Chapter 6 Exam

_____ is a coarse-grained sedimentary rock formed by the cementation of rounded gravel.

Conglomerate

______ forms from limestone when the calcium in calcite is partially replaced by magnesium.

Dolomite

Rock salt is composed of the mineral ______.

Halite

_____ are massive deposits of limestone.

Reefs

All evaporites have a crystalline texture.

True

Sedimentary structures are features found in sedimentary rocks that provide clues that help interpret their transport and deposition.

True

Sediments are unconsolidated, which means the grains are separate and unattached to one another.

True

Sorting is the process by which sediment grains are selected and separated according to grain size.

True

The environment of deposition is determined by the location in which deposition occurs.

True

A(n) ___ is sandstone containing a significant amount of feldspar.

arkose

_______ sediments are deposited or precipitated as a result of the actions of organisms.

biochemical

_______ limestones are precipitated through the actions of organisms.

bioclastic

___ is a sedimentary rock formed by the cementation of coarse angular fragments of rubble.

breccia

The most common cements are _____ and ____.

calcite; quartz

______ are sedimentary rocks deposited by direct precipitation of minerals from water.

chemical rocks

A sedimentary rock that consists of sediment grains bound by cement into a rigid framework is called _______.

clastic

Peat is a brown lightweight unconsolidated deposit that ultimately can transform into ____.

coal

In sandstone, a thick bed will often consist of a series of thinner inclined beds called ____.

cross beds

A(n) ____ is a body of sediment deposited when a river flows into standing water, like a lake or sea.

delta

The most common type of sedimentary rocks are ____.

detrital

___ are features found within sedimentary rock that formed during or shortly after deposition.

sedimentary structures

____ is the process by which sediment grains are selected and separated according to grain size by agent of transportation.

sorting

The principle of ___ holds that, in a stack of horizontal layers the oldest layer is on the bottom and the layers become younger upward.

superposition

Sand grains can be distinguished from silt grain by ____.

the gritty feel between the fingers.

Under what conditions is a sediment considered to be well-sorted?

when the grains are nearly all the same size

_____ is a term that describes a series of visible layers in sedimentary rock.

bedding

Sedimentary rock on ____ will enable planetary geologists to one day unravel its history.

mars

Silt is mostly composed of ___ grains.

quartz

Chalk is not a sedimentary rock.

False

Plate tectonics do not influence the distribution of sedimentary rocks.

False

The principle of superposition states that in a stack of horizontal layers the oldest layer is on top.

False

A sandstone with more than 25% sand-sized feldspar is an arkose.

True

Clay is the finest sediment.

True

Detrital sedimentary rocks form from cemented sedimentary grains that are fragments of a preexisting rock.

True

Dolostone (dolomite) often forms from limestone.

True

Limestone is a sedimentary rock composed mostly of the mineral calcite.

True

Lithification is the general term for the processes that convert loose sediment into a sedimentary rock.

True

Most sediment is transported some distance by gravity, wind, water or ice.

True

Most shale contains both clay-sized and silt-sized particles.

True

Mud cracks form only in sediment exposed above water.

True

Sedimentary breccia is a sedimentary rock formed by cementation of coarse angular fragments of rubble. False

True

Sedimentary rocks can form from the deposition of solid particles eroded from pre-existing rock or from the deposition of the hard parts of organisms.

True

Continental environments include all of the following except __.

coral reefs

A(n) ___ is a body of rock of considerable thickness that is large enough to be mappable and with characteristics that distinguish it from adjacent rocks.

formation

A _____ is a layer of sedimentary rock with a vertical change in particle size, usually from coarse at the bottom to fine at the top.

graded bed

In order of decreasing size (largest listed first), sedimentary grain sizes include __.

gravel, sand, silt, and clay

A(n) ______ is sandstone in which more than 15% of the rock's volume consists of fine-grained matrix.

graywacke

The two primary types of carbonate sedimentary rocks are ___ and dolostone.

limestone

______ is the general term for the processes that convert loose sediment into sedimentary rock.

lithification

___ are polygonal patterns that form in very fine sediment as it dries.

mud cracks

_____ form(s) only in fine-grained sediments that are exposed to air.

mudcracks

____ limestones have a clastic texture.

oolitic

Oil and natural gas originate from _____ in marine sediments.

organic matter

Asymmetrical _____ are produced by current flowing in a single direction.

ripple marks

Boulders include all rounded particles coarser than 2 mm in diameter.

False

Carbonate rocks contain the _____ ion as part of their chemical composition.

CO32-

_____ are precipitated as a result of inorganic processes.

Oolitic limestones

___ is a hard, compact, very fine-grained sedimentary rock composed entirely of silica.

chert

_______ is an organic rock formed from the compression and alteration of plant remains such as leaves, twigs, and tree trunks.

coal

______ is the shift to a tighter packing of sediment grains due to the weight of overburden.

compaction