k sedimentary rocks

Sedimentary Environments


Fossil

Sedimentary rocks record environmental information


Continental Shelf

10-15K feet of compacted sand and mud


Lithification: Compaction and cementation

At depth, SiO2 and CaCO3 go into solution,
water is driven out (dewatering).
This solution permeates throughout open
pore spaces, forming a cement.


Cemented Sandstone

SiO2 cement


Cemented Limestone

CaCO3 cement

Classification of Sedimentary
Rocks


Clastics

Increasing
water
energy


Clastic Sedimentary Rock


Fast Stream
Fast moving water does
not allow clay-sized particles
to accumulate. They stay in
suspension.
Larger particles, like pebbles,
drop through the water column
and accumulate.


Breccia


Biogenic rocks -

Limestone

Accumulation of dead critters.
Shallow, warm, marine environment.


Limestone Thin Section

Fossils cemented together by CaCO3 cement.


Biogenic rocks -

Coal
Accumulation of organic
material in a swampy
environment. Anaerobic, dark,
murky water.


Lagoon

Care for a swim?


Chemical rocks -

Evaporite - Salt

What happens when salty water evaporates?

Salt Flat

Wet in the spring and early summer
Water evaporates in late summer and fall


Chemical rocks -

Chert

Microcrystalline silica
Deep water ocean environment,
too cold for CaCO3 precipitation.


Continental Slope


Transatlantic Cable


Turbidity Current


Turbidite Layers


Sea level
facies change

Mud

Sand

North Carolina


OIL