Stromatolite

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Stromatolite

Stromatolites (from Greek st??µa, stroma, mattress, bed, stratum, and ?????, lithos, rock) are layered accretionary structure

Structure

Structure is a fundamental and sometimes intangible notion covering the recognition, observation, nature , and stability of patterns and relationships of entities....
s formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilm

Biofilm

A biofilm is a structured community of microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface....
s of microorganism

Microorganism

A microorganism or microbe is an organism that is microscopic . The study of microorganisms is called microbiology, a subject that began with Anton van Leeuwenhoek's discovery of microorganisms in 1675, using a microscope of his own design....
s, especially cyanobacteria

Cyanobacteria

Cyanobacteria, also known as blue-green algae, blue-green bacteria or Cyanophyta, is a phylum of bacteria that obtain their energy through photosynthesis....
(commonly known as blue-green algae

Algae

Algae are a large and diverse group of simple, typically autotrophic organisms, ranging from unicellular to multicellular forms. The largest and most complex marine forms are called seaweeds....
).

riety of stromatolite morphologies exist including conical, stratiform, branching, domal, and columnar types.

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Encyclopedia

Stromatolites (from Greek st??µa, stroma, mattress, bed, stratum, and ?????, lithos, rock) are layered accretionary structure

Structure

Biofilm

A biofilm is a structured community of microorganisms encapsulated within a self-developed polymeric matrix and adherent to a living or inert surface....
s of microorganism

Microorganism

Cyanobacteria

Algae

Morphology

A variety of stromatolite morphologies exist including conical, stratiform, branching, domal, and columnar types. Stromatolites occur widely in the fossil record of the Precambrian

Precambrian

The Precambrian is an informal name for the supereon comprising the eon of the geologic timescale that came before the current Phanerozoic eon....
, but are rare today. Very few ancient stromatolites contain fossil

Fossil

Fossils are the preserved remains or trace fossil of animals, plants, and other organisms from the remote past. The totality of fossils, both discovered and undiscovered, and their placement in fossiliferous Rock formations and sedimentary rock layers is known as the fossil record....
ized microbes. While features of some stromatolites are suggestive of biological activity

Biota

Biota may refer to:* Biota , the plant and animal life of a region* Biota , a superdomain in taxonomy* Biota , an evergreen Pinophyta tree, Platycladus orientalis...
, others possess features that are more consistent with abiotic (non-organic) precipitation. Finding reliable ways to distinguish between biologically-formed and abiotic (non-biological) stromatolites is an active area of research in geology

Geology

Geology is the science and study of the solid and liquid matter that constitute the Earth. The field of geology encompasses the study of the composition, structural geology, physical properties, dynamics, and History of the Earth of Earth materials, and the processes by which they are formed, moved, and changed....
.

Fossil record

Stromatolites were much more abundant on the planet in Precambrian times. While older, Archean

Archean

The Archean is a geology eon before the Proterozoic and Paleoproterozoic, before 2.5 Ga . Instead of being based on stratigraphy, this date is defined chronometrically....
fossil

Fossil

Colony (biology)

In biology, a colony refers to several individual organisms of the same species living closely together, usually for mutual benefit, such as stronger defences or the ability to attack bigger prey....
of single-celled blue-green bacteria

Cyanobacteria

Proterozoic

The Proterozoic is a eon representing a period before the first abundant complex life on Earth. The Proterozoic Eon extended from 2500 annum to 542.0 ? 1.0 Ma , and is the most recent part of the old, informally named ?Precambrian? time....
) fossils may be primordial forms of the eukaryote chlorophytes

Chlorophyta

Chlorophyta, a division of green algae, includes about 7000 species of mostly Aquatic ecosystem photosynthetic eukaryotic organisms. Like the land plants , green algae contain chlorophylls a and b, and store food as starch in their plastids....
(that is, green algae

Green algae

The green algae are the large group of algae from which the embryophytes emerged. As such, they form a paraphyletic group, although the group including both green algae and embryophytes is monophyletic ....
). One genus

Genus

A genus is a low-level taxonomic rank used in the classification of living and fossil organisms. The taxonomic ranks are domain , kingdom , phylum, class , order , family , genus, and species....
of stromatolite very common in the geologic record

Geologic time scale

File:Geologic clock.jpgThe geologic time scale is a chronology schema relating stratigraphy to time that is used by geologys and other earth sciences scientists to describe the timing and relationships between events that have occurred during the history of the Earth....
is Collenia
Collenia

Collenia is a genus of cyanobacteria that may form stromatolites....
. The earliest stromatolite of confirmed microbial origin dates to .

Stromatolites are a major constituent of the fossil record for about the first 3.5 billion years of life on earth, with their abundance peaking about 1,250 million years ago. They subsequently declined in abundance and diversity, which by the start of the Cambrian had fallen to 20% of their peak. The most widely-supported explanation is that stromatolite builders fell victims to grazing creatures (the Cambrian substrate revolution

Cambrian substrate revolution

The "Cambrian substrate revolution" or "Agronomic revolution", evidenced in trace fossils, is the diversification of Burrow during the early Cambrian period....
), implying that sufficiently complex organisms were common over 1 billion years ago.

The connection between grazer and stromatolite abundance is well documented in the younger Ordovician

Ordovician

The Ordovician is a geologic period, the second of six of the Paleozoic era , and covers the time between 488.3?1.7 to 443.7?1.5 million years ago ....
evolutionary radiation

Evolutionary radiation

An evolutionary radiation is an increase in taxonomy diversity or Morphology disparity, due to adaptation change or the opening of ecospace. Radiations may affect one clade or many, and be rapid or gradual; where they are rapid, and driven by a single lineage's adaptation to their environment, they are termed adaptive radiations....
; stromatolite abundance also increased after the end-Ordovician

Ordovician-Silurian extinction events

The Ordovician?Silurian extinction event or quite commonly the Ordovician extinction, was the third-largest of the five major extinction events in Earth's history in terms of percentage of Genus that went extinct and second largest overall in the overall loss of life....
and end-Permian extinctions decimated marine animals, falling back to earlier levels as marine animals recovered.

While prokaryotic

Prokaryote

The prokaryotes are a group of organisms that lack a cell nucleus , or any other cell membrane-bound organelles. They differ from the eukaryotes, which have a cell nucleus....
cyanobacteria themselves reproduce asexually through cell division, they were instrumental in priming the environment for the evolutionary development

Timeline of evolution

This timeline of the evolution of life outlines the major events in the development of life on the planet Earth . For a thorough explanatory context, see the history of Earth, and geologic time scale....
of more complex eukaryotic

Eukaryote

Animals, plants, fungus, and protists are eukaryotes , organisms whose Cell are organized into complex structures enclosed within Cell membrane....
organisms. Cyanobacteria are thought to be largely responsible for increasing the amount of oxygen

Oxygen

Oxygen no O2 produced; 2) O2 produced, but absorbed in oceans & seabed rock; 3) O2 starts to gas out of the oceans, but is absorbed by land surfaces and formation of ozone layer; 4-5) O2 sinks filled and the gas accumulates]]...
in the primeval earth's atmosphere

Atmosphere

An atmosphere is a layer of gases that may surround a material body of sufficient mass, by the gravity of the body, and are retained for a longer duration if gravity is high and the atmosphere's temperature is low....
through their continuing photosynthesis

Photosynthesis

File:Seawifs global biosphere.jpgPhotosynthesis is a metabolic pathway that converts carbon dioxide into organic compounds, especially sugars, using the energy from sunlight....
.

Cyanobacteria use water

Water

Water is a common chemical substance that is essential for the survival of all known forms of life. In typical usage, water refers only to its liquid form or States of matter, but the substance also has a solid state, ice, and a gaseous state, water vapor or steam....
, carbon dioxide

Carbon dioxide

Carbon dioxide is a chemical compound composed of two oxygen atoms covalent bond to a single carbon atom. It is a gas at standard temperature and pressure and exists in Earth's atmosphere in this state....
, and sunlight

Sunlight

Sunlight, in the broad sense, is the total spectroscopy of the electromagnetic radiation given off by the Sun. On Earth, sunlight is Filter ed through the Earth's atmosphere, and the solar radiation is obvious as daylight when the Sun is above the horizon....
to create their food. The byproducts of this process are oxygen

Oxygen

Calcium carbonate

Calcium carbonate is a chemical compound with the chemical formula CalciumCarbonOxygen3. It is a common substance found as Rock in all parts of the world, and is the main component of seashells, snails, and eggshells....
(lime

Lime (mineral)

Lime is a general term for calcium-containing inorganic materials, in which carbonates, oxides and hydroxides predominate. Strictly speaking, lime is calcium oxide or calcium hydroxide....
). A layer of mucus

Mucus

In vertebrates, mucus is a slippery secretion produced by, and covering, mucous membranes. It is a viscous colloid containing antiseptic enzymes and immunoglobulins that serves to protect Epithelium in the respiratory,...
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

Limestone

File:Limestone Formation In Waitomo.jpgLimestone is a sedimentary rock composed largely of the mineral calcite . The deposition of limestone strata is often a by-product and indicator of biological activity in the geology record....
. 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.

Modern occurrence

Modern stromatolites are mostly found in hypersaline

Salinity

Salinity is the saltiness or dissolved salt content of a body of water. Salinity in Australian English and North American English may also refer to the salt in soil ....
lakes and marine lagoon

Lagoon

A lagoon is a body of comparatively shallow sea water or brackish water separated from the deeper sea by a shallow or exposed Bar , reef, or similar feature....
s where extreme conditions due to high saline levels exclude animal grazing. One such location is Hamelin Pool Marine Nature Reserve

Hamelin Pool Marine Nature Reserve

Hamelin Pool Marine Nature Reserve is located in the Shark Bay, Western Australia of Western Australia adacent to the Hamelin Pool Station pastoral lease and within 20 km of the Overlander, Western Australia on the North West Coastal Highway....
, Shark Bay

Shark Bay

Shark Bay may refer to the following locations in Western Australia:* Shire of Shark Bay* the locality of Shark Bay, now known as Denham, Western Australia...
in Western Australia

Western Australia

Western Australia is a States and territories of Australia occupying the entire western third of the Australia . The nation's largest state and the second largest subnational entity in the world, it has 2.1 million inhabitants , 85% of whom live in the south-west corner of the state....
where excellent specimens are observed today, and another is Lagoa Salgada, state of Rio de Janeiro

Rio de Janeiro

Rio de Janeiro , is the second largest city of Brazil and South America, behind S?o Paulo, and the third largest metropolitan area in South America, behind S?o Paulo and Buenos Aires....
, Brazil

Brazil

Brazil , officially the Federative Republic of Brazil , is a country in South America. It is the List of countries and outlying territories by total area country by geographical area, occupying nearly half of South America, the List of countries by population country, and the fourth most populous democracy in the world....
, where modern stromatolites can be observed as bioherm (domal type) and beds. Inland stromatolites can also be found in saline waters in Cuatro Ciénegas

Cuatro Ciénegas

Cuatro Ci?negas is a city in the northern Mexico States of Mexico of Coahuila. It stands at , at an average elevation of 740 metres above sea level....
, a unique ecosystem

Ecosystem

An ecosystem is a natural unit consisting of all plants, animals and micro-organisms in an area functioning together with all of the non-living physical factors of the environment....
in the Mexican desert. Modern stromatolites are only known to prosper in an open marine environment in the Exuma Cays in the Bahamas (for excellent underwater photos, see # 197-209: http://strata.geol.sc.edu/Bahamas/BahamasGalleryIndex_3.html).

Layered spherical growth structures named oncolite

Oncolite

Oncolites are sedimentary structures formed out of oncoids, which are layered spherical growth structures formed by cyanobacterial growth....
s are similar to stromatolites, and are also known from the fossil record.

External links

(RIBS)

Stromatolite

Morphology

Fossil record

Modern occurrence

See also

External links