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9 Cards in this Set
- Front
- Back
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faunal succession
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observation that assemblages of fossil plants and animals follow or succeed each other in time in a predictable manner. Sequences of successive strata and their corresponding enclosed faunas have been matched together to form a composite section detailing the history of the Earth, especially from the inception of the Cambrian Period, which began about 540 million years ago. Faunal succession occurs because evolution generally progresses from simple to complex in a nonrepetitive and orderly manner. Because members of faunas can be distinguished from one another through time and because of the wide geographic distribution of organisms on the Earth
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lateral continuity
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The principle of lateral continuity states that layers of sediment initially extend laterally in all directions; in other words, they are laterally continuous. As a result, rocks that are otherwise similar, but are now separated by a valley or other erosional feature, can be assumed to be originally continuous.
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superposition
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Sedimentary layers are deposited in a time sequence, with the oldest on the bottom and the youngest on the top.
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original horizontality
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all sedimentary structures are originally deposited horizontaly
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cross-cutting relations
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If rock unit A cuts through rock unit B then rock unit B must have been there before A.
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included fragments
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If a rock contains fragments, the fragments are older than the rock.
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angular unconformity
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Angular unconformity is an unconformity where horizontally parallel strata of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers.
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nonconformity
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A nonconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock. Namely, if the rock below the break is igneous or has lost its bedding by metamorphism, the plane of juncture is a nonconformity
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disconformity
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Disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition.
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