Question

Complete Data Table 2 using the Geologic Time Scale (Resource 10) and the Key to Index Fossils (Resource 11) in the DataBank to determine approximate absolute ages for the rock layers in the block diagram (Figure 1) that display index fossils.

Just need help finding approx. age!

ROCK INDEX FOSSIL PERIOD APPROX. AGE
C Tetragraptus fructicosus ordovician
E Dictyoclostus americanus pennsylvanian
A Paradoxides pinus cambrian

Answer 1

Okay, so you look at rock C and see the index fossil is Tetragraptus fructicosus. Sounds like a disease you get from eating too much fruit :-)

Now you look at your color table here http://assets.openstudy.com/updates/attachments/53276cc8e4b087b3d4107786-ali1029-1395092790550-img_3739.jpeg

and find the row where Tetragraptus fructicosus is listed.

Answer 2

Sorry, wrong link! http://assets.openstudy.com/updates/attachments/53276a15e4b087b3d41074bd-ali1029-1395092276221-img_2346.jpeg

Answer 3

which is the ordovician period, correct?

Answer 4

Having gotten the period, you look at the first link I gave you to find the approximate age of that period.

So for our friend T.f. we have Ordovician, and that is 443 to 490 mya.

Answer 5

ah i see, so i wouldn't just pick a random number, I would just put 443-490?

Answer 6

Yes, I believe you would fill in the range. After all, you don't really have any more information with which you could narrow it down to a smaller interval...

Answer 7

You know, like 473,576,132 years ago, last Tuesday at about 5:18 PM :-)

Answer 8

haha!

Answer 9

thats what i thought but i wasn't sure if i needed to do more of the crazy math that you did earlier:p

Answer 10

Yeah, the math would only help if you had a reading on the U-235 content of the rock layer, and that's not the point of this particular exercise. One of the concepts being developed here, I think, is that by looking at those index fossils (or radioactive dating, for that matter), you can determine the age of a layer, and from that draw some conclusions about whether part of the geological formation has been pushed up or buried or whatever when you look at other areas nearby.

Answer 11

that makes sense! thank you very much! :)

Answer 12

It's all a big whodunit mystery, and you're looking for clues that can help you deduce what happened. Col. Mustard, in the library, with a strike-slip fault :-)

Answer 13

(have you ever seen or played the game Clue?)

Answer 14

haha yes i have actually!! :D

Answer 15

I probably last played it before you were born, but I still remember the old TV commercial :-)

https://www.youtube.com/watch?v=jj6izHRLHOI

Answer 16

lol oh wow! I've only played the newest version!!