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14 Cards in this Set
- Front
- Back
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relative dating
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specify the age of one feature with respect to another( A is before B, B is before C)
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absolute/numerical dating
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age of feature given in years, duration of age
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radiometric dating systems with long-lived decay
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U-Pb, K-Ar are millions to billions of years in halflife
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radiometric dating system with short-lived decay
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14C is thousands of years in halflife
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What rock types can / cannot be dated numerically (absolutely)?
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sedimentary
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What minerals are best for dating?
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U: zircon, uranite
K: mica, feldspar, hornblende |
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TYPES OF UNCONFORMITIES
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tilted or folded rocks that have been eroded and layers are exposed
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TYPES OF UNCONFORMITIES
nonconformity |
sed rocks overlie basement(older intrusive igneous and/or metamorphic rocks)
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TYPES OF UNCONFORMITIES
disconformity |
unconformity parallel to two sed sequences it separates (time gap between layers)
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What factors favor the production and preservation of fossils?
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1 death in anoxic environment
2 rapid burial 3 presence of hard parts 4 lack of diagenesis or metamorphism |
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Death in anoxic (Oxygen free) environment
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dies in oxygen rich environment, bacteria will digest carcass, in air skeleton weathers and turns to dust
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rapid burial
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in a depositional environment where sediments accumulate rapidly so can it be buried before eaten, rot, oxidized
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presence of hard parts
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Skeletons, shells, etc… because soft flesh decays much faster
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Lack of diagenesis or metamorphism
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D-changes that occur in a sed rock as a result of deep burial and subsequent reaction with groundwater. M-changes in rocks recrystallization and fabric as a result of shearing and changes in pressure and temperature
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