Sedimentary Petrology 03: Sedimentary rock classification - Part 1.

This video lecture series on Sedimentary Petrology (Undergraduate course GY 402) was made by Dr. Douglas W. Haywick from the Department of Earth Sciences at University of South Alabama.

Some of the contents on this page is outside the scope of the lecture.

Sediment motions

  • Rest (no movement)
  • Roll
  • Slide
  • Saltation ("bouncing")
  • Suspension
  • Mass flow (viscous flow)

Sediment gravity flow

Clastic Sedimentary Rocks
Name of Rock Sediment Type Texture
Conglomerate gravel - rounded fragments coarse - over 2 mm
Breccia gravel - angular fragments coarse - over 2 mm
Sandstone sand medium - 1/16 to 2mm
Siltstone mud fine - 1/256 to 1/16 mm
Shale mud very fine - less than 1/256 mm
Chemical Sedimentary Rocks
Name of Rock Composition Texture
Crystalline Limestone Calcite - CaCO3 coarse to fine crystalline
Fossiliferous Limestone Calcite - CaCO3 visible fragments of shells
Chert Quartz - SiO2 very fine crystalline
Gypsum Gypsum - CaSO3-2H2O fine to course crystalline
Rock Salt Halite - NaCl fine to course crystalline
Bituinous Coal Organic Matter fine
  • Turbidity current
  • Fluidized sedimental flow
  • Grain flow
  • Debris flow

Sediment support mechanism

  • Turbulence
  • Upward intergranular flow
  • Grain interaction
  • Matrix strength

Sedimentary rock classification

Sedimentary rock is classified into two groups based on how they form. They are clastic and chemical.

Clastic sedimentary rock

Clastic sedimentary rock is formed as bits of weathered rock become cemented together. Because all kinds of rock are subject to weathering many different minerals can make up this group of rocks. Clays and quartz are the most common.

Clastic sedimentary rock classification

Classification of clastic sedimentary rocks is done according to the size of the sediments that make up the rock.

Chemical sedimentary rock

Chemical sedimentary rocks form from dissolved minerals that are precipitated or separated from water. This happens most frequently when water evaporates leaving the minerals behind.

See also