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20 Cards in this Set
- Front
- Back
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What is a Body Fossil? |
Hard parts of the skeleton. (such as skeleton or shell) |
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What is Replacement? |
the atom by atom substitution of one mineral for another. |
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Out of Calcite and Aragonite, which is more stable? |
Calcite. |
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What is polymorph? |
a mineral that has the same composition but occurs in different crystal forms. |
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True or False; Aragonite can change into calcite if left for long periods of time? |
True. Calcite is more stable and therefor it decays into this form. |
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What is Silicification? |
when minerals which have been dissolved in the groundwater, crystallize and fill any pores or voids. |
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What is Pyritisation? |
The replacement of the original mineral by iron pyrites. |
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True or False; Pyritisation occurs in anaerobic environments? |
True. This is where the sulphur bacteria are the only living organisms. |
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How do the sulphur bacteria respire? |
they use the bacteria in the environment to respire. |
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How is the original material replaced in pyritisation? (process description) |
sulphur bacteria use the sulphur in the environment to respire, which causes it to turn into bisulphate. This then reacts with any iron in the environment to form iron pyrites. This then replaces the fossil material. |
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Where does Pyritisation occur? |
deep sea environments with anoxic sea bed. also in shallow swamps. |
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What is Carbonisation? |
a process which removes volitiles and gases from within the organic material, because of an increase of pressure and temperature due to overlying rocks. This leaves a thin carbon film. |
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What is Mould and Cast preservation? |
when the fossils contain physical characteristics of the organism because they have been pressed into the rocks. |
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what are external moulds? |
the impression of the outside of the organism into the rock? |
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which type of mould leaves the impression of the organism on the outside of the rock? |
external mould. |
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what is an internal mould? |
when mud enters the empty shell and moulds to the structures of the outside. |
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True or False; a cast is the original impression of the organism? |
True. |
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What type of impression of the original organism does a mould create? |
a reverse impression. |
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How is an internal cast created? |
when an internal mould is filled with sediment or cement. |
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How is an external cast created? |
when an external mould is filled with sediment or cement. |
