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 may return this material to the biosphere. Events of the fossilisation: death before and after burial.

Palaeontology and Earth history – evolution

Time A B C

Palaeontology and palaeobiogeography Mesosaurus

NEW ZEALAND MOA KIWI TUATARA

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, palaeoenvironmental and palaeoclimatic data. In particular, microfossils are very useful for isotopic analyses (O 18 /0 16 ) 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 LIVING FOSSILS

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

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

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) indicate warm conditions. After Roberts (1998) a c b 1 cm

18 O/ 16 O Emiliani (1955) Foraminifers are single-celled mostly marine organisms. Those with calcareous (CaCO 3 ) shell provide good material for oxygen isotopes analyses. 18 O/ 16 O shell === 18 O/ 16 O water 18 O ► heavier isotope 16 O ► lighter isotope

Interglacial phase Glacial phase Increase of m.s.l. Decrease ice volume Decrease of m.s.l. Increase ice volume increase 18 O content in sea-water and shells No variations of 18 O/ 16 O 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 orbit 100, ,000yrs Precession of polar axis 23,000yrs Axial tilt (obliquity) 41,000yrs This produces variations of solar radiations in different seasons and latitudes.

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.

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 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/ λ log e (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 (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 anni TIME RANGE: milioni di anni RISOLUZIONE: stagionale TIME RANGE: anni BP