Using Fossils For Relative Dating
Alphabetical Cards (TC, CGA, AU, UBN, BN, NO, OXD, DM)
“T” is the oldest fossil, therefore must come at the base of the sequence. Work out the sequence.
Question
How do you know “T” is older than “G”?
Answer
T is the oldest, but G does not appear until a sequence
above = younger
2.
Explain why “D” in the rock layer represented
by DM is the same age as “M.”
In the same layer, so must be the same age
3.
Explain why “D” in the rock layer represented
by the OXD is older than “D” in the rock layer
represented by DM.
It is below, therefore must be older
1.
Fossil Cards (F, R, T, A, N, L, S, O)
Using the log sequence, work out the card sequence, then answer the questions.
1.
2.
3.
4.
5.
6.
7.
8.
Question
The sequence represents marine sediments.
How do we know this?
Which of the two oldest fossils is the best one
for dating? Why?
Which bed(s) has the finest grain size? How
do you know?
If the fossils in the sequence were true to
their extinction patterns, when did the P/T and
K/T mass extinctions occur in this sequence?
How do you know?
What is represented by the undulating bed
boundary between 5 and 6?
Give a history of the sequence with evidence
for your conclusions.
Coral is a shallow marine fossil, why would this
be found in fine-grained sediments.
If included fragments of bed 6 were found in
bed 5, what would be the significance of this?
Answer
In each sequence there is at least one marine animal.
Brachiopod, because it only spans two time periods.
3/7 – smallest width on a log sequence
P/T : 3-4 (trilobites died out)
K/T : 7-8 (ammonites died out)
Erosional surface – unconformity (time break)
1 - Shallow waters
2/3 - Becoming deeper – sea level rise
4 - Sudden drop in sea level but smooth contact, so
never exposed
5-6 – shallow marine (limestone)
7 – sudden deepening = quick sea level rise
8 – sea level rise but still marine as no erosional
surface.
Reworked – death assemblage
Included fragments must be older than the bed they
are found in. The sequence must be upside down.
Using Fossils For Relative Dating
Alphabetical Cards
“T” is the oldest fossil, therefore must come at the base of the sequence. Work out the sequence.
1.
Question
How do you know “T” is older than “G”?
2.
Explain why “D” in the rock layer represented
by DM is the same age as “M.”
3.
Explain why “D” in the rock layer represented
by the OXD is older than “D” in the rock layer
represented by DM.
Answer
Fossil Cards
Using the log sequence, work out the card sequence, then answer the questions.
1.
Question
The sequence represents marine sediments.
How do we know this?
2.
Which of the two oldest fossils is the best one
for dating? Why?
3.
Which bed(s) has the finest grain size? How
do you know?
4.
If the fossils in the sequence were true to
their extinction patterns, when did the P/T and
K/T mass extinctions occur in this sequence?
How do you know?
What is represented by the undulating bed
boundary between 5 and 6?
Give a history of the sequence with evidence
for your conclusions.
5.
6.
7.
Coral is a shallow marine fossil, why would this
be found in fine-grained sediments.
8.
If included fragments of bed 6 were found in
bed 5, what would be the significance of this?
Answer