CHAPTER 7: SEDIMENTARY ROCKS, Module 7 Study Guide
Limestone (crystalline)
A chemical sedimentary rock composed chiefly of calcite. Limestone can form by inorganic means or from biochemical processes.
Diagenesis
A collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification.
Turbidity current
A downslope movement of dense, sediment-laden water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension.
Mud cracks
A feature in some sedimentary rocks that forms when wet mud dries out, shrinks, and cracks.
Depositional environment
A geographic setting where sediment accumulates. Each site is characterized by a particular combination of geologic processes and environmental conditions.
Sedimentary environment
A geographic setting where sediment accumulates. Each site is characterized by a particular combination of geologic processes and environmental conditions.
Bedding plane
A nearly flat surface that separates two beds of sedimentary rock. Each bedding plane marks the end of one deposit and the beginning of another having different characteristics.
Facies
A portion of a rock unit that possesses a distinctive set of characteristics that distinguishes it from other parts of the same unit.
A graywacke is... A limestone with abundant, sand-sized quartz grains A sandstone with the sand grains embedded in a clay-rich matrix A dark-gray, calcite-rich mudstone or shale containing pyrite A siliceous, chemical sedimentary rock with color bands
A sandstone with the sand grains embedded in a clay-rich matrix
Graded bedding
A sediment layer characterized by a decrease in sediment size from bottom to top.
Breccia
A sedimentary rock composed of angular fragments that were lithified.
Conglomerate
A sedimentary rock composed of rounded, gravel-size particles.
Evaporites
A sedimentary rock formed of material deposited from solution by evaporation of the water.
Clastic texture
A sedimentary rock texture consisting of broken fragments of preexisting rock.
Organic reef
A structure formed in a warm, shallow, sunlit ocean environment that consists primarily of the calcite-rich remains of corals as well as the limy secretions of algae and the hard parts of many other small organisms.
Cross-bedding
A structure in which relatively thin layers are inclined at an angle to the main bedding. Cross-bedding is formed by currents of wind or water.
Crystalline texture
A term for the texture of sedimentary rocks in which the minerals form a pattern of interlocking crystals.
Biochemical
A type of chemical sediment that forms when material dissolved in water is precipitated by water-dwelling organisms. Shells are common examples.
Compaction
A type of lithification in which the weight of overlying material compresses more deeply buried sediment. It is most important in the fine-grained sedimentary rocks such as shale.
Salt flat
A white crust on the ground that is produced when water evaporates and leaves behind its dissolved materials.
Which of the following statements concerning sedimentary rocks is true? Sedimentary rocks may contain fossils that provide clues about ancient life forms and environments Sedimentary rocks often display stratification Sedimentary rocks preserve the layering of the original sediments Sedimentary rocks are composed of particles and constituents derived from weathering and erosion of other rocks All of the above
All of the above
Which of the following is not a type of limestone? Coquina Chalk Arkose Travertine
Arkose
Which of the following is the correct order, from left to right, of decreasing particle sizes in detrital sedimentary rocks? Shale, breccia, sandstone, siltstone Conglomerate, shale, sandstone, siltstone Breccia, shale, conglomerate, sandstone Breccia, sandstone, siltstone, shale
Breccia, sandstone, siltstone, shale
Which type of carbonate sedimentary rock consists mainly of tiny, microscopic marine fossils composed of calcite? Dolostone Travertine Coquina Chalk Oolitic limestone
Chalk
What is the name of the sedimentary rock shown in the image? Conglomerate Limestone Breccia Mudstone
Conglomerate
What is the name of the sedimentary rock shown in the image? Chert Coquina Shale Rock gypsum
Coquina
What is the name of the sedimentary structure depicted in the image? Mud cracks Ripple marks Cross-bedding Graded bedding Bioturbation structures
Cross-bedding
Which of the following features of sedimentary rocks is not a sedimentary structure? Degree of compaction and lithification Stratification Mud cracks Ripples Graded bedding
Degree of compaction and lithification
Which of the following best describes bedded gypsum and halite? Detrital sedimentary rocks Varieties of calcium carbonate Evaporites; chemical sedimentary rocks Varieties of coal
Evaporites; chemical sedimentary rocks
Coal beds originate in... Shallow lakes in a dry, desert region Channels in fast-moving streams Deep, marine basin below wave action Freshwater coastal swamps and bogs
Freshwater coastal swamps and bogs
Detrital sedimentary rocks are classified mainly on the basis of... Colors of the cementing minerals Grain sizes of the detrital particles Compositions of soluble minerals Degree of compaction and lithification
Grain sizes of the detrital particles
Which of the following sediment undergoes the most compaction and reduction in volume during burial and lithification to sedimentary rock? Marine mud Desert dune sand Pebbly sand Coarse gravel
Marine mud
Cementation
One way in which sedimentary rocks are lithified. As material precipitates from water that percolates through the sediment, open spaces are filled and particles are joined into a solid mass.
Beds (strata)
Parallel layers of sedimentary rock.
Strata (beds)
Parallel layers of sedimentary rock.
Flint, chert, and jasper are microcrystalline forms of ________ Quartz Hematite Halite Calcite
Quartz
What common mineral is found in igneous rocks and is also abundant in detrital sedimentary rocks? Plagioclase feldspar Pyroxene Quartz Biotite mica
Quartz
Which of the following sedimentary features can each be used to determine paleocurrent directions? Ripple marks and cross-bedding Mud cracks and graded bedding Fossils and bioturbation structures Grain size sorting and degree of compaction
Ripple marks and cross-bedding
Detrital sedimentary rock
Rocks that form from the accumulation of materials that originate and are transported as solid particles derived from both mechanical and chemical weathering.
Zircon and tourmaline are dense, insoluble, chemically stable, minor minerals of igneous and metamorphic rocks. In which sedimentary rock might you expect to find these minerals concentrated? Sandstone lithified from quartz-rich beach sand Limestone representing lithified coral-reef carbonates Mudstone far offshore on the continental slope Evaporite deposits of gypsum and rock salt
Sandstone lithified from quartz-rich beach sand
Chemical sedimentary rock
Sedimentary rock consisting of material that was precipitated from water by either inorganic or organic means.
Oolitic limestone is most likely to form in what type of depositional environment? Quiet, muddy, lagoons and bays Shallow, clear, marine waters with vigorous current activity Deep, marine waters below most wave action Acidic, organic-rich waters in freshwater swamps and bogs
Shallow, clear, marine waters with vigorous current activity
A cherty limestone would contain which major constituents? Iron oxide and calcite Silica and iron oxide Clay minerals and feldspars Silica and calcite
Silica and Calcite
Ripple marks
Small waves of sand that develop on the surface of a sediment layer by the action of moving water or air.
Sorting
The degree of similarity in particle size in sediment or sedimentary rock.
Lithification
The process, generally involving cementation and/or compaction, of converting sediments to solid rock.
Fissility
The property of splitting easily into thin layers along closely spaced, parallel surfaces, such as bedding planes in shale.
Fossil
The remains or traces of organisms preserved from the geologic past.
Which of the following is a form of calcium carbonate typically found as cave deposits? Chert Travertine Opal Gypsum
Travertine
Detrital sedimentary rocks have clastic textures. True False
True
Graded bedding is usually associated with beaches and desert sand dunes True False
True
Sediment
Unconsolidated particles created by the weathering and erosion of rock by chemical precipitation from solution in water, or from the secretions of organisms, and transported by water, wind, or glaciers.
Turbidity current
a downslope movement of dense, sediment-laden water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension
Environment of deposition/ sedimentary environmental
a geographic setting where sediment is accumulating
Facies
a portion of a rock unit that possesses a distinctive set of characteristics that distinguishes it from other parts of the same unit
Organic reef
a sedimentary rock structure of significant dimensions erected by, and composed almost exclusively of the remains of, corals, algae, bryozoans, sponges, and other sedentary or colonial organisms.
Salt flat
a white crust on the ground that is produced when water evaporates and leaves behind its dissolved materials
What does each of the following sedimentary rock characteristics tell us about proximity to source rocks, distance of sediment transport, and current energy? (a) Compositionally heterogeneous, angular and poorly sorted grains, (b) quartz and clay rich, well sorted grains, and (c) greater than 95% quartz, rounded and very-well sorted grains.
a. close to source rocks, transported short distance, low energy b. far from source rocks, transported long distance, high energy c. farther from source rock, transported longer distance, higher energy
Clastic texture
broken fragments of preexisting rocks
Diagenesis
collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification
Chemical sedimentary rock
consists of material that was precipitated from water by either inorganic or organic means
Sedimentary environment
continental, marine, and transitional
Graded bedding
decrease in sediment size from bottom to top due to turbidity currents
Sorting
degree of similarity in particle size in sediment or sedimentary rock
Describe the differences between detrital and chemical sediments and sedimentary rocks.
detrital - formed from accumulation of material that originates and is transported as solid particles chemical - formed from when ions in a solution are precipitated by either inorganic or biological processes organic - formed from the carbon-rich remains of organisms (coal)
Detrital sedimentary rock
form from accumulation of materials that originate and are transported as solid particles derive from both mechanical and chemical weathering
Mud cracks
indicate that sediment was alternately wet and dry (tidal flats, shallow lakes, desert basins)
Strata/Beds
layer on layer accumulates; each stratum is unique; most common
Bedding plane
nearly flat surface that separates two beds of sedimentary rock; marks the end of one deposit and the beginning of another having different characteristics
Cementation
one way sedimentary rocks are lithified; material precipitates from water that percolates through the sediment, open spaces are filled and particles are joined into a solid mass
Fissility
proper of splitting easily into thin layers along closely spaced, parallel surfaces, such as bedding planes
Fossil
remains or traces of organisms preserved from the geological past
Describe how currents sort sediment during transport. How are the sizes and shapes of sediment changed during transport?
rounded, well sorted --> mature angular, poorly sorted --> immature
Evaporites
sedimentary rock formed of material deposited from solution by evaporation of the water
Ripple marks
small waves of sand that develop on the surface of a sediment layer though the action of moving water or air
Cross-bedding
structure where thin layers are inclined at an angle to the main bedding; formed by currents of wind or water
Bioturbation
the disturbance of sedimentary deposits by living organisms
Lithification
the process, generally involving cementation and/or compaction, of converting sediments to solid rock
Biochemical
type of chemical sediment that forms when material dissolved in water is precipitated by water-dwelling organisms (shells)
Compaction
type of lithification when the weight of overlying material compresses more deeply buried sediment; most important in the fine-grained sedimentary rocks such as shale
Sediment
unconsolidated particles created by the weathering and erosion of rock
How do currents modify the composition of sediments during transport? Describe the composition of an immature sediment; a mature sediment.
unstable minerals --> immature stable minerals --> mature
Describe the stages leading to formation of a detrital sedimentary rock.
weathering, erosion, transportation, deposition, compaction, and lithification.
Crystalline texture
when the minerals form a pattern of interlocking crystals
