Sedimentary Rocks Review

A collection of flashcards to help review key concepts related to igneous and sedimentary rocks, including definitions and classifications.

Clastic Sedimentary Rocks

Rocks composed of clasts (grains of eroded rocks), classified by grain size.

Sorting

Describes the size relationships of grains in a sedimentary rock and ranges from very poorly sorted to well sorted.

Roundness

Describes the smoothness of individual grains in sedimentary rocks.

Depositional History

Determined by sorting and roundness, indicating origination and transport distance of clasts.

Depositional Environment

Where clasts settle out of solution, classified as high or low energy, and continental, transitional, or marine.

Chemical Sedimentary Rocks

Form from precipitation of minerals in water, including limestone and evaporites.

Biochemical Sedimentary Rocks

Form from activity of microorganisms incorporating chemical components into hard parts.

Peat

Accumulated plant material in marshes, classified with chemical and biochemical rocks.

Rock Cycle

The continuous process of rock formation, including igneous, sedimentary, and metamorphic rocks.

Quartz sandstone

Clastic

• Medium sand sized grains

• Well sorted

• Depositional environments: continental, transitional, marine

(anywhere sand is deposited)

Coquina

Biochemical

• Cemented shell fragments

• Reactive to HCl

• Depositional environment: transitional (beaches)

Conglomerate

Clastic

• Gravel (and other sizes)

• Well rounded (transported)

• Poorly sorted

• Depositional environment: continental

Arkose

Clastic

• Medium sand sized grains

• Angular grains (short transport)

• Poorly sorted (short transport)

• Depositional environment: continental

Commonly pink to light red color

Greywacke

Clastic

• Sand sized quartz and rock fragments mixed with clay

• Salt and pepper look

• Depositional environment: marine

Mudstone

Clastic (even though the clasts aren’t visible)

• Silt or clay sized grains

• Siltstone, shale, and claystone are types of this rock

• I will say “be specific” if I’m looking for one of the types of this rock

• Depositional environment: transitional, marine

Micrite

Chemical/biochemical (can form either way)

• Composed of calcium carbonate

• HCl reactive

• Massive, microcrystalline lime mudstone

• Conchoidal fracture

• Depositional environment: marine

Chert

• Chemical/biochemical

• Composed of SiO2

• Hard, dense, conchoidal fracture, cryptocrystalline

• Depositional environment: marine

Shale

• Clastic (a type of mudstone)

• Clay sized clasts

• Smooth-feeling mixture of clay

• Laminated (layered)

• Depositional environments: continental, transitional, marine

Lignite

Biochemical

• Composed of plant material

• Low density, block, matte luster

• Low grade coal

• Depositional environment: continental

Fossilferous limestone

• Biochemical

• Composed of calcium carbonate

• HCl reactive

• Abundant fossils in massive calcareous matrix

• Depositional environment: marine

Rock salt

Chemical

• Composed of halite

• Crystalline with salty taste

• Depositional environment: continental