Sediments - unconsolidated particles created by 1. The weathering of rock 2. The secretions of organisms or decomposition of organic matter 3. Chemical precipitation
Sedimentary Rock Formation 1.Weathering – breakdown both physically (clasts) or chemically 2.Erosion – loosening of weathered products (clasts) and initial transport 3.Transportation – movement of materials via wind, water, or ice; sorting and rounding can occur 4.Deposition – material settles out of the transporting medium 5.Lithification – process of either cementation or compaction of the material
W. W. Norton
Sedimentary Rocks Composed of lithified sediments - by compaction – weight of overlying sediment compresses sediment, important in fine-grained sediments - by cementation – materials carried in solution precipitates minerals - iron oxides, carbonates, silica Two Classifications - clastic -nonclastic
Fig W. W. Norton
Sedimentary Rocks Clastic Rock – composed of fragments of preexisting rocks. Nonclastic Rock – composed of chemical precipitates or biochemical matter.
Daily Question Use a Venn diagram to compare and contrast clastic, chemical nonclastic, and biochemical nonclastic sedimentary rocks. Identify at least five characteristics. Clastic Chemical Biochemical
Types of Sediments - Clastic Broken fragments of rock produced by weathering. Classified according to size. Range in size from largest boulder to smallest clay particle.
The size, shape, and distribution of particles that collectively make up a rock Clastic Texture Increasing distance from source
Which sample is closer to the source of sediment?
Sorting - a function of transport mechanism 1. Water 2. Wind 3. Glaciers
Sorting by Wind
Fig. 7.26a Stephen Marshak
Fining up Graded Beds
Texture and Transport Distance In general, as transport distance increases, rounding and sorting increase. Examples: Breccia – cemented close to source Conglomerate – transported then cemented
Types of Sediments - Biogenic Terrestrial sediments - mainly plant matter ex. Coal Marine sediments - mainly carbonates Corals - large components of reefs. Bivalves, gastropods, foraminifers - whole or partial skeletons form sand and gravels. Algae, crinoids, echinoderms, bryozoans - disintegrate to form some sand particles and lime mud. Diatoms, Radiolaria – bedded chert sio 2
Types of Sediments - Chemical Inorganic process, no biological activity involved. Formed by minerals precipitating from solution. i.e. – Ca 2+ + CO 3 2- = CaCO 3 Na + + Cl - = NaCl
Chemical Sediments 1.Terrestrial - Evaporites: Gypsum - CaSO 4. H 2 O Anhydrite -CaSO 4 Halite - NaCl