How do sedimentary rocks form?

Shale:

(most common sedimentary rock) made of very fine-grained sediment and composed mainly of clay minerals.

There are also different marine environments. How might you identify a coastal beach sand vs a carbonate reef deposit vs a deep marine deposit?****

Beach: sand grains Reef deposit: shells Deep marine: fine, organic grains

What are the 4 classes of sedimentary rocks?

Detrital (clastic) Biochemical (shells produced by living organisms) Organic (not mineral, but rock [minerals are inorganic]) Chemical (comprised of minerals precipitated from water solution)

How do evaporites or inorganic crystalline limestone form?

Inorganic limestone forms when chemical changes or high water temperatures increase the concentration of calcium carbonate to the point that it precipitates

Ripple marks

may indicate a beach or stream channel environment

Bed (strata)=

parallel layers of sedimentary rock

Strata (bed)=

parallel layers of sedimentary rock

Formation

rock unit that is distinctive enough in appearance that a mapper can tell it apart from the surrounding rock layer

Sandstone:

rocks when sand-size grains prevail.

Sediment=

unconsolidated particles created by the weathering and erosion of rock, by chemical precipitation from solution in water, or from the secretions of organisms and transported by water, wind, or glaciers.

Conglomerate:

If the sediment is rounded and the gravel-size particles predominate

1. Detrital rocks

-form from the solid products of weather -Mainly clay minerals and quartz -Classified by particle size- sometimes mineral composition

What are the 5 steps that turn existing rocks into a new sedimentary rock?

1. Weathering (sediment) 2. Erosion (sediment) 3. Transport 4. Deposition 5. Lithification

What are the differences between a conglomerate, a sandstone, a siltstone, and a shale?

All are detrital rocks but all have different size particles

How does coal (an organic sedimentary rock) form?

Coal is the end product of the burial of large amounts of plant material over extended periods. -Accumulation of large quantities of plant remains (normally in a swamp)- temps and pressures get higher and higher and drive off impurities and volatiles

2. Chemical sedimentary rocks

Derived from material (ions) that is carried in solution to lakes and seas then precipitates and form chemical solutions as a result of physical processes

What are chemical sedimentary rocks composed of?

Derived from material (ions) that is carried in solution to lakes and seas then precipitates and form chemical solutions as a result of physical processes.

3. Biochemical sedimentary rocks

Derived from material (ions) that is carried in solution to lakes and seas then precipitates indirectly through life processes of water-dwelling organisms that form materials called biochemical sediments

What does the term "depositional environment" mean?

Describes the combination of physical, chemical and biological processes associated with deposition of a particular type of sediment

Can you think of an example of chemical sedimentary rocks

Ex: salt left behind as a body of saltwater evaporates

There are many different sedimentary environments on land: Glaciers, mountain streams, desert dunes, rivers, and lakes. How might you recognize that the sediment of a sedimentary rock was deposited in a given environment - say a lake or a sand dune? Or a river or a glacier?

Lake: very small clasts (silt and clay) Sand: sand sized clasts (sand) 66 River: round, different sizes Glacier: lots of rock debris, different size pieces

4. Organic

Made of organic carbon, the soft tissue of living things Ex: coal

how does sediment form

Weathering- gravity and erosional agents (running water, wind, waves) remove products of weathering and bring them to new location where they are deposited- then particles deposited- the sediment may become lithified or "turned to rock"

Cross beds=

a structure in which relatively thin layers are inclined at an angle to the main bedding- formed by currents of water or wind

clasts=

chunks of rock

Siltstone:

fine-grained rock composed of clay-sized sediment intermixed with slightly larger silt sized grains.

Bedding plane=

flat surfaces along which rocks tend to separate or break- marks the end of one episode of sedimentation and the beginning of another- separates the stratas