Rock units relative dating activity

Rock units relative dating activity

Use this information to sequence

Crests of the first set are preserved in the troughs of the second set, hence, the ladderback appearance. Use this information to sequence the cards in a vertical stack of fossils in rock strata.

Crests of the first set

This also means that fossils found in the lowest levels in a sequence of layered rocks represent the oldest record of life there. If certain fossils are typically found only in a particular rock unit and are found in many places worldwide, they may be useful as index or guide fossils in determining the age of undated strata. Carefully examine the second set of cards which have sketches of fossils on them. Find a rock layer that has at least one of the fossils you found in the oldest rock layer. Locally, physical characteristics of rocks can be compared and correlated.

Record all of your work in a word processing document. Specific rock formations are indicative of a particular type of environment existing when the rock was being formed.

Record all of your work in

After you have arranged the cards in order, write your sequence of letters using each letter only once on a separate piece of paper. Stratigraphic Section for Set B. Spread the cards with the nonsense syllables on the table and determine the correct sequence of the eight cards by comparing letters that are common to individual cards and, therefore, overlap. The brachiopod, crinoid, eurypterid, foraminifera, gastropod, horn coral, pelecypod, and trilobite could probably not be used as index fossils since they overlap more than one stratum.

Specific rock formations are

On a larger scale, even between continents, fossil evidence can help in correlating rock layers. This would also mean that fossils found in the deepest layer of rocks in an area would represent the oldest forms of life in that particular rock formation.

Name three organisms represented

This will enable your teacher to quickly check whether you have the correct sequence. The sequence must be exactly in the order as written. An earlier current-formed ripple set at bottom of slide was later modified by a second ripple train migrating at right angles to the first. Keep in mind that extinction is forever.

Name three organisms represented that probably could not be used as index fossils and explain why. The cards should be duplicated, laminated, and cut into sets and randomly mixed when given to the students. It may be useful to share with students after they have completed Set B and answered the Interpretation Questions. The graptolite, placoderm, ammonite, ichthyosaur, and shark's tooth could possibly be used as index fossils since they are found in only one layer.