The dating lab, introduction
Technically, however, given only this set of strata, one cannot say that the shark's tooth and ichthyosaur could be Dating concertinas as index fossils because we do not know if they continue in younger rock layers above this set of strata.
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It is recommended that students complete Procedure Set A and answer the associated Interpretation Questions correctly before proceeding to Set B. The following question may help clarify this point.
On a larger scale, even between continents, fossil evidence can help in correlating rock layers. All of the fossils represented would be found in sedimentary rocks of marine origin.
Sequencing the rock layers will show the students how paleontologists use fossils to give relative dates to rock strata. This will enable your teacher to quickly check whether you have the correct sequence.
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The sequence must be exactly in The dating lab order as written. When you complete this activity, you will be able to: Relative dating tells scientists if a rock layer is "older" or "younger" than another.
Scientific measurements such as radiometric dating use the natural radioactivity of certain elements found in rocks to help determine their age.
By using this information from rock formations in various parts of the world and correlating the studies, scientists have been able to establish the geologic time scale. Explore this link for additional information on the topics covered in this lesson: Return to top To enhance this activity, have students match the fossil sketches to real fossils.
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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.
By matching partial sequences, the truly oldest layers with fossils can be worked out. Once an organism disappears from the sequence it cannot reappear later.
This also means that fossils found in the lowest levels in a sequence of layered rocks represent the oldest record of life there. By correlating fossils from various parts of the world, scientists are able to give relative ages to particular strata.
In reading earth history, these layers would be "read" from bottom to top or oldest to most recent. Figure 2-A gives some background information on the individual fossils.
Each card represents a particular rock layer with a collection of fossils that are found in that particular rock stratum. The fossils represented by the letters on this card are "younger" than the "T" or "C" fossils on the "TC" card which represents fossils in the oldest rock layer.
The first card in the sequence has "Card 1, Set A" in the lower left-hand corner and represents the bottom of the sequence.
The letters on the other cards have no significance to the sequencing procedure and should be ignored at this time. Return to top 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.
Marine sedimentary rocks such as limestone, shale, and sandstone might contain fossils similar to those depicted in this activity.
The cards should be duplicated, laminated, and cut into sets and randomly mixed when given to the students. Specific rock formations are indicative of a particular type of environment existing when the rock was being formed.