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FOSSILS Traces of the past……
FOSSILS
Traces of the past……
What happened before
Fossils are traces of things that happened long ago
Plants and animals can become fossils
We have only discovered a small number of the
plants and animals from the past
Fossils are not the original, only a copy
Plants The most famous example of
fossilized plants is petrified
wood. It is the result of
a tree or tree-like plants
having completely
transitioned to stone by the
process of permineralization.
All the organic
materials have been
replaced
with minerals (mostly
a silicate, such as quartz),
while retaining the original
structure of the stem tissue.
The petrifaction process occurs
underground, when wood
becomes buried
under sediment or volcanic
ash and is initially preserved due
to a lack of oxygenwhich inhibits
aerobic decomposition.
Plants
Ferns, tree leaves, and other plants have been
found, too
Animals
The most famous fossils are of dinosaurs
There are also fossils of sea creatures and mammals
Sometimes many fossils are found in one place
because of a flood, earthquake, or other disaster
How fossils are found
Fossils are often found by accident
Paleontologists and geologists use clues in the rocks
to find good places to hunt for fossils
Excavating fossils is hard work, and must be done
carefully
How are fossils made?
A fossil is made when a plant or animal is covered
quickly with mud or ash
The organism’s tissues are replaced over a long
period of time with minerals from the soil it was
buried in
Fossils can be dated by the layer of rock they were
found in, or by radiocarbon dating
Clues to the past
Many fossils give us an idea of what life was like
long ago
Plants give clues about the diet of animals
Animals give clues about the availability of plants
and the climate when they lived
Many clues fit together to make a more complete
picture of what the world was like long ago
Can we ever really know?
No matter how many clues we have, we can never
really know what life was like long ago. ‘THEORY’
We can make an educated guess, and fill in the
gaps using what we know about life today.
It’s fun to imagine what it was like when the
dinosaurs lived. Try it next time you feel bored!
Methods of dating
Relative dating Like stacking
newspapers.
The one at the bottom is
the oldest
Methods
Radiometric dating/absolute dating
Radiometric dating or radioactive dating is a technique used
to date materials such as rocks or carbon, in which trace
radioactive impurities were selectively incorporated when they were
formed. The method compares the abundance of a naturally
occurring radioactive isotope within the material to the abundance of
its decay products, which form at a known constant rate of decay.[1] The use
of radiometric dating was first published in 1907 by Bertram
Boltwood[2] and is now the principal source of information about
the absolute age of rocks and other geological features, including the age
of fossilized life forms or the age of the Earth itself, and can also be used
to date a wide range of natural and man-made materials.
Fossil find in South Africa
Stomatolites – Rocks in
Barberton area contain
bacteria dating back
40 million years.
Earliest form of life.
Started converting to
blue green-algae,
which captured grains
of sediment and
became mineralised.
Soft bodied animals
The multicellular
animals have been
unearthed near
Mariental in Namibia
and are called Naman
fauna
Early Land plant
Rhyinophytes discovered in
Grahams own dating back
400mil year. Stems were
smooth and lacked leaves
and ended in spores
bearing structures called
sporangia.
Forests of primitive plants
In te Permian period vast
forests of the seed fern
Glossopteris dominated
much of the southern land
mass (Gondwana)
Coelacanth “living fossils”
Appeared 400mil years
ago and then seem to
have disappeared
(extinct) but discovered
again in 1938 of the
coast of East London.
Can also be seen in
uShaka tanks in Durban.
Mammal like reptiles
Terapsids were
discovered in the
Karoo group. Most
important finding
found in Beaufort
West.
Transitional stage
between reptiles
and mammals
Dinosaurs
Lesotho and
Drakensberg
sedimentary rock date
back to Triassic and
early Jurassic eras.
Ladybrand in Free
state is known for
Euskelosaurus
dinosaurs
First Mammals
The first appeared
in the late Triassic
rocks.
Megazostrodon was
found in Elliot in
Eastern Cape.
Humans and prehumans
Found in Gauteng, North
West, Free State,
KwaZulu-Natal and
Limpopo.
Cradle of Humankind site
at Sterkfontein Cave.
Australopithecus
africanus.
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