ch 6 hw
The mineralogical composition of sedimentary rocks is an indicator of the depositional environment
False
Quartz, feldspar, and clay minerals are the most common constituents of sedimentary rocks.
True
Alluvial fans commonly occur in the marine environment.
false
Because wind has a limited capacity to transport sediment, wind deposits are poorly sorted.
false
Fluvial deposits are considered part of the transitional sedimentary environment.
false
Glacial deposits are composed only of particles of gravel size and larger.
false
In bioturbation, most of the original sedimentary structures are preserved.
false
Sand dunes are most likely formed in a wet tropical environment.
false
The chemical formula for dolomite is CaCO3.
false
The most important source rocks for fuels we use today are igneous rocks.
false
A well-sorted sediment contains particles that are of about the same size.
true
At various times during Earth's history, the western half of the United States has been covered by an inland sea.
true
Cross-bedding can form via wind or water currents.
true
Current flow direction can be determined by cross-beds and some ripple marks.
true
Deltas form when streams or rivers encounter a standing body of water, such as an ocean or lake.
true
Dense marine flows composed of a mixture of water and sediment are called turbidity currents.
true
Graded beds refer to sedimentary beds that show a decrease in grain size from bottom to top.
true
Lagoons and reefs are sites of carbonate deposition.
true
Most sedimentary rocks are deposited by water or underwater.
true
Mud cracks indicate an episode of deposition and perhaps flooding followed by drier conditions.
true
Pelagic clay deposits are associated with deep marine environments.
true
Pelagic oozes are derived from the shells of microscopic marine organisms.
true
Rocks above and below a bedding plane may have different physical properties.
true
Sedimentary structures form prior to lithification.
true
The most common detrital sedimentary rocks are sandstones and mud rocks.
true
____ are transitional environments because they ____.
Barrier islands; involve marine and continental processes
____ would indicate deposition occurred in a high-energy environment.
Conglomerates
A deposit of sediment where a stream or river enters a lake or the ocean is called a(n) ____.
Delta
In a well-sorted rock, ____.
all grains are about the same size
A long sand body more or less parallel with a shoreline but separated from it by a lagoon is a ____.
barrier island
The churning of sediments by organisms that burrow through it is ____.
bioturbation
Limestone deposits most likely form in which environments?
carbonate reefs
From continent to deep-ocean, basin what is the order of offshore environments?
continental shelf continental slope, continental rise
Current ripple marks differ from wave ripple marks because ____.
current ripple marks are asymmetrical
Prograding delta deposits differ from turbidity current deposits because ____.
delta deposits coarsen upwards, with fine sediments on bottom and coarse sediments on top
Large-scale cross-beds (greater than 10 ft. in height) commonly indicate a ___________ sedimentary environment.
desert dune
A sample of deep-sea sediments would be expected to contain ____.
fine-grained clays and ooze
Till deposits are associated with ____.
glaciers
A sedimentary layer in which grain size decreases from the bottom up is ____.
graded bedding
Turbidity currents deposit sediments in ____ beds with ____.
graded; fine sediments on top and coarse sediments on bottom
The most common chemical sedimentary rock is ____.
limestone
Fine-grained clays, silts and muds would always indicate a ____ environment.
low-energy
Deltas grow larger through the process of ____.
progradation
Fluvial is a term referring to ____.
river activity and river deposits
The degree to which detrital particles have had their sharp edges and corners smoothed off by abrasion is ____.
rounding
Analysis of ____ is the best way to determine depositional environments.
sedimentary structures
The majority of sediment transported across the continental shelf travels through ____.
submarine canyons
Herringbone crossbeds develop in tidal flats because ____.
tidal inflows and outflows
Example of a biogenic sedimentary structures is ____.
trace fossil
Graded bedding forms when ____.
turbidity currents deposit first coarse-grained sediment then fine-grained sediment
