Sedimentary and Metamorphic Rocks

Made from sediment / organic matter Rock goes through weathering and erosion, and is

broken down into tiny fragments, some of which may be chemically altered Sediment

Sediment is compacted and cemented Squeezed together; dissolved minerals crystallize and act as

“cement” to bond sediment together COMPACTION AND LITHIFICATION

Sedimentary Rocks

How do sedimentary rocks form? Clastic

Sediment is compacted and cemented Further classified by size of sediment grain Sediment is held together by matrix material (“cement”)

Chemical; biogenic Dissolved substances precipitate out of solution leaving a solid

product OR Made from organic matter May CONTAIN FOSSILS! Tells about previous conditions on earth!

Classifying Sedimentary Rocks

Sandstone – beaches, desert Ripples, sand dune patterns in layers to determine which environment

Shale; mudstone – deep, calm water Water must be deep, calm enough for fine sediment grains to deposit Lake and ocean bottoms

Limestone – deepest water, coral reefs Shelled organisms die, CaCO3 accumulates

Conglomerate – rivers; glaciers Rivers transports differently-sized particles that deposit along shore,

riverbed, etc.; cemented together with mud to form stone Rivers can transport materials long distances

Coal – swamp Halite – dried up body of salt water

Depositional Environment

C. Chesterman, 1979

Sedimentary rock samples (left; and sedimentary rocks in outcrop. Note the layers, or strata, that you can see in the sedimentary rock.

Previous existing rocks that go through extreme T and P changes that chemically alters the rock (ROCK DOES NOT MELT)

Contact metamorphism -- comes into contact with magma (small scale)

Regional metamorphism -- large, extreme changes and deformation

Metamorphic Rocks

Heat Magma Change in location (depth) of rock

E.g. - Cookies! Minerals become unstable and recrystallize

Heat is energy source that drives change Pressure

Causes mineral grains to compact Can create a new density or cause minerals to recrystallize

Hydrothermal solution Hot water / mineral solutions that dissolve some substances in

mineral, deposit new ones, causes change in composition

Agents of Metamorphism

Degree of foliation Minerals recrystallize, can be re-oriented Appears layered / banded Due to preferred orientation of mineral (stress and strain!)

How Metamorphic Rocks are Classified

Nonfoliated Not banded Usually only one mineral in rock composition

Classification cont’d

Rock type: type of metamorphism Volcanism, mountain building

Parent rock type -- history Shale / siltstone - slate -> schist -> gneiss with T or P

Sometimes just burial Granite, Schist -> Gneiss……with intense T or P

Mountain building Can determine direction of force from foliation More T and P -> Melting of Gneiss….back to Granite!

Limestone -> marble Sandstone -> quartzite Organic coal -> anthracite coal (just burial…increased P, Low T)

Metamorphism, Environment, and History

Formation of Coal

C. Chesterman, 1979

Here are a few examples of metamorphic rocks (samples to the right, rock outcrop above).