12: Sediments Flashcards
How do sediments form
Material is whether then flows and deposits in a river or basin (detrital or clastic sediments)
How is sediment transported?
Either in suspension (liquid) or solution (dissolved)
What are clastic rocks?
Formed from broken rock fragments weathered n eroded by riv. glacier. wind. sea waves. Then solidified. Defined by grain size
How can you tell how far a rock has travelled?
More angular= less distance
More round= tumbled a lot travel far
What does long distance transport mean in terms of sorting and roundness?
well-rounded and well-sorted sediments
Shale composition and make-up
Clastic. Fine silt/clay. Deposition occured under a weak water current.
What’s an evaporitic rock?
Form from dissolved chemical substances in depositional basins when the liquid evaporates out
Why does graded bedding occur?
Heavier, more course units will sink to the bottom
How cross bedding occur?
Water flowing from right to left and depositing sediments
What is sed. facies
Unit that along its length will change its rock type due to diff. conditions. Refining upwards sequence (Mud n clay on top)
What occurs during sed. trangression?
rise in sea level= offshore further down facies will be deposited on top of nearshore facies. Coarsening sequence
How do turbidites form?
Turbidity flows (earthquake wave action) cause packages of sediment to be slid downhill, liquified then sorted into solid packages with graded bedding.
