Term
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Definition
| Form by deposition, accumulation, compaction, and cementation of mineral/organic particles, or through precipitation of minerals from water. |
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Term
| Why are sedimentary rocks important? |
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Definition
They give us information about past climate/ecosystems and how those environments changed through time.
The type of sediment or chemical precipitate can tell you a lot about the environment of deposition.
Example: Coal originates from forests and swamps. Therefore, if there is coal in a sedimentary rock, it shows us what the environment used to be like in that area. |
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Term
| How is sediment converted into sedimentary rock? |
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Definition
| 1. Accumulation of sediment in a sedimentary basin, such as this deltaic environment. 2. Burial and compaction of sediment as it accumulates. 3. Cementation of the sediment by cementing agents dissolved in groundwater. |
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Term
| Where can sedimentary rocks be found? |
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Definition
Sediment and chemical precipitates can accumulate in a variety of sedimentary environments.
However, they will always gravitate towards lower areas. |
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Term
| What are the 2 types of sedimentary rocks |
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Definition
1. Clastic
2. Chemical/Biochemical |
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Term
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Definition
Pieces glued together
Classified based on TEXTURE
Texture = size, shape, sorting of CLASTS
Fine-grained (shale, siltstone)
Medium-grained (sandstone)
Coarse-grained (conglomerate, breccia)
(This is different from texture in igneous rocks which is determined by the size of CRYSTALS, not clasts) |
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Term
| What is the connection between grain size and depositional environment |
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Definition
The lower the energy of the depositional environment, the smaller the grain size of the clastic sedimentary rock. (Sediment traveled a long distance from it's source and is sorted well according to size.)
The higher the energy of the depositional environment, the larger the grain size of the clastic sedimentary rock. (Sediment travels a short distance from it's source and is poorly sorted.) |
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Term
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Definition
Coarse-Grained
Rounded grains
Forms from sedimetn deposited in a fast-moving river
Traveled a short distance from it's source
Moderately to poorly sorted |
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Term
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Definition
Course-grained
Angular grains
Moderately to poorly sorted |
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Term
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Definition
Medium-grained
Often consists of quartz, feldspar, rock fragments, and/or clay |
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Term
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Definition
Fine-grained
Commonly massive
Feels gritty on teeth |
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Term
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Definition
Very fine-grained
Commonly laminated or massive
Feels smooth on teeth
Often can be scratched with fingernail.
Forms deep in oceanic basins, water/particles move very slowly
Sediment travels a long distance from it source |
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Term
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Definition
| traveled far from the source |
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Term
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Definition
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Term
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Definition
1. Silica (SiO2)
2. Fe-oxide (Fe2O3)
3. Cacite
4. Clays
5. Tar (organics) |
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Term
| Chemical and Biochemical Sedimentary Rocks |
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Definition
Minerals precipitates from water and clump together. (rock salt, rock gypsum, dolomite)
Composed of sediment of biological origin. (coal, fossiliferous limestone) |
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Term
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Definition
Composed of Calcite
White/gray/black
May contain fossils or be crystalline
Warm, shallow waters |
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Term
| Why is limestone created primarily in warm, shallow water? |
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Definition
| Warm water typically holds less CO2 than cold water, which causes the solubility of calcite to decrease. |
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Term
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Definition
Composed of Silica (Quartz - scratches glass)
Dense, microcrystalline texture
White to black
Sometimes shows choncoidal fracture
*Chert is composed of almost pure silica (SiO2) that tends to precipitate in deep ocean basins. |
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Term
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Definition
| Chert, like obsidian and quartz, fractures conchoidally, which makes it an ideal material to construct arrowheads and axe blades |
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Term
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Definition
Composed of Gypsum
Massive, crystalline
White to yellow
Can be scratched with fingernail |
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Term
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Definition
Composed of Halite
Massive, crystalline
Clear to white
Tastes like salt |
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Term
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Definition
Composed of plant debris (mostly carbon)
Plant fossils may be present
Combustible
Black and nonporuous |
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Term
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Definition
| Deltas form when rivers flow into a still body of water (i.e., a lake or marine embayment) and deposit sediment as the stream’s energy is reduced. Deltas are subdivided into three distinct layers: 1. Topset, 2. Foreset beds, and 3. Bottomset beds. |
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Term
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Definition
| Cross-beds develop in wind-blown sediment(ex: barchan sand dunes). Sand grains saltate (bounce) along the stoss-face and then avalanche down the steep, lee face, where wind velocities are reduced. |
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Term
| Why do "graded beds" form? |
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Definition
Graded beds form because large sediment grains settle faster in a water column than smaller sediment grain.
In an event such as a submarine landslide, a turbidity current may be created with a chaotic mixture of sediment suspended in the water. It will settle out onto the bottom of the ocean floor and be graded with the largest grains on the bottom of the “turbidite layer.” |
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Term
| What types of sedimentary rocks are most likely to contain fossils? |
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Definition
| fine-grained clastic sedimentary rocks or biogenic sedimentary rocks |
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