ONLINE LESSON 2. WED 14/7/21 DATING TECHNIQUES IN PALAEONTOLOGY
(read pages 59,60)
1. Define relative dating.
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2. Relative dating relies on 2 basic facts. What are they?
i………………………………………….
ii……………………………………………………………………………………….
3. Where do sedimentary rocks form?.................................................................
4. A stratum is a s________________ r_________ layer.
Have a look at the rock strata below (a sedimentary rock made over many years –
layer upon layer of sediments are laid down that trap dead plants and animals as
fossils). The layers get older as we move down the strata - the top layer is the
youngest/oldest (circle the correct one). The bottom layer is the youngest/oldest
layer (circle the correct one). This is how we date fossils that are trapped in these
layers – it does not tell us the EXACT age in years but gives us an idea which fossil
is older or younger than others. Using rock layers this way is called stratigraphy
and the law that describes this is called the LAW OF SUPERPOSITION.
5.Now answer these by studying the diagram of rock strata above:a.
b.
c.
d.
Look at the 2nd picture. How many rock layers are there? _____________
Layer A is the y _____________layer and layer D is the o__________ layer.
Layer ___ formed first, then was followed by Layers C, ___ and ___.
Shelled Organisms trapped in these layers can be now compared for relative
dating. In the space below, draw the organisms in the correct order they were
laid down and trapped in the layers above in Picture 2. Start with the oldest
organism.
6. INDEX FOSSILS Page 60
a. What does the fossil record indicate about species on Earth and for how
long they existed on Earth?
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b. What are INDEX FOSSILS?
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Name 2 species below (now extinct) are used as index fossils. (Pg 60)
A……………………………..
T…………………………….
c. If a species is an index fossil it must have the following 4 features (Pg 59)
i)_______________________________________________
ii)______________________________________________
iii)______________________________________________
iv)______________________________________________