Diapositiva 1

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• Applications of the
  palaeontology
• - study of the evolution
• - interpretation of spatial distribution of
  ancient organisms
• (palaeobiogeography
• datation of the rocks (biostratigraphy)
• interpretation of ancient environments
  (palaeoecology)
• reconstruction of palaeoclimates.
• Most of these applications need other
  disciplines geology,
• sedimentology, geomorphology, geochemistry,
  astronomy,
• magnetostratigraphy, archaeology, etc.

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Fossilisation is a transfer of material from the
biosphere to the lithosphere. In long term,
weathering of rocks may return this material to
the biosphere.
Events of the fossilisation death before and
after burial.
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Palaeontology and Earth history evolution
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C
B
A
Time
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Palaeontology and palaeobiogeography
Mesosaurus
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NEW ZEALAND
MOA
KIWI
TUATARA
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Palaeontology and Biostratigraphy
a
Several fossils indicate relative ages.
Trilobites (a) are Palaeozoic in age. Nummulites
(b) are Eocenic in age. Ichthyosaurs (c) belong
to the Jurassic and Cretaceous.
b
0.5 cm
1 cm
c
20 cm
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Geological Time Line
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CORES
Marine sediments
Palaeontology provides biostratigraphic,
palaeoenvironmental and palaeoclimatic data. In
particular, microfossils are very useful for
isotopic analyses (O18/016) on their skeletal
parts.
Coccolithophores
Diatoms
Foraminifers
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Palaeontology can help magnetostratigraphy and
vice versa. Magnetostratigraphy summarizes the
variations of the polarity of the magnetic field
of the Earth. Thus, from the recent to the past,
several chrons with different polarity (normal
and reversed) have been recognized. Each chron
can be controlled by biostratigraphy and
radiometric datings.
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Palaeontology and (Palaeo)ecology
a
Most fossils are good environmental markers.
Rudists (a) are reef-builders in ancient tropical
seas. Agrichnia (b) fossil traces indicate marine
deep-water bottoms. Some gastropods (c) are
typical of lagoons.
c
b
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LIVING FOSSILS
Lake sturgeon
Ginko biloba
Limulus
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Palaeontology needs the knowledge of the
present-time environment and organisms in order
to transfer these data in the past.
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Palaeontology highlights the morphological
analogies of the organisms that live in similar
environments in order to interpret the
palaeoenvironments.
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Pollution markers?
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Palaeontology and (Palaeo)climate
a
Some fossils indicate well defined climatic
conditions. Wooly mammoths (a) and penguins (b)
are Typical of cold conditions. Organic builders
corals (c) indicate warm conditions.
After Roberts (1998)
b
1 cm
c
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18O/16O
Emiliani (1955)
Foraminifers are single-celled mostly marine
organisms. Those with calcareous (CaCO3) shell
provide good material for oxygen isotopes
analyses.
18O/16O shell 18O/16O water
18O ? heavier isotope
16O ? lighter isotope
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Interglacial phase
Decrease ice volume
Increase of m.s.l.
No variations of 18O/16O in sea-water and shells
Glacial phase
Increase ice volume
Decrease of m.s.l.
increase 18O content in sea-water and shells
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Milankovitchs theory
Orbital variations produce climatic changes.
Actually, the variations of positions of the
Earth with respect to Sun determine climatic
changes.
Precession of polar axis 23,000yrs
Axial tilt (obliquity) 41,000yrs
Eccentricity of Earth orbit 100,000-400,000yrs
This produces variations of solar radiations in
different seasons and latitudes.
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Scenario 1 sea ingression Marine biotopes
increase producing the development of marine
life. Terrestrial biotopes decrease. Terrestrial
life declines.
Scenario 2 sea regression Terrestrial biotopes
increase. Terrestrial life develops. Marine
biotopes decrease. Marine life declines.
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Marine terraces
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Fossils give a relative chronology, that can
helped by radiometric datings. These datings can
give a numeric age to the stratigraphic
units. The chemical properties of an element are
related to the number of protons of the nucleus
of the atom. The atomic weight of the element is
related to the neutrons number. Thus, the same
element can present atoms with different atomic
weight (isotopes). These isotopes can stable or
unstables. The latter produce alpha particles (2
neutrons 2 protons) and emit/capture
electrons, originating stable isotopes of
other elements. The process of radioactive decay
of a progenitor radionuclide to a descending
nuclide (descending daugther) occurs trough a
half-life typical of each isotope. t 1/ ? loge
(D/P 1) Knowing the initial ratio between
parent (P) and daughter (D), it is possible
to determine their ratio in the sample. Thus, on
the basis of the half-life and the decay constant
(?) it is possible to obtain the radiometric age
of the sample.
)
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Pollens and spores
Changes of floral scenarios
RISOLUZIONE 50 anni TIME RANGE milioni di anni
Dendrochronology
Thickness of the rings
RISOLUZIONE stagionale TIME RANGE 500-770 anni
BP