Term
| principle of superposition |
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Definition
| the oldest beds are the base of the sequence and successively younger layers lie above. |
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Term
| Principle of Original Horizontality |
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Definition
| that strata are deposited with a horizontal orientation. Strata that are not horizontal must have been disturbed subsequent to deposition. |
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Term
| Principle of Lateral Continuity |
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Definition
| When they were originally deposited, strata extended in all directions within their basin until they thinned to zero or terminated along the margins of their basin. |
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Term
| Principle of Inclusion (Included Fragments) |
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Definition
Basically, clasts (including xenoliths in an igneous rock) will always be older than the rock of which they are a part. In other words, any rock represented by fragments included in another rock must be older than the enclosing one.
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Term
| Principle of Cross-Cutting Relationships |
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Definition
| Any igneous rock (or fault or unconformity) must be younger than the rocks through which it cuts |
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Term
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Definition
there is a regular, definite progression of fossil forms in going from lower (older) to higher (younger) strata.
UNIQUE |
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Term
| Principle of Fossil Correlation |
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Definition
| similar assemblages of fossils are of the same age, and therefore the strata in which they are entombed must also be of the same age. |
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Term
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Definition
large intervals of time during with deposition ceased, erosion possibly removed some portion of the geologic record, and then deposition began again.
Three types: disconformity, angular unconformity and nonconformity |
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Term
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Definition
an erosional or non-depositional interval between sedimentary strata
surface of erosion between PARALLEL strata
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Term
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Definition
a parallel unconformity between sedimentary strata
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Term
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Definition
interval between sedimentary strata that meet at an obvious angle to one another.
May be the result of folding or tilting of the older strata
Surface of erosion between non-parallel strata |
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Term
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Definition
an interval of time lost as indicated between underlying igneous or metamorphic rocks and sedimentary rocks.
DOESN'T INCLUDE EXTRUDED VOLCANICS, ASHFALLS, or PYROCLASTIC FLOWS!!
surface of erosion between sedimentary strata above, and igneous or metamorphic rock below |
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Term
| Radiometric Age Dating (Absolute Dating) |
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Definition
based upon the rate at which unstable (radioactive) isotopes of elements decay into their more stable daughter isotopes.
Calculated based upon experiment and calculations, and not often upon direct observation |
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Term
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Definition
the interval of time it takes for one half of an originally pure (100%) sample of a radioactive parent to decay into its' morestable daughter isotope.
Determined by the decay rate |
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Term
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Definition
| can only be used on organic material less than about 70,000-80,000 years old. |
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Term
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Definition
| fault whose movement is parallel to the strike of the fault plane |
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Term
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Definition
| fracture with no offsetting motion |
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Term
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Definition
| fracture with offsetting motion |
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Term
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Definition
abundant
geographically wide-randing
readily preserved
identifiable with a specific interval of geologic time
useful in estimating relative ages of rock bearing fossils
helpful in correlating rocks bearing similar fossils
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