Chapter 4 – Sedimentary & Metamorphic
Source: other rocks. Sediments formed from the wearing down of other rocks. Eg sand, ions in solution, animal shells
Process: deposition, precipitation (things coming out of a solution) and cemented
Product: sedimentary rocks. Eg Limestone is found in coral reefs
Compaction: When cement piles on top of one another, it gets squished and there’s less air between the grains and
they get compacted. Eg: loose sediments like sand turned into a sedimentary rock
Cementation: Something sticky is able to stick the grains together. Often, it is silica or calcite cement that sticks them
together that turns them from loose sediment into a rock
Lithification - turning sediments into rocks
Depositional environment aka as environment of formation:
Different places where sediments gather together and form sedimentary rocks. Common ones are a beach. You mostly
find sediments such as sand. A sedimentary rock found on the beach would be a sandstone. In the deep water there are
sediments such as clay or silt. They form a mudstone of shale. Clay forms shale.
Clastic sediments- broken parts of other rocks. Sand, silt, pebbles, boulders are examples of clastic sediments. They
make clastic sedimentary rocks. Using this you can make chemical or biological rocks.
You can form limestone from coral reefs. This would be biological or biochemical sedimentary rocks.
Making sedimentary rocks: Read in detail 7.3, 15.1 - 15.4 1) Physical weathering and 2) chemical weathering.
Igneous rocks need to undergo weathering in order to be turned into sediments.
Clastic sediments are moved and deposited by water, wind and glaciers.
Clastic sediments named by size (clay, silt, sand, pebbles, boulders)
Clastic sediments are named by grain size (mudstone/shale, sandstone, conglomerate)
Conglomerate: made of a mixture of sediments larger than sand.
How round and angular a rock tells us their distance of traveling
When you transport sediments, the further distance you transport it, there's more chance for it to get rubbed and
eroded against each other and as a result they get rounded and smooth. Eg: on a beach
But the rocks on a mountain would be angular and sharp because they haven't really travelled far.
Clastic sedimentary rocks to know:
Breccia: this word means broken. The pieces are angular clasts
Conglomerate: more rounded clasts than breccia sandstone
Sandstone is formed by sand moving by wind or water such as sand dunes and beach ripples
Shale – soft sedimentary rock that is easy to erode. Siltstone: finer than sandstone, clastic, silt sized particles
Non clastic sedimentary rocks to know: (precipitate by water or deposited by organisms)
BIF - banded iron formation
Gypsum – walls in our house. Evaparoite. Dolostone – similar to limestone. It has MG and CA
Halite – used on French fries, on driveways during snow
Limestone – Its clastic, sedimentary or chemical. Made up of creatures & bits that make up the C reef. You could also
precipitate the mineral from the water.
Evaporates can form in shallow, restricted basins surrounded by fringing reefs: Sea water evaporates rapidly,
precipitating salts. Can form minerals if water evaporates. Eg: halite, gypsum
Biogenic sedimentary rocks - Marine organisms - limestone, chalk
Loose sediments: - show structures (Ex ripples - how/where sediment was deposited). They need to be lithified as in be
made into rock.
Graded bedding – sediments sorted by gra