Geology Chapter 7 - Sedimentary environments and rocks
Carbonate rocks exposed at the surface in wet environments will ______.
dissolve and weather readily
The type of carbonate rock that is formed when magnesium replaces calcium in limestone to form a different mineral is _________.
dolomite
Carbonate rocks found in _________ environments are commonly massive, gray in color, and are erosion-resistant, whereas carbonate rocks found in _________ environments are often pitted, holey, and very fractured.
dry wet
Fine-grained clastic rocks are ______.
easily eroded
By studying ancient sedimentary rocks, scientists can better understand modern _________ processes.
environmental
Limestone that forms in continental environments is created through ______ in arid environments and through ______ in springs and caves.
evaporation; precipitation
The most common clastic sedimentary rocks are made of the clasts that are ______.
fine grained (smaller than sand)
The adjective _________ refers to the processes and sediment of streams and rivers.
fluvial
The red rocks of Red Rock Amphitheater west of Denver are relatively old compared to other rocks in the area, yet they are at the surface because of ______.
folding and faulting
A rock unit that is distinct and laterally traceable is called a(n) _________.
formation
Some of the most informative clues found in sedimentary rocks are indicated by _________, as they suggest whether the rock was deposited on land or in the water and reveal many specifics about past climatic conditions.
fossils
Which of the following statements correctly describes the geologic history shown in this geologic diagram?
The sedimentary rocks were deformed by tectonic forces. A sequence of sedimentary rocks originally was deposited in horizontal layers.
A sandstone with a history that can be traced to beach deposits will likely include sand and ______.
pieces of shells pebbles and larger clasts
Rocks rich in what mineral tend to have a poor solubility during weathering?
quartz
What is a carbonate rock?
A carbonate rock is a sedimentary rock that consists of carbonate ions bonded to other elements.
Which of the following best describes the way(s) in which limestone forms?
A combination of biological and inorganic processes
The vast ocean seafloor is covered with _________-sized sediments more than any other size deposit. This is the primary reason that shale is a very common sedimentary rock.
clay
Which of the following processes would be most likely to form the well-rounded clasts found in a conglomerate rock sample?
A long distance of transport Wave action along a beach
The black sand beaches in Hawaii reflect what origin for the sand?
Basaltic volcanoes
Match the attribute found in sedimentary rocks to the type of information it provides.
Bed thickness - Small or large depositional events Color - Formed on land or in the water Clast size - Distance of transportation Fossils - Formed on land or in the water, and type of climate Cross beds - Direction of wind or water current
What is the most likely location for a lagoon?
Between the shore and a reef
Breccia and conglomerate are the coarsest types of clastic sedimentary rocks. Match the rock type to the shape of clast.
Breccia - Angular clasts Conglomerate - Rounded clasts
Match the rock with its environment of deposition.
C (shale and limestone): shallow sea A (red sandstone): large sand dune B (tan sandstone with shells): beach sand D (breccia): mountainous area
Identify from the following list possible environments or conditions that can lead to the formation of clay or silt deposits.
Chemical weathering of soils Windblown material generated by glaciers Bottoms of lakes Floodplains of river systems
Choose all those statements that correctly describe limestone.
Commonly includes shells Forms in water from various processes Is known as a carbonate Gray or yellowish in color
Which process removes excess water from sediment and can reduce the volume of the sediment by 40%?
Compaction
The coarsest types of clastic sedimentary rocks are breccia and conglomerate. ______ has rounded clasts, whereas ______ has angular clasts.
Conglomerate; breccia
What are the three types of beds formed by sedimentary layers?
Graded Cross Parallel
Match the resource found in sedimentary rocks with its most common, current societal use.
Groundwater - Fresh supplies essential to life Petroleum - Transportation and energy Coal - Electrical energy Salt - Food, medicine, industry Limestone (cement) - Construction
What can geologists learn by studying sequences of ancient sedimentary rocks?
How climate changed over time How environments changed over time
Which of these describe the Dakota Formation represented in the geologic diagram? (See the section 7.15 in the text if you need more information about the rocks.)
It has been folded and faulted into its current position. It is younger than the Paleozoic sandstone and conglomerate.
The angular clasts typical of breccia indicate what about the distance of transport?
It represents a short distance of transport.
The effect of transportation on a pebble's particle size is best summarized by which statement?
Its size decreases.
Earth materials that are soluble in water or react to a weak acid commonly have what type of appearance?
Pitted Grooved
Identify the factors that strongly influence the size, shape, and/or sorting of sedimentary clasts.
Steepness of slope Strength of current Sediment supply Agents of transport
Match the nonclastic sedimentary rock with the process by which it typically forms.
Rock salt and gypsum - Evaporation Dolostone - Chemical replacement Chert and iron-rich formations - Precipitation
Which of these resources are contained in sedimentary rocks?
Salt Coal Uranium Water
Which of these rock types are clastic sedimentary rocks?
Shale Conglomerate Sandstone
Fine-grained rocks are the most common type of clastic rocks. Select all of the following rock types that are fine-grained clastic rocks.
Shale Siltstone Mudstone
Match the predominant sediment size (left) to its rock type (right)
Slit - siltstone Clay - shale Slit mixed with clay - mudstone
Which of these rocks were deposited completely under water?
The middle limestone The grey shales
Which of the following interpretations is the least likely for these red titled sandstones, conglomerates, and breccias?
They were deposited in deep water.
What can be inferred about the rocks in the photographs?
They were deposited on land or along the shore. The climate was warm enough for life.
A formation is defined as ______.
a rock unit that is distinct and laterally traceable
A very well-sorted sandstone with large-scale cross-bedding indicates the sand was likely ______.
deposited by the wind in dunes
Nonclastic sedimentary rocks formed by both biological and chemical processes are known as ______ rocks.
biochemical
The hot spot volcanoes of Iceland and Hawaii create a tremendous amount of basalt, so nearby beaches are made of ______ sand.
black
The rounded clasts in this sedimentary deposit were likely transported ______, and were rounded by a rolling action during this transport.
by flowing water
A sandstone containing mostly sand but mixed with rounded pebbles and pieces of shells indicates deposition ______.
by waves at the beach
Limestone and other related sedimentary rocks are also called _________ rocks because they are composed of carbonate ions bonded to other elements.
carbonate
A soft, very fine-grained limestone formed via the accumulation of the calcium carbonate remains of microorganisms is known as ______.
chalk
After sediment is buried, the process of _________ pushes clasts together and pressure forces out excess water.
compaction
The three types of sedimentary layers are graded beds, _________ beds, and parallel beds.
cross
A sandstone with a pinkish or reddish color that is the result of oxidation of iron-bearing minerals indicates the sand was ______
deposited on land and exposed to air
When we say that sediment lithifies, we mean that it ______.
hardens into sedimentary rock
Because shales and siltstones are easily eroded, the areas where they are exposed typically ______.
have soft slopes and soil cover
The typical large clasts found in breccia indicate that the energy levels of the transporting agent were ______.
high
Limestone is formed ______ by organisms such as coral that extract calcium carbonate from the water to form their shells and skeletons.
in reefs in oceans in seawater
A nearshore water that is sheltered from wave action by a reef or islands will form a(n) _________.
lagoon
The nonclastic sedimentary rock _________ forms from the accumulation of calcium carbonate, often from the remains of animals.
limestone
Travertine is a type of ______ that forms through precipitation in springs, lakes, and caves.
limestone
Sedimentary clasts are ______.
loose fragments of rocks and minerals
Lithifies is defined as ______.
loose sediment hardening into sedimentary rock
Clay and silt-sized particles tend to be deposited in areas of ______ energy.
low
Most of the material contained within nonclastic sedimentary rocks consists of ______.
materials formed through biological activity such as making shells or other hard parts minerals precipitated from solution as water evaporates
Lime muds and clastic limestone sands are deposits that form carbonate rocks in ______ environments.
nearshore
Shale is a common sedimentary rock because ______.
one of the places clay is deposited is very widespread (the seafloor)
Sedimentary rocks are usually comprised of material that comes primarily from ______.
other locations
Sediment is often formed from ions in the solution. The ions are _________ by inorganic chemical reactions or biological activity (e.g., corals).
precipitated
Sedimentary facies shift toward the sea as the sea moves out during a ______.
regression
When the sea retreats because sea level drops and/or land is uplifted, a(n) _________ occurs.
regression
Different environments tend to produce sandstones that ______.
reveal clues about their differing origins
As boulders are moved downstream and weathering breaks them into smaller clasts, they first become cobbles, then pebbles, and finally _________, or smaller particles.
sand
Sandstone is defined by being mostly or wholly composed of _________ -sized grains. (Hint: We are not looking for a number here, but a term.)
sand
Sandstone is common because ______.
sand occurs in many environments
Sandstone is, by definition, largely composed of ______.
sand-sized grains
Loose fragments of rocks and minerals are referred to as _________.
sediment
Clastic sedimentary rocks are classified primarily on the basis of ______.
sediment size
Geologists use _________ rocks to determine past environments of deposition on Earth's surface. These types of rocks preserve a variety of characteristics that might suggest temperature, elevation, geographic location, and changes in climate.
sedimentary
Many resources that are essential to our modern lifestyles are found in _________ rocks. Examples include uranium, coal, petroleum, salt, and groundwater.
sedimentary
Petroleum, coal, and water are all resources found most frequently in ______ rocks.
sedimentary
Sandstone, conglomerate, and shale are types of common clastic _________ rocks.
sedimentary
The distance that sediment has been transported from its source area is a key factor controlling clast _________, shape, and sorting.
size
The primary characteristic used to classify clastic sedimentary rocks is the _________ of clasts.
size
Geologists use characteristics such as bedding, mudcracks, and color preserved in sedimentary rocks to determine ______.
the environment in which the rocks were deposited
Fluvial refers to ______.
the processes and sediment of streams and rivers
Many sedimentary rocks exposed in the Denver region are tilted at a high angle to the horizontal, indicating that ______.
they were deformed after they were deposited and lithified
The advance of the sea across a region is known as a ______.
transgression
The movement of the sea across a region that was previously dry is caused by a rise in sea level and/or the lowering of the land surface; this is called a(n) _________.
transgression
Sedimentary clasts (pieces of other rocks) are formed by ______.
transport weathering
True or false: Clastic sedimentary rocks are usually comprised of sediment that comes mainly from other locations.
true
True or false: Fine-grained clastic rocks are composed of grain sizes that are too small to see unaided.
true