Sedimentary Rocks
“Any loose, solid particle that may become entrained by a fluid.”
sedimentary rock
- sediment: any loose, solid particle / grain
- sedimentary rock: rock composed of sediment grains
types of sedimentary
detritus
Results of physical weathering
- detritus particles: water / ice / wind
- results in sediment
silicilastics
chemical weathering; non-congruent weathering
- clays
- resistant silicates (quartz, zircon)
carbonates
“precipitate”
carbonates results in congruent dissolution (fully weathered)
Stratigraphy
Each layer of deposit.
rule of superposition
“the law of original horizontality”; when we say “top” we mean the thing that was on top originally.
- oldest rocks on the bottom
- younger rock on top younger
Youngest rock cuts across the rocks.
Uniformitarianism
We can use the information we have about the current as a key to infer about the past. For instance, we can observe the current zones of erosion, where grains of sand move from one area to another.
Forming Detritus
“Source to Sink systems”.
- source: some uplifted terrains, like mountains
- transfer zone: rivers / dunes
- sink: ocean
“if you see a lot of quartz sitting somewhere, you know that the weathering moved a lot of things away”
“bigger forces carry bigger particles”
deposit
- argular
- subangular
- subrounded
- rounded
the rounder, the farther away it is from orignial transport
sorting
- poorly sorted (more standard deviation in gran size)
- …
- very well sorted
the more poorly sorted something is, the closer it is to depsite sit
forming Carbonates
Dead things leave their skeletons behind.
- distinctive rock types and sedimentary structures
- compaction, cement formation, lithofication
Removing Co2 from a place and then CaCO3 grow in place