Sedimentary Structures Flashcards
Sediment stops in an….
Environment of Deposition
What clues can we use to reconstruct ancient ones?
Sediment itself (Chemistry, sorting, rounding) Sedimentary Structures (patterns in the rock)
Layer of sediment forms in a particular environment
Beds are the large, main units of deposition.
Beds
Some environments create these internal layers
Cross Beds
Waves constantly wash back and forth
Symmetrical Ripples
Wind or stream flows in one direction all the time
Asymmetrical Ripples
High energy streams =
Boulders and gravel
Moderate energy rivers =
Sand, silt, mud
High energy beach =
Sand and gravel
Low energy deep ocean =
silt and mud
Other environments make beds that are uniform or…
Massive
Every main bed has cross-beds that slope in the same direction
Unidirectional Cross Beds
Unidirectional Cross Beds meaning:
Wind or water was always pushing sediment in the same direction (like a river)
Cross beds that change slope from one bed to another
Bidirectional Cross-Beds
Bidirectional Cross-Beds meaning:
Wind or water changed direction (beaches or deserts)
