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relative dating
Chapter 17
absolute dating
Chapter 17
principle of superposition
Chapter 17
principle of original horizontality
Chapter 17
principle of lateral continuity
Chapter 17
principle of cross‐cutting relationships
Chapter 17
principle of inclusions
Chapter 17
principle of fossil succession
Chapter 17
unconformity
Chapter 17
disconformity
Chapter 17
angular unconformity
Chapter 17
nonconformity
Chapter 17
correlation
Chapter 17
guide fossil
Chapter 17
radioactive decay
Chapter 17
half‐life
Chapter 17
carbon‐14 dating technique
Chapter 17
The process of determining the age of an event as compared to other events; involves placing geologic events in
their correct chronological order, but does not involve the consideration of when the events occurred in number
of years ago.
Uses various radioactive decay dating techniques to assign ages in years
before the present to rocks.
A principle holding that in a vertical sequence of undeformed sedimentary rocks, the relative ages of the rocks can be determined by their position in the
sequence—oldest at the bottom followed by successively younger
layers.
According to this principle, sediments are deposited in horizontal or nearly
horizontal layers.
A principle holding that rock layers extend outward in all directions until
they terminate.
A principle holding that an igneous intrusion or fault must be younger than the rocks it intrudes or cuts
across.
A principle holding that inclusions or fragments in a rock unit are older than
the rock unit itself; for example, granite inclusions in sandstone are
older than the sandstone.
A principle holding that fossils, and especially groups or assemblages of fossils, succeed one another through
time in a regular and predictable order.
A break in the geologic record represented by an erosional surface separating younger strata from older
rocks.
An unconformity above and below which the rock layers are parallel.
An unconformity below which older rocks dip at a different angle (usually
steeper) than overlying strata.
An unconformity in which stratified sedimentary rocks overlie an erosion
surface cut into igneous or metamorphic rocks.
Demonstration of the physical continuity of rock units or biostratigraphic units, or
demonstration of time equivalence as in time‐stratigraphic correlation.
Any easily identified fossil with an
extensive geographic distribution and short geologic range useful for
determining the relative ages of rocks in different areas
The spontaneous change of an atom to
an atom of a different element by emission of a particle from its nucleus (alpha and beta decay) or by electron
capture.
The time necessary for half of the
original number of radioactive atoms of an element to decay to a stable daughter product; for example, the half‐life for potassium 40 is 1.3 billion
years.
Absolute dating technique relying on the ratio of C14 to C12 in an organic
substance; useful back to about 70,000 years ago.