Basic Stratigraphic Concepts (Chapter 2) Flashcards

1
Q

Principle of Uniformitarianism

A
  • present physical laws and geological processes occurring today also occurred in the past.
  • Ex: gravity
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2
Q

Principle of Original Horizontality

A

most sediments or extrusive igneous rocks are deposited in horizontal layers

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3
Q

Principle of Lateral Continuity

A

rocks extends in all direction until they end allows for correlation of rock units across different areas

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4
Q

Principle of Superposition

A
  • where a sequence of rocks is undisturbed:
    • oldest sedimentary rock layer is at bottom
    • youngest at top
  • allows for relative dating of when the layer is formed compared to each other
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5
Q

Principle of Cross-Cutting

A
  • when layers or geological features cut across layers of rocks or sediments, features are younger than rocks they cut
  • ex: intrusive dike is younger than layers of rock it cuts
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6
Q

Principle of Inclusion

A
  • rocks found within other rocks must be older than rocks that incorporate them
  • ex: sandstone pieces that cut part of the mudstone are older than matrix
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7
Q

Principle of Fossil Succession

A

organisms existed on Earth change over time rock layer that contains older fossils is older than rock layer containing younger fossils

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8
Q

Correlation

A
  • matching of rock units base on shared similarities
  • similarities: lithology, fossils found, age, environment of deposition, or stratigraphic location
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9
Q

Lithostratigraphic unit

A

based on rock characteristics

e.g. mineralogy, grain size

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10
Q

time-stratigraphic unit

A

an interval of rock, based on the time it was created

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11
Q

unconformity

A

gaps in succession of rocks, older may have been folded & uplifted before younger layer

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12
Q

conformity

A

no apparent disruption in deposition of sediments appeared to have occurred

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