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Chapter 9

GEOL 1010 Chapter Notes - Chapter 9: Atomic Number, Beta Particle, Nonconformist

Geological Sciences
Course Code
GEOL 1010
Pamela Stephens

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Chapter 9 Key Terms
Relative dates are when we place rocks in their proper sequence of formation (order, rock a
was formed first, rock b was formed second etc.)
Law of superposition states that the oldest layer of sedimentary rocks is older than the one
above it, and younger than the one below it (youngest on top, oldest on bottom).
The principle of original horizontality states that if a rock layer is flat, it has not been disturbed.
The principle of lateral continuity refers to the fact that sedimentary beds originate as
continuous layers that extend in all directions until they eventually grade into a different type
of sediment (google this later their def makes no sense)
The principle of cross-cutting relationships states that geologic features that cut across rocks
must form after the rocks they cut through (igneous intrusions).
Inclusions are fragments of one rock unit that have been enclosed within another. The rock
mass that contains the inclusion is the younger of the two.
Conformable rocks are rocks that have been deposited without interruption. These breals are
called unconformities. An unconformity represents a long period during which a deposition
ceased, erosion removed previously formed rocks, and then deposition resumed. Uplift and
erosion are followed by subsidence and renewed sedimentation. Unconformities are important
because they help identify what intervals of time are missing from the geologic record.
Angular unconformity is when tilted ro folded sedimentary rocks are overlain by younger flat
lying strata.
Disconformity is a gap rock record that represents a period during which erosion rather than
deposition is occurring.
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