Relative susceptibility To weathering

Products of Weathering

Factors influencing Weathering Rates Rock structures – chemical/mineral composition, physical features Topography Climate Vegetation Time

Sediments and Sedimentary Rocks

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 Weathering – breakdown both physically (clasts) or chemically Erosion – loosening of weathered products (clasts) and initial transport Transportation – movement of materials via wind, water, or ice; sorting and rounding can occur Deposition – material settles out of the transporting medium 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. 7.16 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.

Clastic Texture Increasing distance from source The size, shape, and distribution of particles that collectively make up a rock 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

Graded Beds Fining up

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 sio2

Coral (carbonate)

Foramanifera

Diatoms

Types of Sediments - Chemical Inorganic process, no biological activity involved. Formed by minerals precipitating from solution. i.e. – Ca2+ + CO32- = CaCO3 Na+ + Cl- = NaCl

Chemical Sediments Terrestrial - Evaporites: Gypsum - CaSO4 . H2O Anhydrite -CaSO4 Halite - NaCl

Chemical Sediments 2. Marine Carbonates - CaCO3 (limestone) Chert (Quartz) – SiO2

Bedding – Layering or stratification in sedimentary rock

Fig. 7.25abc W. W. Norton

Cross Bedding – water or wind

Ripple Marks

Sedimentary Environments

Sedimentary Systems and Plate Tectonics