Clastic / Physical / Detrital Chemical Bioclastic/Biochemical Sedimentary Rocks Clastic / Physical / Detrital Chemical Bioclastic/Biochemical

ss, cong sh ss, sh ss, slt, sh ss till ls sh ss, slt, sh graywacke chert, chalk, sh Fig. 06.38

Sedimentary Rocks Clastic/Physical/Detrital Sedimentary Rocks classified by texture (grain size, roundness) Conglomerate (with rounded gravel) Breccia (with angular gravel) Sandstone (sand) Siltstone (silt) Claystone or Mudstone (clay) Shale – fissile (clay)

Sedimentary Rocks Chemical Sedimentary Rocks classified by composition Limestone (many varieties) – Calcite, Dolomite oolitic LS, crystalline LS, travertine, dolostone Chert – Silica Evaporites – Halite, Gypsum, Sylvite, Anhydrite Rock Salt, Rock Gypsum

Sedimentary Rocks Biochemical/Bioclastic Sedimentary Rocks Limestone (many varieties) – Calcite, Dolomite coquina, fossiliferous LS, chalk, micrite Chert – diatoms, silica Coal peat, lignite, bituminous coal anthracite – actually metamorphic

Sedimentary clasts are classified by grain size (the size of the individual clasts) using the Wentworth Scale: Wentworth Scale Boulders Cobbles Gravel (pebbles) Sand Silt Clay Larger clasts require more energy to transport Smaller clasts require less energy to transport http://www.glossary.oilfield.slb.com/

Evaporites Siliceous Rocks Coal and Peat Carbonates minerals precipitated from evaporating water Siliceous Rocks Silica and opalline silica precipitate either organically or inorganically Coal and Peat Carbon-rich deposits formed from build-up of plant material in swamps Carbonates Variety of limestones composed of calcite, aragonite, and dolomite precipitated either organically or inorganically http://csmres.jmu.edu/geollab/Fichter/SedRx/chembiokey.html