General history of foraminifera

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Lecture 12
General history of foraminifera and their
applications
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General history of foraminifera

• Principle steps in the evolution of the
  foraminifera.
• Although acritarchs are known from Upper
  Precambrian rocks, there are no examples of
  foraminifera of this age.
• Ammodiscaceans resembling Bathysiphon and
  Tolypammina have been reported from Lower
  Cambrian rocks.
• Foraminifera with hard tests were scarce until
  Devonian, during which period the Fusulina began
  to flourish, culminating in the complexly
  constructed tests of Fusulinacea in Late
  Carboniferous and Permian times.
• This suborder died out at the end of the
  Paleozoic.
• Miliolina first appeared in the Early
  Carboniferous, arising probably from the
  agglutinated Ammodiscacea.

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• Important Mesozoic events include the appearance
  and radiation of the Rotaliina (largely from
  endothyracean stock), Miliolina and complex
  Textulariina in the Jurassic, followed by the
  appearance of the first planktonic foraminifera.
• The planktonic Globotruncanidae became extinct at
  the end of the Cretaceous.
• A relatively rapid radiation followed in the
  Paleocene with the appearance of the planktonic
  Globigerinidae and Globorotalidae and in the
  Eocene with development of nummulites and
  soritids in the Old World and orbitoids in the
  New World.
• Orbitoides died out in the Miocene, since which
  time larger foraminiferal stocks have
  progressively dwindled in the distribution and
  diversity, mostly because of the climatic
  deterioration.
• Planktonic have also diminished in diversity
  since Late Cretaceous time, the "boom" periods of
  the Eocene and Miocene corresponding with warmer
  climatic phases.

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Application of micropaleontology

• Commercial, or industrial micropaleontology is
  generally associated with
• Petroleum industry.
• Exploration and mapping of surface and subsurface
  stratigraphic units.
• Implication of recent coccolith sedimentation
  pattern for paleooceanographic studies.
• Ostracodes are used as paleoenvironmental
  indicators.
• Importance of benthic foraminifera which are
  associated with biogenic gas seep.
• Application of micropaleontology in hydrocarbon
  exploration.
• Micropaleontology is used also in engineering and
  economic geology.

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Applications of Foraminifera

• Foraminifera are in many respects ideal zonal
  indices for marine rocks, being small, abundant,
  widely distributed and often extremely diverse.
• Planktonic foraminifera provide the basis of
  important schemes for intercontinental
  correlation of Mesozoic (especially Upper
  Cretaceous) and Cainozoic rocks.
• Benthic foraminifera tend to be more restricted
  in distribution but provide useful schemes for
  local correlation and sometimes for
  intercontinental correlation.

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Applications of Foraminifera
cont.

• Environmental interpretations that use fossil
  foraminifera are founded mainly on comparisons
  with the numerous studies of Recent ecology.
• For examples, changes in depth, salinity and
  climate can be traced in late glacial and post
  glacial raised beaches and beach deposits from
  studies of their foraminifera.
• For studies of paleogeography and paleosalinity
  at more remote periods, Murray and Wright (1974)
  used the ratios between Textulariina, Miliolina
  and Rotaliina, as well as diversity studies of
  fossil populations.

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Applications of Foraminifera
cont.

• The narrow temperature ranges of Recent
  planktonic species have become useful tools in
  paleoclimatology, especially of Quaternary
  sediments.
• Plots of the changing proportions of warm-to
  cold-water species, of selected indicator
  species, or of coiling directions through a cored
  interval may allow the construction of
  paleotemperature curves in some shallow-water
  Recent sediments, the Quaternary of the deep sea
  or even for the whole Neogene.
• Studies on the oxygen isotope ratios of
  calcareous foraminiferid shells can also yield
  information on paleotemperatures, such as the
  long Cainozoic history of climatic cooling and
  glaciations.
• Estimates of the relative rates of sedimentation
  have been calculated by comparing the proportion
  of living to dead (or living to total)
  foraminifera in benthic populations.