ch 6 hw

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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


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