6. http://www.earth-time.org/trollart.html
Fossils can be dated relative to one another by noting their
positions in layers of rocks, known as strata. Thus fossils
found in lower strata (layers) were generally deposited
earlier and are older than those on upper layers.
This is called the Law of Superposition
Rock Layers and Fossil Dating
7. Fossil Types for our Core Samples
Ammonit
e
Trilobite
Elrathi kingi
Knightia
Fern
Alethopteris serii
8. Fossils can be dated relative to one another by
noting their positions in layers of rocks, known as
strata. Thus fossils found in lower strata (layers)
were generally deposited earlier and are older.
This is called the Law of Superposition. Click on
the image at the left to see this phenomena.
Scientists can date the rocks, this gives us the
general age of the fossils.
In the example at right, we can deduce that the oldest rocks are those that are cut
through by other rocks. The next oldest rocks are those that are “doing the
cutting” through the oldest rocks, and the youngest rocks lie on top of these layers
and are not cut through at all. By making careful observations, we can detect these
interruptions in the vertical pattern and use them to get more information about
the relative ages of different layers.
Sometimes geologic processes interrupt this
straightforward, vertical pattern . For
example, a mass of rock may cut across other
layers, erosion may interrupt the regular
pattern of deposition, or the rock layers may
even be bent and turned upside-down. Click on
the image on the right to see this,.
Rock Layers and Fossil Dating
Learn More At: http://evolution.berkeley.edu/evosite/evo101/IIE1bStratigraphy.shtml
