Chapter 10 Sedimentary Rocks

Sedimentary Rocks Accumulations of various types of sediments Compaction: pressure from overlying sediments squeezes out air and water Cementation: dissolved minerals in water form a “glue” that holds sediments together

Sedimentary Rocks Classified by… Kind of sediments Size of sediments that form them

Clastic Sedimentary Rocks Rock fragments carried by wind, water, ice and deposited Classified by size

Clastic Conglomerate: Rounded gravel fragments or pebbles

Clastic Conglomerate wall

Clastic Breccia: Angular gravel fragments with sharp corners

Clastic Breccia wall

Clastic Sandstone: Sand-sized grains Mostly quartz Pore spaces- allow groundwater and oil to flow

Clastic Shale Clay-sized particles Cemented and compacted under pressure Flat, flaky layers

Chemical Sedimentary Rocks Minerals dissolved in water, settle out with change in temperature Ex. Limestone when calcite settles out of ocean water Evaporites: dissolved minerals left over when water evaporates; turns to rock

Chemical Ex: Gypsum, halite Ex: Great Salt Lake, UT

Organic Sedimentary Rocks Organic: formed from the remains of living things Ex: coal

Organic Limestone Shell build up on ocean floor, from Clams Oysters Plankton Ex: chalk

Organic White Cliffs of Dover, England

Sedimentary Rock Features Easily identifiable Include: Stratification (layering) Ripple marks Mud cracks Fossils Concretions

Stratification Change in type of sediment deposited Layers!! Vary in thickness

Stratification Cross bedding

Stratification Graded bedding: where in the layer do you think the largest and heaviest grains of sediment settle?

Ripple Marks Formed by action of wind or water on sand Preserved when sand  sandstone

Mud Cracks Formed when muddy deposits dry and shrink River plains, dry lake bed New deposits fill in

Fossils Remains or traces of ancient plants and animals Buried as sediments build up Hardest parts sometimes remain, but often dissolve into rock

Concretions Lumps, or nodules, of rock with composition different from main rock body Minerals precipitated from solutions build up around rock particles

Concretions Groundwater deposits quartz, calcite Geodes