to sink to the ocean floor, carbon and silica were sequestered along continental margins. The carbon sequestered along continental margins has become the major petroleum reserves of today. [12] Diatom evolution marks a time in Earth's geologic history of significant removal of carbon dioxide from the atmosphere while simultaneously increasing atmospheric oxygen levels. [12]

How scientists use paleo-ooze

Paleoceanographers study prehistoric oozes to learn about changes in the oceans over time. [9] The sediment distribution and deposition patterns of oozes inform scientists about prehistoric areas of the oceans that exhibited prime conditions for the growth of siliceous organisms. [9]

Scientists examine paleo-ooze by taking cores of deep sea sediments. [9] Sediment layers in these cores reveal the deposition patterns of the ocean over time. Scientists use paleo-oozes as tools so that they can better infer the conditions of the paleo oceans. [9] Paleo-ooze accretion rates can be used to determine deep sea circulation, tectonic activity, and climate at a specific point in time. Oozes are also useful in determining the historical abundances of siliceous organisms. [21]

Burubaital Formation

The Burubatial Formation, located in the West Balkhash region of Kazakhstan, is the oldest known abyssal biogenic deposit. [20] The Burubaital Formation is primarily composed of chert which was formed over a period of 15 million years (late Cambrian-middle Ordovician). [20] It is likely that these deposits were formed in an upwelling region in subequatorial latitudes. [20] The Burubaital Formation is largely composed of radiolarites, as diatoms had yet to evolve at the time of its formation. The Burubaital deposits have led researchers to believe that radiolaria played a significant role in the late Cambrian silica cycle. [20] The late Cambrian (497-485.4 mya) marks a time of transition for marine biodiversity and is the beginning of ooze accumulation on the seafloor. [20]

Distribution shifts during the Miocene

A shift in the geographical distribution of siliceous oozes occurred during the Miocene. [9] Sixteen million years ago there was a gradual decline in siliceous ooze deposits in the North Atlantic and a concurrent rise in siliceous ooze deposits in the North Pacific. [9] Scientists speculate that this regime shift may have been caused by the introduction of Nordic Sea Overflow Water, which contributed to the formation of North Atlantic Deep Water (NADW). The formation of Antarctic Bottom Water (AABW) occurred at approximately the same time as the formation of NADW. [9] The formation of NADW and AABW dramatically transformed the ocean, and resulted in a spatial population shift of siliceous organisms. [9]

Paleocene plankton blooms

The Cretaceous-Tertiary boundary was a time of global mass extinction, commonly referred to as the K-T mass extinction. While most organisms were disappearing, marine siliceous organisms were thriving in the early Paleocene seas. One such example occurred in the waters near Marlborough, New Zealand. [22] Paleo-ooze deposits indicate that there was a rapid growth of both diatoms and radiolarians at this time. Scientists believe that this period of high biosiliceous productivity is linked to global climatic changes. This boom in siliceous plankton was greatest during the first one million years of the Tertiary period and is thought to have been fueled by enhanced upwelling in response to a cooling climate and increased nutrient cycling due to a change in sea level. [22]

See also

Related Research Articles

<span class="mw-page-title-main">Diatom</span> Class of microalgae, found in the oceans, waterways and soils of the world

A diatom is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion tonnes of silicon each year from the waters in which they live, and constitute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of fresh-water lakes.

<span class="mw-page-title-main">Chert</span> Hard, fine-grained sedimentary rock composed of cryptocrystalline silica

Chert is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood.

<span class="mw-page-title-main">Radiolaria</span> Phylum of single-celled organisms

The Radiolaria, also called Radiozoa, are protozoa 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 ectoplasm. The elaborate mineral skeleton is usually made of silica. They are found as zooplankton throughout the global ocean. As zooplankton, radiolarians are primarily heterotrophic, but many have photosynthetic endosymbionts and are, therefore, considered mixotrophs. The skeletal remains of some types of radiolarians make up a large part of the cover of the ocean floor as siliceous ooze. Due to their rapid change as species and intricate skeletons, radiolarians represent an important diagnostic fossil found from the Cambrian onwards.

<span class="mw-page-title-main">Biological pump</span> Carbon capture process in oceans

The biological pump (or ocean carbon biological pump or marine biological carbon pump) is the ocean's biologically driven sequestration of carbon from the atmosphere and land runoff to the ocean interior and seafloor sediments. In other words, it is a biologically mediated process which results in the sequestering of carbon in the deep ocean away from the atmosphere and the land. The biological pump is the biological component of the "marine carbon pump" which contains both a physical and biological component. It is the part of the broader oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO3) formed into shells by certain organisms such as plankton and mollusks (carbonate pump).

<span class="mw-page-title-main">Diatomaceous earth</span> Soft, siliceous sedimentary rock

Diatomaceous earth, diatomite, celite or kieselgur/kieselguhr is a naturally occurring, soft, siliceous sedimentary rock that can be crumbled into a fine white to off-white powder. It has a particle size ranging from more than 3 mm to less than 1 μm, but typically 10 to 200 μm. Depending on the granularity, this powder can have an abrasive feel, similar to pumice powder, and has a low density as a result of its high porosity. The typical chemical composition of oven-dried diatomaceous earth is 80–90% silica, with 2–4% alumina, and 0.5–2% iron oxide.

<span class="mw-page-title-main">Microfossil</span> Fossil that requires the use of a microscope to see it

A microfossil is a fossil that is generally between 0.001 mm and 1 mm in size, the visual study of which requires the use of light or electron microscopy. A fossil which can be studied with the naked eye or low-powered magnification, such as a hand lens, is referred to as a macrofossil.

High-nutrient, low-chlorophyll (HNLC) regions are regions of the ocean where the abundance of phytoplankton is low and fairly constant despite the availability of macronutrients. Phytoplankton rely on a suite of nutrients for cellular function. Macronutrients are generally available in higher quantities in surface ocean waters, and are the typical components of common garden fertilizers. Micronutrients are generally available in lower quantities and include trace metals. Macronutrients are typically available in millimolar concentrations, while micronutrients are generally available in micro- to nanomolar concentrations. In general, nitrogen tends to be a limiting ocean nutrient, but in HNLC regions it is never significantly depleted. Instead, these regions tend to be limited by low concentrations of metabolizable iron. Iron is a critical phytoplankton micronutrient necessary for enzyme catalysis and electron transport.

The carbonate compensation depth (CCD) is the depth, in the oceans, at which the rate of supply of calcium carbonates matches the rate of solvation. That is, solvation 'compensates' supply. Below the CCD solvation is faster, so that carbonate particles dissolve and the carbonate shells (tests) of animals are not preserved. Carbonate particles cannot accumulate in the sediments where the sea floor is below this depth.

<span class="mw-page-title-main">Pelagic sediment</span> Fine-grained sediment that accumulates on the floor of the open ocean

Pelagic sediment or pelagite is a fine-grained sediment that accumulates as the result of the settling of particles to the floor of the open ocean, far from land. These particles consist primarily of either the microscopic, calcareous or siliceous shells of phytoplankton or zooplankton; clay-size siliciclastic sediment; or some mixture of these. Trace amounts of meteoric dust and variable amounts of volcanic ash also occur within pelagic sediments. Based upon the composition of the ooze, there are three main types of pelagic sediments: siliceous oozes, calcareous oozes, and red clays.

Lithogenic silica (LSi) is silica (SiO2) derived from terrigenous rock (Igneous, metamorphic, and sedimentary), lithogenic sediments composed of the detritus of pre-existing rock, volcanic ejecta, extraterrestrial material, and minerals such silicate. Silica is the most abundant compound in the Earth's crust (59%) and the main component of almost every rock (>95%).

<span class="mw-page-title-main">Biogenic silica</span> Type of biogenic mineral

Biogenic silica (bSi), also referred to as opal, biogenic opal, or amorphous opaline silica, forms one of the most widespread biogenic minerals. For example, microscopic particles of silica called phytoliths can be found in grasses and other plants.

<span class="mw-page-title-main">Radiolarite</span> Type of sedimentary rock

Radiolarite is a siliceous, comparatively hard, fine-grained, chert-like, and homogeneous sedimentary rock that is composed predominantly of the microscopic remains of radiolarians. This term is also used for indurated radiolarian oozes and sometimes as a synonym of radiolarian earth. However, radiolarian earth is typically regarded by Earth scientists to be the unconsolidated equivalent of a radiolarite. A radiolarian chert is well-bedded, microcrystalline radiolarite that has a well-developed siliceous cement or groundmass.

<span class="mw-page-title-main">Marine sediment</span>

Marine sediment, or ocean sediment, or seafloor sediment, are deposits of insoluble particles that have accumulated on the seafloor. These particles have their origins in soil and rocks and have been transported from the land to the sea, mainly by rivers but also by dust carried by wind and by the flow of glaciers into the sea. Additional deposits come from marine organisms and chemical precipitation in seawater, as well as from underwater volcanoes and meteorite debris.

Hemipelagic sediment, or hemipelagite, is a type of marine sediment that consists of clay and silt-sized grains that are terrigenous and some biogenic material derived from the landmass nearest the deposits or from organisms living in the water. Hemipelagic sediments are deposited on continental shelves and continental rises, and differ from pelagic sediment compositionally. Pelagic sediment is composed of primarily biogenic material from organisms living in the water column or on the seafloor and contains little to no terrigenous material. Terrigenous material includes minerals from the lithosphere like feldspar or quartz. Volcanism on land, wind blown sediments as well as particulates discharged from rivers can contribute to Hemipelagic deposits. These deposits can be used to qualify climatic changes and identify changes in sediment provenances.

Reverse weathering generally refers to the formation of a clay neoformation that utilizes cations and alkalinity in a process unrelated to the weathering of silicates. More specifically reverse weathering refers to the formation of authigenic clay minerals from the reaction of 1) biogenic silica with aqueous cations or cation bearing oxides or 2) cation poor precursor clays with dissolved cations or cation bearing oxides.

<span class="mw-page-title-main">Silica cycle</span> Biogeochemical cycle

The silica cycle is the biogeochemical cycle in which biogenic silica is transported between the Earth's systems. Silicon is considered a bioessential element and is one of the most abundant elements on Earth. The silica cycle has significant overlap with the carbon cycle and plays an important role in the sequestration of carbon through continental weathering, biogenic export and burial as oozes on geologic timescales.

<span class="mw-page-title-main">Protist shell</span> Protective shell of a type of eukaryotic organism

Many protists have protective shells or tests, usually made from silica (glass) or calcium carbonate (chalk). Protists are a diverse group of eukaryote organisms that are not plants, animals, or fungi. They are typically microscopic unicellular organisms that live in water or moist environments.

<span class="mw-page-title-main">Silicification</span> Geological petrification process

In geology, silicification is a petrification process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO2). Silica is a naturally existing and abundant compound found in organic and inorganic materials, including Earth's crust and mantle. There are a variety of silicification mechanisms. In silicification of wood, silica permeates into and occupies cracks and voids in wood such as vessels and cell walls. The original organic matter is retained throughout the process and will gradually decay through time. In the silicification of carbonates, silica replaces carbonates by the same volume. Replacement is accomplished through the dissolution of original rock minerals and the precipitation of silica. This leads to a removal of original materials out of the system. Depending on the structures and composition of the original rock, silica might replace only specific mineral components of the rock. Silicic acid (H4SiO4) in the silica-enriched fluids forms lenticular, nodular, fibrous, or aggregated quartz, opal, or chalcedony that grows within the rock. Silicification happens when rocks or organic materials are in contact with silica-rich surface water, buried under sediments and susceptible to groundwater flow, or buried under volcanic ashes. Silicification is often associated with hydrothermal processes. Temperature for silicification ranges in various conditions: in burial or surface water conditions, temperature for silicification can be around 25°−50°; whereas temperatures for siliceous fluid inclusions can be up to 150°−190°. Silicification could occur during a syn-depositional or a post-depositional stage, commonly along layers marking changes in sedimentation such as unconformities or bedding planes.

<span class="mw-page-title-main">Silicon isotope biogeochemistry</span> The study of environmental processes using the relative abundance of Si isotopes

Silicon isotope biogeochemistry is the study of environmental processes using the relative abundance of Si isotopes. As the relative abundance of Si stable isotopes varies among different natural materials, the differences in abundance can be used to trace the source of Si, and to study biological, geological, and chemical processes. The study of stable isotope biogeochemistry of Si aims to quantify the different Si fluxes in the global biogeochemical silicon cycle, to understand the role of biogenic silica within the global Si cycle, and to investigate the applications and limitations of the sedimentary Si record as an environmental and palaeoceanographic proxy.

Biogenous ooze is marine sediment that accumulates on the seafloor and is a byproduct of the death and sink of the skeletal remains of marine organisms.

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  17. 1 2 Kemp, A. E. S.; Pearce, R. B.; Grigorov, I.; Rance, J.; Lange, C. B.; Quilty, P.; Salter, I. (2006-10-13). "Production of giant marine diatoms and their export at oceanic frontal zones: Implications for Si and C flux from stratified oceans" (PDF). Global Biogeochemical Cycles. 20 (4): n/a. Bibcode:2006GBioC..20.4S04K. doi:10.1029/2006gb002698. ISSN   0886-6236. S2CID   39371561.
  18. ↑ Danelian, Taniel; Aitchison, Jonathan C.; Noble, Paula; Caridroit, Martial; Suzuki, Noritoshi; O'Dogherty, Luis (September 2017). "Historical insights on nearly 130 years of research on Paleozoic radiolarians". Geodiversitas. 39 (3): 351–361. doi:10.5252/g2017n3a2. ISSN   1280-9659. S2CID   134007679.
  19. 1 2 3 4 5 6 7 Renaudie, Johan; Drews, Effi-Laura; Böhne, Simon (2018-08-20). "The Paleocene record of marine diatoms in deep-sea sediments". Fossil Record. 21 (2): 183–205. doi: 10.5194/fr-21-183-2018 . ISSN   2193-0074.
  20. 1 2 3 4 5 6 Tolmacheva, Tatiana J.; Danelian, Taniel; Popov, Leonid E. (2001). "Evidence for 15 m.y. of continuous deep-sea biogenic siliceous sedimentation in early Paleozoic oceans". Geology. 29 (8): 755. Bibcode:2001Geo....29..755T. doi:10.1130/0091-7613(2001)029<0755:efmyoc>2.0.co;2. ISSN   0091-7613.
  21. ↑ KELLER, GERTA; BARRON, JOHN A. (1983). "Paleoceanographic implications of Miocene deep-sea hiatuses". Geological Society of America Bulletin. 94 (5): 590. Bibcode:1983GSAB...94..590K. doi:10.1130/0016-7606(1983)94<590:piomdh>2.0.co;2.[ verification needed ]
  22. 1 2 Hollis, C. J.; Rodgers, K. A.; Parker, R. J. (1995-09-01). "Siliceous plankton bloom in the earliest Tertiary of Marlborough, New Zealand". Geology. 23 (9): 835–838. Bibcode:1995Geo....23..835H. doi:10.1130/0091-7613(1995)023<0835:SPBITE>2.3.CO;2. ISSN   0091-7613.
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