Geology 1001 Midterm: Ch. 5
Sedimentary environments are based on what 4 things?
1. Location & plate tectonic setting 2. Transport agent 3. Organic process modify sediments 4. Climate
Bioturbation is the reworking of soils and sediments by ____ and ____.
Animals, plants
How are clastic sedimentary rocks classified?
Based on their size of clast (rock fragments) that comprise them, grain size, chemical composition
Cross-bedding are sets of ____ ____ within rock layers that are ____ at angles as large as 35 degrees from the horizontal bed.
Bedded material, inclined
Clastic rocks are composed of predominantly ____ ____ or older weathered and eroded rocks.
Broken pieces
Diagenesis is the ____ of sediment's texture during and after formation.
Change
What are the 3 types of sedimentary rocks?
Clastic, biochemical, chemical
Diagenesis has what 3 steps?
Compaction, dewatering cementation & mineral changes
What are some effects of bioturbation?
Diagenesis, displacement of microorganisms and non-living particles
What are evaporite rock environments due to?
Evaporation of sea/lake water
In a current of water or air, the larger and denser grains fall ____ than the smaller grains.
Faster
What is a sedimentary environment?
Geographic location that has a peculiar combination of geological process
Sorting is a measure of what?
How similar grain sizes are within a sediment or rock
Sedimentary rocks cover most of what?
Land surface and seafloor
What is angularity the measure of?
Measure of the distance of transportation
Sedimentary structures are structures formed during what?
Sediment deposition
Size determines what?
Settling velocity
What are several examples of carbonate rock environments? What are they due to?
Shelled organisms, precipitation from seawater
What's the different between symmetrical ripples and asymmetrical?
Symmetrical -currents flowing opposite ways -equal slopes Asymmetrical -currents flowing same way -gentler & steeper slopes
Diagenesis occurs at ____ and ____ less than that required for metamorphic rocks.
Temperatures, pressures
Sorting tells us about the relative strength of what?
The current before it dropped its cargo
Your physical geography determines the what in the sedimentary rock cycle?
The dominant process at work in the sedimentary rock cycle
What does it mean when more of the corners of an individual grain in a clastic rock are rounded rather than angular?
The rock has been transported a longer distance
The physical features of sedimentary environments include was 2 things?
Water depth, persistence of currents
What 2 things does erosion include?
Weathering and transportation
What does cross-bedding indicate about the rock's climate?
Wind-blown conditions in either a desert or a beach
Bedding sequences are successions of rock that help geologists do what?
Work out the past environment
What does clast size indicate?
ancient relative current velocity
What sediments are formed in carbonate environments? Evaporite?
1. Carbonate sand/mud, reefs 2. Gypsum, borates, halite, other salts
Weathering is the ____ of rocks and is caused by what environmental features?
-Dissolving -Water, ice, acid, plants, animals, changes in temperature
What are the properties of poorly-sorted rocks vs. well-sorted?
-Poorly= large and small grains jumbled together -Well= All grains same size
Sediment deposition is caused by what and results in what?
-Wind, ice, water, gravity -Builds of layers of sediment
