Sapropel (a contraction of Ancient Greek words ''sapros'' and ''pelos'', meaning

putrefaction Putrefaction is the fifth stage of death, following pallor mortis, livor mortis, algor mortis, and rigor mortis. This process references the breaking down of a body of an animal Post-mortem interval, post-mortem. In broad terms, it can be view ...

and mud (or clay), respectively) is a term used in

marine geology Marine geology or geological oceanography is the study of the history and structure of the ocean floor. It involves geophysical, Geochemistry, geochemical, Sedimentology, sedimentological and paleontological investigations of the ocean floor and ...

to describe dark-coloured

sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...

s that are rich in

organic matter Organic matter, organic material or natural organic matter is the large source of carbon-based compounds found within natural and engineered, terrestrial, and aquatic environments. It is matter composed of organic compounds that have come fro ...

. Organic

carbon Carbon () is a chemical element; it has chemical symbol, symbol C and atomic number 6. It is nonmetallic and tetravalence, tetravalent—meaning that its atoms are able to form up to four covalent bonds due to its valence shell exhibiting 4 ...

concentrations in sapropels commonly exceed 2 wt.% in weight. The term sapropel events may also refer to cyclic oceanic

anoxic event An anoxic event describes a period wherein large expanses of Earth's oceans were depleted of dissolved oxygen (O2), creating toxic, euxinic ( anoxic and sulfidic) waters. Although anoxic events have not happened for millions of years, the geol ...

s (OAE), in particular those affecting the

Mediterranean Sea The Mediterranean Sea ( ) is a sea connected to the Atlantic Ocean, surrounded by the Mediterranean basin and almost completely enclosed by land: on the east by the Levant in West Asia, on the north by Anatolia in West Asia and Southern Eur ...

with a periodicity of about 21,000 years.

Formation

Sapropels have been recorded in the Mediterranean sediments since the closure of the Eastern

Tethys Ocean The Tethys Ocean ( ; ), also called the Tethys Sea or the Neo-Tethys, was a prehistoric ocean during much of the Mesozoic Era and early-mid Cenozoic Era. It was the predecessor to the modern Indian Ocean, the Mediterranean Sea, and the Eurasia ...

13.5 million years ago. The formation of sapropel events in the

occurs approximately every 21,000 years and last between 3,000 and 5,000 years. The first identification of these events occurred in the mid-20th century. Since then, their formulative conditions of have been investigated. The occurrence of sapropels has been related to the Earth's orbital parameters (

Milankovitch cycles Milankovitch cycles describe the collective effects of changes in the Earth's movements on its climate over thousands of years. The term was coined and named after the Serbian geophysicist and astronomer Milutin Milanković. In the 1920s, he pr ...

). The

precession Precession is a change in the orientation of the rotational axis of a rotating body. In an appropriate reference frame it can be defined as a change in the first Euler angle, whereas the third Euler angle defines the rotation itself. In o ...

cycles influence the African monsoon, which influences the Mediterranean circulation through increases in freshwater inputs. Sapropels develop during episodes of reduced oxygen availability in bottom waters, such as an oceanic

(OAE). Most studies of formational mechanisms infer some degree of reduced deep-water circulation. Oxygen can only reach the deep sea by new deep-water formation and consequent "ventilation" of deep basins. There are two main causes of OAE: reduction in deep-water circulation or raised oxygen demand from upper level. A reduction in deep-water circulation will eventually lead to a serious decrease in deep-water oxygen concentrations due to biochemical oxygen demand associated with the decay of organic matter. This sinks into the deep sea as a result of export production from surface waters. Oxygen depletion in bottom waters then favors the enhanced preservation of the

during burial by the sediments. Organic-rich sediments may also form in well-ventilated settings that have highly productive surface waters; here the high surface demand simply extracts the oxygen before it can enter the deep circulation current thus depriving the bottom waters of oxygen.

Significance

Sapropelic deposits from global ocean anoxic events form important oil

source rock In petroleum geology, source rock is a sedimentary rock which has generated hydrocarbons or which has the potential to generate hydrocarbons. Source rocks are one of the necessary elements of a working petroleum system. They are organic-rich sedim ...

s. Detailed process studies of sapropel formation have concentrated on the fairly recent eastern Mediterranean deposits, the last of which occurred between 9.5 and 5.5 thousand years ago. The Mediterranean sapropels of the

Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...

reflect increased density stratification in the isolated Mediterranean basin. They record a higher organic carbon concentration than non-sapropel times; an increase in the δ¹⁵N and corresponding decrease in δ¹³C tells of rising productivity as a result of nitrogen fixation. This effect is more pronounced further east in the basin, suggesting that increased precipitation was most pronounced at that end of the sea.

In the Black Sea

In the

Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...

, sapropels are distributed at a depth of 500 to 2200 m, and in different morpholithological zones they have different thicknesses. Deep sea sediments are called the sediments formed outside the zone of influence of hydrogenic factors such as wind-driven waves and internal waves as well as of the transgressive and regressive cycles of the Black Sea basin. Here, under the conditions of relative stagnation, can be observed uninterrupted cross-sections because this area was under the sea level during the entire Pleistocene and

Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

. Deep sea organogenic mineral sediments (DSOMS) are those sediments that contain more than 3% organic carbon. The sapropels form a single horizon with constant thickness typical of the Black Sea basin. Analogues of the sapropels on the

continental shelf 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 islan ...

and the upper part of the

continental slope A continental margin is the outer edge of continental crust abutting oceanic crust under coastal waters. It is one of the three major zones of the ocean floor, the other two being deep-ocean basins and mid-ocean ridges. The continental margi ...

are the green aleurite-

pelite A pelite () or metapelite is a metamorphism, metamorphosed fine-grained sedimentary rock, i.e. mudstone or siltstone. The term was earlier used by geologists to describe a clay-rich, fine-grained clastic sediment or sedimentary rock, i.e. mud or ...

, oozes with accumulation of plant

detritus In biology, detritus ( or ) is organic matter made up of the decomposition, decomposing remains of organisms and plants, and also of feces. Detritus usually hosts communities of microorganisms that colonize and decomposition, decompose (Reminera ...

and decomposed shells of '' Mytilus galloprovincialis''. The transition from aleurite-pelitic oozes to sapropels is facial. The organic matter in the sapropels is of heterogeneous origin. They are composed primarily of planktogenic organisms (about 80%) and continental organic matter (20%). The

plankton Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are ca ...

ic organisms are well preserved in most cases under the conditions of the

hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...

zone. The main components of the sapropels are the

dinoflagellate The Dinoflagellates (), also called Dinophytes, are a monophyletic group of single-celled eukaryotes constituting the phylum Dinoflagellata and are usually considered protists. Dinoflagellates are mostly marine plankton, but they are also commo ...

cysts,

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 ...

algae, coccolithophorids, peridiniales. The mineral part of sapropel muds is represented by a poly-component mixture of

clay minerals Clay minerals are hydrous aluminium phyllosilicates (e.g. kaolin, Al2 Si2 O5( OH)4), sometimes with variable amounts of iron, magnesium, alkali metals, alkaline earths, and other cations found on or near some planetary surfaces. Clay mineral ...

. The minerals

illite Illite, also called hydromica or hydromuscovite, is a group of closely related non-expanding clay minerals. Illite is a secondary mineral precipitate, and an example of a phyllosilicate, or layered alumino-silicate. Its structure is a 2:1 sandw ...

and

montmorillonite Montmorillonite is a very soft phyllosilicate group of minerals that form when they precipitate from water solution as microscopic crystals, known as clay. It is named after Montmorillon in France. Montmorillonite, a member of the smectite grou ...

predominate,

chlorite The chlorite ion, or chlorine dioxide anion, is the halite (oxyanion), halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as s ...

and

kaolinite Kaolinite ( ; also called kaolin) is a clay mineral, with the chemical composition Al2 Si2 O5( OH)4. It is a layered silicate mineral, with one tetrahedral sheet of silica () linked through oxygen atoms to one octahedral sheet of alumina () ...

occur in subordinate quantities. Individual grains of

quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...

feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...

volcanic glass Volcanic glass is the amorphous (uncrystallized) product of rapidly cooling magma. Like all types of glass, it is a state of matter intermediate between the closely packed, highly ordered array of a crystal and the highly disordered array of liqu ...

and others are rarely found among them.

Carbonate mineral Carbonate minerals are those minerals containing the carbonate ion, . Carbonate divisions Anhydrous carbonates *Calcite group: trigonal **Calcite CaCO3 **Gaspéite (Ni,Mg,Fe2+)CO3 **Magnesite MgCO3 **Otavite CdCO3 **Rhodochrosite MnCO3 **Sider ...

s are mainly represented by

calcite Calcite is a Carbonate minerals, carbonate mineral and the most stable Polymorphism (materials science), polymorph of calcium carbonate (CaCO3). It is a very common mineral, particularly as a component of limestone. Calcite defines hardness 3 on ...

and dolomite. It is generally accepted that the main source of hydrogen sulfide in the Black Sea today are the processes of anaerobic decomposition of organic matter by

sulfate-reducing bacteria Sulfate-reducing microorganisms (SRM) or sulfate-reducing prokaryotes (SRP) are a group composed of sulfate-reducing bacteria (SRB) and sulfate-reducing archaea (SRA), both of which can perform anaerobic respiration utilizing sulfate () as termina ...

(SRB). The organic substance that is fixed at the bottom of the basin in the form of organogenic-mineral sediments (sapropels) is a product of the mass extinction of the plankton biomass as a result of the Black Sea flood. There is an excess of a huge amount of organic matter, which creates favorable conditions for the development of bacterial sulfate reduction. Dimitrov D. (2010).
Geology and Non-traditional resources of the Black Sea
'. LAP – Lambert Academic Publishing. . 244 p.

Bibcode The bibcode (also known as the refcode) is a compact identifier used by several astronomical data systems to uniquely specify literature references. Adoption The Bibliographic Reference Code (refcode) was originally developed to be used in SIM ...

br>2012QuInt.279R.119D
doibr>10.1016/j.quaint.2012.07.527
/ref> Sapropel 2009

Non-conventional source of energy

Bulgarian Professor Petko Dimitrov is the creator of the idea for the application of sapropel sediments from the bottom of the Black Sea as a natural ecological

fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...

and biological products. Dimitrov P., et al. (2000)
Amendment for soils and substrates
doibr>10.13140/RG.2.2.28181.63205
Patent BG No. 63868, Register No. 104106. According to the Romanian tycoon

Dinu Patriciu Dan Costache (Dinu) Patriciu (; 3 August 1950 – 19 August 2014) was a Romanian billionaire businessman and politician. At the time of his death, Patriciu was the richest man in Romania. His wealth was based on the Rompetrol company (the second ...

, the sapropel sediments have the potential to be a source of non-conventional energy.Patriciu: Examination of sapropelic mud in Black Sea could last 2-3 years
19 June 2009, wall-street.ro, retrieved at 30 July 2010 Patriciu has created a marine exploration project in the Black Sea which examines the sapropel sediments of that region. Sediment cores are collected and investigated by several universities and research institutes across the world.

References

External links