Fossils and sedimentary rocks

1. Welcome to the
Fossils and
Sedimentary Rocks
Workshop

2. Why don’t we find more
dinosaur fossils?

3. • Most rotted away and/or were eaten by
other animals.

4. Occasionally bodies got covered up
before this could happen e.g. a flash
flood or landslide

5. Many
remained
buried
under
metres of
rock!

6. “Porous” rocks
Sedimentary rocks make up 20% of all rocks on
Earth.
Sedimentary rocks get their name because they
are made up of “sediment”. This is small pieces of
old rock or shells.

8. What is weathering?
• Physical?
• Chemical?
• Biological?
What effect
do you think
these
conditions
may have on
rocks? Does
it depend on
rock type?

9. What is weathering?
• Physical weathering happens because of temperature
changes. Freezing and thawing, thermal expansion
• Chemical weathering happens when acids in rain react
with substances in the rock.
• Biological weathering happens when plants and
animals break up rocks.

10. Sedimentary Rock
Sedimentation Compaction Cementation

11. Ammonites
Trilobites
Ferns (Plants)
Chrinoids
(related to
starfish) Footprint casts

14. Fossils in rock layers tell us….
1. How long ago they existed – deeper=older
2. How they evolved
3. What they looked like
The fossil record is incomplete – why?
• Few plants and animals become fossils
• Soft parts of plants and animals don’t form fossils
• Some fossils have not been discovered