CHAPTER 7: SEDIMENTARY ROCKS

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.