EARTH MATERIALSEQ:What are sedimentary rocks?

Rocks that form from the burial, compression, and cementation (lithification) of the deposits of weathered remains of other rocks (clastic); by deposition of the results of biogenic activity (organic); and by precipitation from solution (chemical).

Sedimentary Rocks

CLASSROOMUNSQUARED

The Formation of Sedimentary Rocks

Exposed rock Weathering ErosionDeposition Burial Uplift Erosion

Exposure

Weathering is the physical or chemical breakdown of exposed rock (sediments).Sediments + decayed organic matter = soil.

Weathering

Sediment Grain Size

Erosion is the movement of sediments from one location to another. Agents of erosion:

Moving water - river systems (major) Wind – deserts, ergs Glaciers – high elevation and latitude Gravity – avalanches, slump, creep

The Formation of Sedimentary Rocks

Erosion

Environments of Deposition

Deposition, Burial, Compaction/Cementation

Sedimentary Rock Features

Strata Fossils Trace Fossils (tracks, burrows) Ripple marks (currents) Mud cracks Graded bedding (storm deposits) Cross-bedding (tilted dep. surface)

Sedimentary Rocks (Identification Key)

Name Class SedimentSandstone Clastic Sand grains

(quartz)

Siltstone Clastic Silt grains

Conglomerate Clastic Rounded Sand / Gravel / Pebbles

Breccia Clastic Angular Fragments

Shale Clastic Clay

Coal Organic Organic matter

Limestone Precipitate CaCO3

Shell Limestone Organic CaCO3

Chert Precipitate SiO2