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Lecture 12
General history of foraminifera
and
their applications
General history of foraminifera
 Principle steps in the evolution of the foraminifera.
 Although acritarchs are known from Upper Precambrian
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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.
The phylogenetic history of the Foraminiferida
 Important Mesozoic events include the appearance and radiation
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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.
Changes in the specific diversity of planktonic foraminifera through time
Application of micropaleontology
Commercial, or industrial micropaleontology is generally
associated with:
1.
Petroleum industry.
2.
Exploration and mapping of surface and subsurface
stratigraphic units.
3.
Implication of recent coccolith sedimentation pattern for
paleooceanographic studies.
4.
Ostracodes are used as paleoenvironmental indicators.
5.
Importance of benthic foraminifera which are associated
with biogenic gas seep.
6.
Application of micropaleontology in hydrocarbon
exploration.
7.
Micropaleontology is used also in engineering and
economic geology.
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.
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.
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.