Sedimentary Rocks
Rocks from clastic materials
What is a Sedimentary Rock?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 environmentsProvide information about sediment
transportOften 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 environmentsProvide information about sediment
transportOften contain fossils
Sedimentary rocks are also important because they may contain economic resources such as:
CoalPetroleum and natural gasSources of iron, aluminum, and
manganese
Sedimentary rocks are also important because they may contain economic resources such as:
CoalPetroleum and natural gasSources of iron, aluminum, and
manganese
Types of WeatheringTypes 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 WeatheringTypes 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 RockSediments 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 cementationNatural cements include calcite,
silica, and iron oxide
Lithification – sediments are transformed into solid rock by compaction and cementationNatural cements include calcite,
silica, and iron oxide
Iron oxideIron oxide
SilicaSilica
Types of Sedimentary Rocks
Types of Sedimentary Rocks
Rock types are based on the source of the materialDetrital rocks – transported
sediment as solid particlesChemical rocks – sediment that was
once in solution
Rock types are based on the source of the materialDetrital rocks – transported
sediment as solid particlesChemical rocks – sediment that was
once in solution
Chemical Sedimentary RocksChemical Sedimentary Rocks
Consist of precipitated material that was once in solution (in a fluid)
Precipitation of material occurs byInorganic processesOrganic processes (biochemical
origin)
Consist of precipitated material that was once in solution (in a fluid)
Precipitation of material occurs byInorganic processesOrganic processes (biochemical
origin)
CoalCoal
Stages of Coal FormationStages of Coal Formation
ClassificationClassification
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 rocksNon-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 rocksNon-clastic (pattern of interlocking
crystals)
Sedimentary EnvironmentsSedimentary
EnvironmentsContinental
Dominated by stream erosion and deposition
GlacialWind (eolian)
MarineShallow (to about 200 meters)Deep (seaward of continental shelves)
ContinentalDominated by stream erosion and
deposition GlacialWind (eolian)
MarineShallow (to about 200 meters)Deep (seaward of continental shelves)
Transitional (shoreline)Tidal flats (estuaries)LagoonsDeltas
Transitional (shoreline)Tidal flats (estuaries)LagoonsDeltas
And finally, Caves! (cool!)And finally, Caves! (cool!)