CH.6

________, a common mineral found in igneous rocks, is the most abundant mineral in detrital
sedimentary rocks.

Quartz

Which major component of detrital sedimentary rocks only rarely occurs as a primary mineral in
igneous rocks?

clays

________ cement produces bright-red and yellow colors in some sandstone.

Iron oxide

Studies of deep-sea sediment cores have contributed greatly to scientific knowledge of ________.

climatic changes during the last four million years

Which of the following describes the correct order for relative solubility of minerals in sedimentary
rocks?

evaporate minerals are more soluble than calcite and quartz

Which statement concerning sedimentary rocks is not true?

they were originally deposited at depth below the bottom of the sea

Which of the following applies to the basic constituents of halite, gypsum, and sylvite?

transported as dissolved ions; deposited by evaporation

Sedimentary rocks account for about what percentage of the Earth’s outermost 10 kilometers of
rock (first percentage). Also, what percentage of the Earth’s continental area is covered by
sedimentary rocks (second percentage)?

5% & 75%

Detrital grains of which mineral(s) are extremely rare in detrital sediments? Why?

calcite; it is soft and relatively soluble

What is the chemical formula for dolomite, the major mineral in dolostones?

CaMg(CO3)2

Zircon and tourmaline are dense, highly 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

Compaction is a very important part of the lithification process for which of the following
sediments?

mud

mud

silica; calcite

Which of the following best describes bedded gypsum and halite?

evaporates; chemical, sedimentary rocks

________ sandstone contains abundant feldspar, suggesting that the sand was derived by
weathering and erosion of granitic bedrock.

Arkosic

________ cement produces bright-red and yellow colors in some sandstone.

Iron oxide

What is probably the single most important, original, depositional feature in sedimentary rocks?

bedding or stratification

Which of the following would retain the most detailed impressions of fossilized organisms?

very fine-grained volcanic ash deposited in an ancient lake

What is a bittern?

residual brine left after precipitation of halite

________ are further concentrated in a residual brine after NaCl is crystallized.

Potassium, magnesium, and bromine

Which of the following describes the correct order for relative solubility of minerals in sedimentary
rocks?

evaporate minerals are more soluble than calcite and quartz

What is the main difference between a conglomerate and a sedimentary breccia?

breccia clasts are angular; conglomerate clasts are rounded

A graywacke is ________.

a sandstone with the sand grains embedded in a clay-rich matrix

Which type of limestone consists mainly of tiny, marine fossils composed of calcite?

chalk

________ is not a common cementing agent for sandstones.

Fluorite

Detrital sedimentary rocks are classified (named) based on the ________.

grain sizes of the detrital particles

Flint, chert, and jasper are microcrystalline forms of ________.

quartz; (SiO2)

Which of the following sedimentary rocks would you expect to have originally been deposited by
fast-moving streams?

conglomerate

Which type of sediment undergoes the most compaction as it lithifies to sedimentary rocks?

marine mud

Which of the following sedimentary features would typically be found in shales but not in
sandstones?

mud cracks

________ is the most common type of chemical sedimentary rock.

Limestone

________ is a form of calcium carbonate.

Travertine

Which one of the following is not a chemical sedimentary rock or evaporite?

shale

Which of the following is not a type of limestone?

arkose

Oolitic limestone is most likely to form in what type of depositional environment?

shallow, clear, marine waters with vigorous current activity

Which of the following sedimentary features can each be used to determine paleocurrent
directions?

ripple marks and cross stratification

Coal beds originate in ________.

freshwater coastal swamps and bogs

Which characteristic is absolutely necessary for a sedimentary rock to have potential as a possible
reservoir rock for oil or gas?

high porosity

Nonclastic textures are common in which of the following sedimentary rocks?

limestones

Clay and muddy sediments lithify to form shales and mudstones.

True

Detrital sedimentary rocks have clastic textures.

True

Peat is thought to be the original material from which coals are formed.

True

Graywacke sandstones are typically better sorted than sandstones lithified from ancient beach
sands.

False

Clastic particles in a sedimentary breccia are rounded and are about the same size as fine-grained
sand.

False

Many limestones are of biochemical origin.

True

Boulder conglomerates suggest deposition by strong winds in a desert.

False

Mud cracks in a shale or mudstone indicate that the mud or clay was deposited in deep waters of
an offshore marine environment.

False

Chalk, coquina, and ancient coral reefs are primarily composed of microcrystalline quartz.

False

Water is gradually expelled from compacting clay and mud sediments.

True

The mineral dolomite, which is the major mineral of the sedimentary rock dolostone, is a carbonate
of calcium and magnesium.

True

tThe chemical sedimentary rock, conglomerate, is composed of gravel-size, rounded, calcite oolites.

False

Detrital sedimentary rocks are classified according to clastic particle size; chemical sedimentary
rocks are named according to the most abundant minerals.

True

A feldspar-rich sandstone is called an arkose.

True