Origin of Sedimentary Rocks Most common rocks on the earth are igneous. 2 nd common sedimentary
Sedimentary Rock Rocks formed from sediments –1. Sediments cemented together (detrital) –2. Fall out of solution as a precipitate (chemical) –3. plant material pressed together (organic)
Sediments are: Pieces of minerals Pieces of rock Pieces of organic matter Minerals dissolved in water – in solution
Detrital Sedimentary Rocks Also known as clastic sedimentary rocks From Greek klastos, broken; Detrital or clastic sedimentary rocks are rocks made from broken pieces of other rock that have been cemented together to form a new rock
Sizes of sediment designation kind of rock formed (copy chart in notebook)
How sedimentary rocks are formed Strata – layers of rock
Millions of years have gone by and there are many layers of deposited sediment now. Some of the sediment granules have been cemented together by minerals that were dissolved in the water. They have turned into layers of rock.
Compaction Pressure from the upper layers of sediments squeeze out water. Reduce the spaces between the particles They become packed together more tightly. New rock formed
Cementation Water soaks through soil Dissolves minerals such as calcite, hematite and limonite (kinds of cement) Solution moves through open spaces between sediment and fills spaces Minerals fall out of solution (precipitate – solid left from solution) “cement” the sediment together. New rock formed Calcite, hematite, limonite are Kinds of cement.
Classification of Sedimentary Rocks `1. Detrital Sedimentary Rocks – Clastic Lt. Detritus – to wear away Made from broken fragments of other rocks. Compacted and cemented together. Clastic Gr.klastos – broken
conglomerate Rounded gravel sized sediments cemented together
Breccia Angular sediments that are cemented. Found at talus slopes
Sandstone Sand sized sediment cemented together
Shale Clay sized sediment held together by compaction.
Coquina Beach pebbles, shells and animal bodies cemented together Found along shores
Chemical Sedimentary Rocks 2. chemical sedimentary rocks Minerals precipitated out of a solution. –(falls out of solution when water evaporates) Calcite in caves Halite – salt mines ancient salt seas
Limestone Calcium carbonate (CaCO 3 ) carried in ocean water dissolved from animal shells. Deposited on sea or ocean floors Precipitates out of solution. Precipitate – any solid that comes out of solution
Rock salt Found in evaporated salt water lakes or seas. Precipitates out when water is evaporated
Fossiliferous limestone Limestone with fossils. Found in old salt water lakes, bays, seas
Chalk Smashed microscopic shell bodies of sea animals. compacted
Coal Decayed organic matter that had been compacted to form a rock.