Sedimentary rocks

sediment

Solid fragments of inorganic or organic material that come from the weathering of rock and are carried and deposited by wind, water, or ice.

3 types of sedimentary rocks

1. clastic

2. chemical

3. organic

Sedimentary rocks

1. clastic rocks:formed from fragments of OTHER rocks.

e.g. shale, sandstone, conglomerate

2. chemical

3. organic

shale

Shale is a clastic sedimentary rock that is made up of clay-size (less then 1/256 millimeter in diameter) weathering debris. It typically breaks into thin flat pieces.

sandstone

conglomerate

3 types of sedimentary rocks

1. clastic: shale, sandstone, conglomerate

2. chemical: sedimentary rocks formed when form when dissolved materials precipitate from solution (by evaporation or chemical action)

E.g. rock salt, some limestones3. organic

Rock salt (halite)

limestone

3 types of sedimentary rocks

1. clastic: shale, sandstone, conglomerate

2. chemical: rock salt, some limestones3. organic: formed from remains of

plants and animals.E.g. some limestones, coal

limestones

Limestone forming environment

a coral reef system from the Kerama Islands in the East China Sea southwest of Okinawa. Here the entire seafloor is covered by a wide variety of corals which produce calcium carbonate skeletons.

coal

coal

forms from the accumulation and preservation of plant materials, usually in a swamp environment

3 types of sedimentary rocks

1. clastic

2. chemical

3. organic

How do clastic rocks form

Clastic rocks

1. Come from the weathering of other rocks.

2. From small to large fragments, ranging from pebbles to gravels to microscopic flakes.

3. Carried by winds, waves, and water.

4. sediments are deposited when a stream slows down.

Clastic rocks

5. IMPORTANT: Dissolved minerals like silica, calcite, and iron oxide act as cement, or glue.

These minerals settle into the spaces between sand grains or pebbles, and bind the fragments.

Sorting of sediments

conglomerate

conglomerate

Formed from pebbles, sand grains

Quartz is the most common mineral. (it’s very durable)

sandstone

sandstone

Formed largely from grains of quartz.

Up to 30% of sandstones may be air space, making them porous and permeable.

shale

shale

Formed from tiny clay flakes. (of mineral kaolin)

shale

Smooth, soft, brittle