Potassium Feldspar Orthoclase Chemical Weathering

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Potassium Feldspar (Orthoclase) Chemical
Weathering
4 KAlSi3O8 (orthoclase) 4 H (acid) 2 H2O (
water) 4 K (potassium ions) Al4Si4
O10(OH)8 (kaolinite clay)
8 SiO2 (quartz)
Chemical weathering
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Mahakam River Delta From SpaceKalimantan, Borneo
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Stratigraphy

• The study of strata (layers) of rocks with an eye
  toward interpreting the geologic history of the
  region
  
• Closely tied to dating methods
• Uses a variety of methods - fossils, stable
  isotopes, paleomagnetics, sedimentary cycles - to
  correlate and distinguish layers
  
• Very important for oil exploration and mining

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Stratigraphic Principles

• Principle of original horizontality
• Every sedimentary layer is deposited
  horizontally
  

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Stratigraphic Principles

• Principle of cross-cutting relationships
• Any layer that is cut by something else has to be
  older than that something else
  
• Applies to igneous intrusions, faults, veins,
  erosional surfaces, etc.
  

Granitic intrusion From D. McConnell, Geologic Ti
me, http//lists.uakron.edu/geology/natscigeo/Lec
tures/time/gtime1.htm
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Stratigraphic Principles

• Principle of stratigraphic superposition
• Oldest rocks are on the bottom
• Youngest rocks are on the top

Dead Horse Point, UT From D. McConnell, Geologic
Time, http//lists.uakron.edu/geology/natscigeo/L
ectures/time/gtime1.htm
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Stratigraphic Principles

• Principle of original lateral continuity
• Sedimentary layers dont just stops suddenly
• They extend horizontally until they taper out

Millroy, PA
Pictures from D. McConnell, Geologic Time, http
//lists.uakron.edu/geology/natscigeo/Lectures/tim
e/gtime1.htm
Graybull, WY
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Stratigraphic Principles

• Principle of unconformities
• Some stratigraphic sections are incomplete
• Any place where there is missing time is called
  an unconformity
  
• Unconformities normally happen either through
  erosion or non-deposition
  

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The Great Unconformity Grand Canyon, AZ
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Angular Unconformity
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Disconformity
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Nonconformity
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Stratigraphic Thinking
From D. McConnell, Geologic Time,
http//lists.uakron.edu/geology/natscigeo/Lectures
/time/gtime1.htm
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One possible interpretation...