Quiz and Flashcards on Detrital Sedimentary Rocks

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Questions and Answers

What are detrital sedimentary rocks made of?

Volcanic ash and lava

Chemical precipitates

Pieces of pre-existing rocks (correct)

Organic remains

How does the composition of a detrital sedimentary rock change as the rock fragment travels farther from its mountain source?

It becomes more uniform

It becomes larger in size

It becomes less eroded

It becomes more eroded and uniform in composition (correct)

How is the texture of a detrital sedimentary rock determined?

By the amount of organic matter present

By its chemical composition

By its grain size, sorting, and roundness (correct)

By its color and luster

What is a depositional feature in a sedimentary rock?

A visible pattern formed during lithification Signup and view all the answers

Why do geologists study the features preserved in sedimentary rocks?

To interpret what environments existed in the earth's past Signup and view all the answers

What happens to the large grains like cobbles and pebbles when the river exits the mountains?

They are deposited on the side of the river due to the drop in flow and energy Signup and view all the answers

What is a defining characteristic of conglomerate and breccia sedimentary rocks?

Angular to sub-angular grains and very poorly sorted Signup and view all the answers

How do organic chemical rocks like limestone form?

Small ocean organisms pull compounds out of solution to create their shells or skeletal structures Signup and view all the answers

Under what conditions do inorganic chemical rocks form?

In extremely dry environments with high water evaporation Signup and view all the answers

What is a characteristic feature of micritic limestone formed from inorganic processes?

Very fine-grained rock with a very uniform composition Signup and view all the answers

How do detrital or clastic sedimentary rocks form?

By the transportation and deposition of sediment and rock fragments Signup and view all the answers

What is the key process involved in creating both detrital and chemical sedimentary rocks?

Lithification Signup and view all the answers

What role does compaction play in the formation of sedimentary rocks?

It presses the grains tightly together under the overlying weight Signup and view all the answers

What happens as burial continues in the lithification process?

Minerals dissolve in the water and precipitate inside the sand particles Signup and view all the answers

What is the name of the common process involved in forming most sedimentary rocks?

Lithification Signup and view all the answers

Study Notes

Detrital Sedimentary Rocks

Detrital sedimentary rocks are made of fragments of pre-existing rocks that have been transported away from their source and deposited in a new location.
As the rock fragments travel farther from their mountain source, the composition of the detrital sedimentary rock changes, with smaller grains and more rounded shapes indicating greater distance from the source.

Textures of Detrital Sedimentary Rocks

The texture of a detrital sedimentary rock is determined by the size and shape of the rock fragments, as well as the amount of cement between them.

Depositional Features

A depositional feature in a sedimentary rock is a characteristic that forms during or shortly after deposition, such as cross-bedding or graded bedding.

Importance of Sedimentary Rocks

Geologists study the features preserved in sedimentary rocks to gain insights into the geological history of an area, including the environments and processes that operated in the past.

Detrital Sedimentary Rock Formation

As a river exits the mountains, the large grains like cobbles and pebbles are deposited, while the smaller grains continue to be transported.
Conglomerate and breccia sedimentary rocks are defined by their coarse-grained texture, with conglomerate having rounded grains and breccia having angular grains.

Chemical Sedimentary Rocks

Organic chemical rocks like limestone form through the accumulation of calcium carbonate from organic sources, such as shell fragments or coral reefs.
Inorganic chemical rocks form through chemical precipitation, such as when minerals precipitate out of solution in a hypersaline lake.
Micritic limestone formed from inorganic processes is characterized by a fine-grained, microcrystalline texture.

Lithification Process

Detrital or clastic sedimentary rocks form through the lithification process, which involves compaction, cementation, and other processes.
The key process involved in creating both detrital and chemical sedimentary rocks is lithification, which transforms sediment into sedimentary rock.
Compaction plays a crucial role in the formation of sedimentary rocks, as it squeezes out pore space and helps to bind the sediment grains together.
As burial continues in the lithification process, the sediment becomes increasingly compacted and cemented, eventually forming a solid sedimentary rock.
The common process involved in forming most sedimentary rocks is diagenesis, which includes all the changes that occur in sediment after deposition, from compaction to cementation.

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Test your knowledge on the formation of detrital and chemical sedimentary rocks, their components, and the processes involved in their formation.

Detrital vs. Chemical Sedimentary Rocks

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