Lecture 4 Flashcards
What are the two main divisions of sedimentary rocks?
Clastic and non-clastic.
What is a clastic rock?
Clastic rocks are composed of fragments of pre-existing rocks.
What is a non-clastic rock?
Dissolved material (ions) in water. Rocks form when the water evaporates.
In what conditions does lithification occur?
Temperature less than 250 and depths less than 5km.
What are the 3 main divisions of clast size?
Rudites (gravel), sandstones (sand), lutites/mudstone.
What is the clast size of rudites (gravel)?
Greater than 2mm
What is the clast size of sandstone?
Less than 2mm and greater than 1/16mm.
What is the clast size of mudstone?
siltstone is less than 1/16mm and greater than 1/256mm. Claystone is less than 1/256mm.
What are the two divisions of non-clastic rocks?
Biological and chemical.
How to tell a wave vs a stream on structures?
Currents/streams leave asymmetrical ripples while waves leave symmetric ripples.
What is clast size and indicator of?
Energy level at the time of deposition.
