Chapter 6

c. detrital

A sedimentary rock made of fragments of preexisting rocks is: a. organic. b. chemical. c. detrital

most sedimentary rocks are detrital sedimentary rocks formed from cemented sediment grains that are fragments of preexisting rocks. Gravel, sand, slit then clay.

List the detrital sediment particles in order of decreasing grain size.

Shale, Sandstone, Limestone

Name the three most common sedimentary rocks.

b. sand

Particles of sediment from 1/16 to 2 millimeters in diameter are of what size? a. gravel b. sand c. silt d. clay

b. convergent boundary.

Thick accumulations of graywacke and volcanic sediments can indicate an ancient: a. divergent plate boundary. b. convergent boundary. c. transform boundary.

a. formation.

A body or rock of considerable thickness with characteristics that distinguish it from adjacent rock units is called a/an: a. formation. b. contact. c. bedding plane. d. outcrop.

a. the composition of the sediment.

Clues to the nature of the source area of sediment can be found in: a. the composition of the sediment. b. sedimentary structures. c. rounding of sediment. d. all of the preceding

d. lithification

Compaction and cementation are two common processes of: a. erosion. b. transportation. c. deposition. d. lithification

Inorganic: limestones precipitated directly as a result of inorganic processes, by precipitation of calcite from water. biochemical: limestones precipitated through the actions of organisms which are formed on continental shelves in warm, shallow seawater and made up of skeletal remains. Re-crystallized: limestones formed by re-crystallization of calcite due to increase in temperature and pressure.

Describe three different origins for limestone.

flowing air and water, sand grains move as ripples and dunes. avalanches down the dune forming a bed. in stream deposits.

Explain two ways that cross-bedding can form.

Evaporites (crystalline structure): rocks that are formed from the remain precipitate of seawater or saline lake. ex. Rock Gypsum, Rock Salt.

How do evaporites form? Name two evaporites.

deposited by turbidity current.

How does a graded bed form

sedimentary breccias are a course-grained sedimentary rock formed by the cementation of coarse, angular fragments of rubble. It is a talus slope deposit that forms at the base of a steep rock cliff that is being mechanically weathered. Coarse-grained sedimentary rock formed by the cementation of rounded gravel is a conglomerate. it is rounded particles which may have not traveled far and transported only a short distance by a river or a wave.

How does a sedimentary breccia differ in appearance and origin from a conglomerate?

dolomite is a sedimentary rock CaMg(CO3)2 usually forms from the alteration of limestone by magnesium-rich solutions. Most commonly in dry areas.

How does dolomite usually form?

b. a regression

If sea level drops or the land rises, what is likely to occur? a. a flood b. a regression c. a transgression d. no geologic change will take place

a. decreases upward.

In a graded bed, the particle size: a. decreases upward. b. decreases downward. c. increases in the direction of the current. d. stays the same

Dry, cold climate and slow weathering rate is one of the conditions which led to feldspar-rich sandstone. (quick erosion rate and fast weathering rate also play major roles in formation of feldspar-rich sandstone)

Quartz is a common mineral in sandstone. Under certain circumstances, feldspar is common in sandstone, even though it normally weathers rapidly to clay. What conditions of climate, weathering rate, and erosion rate could lead to a feldspar-rich sandstone? Explain your answer

b. the grinding away of sharp edges and corners of rock fragments during transportation.

Rounding is a. the rounding of a grain to a spherical shape. b. the grinding away of sharp edges and corners of rock fragments during transportation. c. a type of mineral. d. none of the preceding

b. shale is visibly layered and fissile; mudstone is massive and blocky.

Shale differs from mudstone in that: a. shale has larger grains. b. shale is visibly layered and fissile; mudstone is massive and blocky. c. shale has smaller grains. d. there is no difference between shale and mudstone

b. Mg

The chemical element found in dolomite not found in limestone is: a. Ca b. Mg c. C d. O e. Al

b. rounding of the grains.

The major difference between breccia and conglomerate is: a. size of grains b. rounding of the grains. c. composition of grains. d. all of the preceding

It is exposed above water, since it needs air for drying. In lake-bottom sediment and in marine sediment we can see Mud Cracks.

What do mud cracks tell us about the environment of deposition of a sedimentary rock?

a convenient rock unit for mapping and classifying rock.

What is a formation?

Coal is a major fuel which is a consolidated plant material. Formed from the compaction of plant material that has not completely decayed. tropical climate or shallow swamps are the likely environments for deposition. The plant fossils in coal beds include leaves, stems, tree trunks, and slumps with roots. (Right where plants grow)

What is the origin of coal?

b. sandstone

Which is not a chemical or organic sedimentary rock? a. rock salt b. sandstone c. limestone d. gypsum

d. travertine

Which is not a type of sandstone? a. quartz sandstone b. arkose c. graywacke d. travertine