Geology 101 Chapter 6 UNLV
conglomerate
In the water, clasts bang into each other and into the riverbed, a process that shatters them into still smaller pieces and breaks off their sharp edges. As the clasts are carried downstream, they gradually become rounded pebbles and cobbles. When the river water slows, these clasts stop moving and form a mound or bar of gravel. Burial and lithification of these rounded clasts produces ______________________.
Arkose
It is generally formed from the weathering of feldspar-rich igneous or metamorphic, most commonly granitic, rocks, which are primarily composed of quartz and feldspar. Created with moderate energy.
Banded Iron
Magnetite/hematite layered with chert
Fine Grained Rocks
Mud, Silt Include: Siltstone
Coal Process
Peat > Lignite > Butiminous Coal > Anthracite Coal
deposition
Process in which sediment is laid down in new locations.
erosion
Processes by which rock, sand, and soil are broken down and carried away (i.e. weathering, glaciation)
Acid Rain
Rain containing acids that form in the atmosphere when industrial gas emissions (especially sulfur dioxide and nitrogen oxides) combine with water.
Medium Grained Rocks
Sand Include: Arkose, Sandstone
Example of Stratographic Sequences
Sandy Sediment > Muddy Sediment > Limey Sediment
clastic (detrital) sedimentary rock
Sedimentary rock that forms when fragments of preexisting rocks are compacted or cemented together.
chemical sedimentary rock
Sedimentary rock that forms when minerals precipitate from a solution or settle from a suspension.
Most common minerals that cement sediment together are (in order from strongest to weakest)
Silica, calcite, hematite
Felsic materials weather...
Slowly; they are generally resistant to weathering.
Tectonic Fracture
The breaking down of a rock from tectonic forces
Frost Wedging
The mechanical breakup of rock caused by the expansion of freezing water in cracks and crevices
Bioturbation
The process by which organisms rework existing sediments by burrowing through muds and sands. Example: roots, burrowing animals
cementation
The process in which minerals precipitate into pore spaces between sediment grains and bind sediments together to form rock.
lithification
The process that converts sediments into solid rock by compaction or cementation.
Mechanical (Physical) Weathering
The type of weathering in which rock is physically broken into smaller pieces. It does NOT change the chemical composition of a rock.
Organic activity can cause mechanical weathering, true or false?
True
mudstone
Very fine-grained sedimentary rock that will not easily split into sheets.
What is necessary for chemical weathering?
Water
regression
When relative sea level falls, the coast migrates seaward—we call this process ______
transgression
When relative sea level rises, the shoreline migrates inland—we call this process ______________.
sorting
____________ of clasts indicates the proportion of clasts in a rock that are the same size.
Sinkhole
a circular depression formed when the roof of a cave collapses; a cavity in the ground, especially in limestone bedrock, caused by water erosion and providing a route for surface water to disappear underground
diagenesis
a collective term for all the chemical, physical, and biological changes that take place after sediments are deposited and during and after lithification
coal
a combustible black or dark brown rock consisting mainly of carbonized plant matter, found mainly in underground deposits and widely used as fuel. It is a rock but NOT a mineral.
sedimentary basin
a depression, created as a consequence of subsidence, that fills with sediment
turbidity current
a downslope movement of dense, sediment-laden water created when sand and mud on the continental shelf and slope are dislodged and thrown into suspension
Alluvial Fan
a fan-shaped mass of material deposited by a stream when the slope of the land decreases sharply
Turbidite
a graded bed of sediment built up at the base of a submarine slope and deposited by turbidity currents
graded bed
a layer of sediment, deposited by a turbidity current, in which grain size varies from coarse at the bottom to fine at the top
Limestone
a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals. This is the second most common sedimentary rock.
oil shale
a soft, fine-grained sedimentary rock from which oil and natural gas are obtained.
dolostone
an abundant carbonate rock composed primarily of dolomite and is formed from limestone where groundwater replaces some calcium with magnesium.
sedimentary structures include...
bedding, cross-bedding, graded bedding, ripple marks, dunes, and mud cracks.
Decaying matter can...
cause a rock to go through chemical weathering faster
The four major classes of sedimentary rocks are...
clastic rocks, biochemical rocks, organic rocks, and chemical rocks
breccia
coarse sedimentary rock consisting of angular fragments; or rock broken into angular fragments by faulting
Types of Chemical Weathering
dissolution, oxidation, hydrolysis
siltstone
fine-grained sedimentary rock generally composed of very small quartz grains
Types of Mechanical Weathering
frost wedging, salt crystal growth, sheeting/unloading, biological activity
Which mineral causes red colored rocks around the Vegas area?
hematite
strata
layers of sedimentary rock
Mud rocks are created at _____ energy.
low
Smaller pieces of rock are more easily moved, therefore...
mechanical weathering facilitates chemical weathering by creating more surfaces
Mafic materials weather...
quickly
Stratigraphic Sequences
relative dating technique; observing patterns of materials in a stratigraphic column to order them in time. Sites with multiple occupations at different times
ripple mark
relatively small elongated ridges that form on a sedimentary bed surface at right angles to the direction of current flow; symmetrical ones found in beaches or tidal flats, bidirectional flow; asymmetrical ones are found in dunes, water or wind flowed in one direction
Salt Wedging
rock disintegration caused by the crystallization of salts from evaporating water
turbidite
rock that forms from a graded bed of sediment built up at the base of a submarine slope and deposited by turbidity currents
biochemical sedimentary rock
sedimentary rock formed from material (such as shells) produced by living organisms; forms from the remains of plants or animals.
Rainwater is naturally...
slightly acidic
As distance of transport increases, grains become...
smaller and more rounded
Hydrolysis
the chemical breakdown of a compound due to reaction with water.
depositional environment
the conditions in which sediment was deposited
compaction
the process by which sediments are pressed together under their own weight
subsidence
the sinking of regions of the Earth's crust to lower elevations
Sedimentary rock can help you determine...
the type of environment that was present at its creation
When sedimentary rocks are mature...
they are usually smaller and about as changed as they are going to get.
When sedimentary rocks are immature...
they still closely resemble the rocks they came from.
Oxidation
A chemical change in which a substance combines with oxygen, as when iron oxidizes, forming rust
travertine
A form of limestone that is deposited by hot springs or as a cave deposit; calcite is coming out of a water solution
Thermal Fracture
A form of weathering brought about by expansion and contraction of the outer surface of a rock caused by intense temperature fluctuations
Chert
A hard, compact, fine-grained sedimentary rock formed almost entirely of silica (quartz). Formed in colder waters.
dune
A hill or ridge of sand piled up by the wind
delta
A landform made of sediment that is deposited where a river flows into an ocean or lake
sandstone
A sedimentary rock formed by cementing grains of sand over time. Formed from moderate energy.
shale
A sedimentary rock formed by the deposition of successive layers of clay. It is the most common sedimentary rock.
evaporite
A sedimentary rock formed of material deposited from solution by evaporation of water in a lake or ocean. Halite and Gypsum are examples of this.
bed
A single layer of sediment or sedimentary rock with a recognizable top and bottom
fossil
A trace of an ancient organism that has been preserved in rock.
sedimentary rock
A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together
Cross bed
A vertical slice cut into a ripple or dune caused by a current of air or water moving in one direction.
Acid Enhanced Dissolution
Acid added to water makes it easier to dissolve rocks
Where is the thickest sedimentary basins?
Along continental margins
Carbonate Platform
An extensive flat, shallow area where both biological and nonbiological carbonates are deposited.
sedimentary structure
Any kind of bedding or other feature (such as cross-bedding, graded bedding, or ripples) formed at the time of sediment deposition.
Coarse Grained Rocks
Boulder, Cobble, Pebble Include: Breccia, Wacke, Conglomerate
Very Fine Grained Rocks
Clay Includes: Mudstone (can't easily break apart), shale (brreaks along bedding), and claystone
What is the difference between conglomerate and breccia?
Conglomerate has rounded edges, breccia has sharp edges and angles. Both are formed from high energy events.
Unloading Fracture
Fracture caused by pressure being removed from a rock
Cooling Fracture
Fracture caused by the cooling of rock
Bicarbonate
HCO3-
