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Sedimentary Rocks Cheat Sheet (DRAFT) by

GEOS100, Sedimentary cheat sheet

This is a draft cheat sheet. It is a work in progress and is not finished yet.

Classi­fic­ation of Sedime­ntary Rocks

made of solid sedime­ntary fragments (eg, mudstone, siltstone, sandstone, and conglo­mer­ate­/br­eccia)
  Clastic - mainly for detrital rocks with distinct sized fragments
made of minerals taken into a solution and reprec­ipi­tated without help from organisms (eg, evaporites like rock salt and iron format­ions)
  Crysta­lline - mainly for chemical rocks with interl­ocking crystals
made of minerals of which organisms played a role in turning to sediment (eg, limestone made of calcite from coral, chert made of a planktonic micro-­org­anism)
  Bioclastic - rocks with skeletal remains

Sedime­ntary Rock Textures

Clastic Texture Particle Size
Sediment Name
Rock Name
Coarse (over 2mm)
Gravel (rounded particles)
Gravel (angular particles)
Medium (1/16 to 2mm)
Sand (or Arkose if abundant feldspar is present)
Fine (1/256 to 1/16 mm)
Very fine (<1/256 mm)

Sedime­ntary Facies

Lateral view of sedime­ntary rock reflects changes in past enviro­nments.
Charac­ter­istics of each facies reflect the enviro­nment in which it formed.
Different sediments often accumulate next to one another at the same time.
The merging of many facies is usually a gradual transi­tion.

Sedime­ntary Glossary

Sedime­­ntary rock - one of the 3 rock types formed by the accumu­lation and cement­­ation of inorganic or organic particles.

Sedime­ntary Enviro­nments

Contin­ental - Dominated by erosion and deposition associated with streams; in frigid enviro­nments, glaciers can move large volumes and sizes of sediment; streams are a dominant factor in moving sediment; wind deposits are well sorted
Transi­tional (shore­line) - quiet water conditions may form tidal flats; higher energy water conditions tend to form beaches, spits, bars, and barrier islands; sheltered, brackish water conditions can form lagoons; deltas are common and form when river velocity slows at river/sea interface and sediment is deposited
Marine - Divided according to depth: shallow ≤200m - may include land derived sediment, skeletal debris, and coral reef accumu­lation; deep >200m: tiny skeletons rain down on sea floor and strong currents may move material from contin­ental shelf to deeper enviro­nments
Tidal flat - shallow, muddy, part of shore
Brackish water - salinized freshwater
Contin­ental shelf - part of a continent submerged under shallow water

Sedime­ntary Rock Types

Biological Sediment
organic matter or bioche­mically produced materials (eg, limest­one).
Chemical Sedime­ntary Rock
precip­itates from a fluid (eg, rock salt),
Silici­clastic made off clasts (sediments or fragments) compacted and cemented together. (eg, sandstone, conglo­mer­ate); also called detrital

Sedime­ntary Structures

Strata beds - Distinct layers of sedime­ntary rocks; formations include multiple individual strata
Bedding planes - horizontal cracks that separate strata
Surface impres­sions - mud cracks or trace fossils
Graded beds - rapid deposition through water; coarse settles first and progre­ssively shrinks in grain size upward through a bed; commonly formed by turbidity currents
Cross-­bedding - Inclined layers in relation to bed formed by movement.
Ripple marks - small waves of sand formed by moving water
  Current ripple marks - stream currents (asymm­etric)
  Oscill­ation ripple marks - waves (symme­tric)