origin of life (life in dark)

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Stromatolites
Presented by Pradeep Gairola M.Sc.3rd
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• Stromatolites an introduction
• Origin of stromatolites
• Characteristic , nature , pattern and record of
  stromatolites
• Classification of stromatolites
• How Modern stromatolites
• Geological distribution
• Environmental interpritation
• Significance
• In Uttarakhand
• In India

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DEFINITION

• Organosedimentary structure produced by sediment
  trapping, binding, and/or precipitation as a
  result of the growth and metabolic activity of
  micro-organisms, principally cyanophytes
  (Awramik et al. 1976).

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Microbial Mat

• A microbial mat is a multi-layered sheet of
  microorganisms, mainly bacteria and archaea.
  Microbial mats grow at interfaces between
  different types of material, mostly on submerged
  or moist surfaces, but a few survive in deserts.
• They colonize environments ranging in temperature
  from 40 C to 120 C. A few are found as
  endosymbionts of animals.

Inside the mat they are experiencing the same
conditions today that they probably experienced 1
to 2 billion years ago,
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Cyanobacteria-

• The cyanobacteria are a group of prokaryotic
  photoautotrophs that contain chlorophyll.
• Chlorophyll is a catalyst that plants use to
  drive the photosynthetic reaction. It is the
  reason that living plants (particularly leaves)
  are colored green.
• Cyanobacteria are also colored. They are
  typically green to blue, however, some are so
  strongly colored that they appear black.
• Some people refer to the cyanobacteria as
  blue-green algae, a classification that treats
  them more as plants than bacteria.

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• Cyanobacteria are aquatic and photosynthetic,
  that is, they live in the water, and can
  manufacture their own food. cause they are
  bacteria, they are quite small and usually
  unicellular, though they be often grow in
  colonies large enough to see. They have the
  distinction of being the oldest known fossils,
  more than 3.5 billion years old, in fact! It may
  surprise you then to know that the cyanobacteria
  are still around they are one of the largest and
  most important groups of bacteria on earth.
• The oxygen atmosphere that we depend on was
  generated by numerous cyanobacteria during the
  Archaean and Proterozoic Eras. Before that time,
  the atmosphere had a very different chemistry,
  unsuitable for life as we know it today.

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Where they are found?

• Cyanobacteria are usually found
• in areas where there is reduced grazing and
  borrowing by other organism, and
• a reduced occurrence of macro-algae and plants.
  
• Favorable condition
• These areas usually include hyper saline
  conditions, but also include habitats of
  increased alkalinity,
• low nutrient levels, elevated or decreased
  temperatures,
• precipitation of mineral material during growth,
  and
• strong wave or current actions (McNamara and
  Awaramik, 1992).

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Characteristic Features of Cyanobacteria

• The storage products are cyanophycean starch and
  protein.
• They are omnipresent, and occur in all possible
  kinds of habitats.
• At night, the cyanobacteria in the microbial mats
  stop producing oxygen and instead survive by
  fermentation.(?)
• They may be unicellular (e.g., Chroococcus,
  Tetrapedia, Gloeocapsa), colonial (e.g.,
  Aphanocapsa, Nostoc, Aphanothece) and filamentous
  (e.g., Oscillatoria).

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ORIGIN OF STROMATOLITESlimiting factors

• The depth of water in which the stromatolites
  developed
• The manner in which stromatolites grow
• The form of the deposit

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The depth of water in which the stromatolites
developed

• Most stromatolites developed in shallow water and
  maximum penetration of light may be considered as
  the most important factor in controlling their
  distribution
• the transparency of fresh water is much less than
  that of the sea water and that stromatolites
  building blue-green algae probably do not form
  large structures below about 10 meters in fresh
  water and 30 meters in the sea. During Belt time
  sea tides of improbably great amplitude (about 10
  feet) would have been required to account for
  such large structures.
• Large stromatolitic structures grew below low
  watermarkon the basis that the blue-green algae
  have had a long time for habitat variations since
  the Paleozoic and that perhaps they were forced
  out of the ocean by competition from better
  adapted forms
• algal mats growing on the bottoms of freshwater
  lakes that would form head-like structures may be
  due to periodic exposure to sub-aerial conditions
  (algal mats have smooth surfaces that conform to
  the lake bottoms)

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• The manner in which stromatolites grow

• Do they grow by the precipitation of lime from
  water as a result of photosynthesis
• Do the algae develop on the surfaces of
  unconsolidated, stratified sediments and merely
  bind the sediments together
• Some algae cause the precipitation of limeeither
  as a loose precipitate or as a hard, stony
  incrustation around the algal colonies
• Several occurrences of this type have been
  reported in the published record.

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• The form of the deposit

• controlled by the growth habit of the algae
• a fine precipitate of lime is deposited about the
  algal filaments
• this deposit of finely divided lime adheres to
  the mucilaginous sheaths of the algae and is
  gradually built up into a spongy porous mass.

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Characteristics of stromatolites

• They form superimposed layers
• one layer is composed of blue algae
  (cyanobacteria) using photosynthesis to growth.
  It grows horizontally during the night and
  vertically during the day
• another layer is composed of sediments and other
  floating particles which have been trap by the
  next layer of blue algae

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• The stromatolites have created a good part of our
  atmosphere rich in oxygen and ozone layer, two
  gas that have allowed the development of more
  complex life form, by using the C02 and rejecting
  oxygen
• Stromatolites are the most ancient fossils, and
  therefore might provide clues to how life evolved
  from very simple to more complex forms.

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Classification of stromatolites (on the basis of
how they grow and the shape of the colony)

• There are two basic types of stromatolites
• Cryptozoons type stromatolites they are more
  hemispherical than other types and the
  hemispheres are depressed, may even be inverted
  cones (turbinate shape) and attached to the
  surface.
• Collenia type stromatolites which are more
  fingerlike than Cryptozoons types
• Oncolithic - unattached , sub-spherical forms
• Thrombolites- Hemispherical stromatolites lacking
  internal laminations

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Stromatolites, 2 BY old, Minnesota
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Geological distribution of stromatolites

• Archaean era
• Proterozoic era
• Riphean
• Ordovicion era

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Geological distribution of stromatolites

• Achaean era
• stromatolites continued to flourish and increase
  in diversity through the Proterozic eon
• This first period of increase lead to 176
  different known forms of stromatolites.
• This diversification considered the most
  significant radiation that affected
  stromatolites, and the bacteria that constructed
  them.
• During this period, the atmosphere went from
  lacking oxygen to plenty of oxygen, anoxic to
  oxic (McNamara and Awaramik, 1992).
• The change from anoxic to an oxic atmosphere
  enabled cyanobacteria to diversify and disperse
  far and wide.
• As well geologically during this period, there
  was a transition to marine environments with
  expansive continental shelves, which provided
  more habitat for stromatolites populate (McNamara
  and Awaramik, 1992).

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Proterozoic era

• Stromatolites continued to increase through the
  middle of the Paleoporterozoic era (early
  Proterozic), and then declined for a short time.
• By the beginning of the Riphean, stromatolites
  were again on the rise, and diversified. During
  this time, stromatolites reached their maximum
  level of diversity, with up to 340 different
  types having been identified (McNamara and
  Awaramik, 1992).
• The cause of the second period of diversification
  of stromatolites is presently unknown. This
  period was also when eukaryots became more
  common, and would have been in competition with
  the stromatolites (McNamara and Awaramik, 1992).

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• The stromatolite continued to increase until the
  middle of the Riphean when they began a sharp
  decline (Awaramik and Sprinkle, 1999).
• The decline in stromatolites, during the
  Proterozoic, continued into the Phanerozoic eon.
• Scientists have attributed this drop in diversity
  and numbers to the increase in grazing metazoans,
  multicellular animals, and sediment disturbance
  by metazoans (McNamara and Awaramik, 1992).
• Some scientists dismiss this claim because there
  is no evidence in the fossil record of an
  increase in metazoans.
• Other theories regrading the decline in
  stromatolite diversity include an increase in the
  occurrences of larger sediment accumulation,
  which would have been less suitable for
  stromatolite construction.
• As well, there could have been an increase in
  nutrient levels. Stromatolites prefer habitats
  with low nutrient levels. In a case at Lake
  Clifton in Western Australia, scientists are
  witnessing algae out competing the cyanobacteria
  because of an increase in nutrient levels
  (McNamara and Awaramik, 1992).

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Ordovician Era

• During the Ordovician, a second decline in
  diversity and numbers occurred.
• This decline corresponds to the radiation of
  benthic marine invertebrates.
• As eukaryotic life radiated in the continental
  shelf areas, stromatolites became an uncommon
  occurrence in the rest of the Phanerozic fossil
  record (McNamara and Awaramik, 1992).
• They retreated to habitats where the pressures
  from these new evolving reef organisms were low
  (Steneck et al, 1998), which is where they can be
  found presently.

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Modern stromatolites

• They were first discovered in Shark Bay,
  Australia in 1956, and through out western
  Australia in both marine and non-marine
  environments (Steneck, Miller, Reid and
  Macintyre, 1998).
• Stromatolites continued to be discovered in
  places, such as the thermal springs of
  Yellowstone National Park, USA, lakes in
  Antarctica, marine environment off the Bahamas,
  and in landlocked pools supersaturated with
  calcite on Aldabra, in the western Indian Ocean
  (McNamara and Awaramik, 1992).

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Environmental interpretation(Logan, et al.,
1964)
Environment Description
Shallow water origin Flat pebble conglomerate ,oolites cracked limestone with stromatolites
Drying, very shallow intertidal environment Crinking of stromatolites structure
Form of stromatolites Depositional environment
LLH-TYPE (Collenia) Found only in protected intertidal mudflats where wave action is not strong
SH-TYPE (Cryptozoons) Occur in exposed intertidal mudflats with strong wave action because scouring action of waves prevents growth of algal mats between stromatolites
SS-TYPE (Oncolties) Low intertidal areas which are exposed to waves and agitated shallow water
Arrangement of laminae w/I these structures provides clues to the frequency of movement Arrangement of laminae w/I these structures provides clues to the frequency of movement
Concentrically arranged spheroids are the result of frequent motion Randomly stacked hemispheroids are the result of less frequent motion

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Significance Of Stromatolites

• In Uttarakhand
• The Gangolihat Dolomite (Deoban Formation) of
  the Calc Zone of Pithoragarh in the Inner Kumaun
  Lesser Himalaya, hitherto regarded of
  Mesoproterozoic age (16001000 Ma) on the
  basis of the so-called Riphean stromatolites, has
  yielded numerous earliest Cambrian protoconodont
  sclerites characterizing the PrecambrianCambrian
  boundary (544 Ma).
• This fossil discovery fosters a firm
  chronostratigraphic correlation between the
  Inner Carbonate Belt and the Krol Belt (Outer
  Carbonate Belt), now both of VendianEarly
  Cambrian age.

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• The age and correlation of the Inner Lesser
  Himalayan carbonates have been conjectural since
  nearly the beginning of the last century.
• Initially, these carbonates were correlated with
  Krol carbonates, and later accepted as that of
  late PaleozoicMesozoic age1417.
• But with the recognition of the stromatolites
  construed to be of Riphean age, first in the
  Pithoragarh area by Valdiya18 and subsequently by
  other workers throughout in the Inner Lesser
  Himalayan carbonates (carbonates of Sirban,
  Jammu, Shali, Deoban, Gangolihat, Dhading and
  Buxa), contiguously extending from the
  HazaraJammu region in the west through
  HimachalGarhwal KumaunNepalSikkimBhutan to
  Arunachal in the east, it was proposed that these
  carbonates are much older than the Krol
  carbonates.

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• In India
• Direct dating of stromatolitic carbonates is a
  good geochronological tool (Moorbath et
  al.,1987 Jahn Cuvellier, 1994).
• There is only one stance in our country where
  this new technique has been attempted (Zachariah
  et al., 1999) on Cuddapah stromatolites.
• Geochemical analysis of stromatolites for
  understanding the marine chemistry and the
  environment is being extensively used.
• Such analyses were initiated in late seventies
  (Schidlowski et al., 1975, 1976).
• In this regard, a few attempts were made in
  India as well (Banerjee,1971 Sathyanarayanet
  al., 1987 Kumar, 1988 Kumar
  Tewari,1995Kumar et al., 2002).

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DISCUSSION

• Stromatolites are complex communities of
  cyanobacteria that have found a way to adapt
  and change to their surroundings.
• They have lasted 3.5 billion years in the
  planets, oceans and are still in existence
  today.
• They are a resilient and amazing organism.

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If stromatolites were once so common, why are
they rare today? The answer seems to be that
stromatolite-building colonies of microbes had no
efficient predators when all life on Earth was
microbial. Today, many larger, multicelled
animalsfish, gastropods, wormsgraze on the
microbes. Only in high-stress environments,
such as the super-salty waters of Shark Bay and
the tide-scoured channels near Lee Stocking
Island, can microbial colonies survive long
enough to build significant structures.
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• Thanks for Attention