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.

Fossilisation is a transfer of material from the biosphere to the lithosphere.In long term, weathering of rocks mayreturn this material to the biosphere.

Events of the fossilisation: deathbefore and after burial.

Palaeontology and Earth history – evolution

Time

A

B

C

Palaeontology and palaeobiogeography

Mesosaurus

NEW ZEALAND

MOA

KIWITUATARA

Palaeontology and Biostratigraphy

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.

1 cm

20 cm

0.5 cm

a

b

c

Geological Time Line

CORES

Marine sediments

CoccolithophoresDiatoms

Palaeontology provides biostratigraphic, palaeoenvironmentaland palaeoclimatic data. In particular, microfossils are very useful for isotopic analyses (O18/016) on their skeletal parts.

Foraminifers

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.

Palaeontology and (Palaeo)ecology

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.

a

b

c

Ginko biloba

Lake sturgeon

Limulus

LIVINGFOSSILS

Palaeontology needs the knowledge of the present-time environment andorganisms in order to transfer these data in the past.

Palaeontology highlights the morphological analogies of the organismsthat live in similar environments in order to interpret the palaeoenvironments.

Cyprideis is the most popular brackish water genus. Its ornamentation varies from smooth to reticulated. Nodosespecimens occur in low salinity waters. Peypouquet (1977) suggested that the nodes of Cyprideis torosa may indicate chelation (heavy metals+organic matter) in low salinity water.

Cyprideis torosa (Jones, 1850)

Cyprideis undosa Van Harten, 1980: pitted (above), nodose (below).

After Carbonel (1980)

Pollution markers?

Palaeontology and (Palaeo)climate

Some fossils indicate well defined climatic conditions.Wooly mammoths (a) and penguins (b) are Typical of cold conditions.Organic builders corals (c) indicatewarm conditions.

After Roberts (1998)

a

c

b

1 cm

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 isotope16O ► lighter isotope

Interglacial phase

Glacial phase

Increase of m.s.l.

Decrease ice volume

Decrease of m.s.l.

Increase ice volume

increase 18O content in sea-water and shells

No variations of 18O/16O in sea-water and shells

Milankovitch’s theory

Orbital variations produce climatic changes. Actually, the variations of positions of the Earth with respect to Sun determine climatic changes.

Eccentricity of Earth orbit100,000-

400,000yrs

Precession ofpolar axis23,000yrs

Axial tilt (obliquity)41,000yrs

This produces variations of solar radiations in different seasons and latitudes.

Scenario 1 – sea ingression

Marine biotopes increase producingthe 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.

Marine terraces

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 otherelements.

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/ λ loge (D/P + 1)

Knowing the initial ratio between parent (P) and daughter (D), it is possible todetermine their ratio in the sample. Thus, on the basis of the half-life and the decay constant (λ) it is possible to obtain the radiometric age of the sample.

)

Pollens and spores

Dendrochronology

Changes of floral scenarios

Thickness of the rings

RISOLUZIONE: 50 anniTIME RANGE: milioni di anni

RISOLUZIONE: stagionaleTIME RANGE: 500-770 anni BP