Deck 5: Sedimentary Environments

Question 1

Most alluvial fans include broad deposits of coarse, cross-stratified sediments laid down in a complex network of channels, which originate in

A) sand dunes.
B) debris flows.
C) playa lakes.
D) braided streams.

Answer 1

D

Question 2

__________ beds, which consist largely of sand and silt, are nearly horizontal, except where they are locally cross-bedded.

A) Delta-front
B) Delta-plain
C) Prodelta
D) Distributary channels

Answer 2

B

Question 3

Among coarse-grained deposits of ancient deserts and arid basins, the sedimentary structure called __________ is characteristic of sand dunes.

A) debris flows
B) braided stream deposits
C) trough cross-stratification
D) varves

Answer 3

C

Question 4

The alternating layers of coarse and fine sediment that typically accumulate in glacial lakes are called

A) moraines.
B) outwashes.
C) dropstones.
D) varves.

Question 5

__________ are waves and shallow currents that flow along the coast and sweep sand parallel to the shoreline.

A) Barrier island-lagoon complexes
B) Longshore currents
C) Tidal deltas and tidal flats
D) Deltaic cycles

Question 6

In the coarse-to-fine vertical sequence in meandering stream deposits, the __________ lie above the point-bar deposits.

A) channel deposits
B) flood plain sediments
C) natural levee deposits
D) channel gravels

Question 7

__________ is loose sediment that contains organic matter and accumulates because of contact with the atmosphere instead of under water.

A) Nodule
B) Humus
C) Caliche
D) Soil

Question 8

Evidence of freshwater lake deposits in geologic history does not come from

A) sediment grain size differences.
B) close association with marine sediments.
C) fish and other freshwater fossils.
D) associated river sediments.

Question 9

Sedimentary deposits in front of a moraine, which consist of well-stratified layers of gravel, cross-bedded sand, and mud, are called

A) outwash.
B) tillite.
C) dropstones.
D) varves.

Question 10

In soils, humus is destroyed by combining with

A) topsoil.
B) caliche.
C) oxygen.
D) aluminum.

Question 11

As a delta progrades, deposits of the __________ will lie directly on top of deposits of the prodelta.

A) delta-plain
B) prodelta
C) delta-front
D) distributary channels

Question 12

In Nebraska, Oligocene and Miocene beavers lived in soil features called

A) nodules of caliche.
B) oxisoils.
C) fossil burrows.
D) unconformities.

Question 13

The lithified, unsorted, heterogeneous material deposited by ancient glaciers is called

A) till.
B) tillite.
C) moraine.
D) outwash.

Question 14

When a barrier island-lagoon complex progrades, ___________ deposits are formed on top of sediments of the lagoon.

A) barrier beach
B) tidal-flat and marsh
C) tidal delta
D) tempestite

Question 15

Meandering river sediments that accumulate inside of a river bend form a __________ deposit.

A) backswamp
B) flood plain
C) point-bar
D) natural levee

Question 16

An example of a depositional environment found along the shores of lagoons is a

A) barrier island-lagoon complex.
B) tidal delta.
C) tidal flat.
D) river-dominated delta.

Question 17

Many preserved sedimentary cycles of meandering stream deposits are actually partial cycles because of

A) deep cutting by a younger channel.
B) sinking or subsiding relative to surrounding terrain.
C) the change from meandering to braiding channels.
D) the development of natural levees.

Question 18

A key characteristic of meandering streams that is NOT a key characteristic of braided streams is

A) the development and preservation of multiple channels.
B) occurrence in gently sloping terrain far from uplands.
C) that they are overloaded or choked with sediments.
D) transportation of mostly gravel and sand and very little silt or clay.

Question 19

(A) Sedimentary feature(s) that provide(s) detailed information about ancient streams choked with sediment is/are known as preserved

A) deposits of halite and gypsum.
B) petroleum and natural gas.
C) bar of gravel and sand.
D) deposits of lakes and lagoons.

Question 20

In a river-dominated delta, the site of functioning distributary channels is called the

A) active lobe.
B) abandoned lobe.
C) bird-foot delta.
D) river-dominated delta.

Question 21

Above depths of 4000 meters, the dominant low-latitude sediment on the sea floor is/are

A) calcareous ooze.
B) siliceous ooze.
C) reef talus.
D) turbidites.

Question 22

The uppermost layer of a complete, river-dominated deltaic cycle is composed of sediments formed in the __________ environment.

A) prodelta
B) delta-front
C) delta-plain
D) marsh

Question 23

The pile of reef debris that has fallen from the steep, wave-swept reef front is called

A) a reef flat.
B) patch reefs.
C) a talus.
D) an atoll.

Question 24

Sandy storm-produced beds in quiet-water shelf deposits are called

A) tidal deltas.
B) talus.
C) tempestites.
D) turbidites.

Question 25

The position of the major deep-sea fans of the world is dependent on the

A) depth of the abyssal plain.
B) slope of the continental rise.
C) location of submarine canyons.
D) proximity to a major desert area.

Question 26

A graded bed formed by the flow of dense sediment-charged water moving down a slope into deeper water is known as a

A) turbidite.
B) turbidity current.
C) calcareous ooze.
D) pelagic sediment.

Question 27

Cooling of seawater in contact with the atmosphere increases the concentration of dissolved

A) carbonic acid.
B) calcium carbonate.
C) cyanobacteria.
D) clay minerals.

Question 28

___________ occur in lagoons behind elongate reefs.

A) Patch reefs
B) Barrier reefs
C) Fringing reefs
D) Atolls

Question 29

Knobby, intertidal structures formed by cyanobacteria are called

A) stromatolites.
B) patch reefs.
C) organic reefs.
D) carbonate platforms.

Question 30

A typical coral atoll emerges as the

A) associated volcano rises from the sea floor.
B) volcano becomes extinct and starts to subside.
C) volcano violently resumes eruptions.
D) oceanic plate subsides and with it, the volcanic island.