SR Formation:
Sedimentary Rocks - Notes
 All are made from SEDIMENT -- any fragment or piece of rock, plant, animal, or
dissolved mineral
 Water and wind break down solid rock into sediment through a process called
WEATHERING.
 Sediment is transported by water, wind and glaciers through a process called
EROSION.
 Sediments are DEPOSITED & BURIED in layers most often in oceans, lakes and other
bodies of water.
 The sediments turn into solid SR through COMPACTION and CEMENTATION.
 Sedimentary rock LAYERS are exposed over time by weathering & erosion.
Organizing SR – 3 types: sorted by the material that forms them.
1. Clastic
2. Chemical
3. Organic
Rock Fragments
Dissolved Minerals
Plants & Animals
1. Clastic – cemented Rock fragments
• Type of rock depends on sediment size.
• The process of sorting of sediments by sediment size is called SEDIMENTATION
SEDIMENTATION – sorting of sediments by size
2. Chemical
 Minerals dissolved in water are precipitated, when the water becomes oversaturated with minerals. Ex: Calcite (CaCO3)
Limestone (Chemical)
– The stalactites and stalagmites you see in caves form this way
 Minerals dissolved in water are deposited when the water evaporates away. Ex:
Halite & Gypsum
Rock Salt & Rock Gypsum
– Shallow seas in arid climates evaporate quickly leaving behind minerals
3. Organic
 Shells from ocean dwellers build up on the ocean floor.
Ex: Calcite (CaCO3)
Limestone (Organic)
 Dead plant material builds up in swamps. Ex:
Peat
Coal
Special SR Characteristics:
Strata – layers
Ripple marks – sand pattern formed by water
Mudcracks – muddy puddle that dried up and cracked
Fossils – the remains or impression of a plant or animal; only found in SR!
Geodes – round, hollow SR with minerals trapped inside