Stromatolite

Stromatolites (/stroʊˈmætəlaɪts, strə-/[1][2]) or stromatoliths (from Greek στρῶμα strōma "layer, stratum" (GEN στρώματος strōmatos), and λίθος lithos "rock")[3] are layered mounds, columns, and sheet-like sedimentary rocks that were originally formed by the growth of layer upon layer of cyanobacteria, a single-celled photosynthesizing microbe.[4][5] Fossilized stromatolites provide records of ancient life on Earth. Lichen stromatolites are a proposed mechanism of formation of some kinds of layered rock structure that are formed above water, where rock meets air, by repeated colonization of the rock by endolithic lichens.[6][7]

Stromatolithe Paléoarchéen - MNHT.PAL.2009.10.1
Stromatolites at Strelley Pool chert (SPC) (Pilbara Craton) - Western Australia
Stromatolites in Sharkbay
Modern stromatolites in Shark Bay, Western Australia

Morphology

SoegininaStromatolitesEstonia
Stromatolites in the Soeginina Beds (Paadla Formation, Ludlow, Silurian) near Kübassaare, Saaremaa, Estonia

Stromatolites are layered bio-chemical accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms (microbial mats) of microorganisms, especially cyanobacteria.[8] They exhibit a variety of forms and structures, or morphologies, including conical, stratiform, branching, domal,[9] and columnar types. Stromatolites occur widely in the fossil record of the Precambrian, but are rare today. Very few ancient stromatolites contain fossilized microbes. While features of some stromatolites are suggestive of biological activity, others possess features that are more consistent with abiotic (non-biological) precipitation.[10] Finding reliable ways to distinguish between biologically formed and abiotic stromatolites is an active area of research in geology.[11]

Formation

Time lapse photography of modern microbial mat formation in a laboratory setting gives some revealing clues to the behavior of cyanobacteria in stromatolites. Biddanda et al. (2015) found that cyanobacteria exposed to localized beams of light moved towards the light, or expressed phototaxis, and increased their photosynthetic yield, which is necessary for survival.[12] In a novel experiment, the scientists projected a school logo onto a petri dish containing the organisms, which accreted beneath the lighted region, forming the logo in bacteria.[12] The authors speculate that such motility allows the cyanobacteria to seek light sources to support the colony.[12] In both light and dark conditions, the cyanobacteria form clumps that then expand outwards, with individual members remaining connected to the colony via long tendrils. This may be a protective mechanism that affords evolutionary benefit to the colony in harsh environments where mechanical forces act to tear apart the microbial mats. Thus these sometimes elaborate structures, constructed by microscopic organisms working somewhat in unison, are a means of providing shelter and protection from a harsh environment.

Fossil record

Some Archean rock formations show macroscopic similarity to modern microbial structures, leading to the inference that these structures represent evidence of ancient life, namely stromatolites. However, others regard these patterns as being due to natural material deposition or some other abiogenic mechanism. Scientists have argued for a biological origin of stromatolites due to the presence of organic globule clusters within the thin layers of the stromatolites, of aragonite nanocrystals (both features of current stromatolites),[11] and because of the persistence of an inferred biological signal through changing environmental circumstances.[13][14]

Stromatolites hoyt mcr1
Stromatolites in the Hoyt Limestone (Cambrian) exposed at Lester Park, near Saratoga Springs, New York.
CambrianStromatolites
Stromatolites (Pika Formation, Middle Cambrian) near Helen Lake, Banff National Park, Canada

Stromatolites are a major constituent of the fossil record of the first forms of life on earth.[15] They peaked about 1.25 billion years ago[13] and subsequently declined in abundance and diversity,[16] so that by the start of the Cambrian they had fallen to 20% of their peak. The most widely supported explanation is that stromatolite builders fell victim to grazing creatures (the Cambrian substrate revolution); this theory implies that sufficiently complex organisms were common over 1 billion years ago.[17][18][19] Another hypothesis is that protozoans like the foraminifera were responsible for the decline.[20]

Proterozoic stromatolite microfossils (preserved by permineralization in silica) include cyanobacteria and possibly some forms of the eukaryote chlorophytes (that is, green algae). One genus of stromatolite very common in the geologic record is Collenia.

The connection between grazer and stromatolite abundance is well documented in the younger Ordovician evolutionary radiation; stromatolite abundance also increased after the end-Ordovician and end-Permian extinctions decimated marine animals, falling back to earlier levels as marine animals recovered.[21] Fluctuations in metazoan population and diversity may not have been the only factor in the reduction in stromatolite abundance. Factors such as the chemistry of the environment may have been responsible for changes.[22]

While prokaryotic cyanobacteria reproduce asexually through cell division, they were instrumental in priming the environment for the evolutionary development of more complex eukaryotic organisms.[15] Cyanobacteria (as well as extremophile Gammaproteobacteria) are thought to be largely responsible for increasing the amount of oxygen in the primeval earth's atmosphere through their continuing photosynthesis (see Great Oxygenation Event). Cyanobacteria use water, carbon dioxide, and sunlight to create their food. A layer of mucus often forms over mats of cyanobacterial cells. In modern microbial mats, debris from the surrounding habitat can become trapped within the mucus, which can be cemented together by the calcium carbonate to grow thin laminations of limestone. These laminations can accrete over time, resulting in the banded pattern common to stromatolites. The domal morphology of biological stromatolites is the result of the vertical growth necessary for the continued infiltration of sunlight to the organisms for photosynthesis. Layered spherical growth structures termed oncolites are similar to stromatolites and are also known from the fossil record. Thrombolites are poorly laminated or non-laminated clotted structures formed by cyanobacteria, common in the fossil record and in modern sediments.[11]

The Zebra River Canyon area of the Kubis platform in the deeply dissected Zaris Mountains of south western Namibia provides an extremely well exposed example of the thrombolite-stromatolite-metazoan reefs that developed during the Proterozoic period, the stromatolites here being better developed in updip locations under conditions of higher current velocities and greater sediment influx.[23]

Modern occurrence

Lake Thetis-Stromatolites-LaRuth
Stromatolites at Lake Thetis, Western Australia
20130118-HighbormeCay-Stromatolite-03
Stromatolites at Highborne Cay, in the Exumas, The Bahamas

Modern stromatolites are mostly found in hypersaline lakes and marine lagoons where extreme conditions due to high saline levels prevent animal grazing. One such location is Hamelin Pool Marine Nature Reserve, Shark Bay in Western Australia where excellent specimens are observed today, Pampa del Tamarugal National Reserve in Chile and another is Lagoa Salgada ("Salty Lake"), in the state of Rio Grande do Norte, Brazil, where modern stromatolites can be observed as bioherm (domal type) and beds. Inland stromatolites can also be found in saline waters in Cuatro Ciénegas, a unique ecosystem in the Mexican desert, and in Lake Alchichica, a maar lake in Mexico's Oriental Basin. The only open marine environment where modern stromatolites are known to prosper is the Exuma Cays in the Bahamas.[24][25]

In 2010, a fifth type of Chlorophyll, namely Chlorophyll f was discovered by Dr. Min Chen from stromatolites in Shark Bay.[26]

Modern freshwater stromatolites

Pavilion Lake microbialite towers
Microbialite towers at Pavilion Lake, British Columbia

Laguna Bacalar in Mexico's southern Yucatán Peninsula in the state of Quintana Roo, has an extensive formation of living giant microbialites (that is, stromatolites or thrombolites). The microbialite bed is over 10 km (6.2 mi) long with a vertical rise of several meters in some areas. These may be the largest sized living freshwater microbialites, or any organism, on Earth.[27]

A little farther to the south, a 1.5 km stretch of reef-forming stromatolites (primarily of the genus Scytonema) occurs in Chetumal Bay in Belize, just south of the mouth of the Rio Hondo and the Mexican border.[28]

Freshwater stromatolites are found in Lake Salda in southern Turkey. The waters are rich in magnesium and the stromatolite structures are made of hydromagnesite.[29]

Another pair of instances of freshwater stromatolites are at Pavilion and Kelly Lakes in British Columbia, Canada. Pavilion Lake has the largest known freshwater stromatolites and has been researched by NASA as part of xenobiology research.[30] NASA, the Canadian Space Agency and numerous universities from around the world are collaborating on a project centered on studying microbialite life in the lakes. Called the "Pavilion Lake Research Project" (PLRP) its aim is to study what conditions on the lakes' bottoms are most likely to harbor life and develop a better hypothesis on how environmental factors affect microbialite life. The end goal of the project is to better understand what conditions would be more likely to harbor life on other planets.[31] There is a citizen science project online called "MAPPER" where anyone can help sort through thousands of photos of the lake bottoms and tag microbialites, algae and other lake bed features.[32]

Microbialites have been discovered in an open pit pond at an abandoned asbestos mine near Clinton Creek, Yukon, Canada.[33] These microbialites are extremely young and presumably began forming soon after the mine closed in 1978. The combination of a low sedimentation rate, high calcification rate, and low microbial growth rate appears to result in the formation of these microbialites. Microbialites at an historic mine site demonstrates that an anthropogenically constructed environment can foster microbial carbonate formation. This has implications for creating artificial environments for building modern microbialites including stromatolites.

'Crayback' stromatolite - Nettle Cave, Jenolan Caves, NSW, Australia
'Crayback' stromatolite - Nettle Cave, Jenolan Caves, NSW, Australia

A very rare type of non-lake dwelling stromatolite lives in the Nettle Cave at Jenolan Caves, NSW, Australia.[34] The cyanobacteria live on the surface of the limestone, and are sustained by the calcium rich dripping water, which allows them to grow toward the two open ends of the cave which provide light.[35]

Stromatolites composed of calcite have been found in both the Blue Lake in the dormant volcano, Mount Gambier and at least eight cenote lakes including the Little Blue Lake in the Lower South-East of South Australia.[36]

See also

References

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Further reading

External links

Alcheringa (journal)

Alcheringa: An Australasian Journal of Palaeontology is a quarterly peer-reviewed scientific journal covering all aspects of palaeontology and its ramifications into the Earth and biological sciences. It is the official journal of the Association of Australasian Palaeontologists. The journal was established in 1975 and is published by Taylor & Francis. The name "Alcheringa" is derived from the Arrernte language of the Arrernte aboriginal people of the Alice Springs area of central Australia. "Alcheringa" (also spelled altjeringa) is the popularized English version of an Arunta expression that means "in the beginning" or "from all eternity". Alcheringa is also the name given to a 2.7-2.8 billion year old stromatolite from the Pilbara region of Western Australia and symbolizes the antiquity of life and its record in sedimentary rocks. An image of the stromatolite is illustrated on the cover of the journal.

Bhojunda Stromatolite Park

Bhojunda Stromatolite Park is located near Bhojunda village which is about 6 km south-west of Chittaurgarh city in Rajasthan, India. It is spread across 8 acres on either side of the Chittaurgarh-Udaipur state highway. It was declared as a National Geological Monument in 1976 by GSI.

Buxa Tiger Reserve

The Buxa Tiger Reserve (BTR) (Bengali: বক্সা ব্যাঘ্র সংরক্ষণ প্রকল্প; Pron: ˈbʌksə) is a 760-square-kilometre (290 sq mi) tiger reserve located inside the Buxa National Park (Bengali: বক্সা জাতীয় উদ্যান Bôksha Jatio Uddan) in West Bengal, India, in the Buxa Hills of the southern hilly area of Bhutan. Animals found in the park include, the tiger, civet, elephant, gaur (Indian bison), Indian boar and red jungle fowl.It is continguous to the Buxa Formation of Mamley in Mamley village of Namchi neighboring state of Sikkim, the stromatolite bearing Dolomite Limestones, which has been declared national geological monument by the Geological Survey of India (GSI), for their protection, maintenance, promotion and enhancement of geotourism.

Collenia

Collenia is genus of fossil cyanobacteria that form a particular type of stromatolites.

Fossil

A fossil (from Classical Latin fossilis; literally, "obtained by digging") is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in amber, hair, petrified wood, oil, coal, and DNA remnants. The totality of fossils is known as the fossil record.

Paleontology is the study of fossils: their age, method of formation, and evolutionary significance. Specimens are usually considered to be fossils if they are over 10,000 years old. The oldest fossils are around 3.48 billion years old to 4.1 billion years old. The observation in the 19th century that certain fossils were associated with certain rock strata led to the recognition of a geological timescale and the relative ages of different fossils. The development of radiometric dating techniques in the early 20th century allowed scientists to quantitatively measure the absolute ages of rocks and the fossils they host.

There are many processes that lead to fossilization, including permineralization, casts and molds, authigenic mineralization, replacement and recrystallization, adpression, carbonization, and bioimmuration.

Fossils vary in size from one-micrometre (1 µm) bacteria to dinosaurs and trees, many meters long and weighing many tons. A fossil normally preserves only a portion of the deceased organism, usually that portion that was partially mineralized during life, such as the bones and teeth of vertebrates, or the chitinous or calcareous exoskeletons of invertebrates. Fossils may also consist of the marks left behind by the organism while it was alive, such as animal tracks or feces (coprolites). These types of fossil are called trace fossils or ichnofossils, as opposed to body fossils. Some fossils are biochemical and are called chemofossils or biosignatures.

Gunflint Range

The Gunflint Range is an iron ore deposit in northern Minnesota in the United States and Northwestern Ontario, Canada. The range extends from the extreme northern portion of Cook County, Minnesota into the Thunder Bay District, Ontario.

The Gunflint Iron Formation is a continuation of the Mesabi Range to the southwest. The two have been separated by the intrusion of the Duluth Gabbro complex. The iron deposit is a banded iron formation of the Early Proterozoic Animikie Group. The Gunflint Iron Formation is overlain by "brecciated and complexly deformed iron formations", which in turn is overlain by ejecta from the "Sudbury meteorite impact event." This Sudbury Impact Layer is overlain by the Rove Formation. Stromatolite structures are evident within the Gunflint Iron Formation.The cherts of the Gunflint (the Gunflint Chert) are noted for containing Precambrian microfossils.

Hamelin Pool Marine Nature Reserve

The Hamelin Pool Marine Nature Reserve is a protected marine nature reserve located in the UNESCO World Heritage–listed Shark Bay in the Gascoyne region of Western Australia. The 127,000-hectare (310,000-acre) nature reserve boasts the most diverse and abundant examples of living marine stromatolites in the world, monuments to life on Earth over 3,500 million years BP.

Holonema

Holonema is an extinct genus of relatively large, barrel-shaped arthrodire placoderms that were found in oceans throughout the world from the Mid to Late Devonian, when the last species perished in the Frasnian-Fammian extinction event. Most species of the genus are known from fragments of the armor, but the Gogo Reef species, H. westolli, is known from whole, articulated specimens. According to these specimens, species of Holonema lived by grazing on stony, horn-shaped, stromatolite-like algae called oncholite, apparently by snipping off the points with a specialized snout.

Isua Greenstone Belt

The Isua Greenstone Belt is an Archean greenstone belt in southwestern Greenland. The belt is aged between 3.7 and 3.8 billion years. The belt contains variably metamorphosed mafic volcanic and sedimentary rocks. The occurrence of boninitic geochemical signatures, characterized by extreme depletion in trace elements that are not fluid mobile, offers evidence that plate tectonic processes in which lithic crust is melted may have been responsible for the creation of the belt. Another theory posits that the belt formed via a process known as vertical plate tectonics.In 2016 melting snow revealed putative 3.7-billion-year-old stromatolite fossils, which would be the oldest by several hundred million years thus far discovered on Earth. If confirmed, the discovery of complex stromatolite structures at Isua so early in the history of the Earth would suggest that life first evolved on Earth over 4 billion years ago. There is currently debate over whether the specimens are indeed biogenic, which has been disputed by another research team that visited the site.

Lake Salda

Lake Salda is a mid-size crater lake in southwestern Turkey, within the boundaries of Yeşilova district depending Burdur Province, and it lies at a distance of about fifty kilometers to the west from the province seat of Burdur.It extends over part of an area known as the Lakes District in southwestern Anatolia.

Salda is often cited as part of the Turkish Lakes Region that corresponds to the lands that extend across inner west- to southern Anatolia, especially in the provinces depending Isparta and Afyonkarahisar, although Lake Salda is geographically separate from the larger lakes which are more to the west and, being a crater lake, is morphologically different.

The lake area covers 4,370 hectares, and its depth reaches 196 meters, making it one of the deeper lakes in Turkey, if not the deepest. The lake sedimentary records show high resolution climate changes that are related to solar variability during the last millennium.It is a popular excursion spot across the region or from beyond, the more so due to the hydromagnesite mineral found along its coasts which are believed to offer remedies for certain dermatological diseases. The shoreline surrounded by black pine forests are also popular among hunters, the game and the fowl available including quails, hares, foxes, boars and wild ducks, aside from the lake's fish. White sandy beaches, limpid water and seven crystal-white islets within the lake complete the scenery.

A township that starts almost at the shore to the southwest of the lake carries the same name, Salda. The local administrative seat of Yeşilova is located to the east of the lake at a distance of about four kilometers and Yeşilova municipality manages the lake's camping facilities.

Its peculiar morphology led a number of academic studies to be conducted on Lake Salda. The unusual alkaline nature of the lake means that is one of the few locations where ancient stromatolite algae still grows.

Lichen stromatolite

Lichen stromatolites are laminar calcretes that are proposed as being formed by a sequence of repetitions of induration followed by lichen colonization. Endolithic lichens inhabit areas between grains of rock, chemically and physically weathering that rock, leaving a rind, which is then indurated (hardened), then recolonized.

List of National Geological Monuments in India

National Geological Monuments of India (Hindi: भारतीय राष्ट्रीय भौगोलिक स्मारक) are geographical areas of national importance and heritage, as notified by the Government of India's Geological Survey of India (GSI), for their protection, maintenance, promotion and enhancement of geotourism.

List of threatened ecological communities of Western Australia

This is a list of threatened ecological communities of Western Australia, as approved by the state Minister for the Environment in December 2006.

Banksia attenuata woodland over species rich dense shrublands

Perched wetlands of the Wheatbelt region with extensive stands of living Swamp Sheoak (Casuarina obesa) and Paperbark (Melaleuca strobophylla) across the lake floor

Shrublands on southern Swan Coastal Plain Ironstones (Busselton area)

Sedgelands in Holocene dune swales of the southern Swan Coastal Plain

Stromatolite like freshwater microbialite community of coastal brackish lakes

Stromatolite like microbialite community of coastal freshwater lakes

Communities of Tumulus Springs (Organic Mound Springs, Swan Coastal Plain)

Shrublands and woodlands of the eastern side of the Swan Coastal Plain

Perth to Gingin Ironstone Association

Shrublands and woodlands on Muchea Limestone

Rimstone Pools and Cave Structures Formed by Microbial Activity on Marine Shorelines

Callitris preissii (or Melaleuca lanceolata) forests and woodlands, Swan Coastal Plain

Shrublands on calcareous silts of the Swan Coastal Plain

Southern wet shrublands, Swan Coastal Plain

Marble Canyon Provincial Park

Marble Canyon Provincial Park is a provincial park in British Columbia, Canada, established in 1956 to protect Marble Canyon, a limestone formation at the south end of the Marble Range. In 2001 the park was expanded to 355 hectares to include all of Pavilion Lake due to the presence of microbialites, a type of stromatolite and the lake's importance to research into astrobiology and other fields. The park is also important in the culture of the Tskway'laxw people in whose territory it is located, and concealed in the side canyons of the gorge there are important pictograph sites. Not included in the park but overlooking Pavilion Lake at its farther end from the main part of the canyon is Chimney Rock, the Secwepemc'tsn name for which, K'lpalekw, means "Coyote's Penis", and is an important spiritual site. A waterfall into Crown Lake, at the park's campground, is famous among ice-climbers as "Icy BC" and the walls of Marble Canyon are a major draw to rock climbers. All three of the park's lakes are popular with recreational fishermen.

Paleontology in Alaska

Paleontology in Alaska refers to paleontological research occurring within or conducted by people from the U.S. state of Alaska. During the Late Precambrian, Alaska was covered by a shallow sea that was home to stromatolite-forming bacteria. Alaska remained submerged into the Paleozoic era and the sea came to be home to creatures including ammonites, brachiopods, and reef-forming corals. An island chain formed in the eastern part of the state. Alaska remained covered in seawater during the Triassic and Jurassic. Local wildlife included ammonites, belemnites, bony fish and ichthyosaurs. Alaska was a more terrestrial environment during the Cretaceous, with a rich flora and dinosaur fauna.

During the early Cenozoic, Alaska had a subtropical environment. The local seas continued to drop until a land bridge connected the state with Asia. Early humans crossed this bridge and remains of contemporary local wildlife such as woolly mammoths often show signs of having been butchered.

More recent Native Americans interpreted local fossils through a mythological lens. The local fossils had attracted the attention of formally trained scientists by the 1830s. Major local finds include the Kikak-Tegoseak Pachyrhinosaurus bonebed. The Pleistocene-aged woolly mammoth, Mammuthus primigenius is the Alaska state fossil.

Pavilion Lake

Pavilion Lake is a lake in Marble Canyon, British Columbia, Canada. It is located between the towns of Lillooet and Cache Creek (29.44 kilometres WNW, as the crow flies, from Cache Creek) and lies along BC Highway 99, 8.85 highway kilometres (northeast then southeast) from Pavilion, British Columbia. Part of a karst formation, the lake is most notable for being home to colonies of microbialites, a type of stromatolite, and has become the subject of astrobiology research by NASA, the Canadian Space Agency, and research institutions from around the world. The research falls under the umbrella of the Pavilion Lake Research Project. The lake area and its foreshore were added to Marble Canyon Provincial Park in order to protect its special scientific and heritage values.

There is a small community of lakeshore residences, some recreational and seasonal only, located on the lake's eastern shore adjacent to the highway. The lake is overlooked by the cliffs of Marble Canyon, which is the southern buttress of the Marble Range, and the forests of the northernmost Clear Range. Also overlooking the lake is Chimney Rock (K'lpalekw in Secwepemc'tsn, "Coyote's Penis"), which like the lake and the canyon have spiritual significance to the adjoining native communities, the Tskwaylaxw people of Pavilion and the Bonaparte band of Secwepemc at Upper Hat Creek. One of the rancheries and a rodeo and pow-wow ground of the Pavilion Band is located at Marble Canyon's south entrance.

Reef

A reef is a bar of rock, sand, coral or similar material, lying beneath the surface of water.

Many reefs result from abiotic processes (i.e. deposition of sand, wave erosion planing down rock outcrops, and other natural processes), but the best known reefs are the coral reefs of tropical waters developed through biotic processes dominated by corals and coralline algae.

Artificial reefs (e.g. shipwrecks) sometimes have a role in enhancing the physical complexity of featureless sand bottoms, in order to attract a diverse assemblage of organisms, especially algae, and fish.

Earth's largest and most famous reef is the Great Barrier Reef in Australia, at a length of 2,300 kilometres (1,400 miles).

Tanja Bosak

Tanja Bosak is a Croatian-American experimental geobiologist who is currently an associate professor in the Earth, Atmosphere, and Planetary Science department at the Massachusetts Institute of Technology. Her awards include the Subaru Outstanding Woman in Science Award from the Geological Society of America (2007), the James B. Macelwane Medal from the American Geophysical Union (2011), and was elected an AGU fellow (2011). Bosak is recognized for her work understanding stromatolite genesis, in addition to her work in broader geobiology and geochemistry.

Virginia Museum of Natural History

The Virginia Museum of Natural History is the state's natural history museum located in Martinsville, Virginia founded in 1984. The museum has several different award winning publications, is affiliated with the Smithsonian Institution, and has more than 22 million items. This includes the first intact stromatolite head ever found in Virginia, which is one of the largest complete 'heads' in the world, at over 5 feet in diameter and weighing over 2 tons.

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