Sedimentary Rocks Rocks from clastic materials

What is a Sedimentary Rock?  Sedimentary rocks are products of mechanical and chemical weathering  They account for about 5% (by volume) of Earth ’ s outer 10 miles, and 75% of surface rocks  Contain evidence of past environments  Provide information about sediment transport  Often contain fossils  Sedimentary rocks are products of mechanical and chemical weathering  They account for about 5% (by volume) of Earth ’ s outer 10 miles, and 75% of surface rocks  Contain evidence of past environments  Provide information about sediment transport  Often contain fossils

 Sedimentary rocks are also important because they may contain economic resources such as:  Coal  Petroleum and natural gas  Sources of iron, aluminum, and manganese  Sedimentary rocks are also important because they may contain economic resources such as:  Coal  Petroleum and natural gas  Sources of iron, aluminum, and manganese

Types of Weathering  Mechanical weathering is the physical breaking apart of Earth materials  Frost wedging = splitting of rocks due to alternate freezing and thawing of water in cracks or voids  Unloading = slabs of rock “ peel ” away due to a reduction in pressure when overlying rock is eroded away  Mechanical weathering is the physical breaking apart of Earth materials  Frost wedging = splitting of rocks due to alternate freezing and thawing of water in cracks or voids  Unloading = slabs of rock “ peel ” away due to a reduction in pressure when overlying rock is eroded away

Types of Weathering  Chemical weathering  Water is the most important agent of chemical weathering  Reactions such as oxidation or dissolution by acids serve to decompose rocks  Clay minerals are the most abundant and stable product of chemical weathering  Chemical weathering  Water is the most important agent of chemical weathering  Reactions such as oxidation or dissolution by acids serve to decompose rocks  Clay minerals are the most abundant and stable product of chemical weathering

Sediments to Rock  Many changes occur to sediment after it is deposited  Diagenesis = chemical, physical, and biological changes that take place after sediments are deposited  Occurs within the upper few miles of Earth ’ s crust  Many changes occur to sediment after it is deposited  Diagenesis = chemical, physical, and biological changes that take place after sediments are deposited  Occurs within the upper few miles of Earth ’ s crust

 Lithification – sediments are transformed into solid rock by compaction and cementation  Natural cements include calcite, silica, and iron oxide  Lithification – sediments are transformed into solid rock by compaction and cementation  Natural cements include calcite, silica, and iron oxide

Iron oxide

Silica

Types of Sedimentary Rocks  Rock types are based on the source of the material  Detrital rocks – transported sediment as solid particles  Chemical rocks – sediment that was once in solution  Rock types are based on the source of the material  Detrital rocks – transported sediment as solid particles  Chemical rocks – sediment that was once in solution

Chemical Sedimentary Rocks  Consist of precipitated material that was once in solution (in a fluid)  Precipitation of material occurs by  Inorganic processes  Organic processes (biochemical origin)  Consist of precipitated material that was once in solution (in a fluid)  Precipitation of material occurs by  Inorganic processes  Organic processes (biochemical origin)

Coal

Stages of Coal Formation

Classification  Sedimentary rocks are classified according to the type of material:  Detrital (mechanical weathering)  Chemical (precipitation from fluid)  According to texture:  Clastic (fragments and particles)  ALL detrital rocks  Non-clastic (pattern of interlocking crystals)  Sedimentary rocks are classified according to the type of material:  Detrital (mechanical weathering)  Chemical (precipitation from fluid)  According to texture:  Clastic (fragments and particles)  ALL detrital rocks  Non-clastic (pattern of interlocking crystals)

Sedimentary Environments  Continental  Dominated by stream erosion and deposition  Glacial  Wind (eolian)  Marine  Shallow (to about 200 meters)  Deep (seaward of continental shelves)  Continental  Dominated by stream erosion and deposition  Glacial  Wind (eolian)  Marine  Shallow (to about 200 meters)  Deep (seaward of continental shelves)

 Transitional (shoreline)  Tidal flats (estuaries)  Lagoons  Deltas  Transitional (shoreline)  Tidal flats (estuaries)  Lagoons  Deltas

And finally, Caves! (cool!)