Deck 13: The Early Paleozoic World

Question 1

In the concentric pattern of sediment deposition around the margin of Laurentia during Middle Cambrian, detritus from land grades laterally into

A) Burgess Shale.
B) shallow-water carbonates.
C) deep-water deposits.
D) volcanic islands.

Answer 1

B

Question 2

The most spectacular Early Cambrian arthropods were the

A) trilobites.
B) mollusks.
C) anomalocarids.
D) brachiopods.

Answer 2

C

Question 3

__________ found as fossils show us that fish first evolved during Cambrian.

A) Sediment flooring cavities
B) Isolated bony plates
C) Thrombolites
D) Teeth and skeletal bones

Answer 3

B

Question 4

__________ are the horn corals, which became well represented on the seafloor during Ordovician.

A) Rugose corals
B) Tabulate corals
C) Stromatoporoids
D) Coral-strome reefs

Question 5

The burrow Treptichnus pedum marks the base of

A) Lower Ordovician.
B) Upper Cambrian.
C) Middle Cambrian.
D) Lower Cambrian.

Question 6

The hard-skeleton burrowers of the Ordovician were

A) nautiloids and graptolites.
B) bivalve mollusks and trilobites.
C) conodonts and conodont ancestors.
D) worms and other soft-bodied organisms.

Question 7

___________ experienced a mass extinction at the end of Cambrian, from which they later recovered.

A) Graptolites
B) Brachiopods
C) Trilobites
D) Conodonts

Question 8

During Ordovician, the decline of stromatolites was due to

A) grazing by marine animals.
B) competition from organic reefs.
C) the mass extinction among trilobites.
D) attacks by predators such as the nautiloids.

Question 9

Cambrian seas

A) rarely encroached on the land and thus marine deposits are rare.
B) did not cover much land area due to continued orogenic activity.
C) were at an all-time low level during the whole of the period.
D) were widespread due to many low-lying land masses.

Question 10

Early Cambrian suspension feeders included

A) anomalocarids and monoplacophorans.
B) archaeocyathids and other sponges.
C) brachiopods and eocrinoids.
D) stromatolites and other animals.

Question 11

The main Ordovician floating animals were the

A) nautiloids.
B) graptolites.
C) conodonts.
D) brachiopods.

Question 12

The earliest known vertebrate animals were the

A) conodonts.
B) brachiopods.
C) archaeocyathids.
D) deposit feeders.

Question 13

The largest Ordovician predator was a

A) variety of stromatoporoid.
B) straight-shelled nautiloid.
C) species of starfish.
D) bivalve mollusk.

Question 14

The oldest organic reefs with skeletal structures formed during __________ and were composed of __________.

A) Late Proterozoic; brachiopods
B) Early Cambrian; archaeocyathids
C) Earliest Cambrian; stromatolites
D) Late Cambrian; sponges

Question 15

Each of the first three Cambrian mass extinctions of trilobites was probably due to

A) gradual climatic cooling.
B) sudden climatic warming.
C) sudden climatic cooling.
D) gradual climatic warming.

Question 16

Pikaia was a swimming chordate whose fossils are found in the

A) Tommotian fauna.
B) Burgess Shale.
C) Rocky Mountains of Colorado.
D) new fossil sites of China.

Question 17

What was the position and orientation of Laurentia with respect to the Late Cambrian equator?

A) Laurentia was near, but not at the equator.
B) Laurentia lay astride the equator.
C) Laurentia was near the northern pole.
D) Laurentia was near the southern pole.

Question 18

The conodontomorphs first appeared during

A) Early Ordovician.
B) Late Cambrian.
C) Middle Cambrian.
D) Early Cambrian.

Question 19

The trilobites first appear during

A) Early Ordovician.
B) Late Cambrian.
C) Middle Cambrian.
D) Early Cambrian.

Question 20

The organism that left tracks on sediment flooring cavities within archaeocyathid reefs as well as fossil remains within sediment in those cavities was a(n)

A) jawless fish.
B) trilobite.
C) thrombolite.
D) echinoderm.

Question 21

The shift toward heavier oxygen and carbon isotopes at the base of the Hirnantian Substage at the top of the Ashgill Stage indicates that

A) Gondwanaland arrived at the south pole.
B) Gondwanaland arrived at the north pole.
C) glaciers spread across Gondwanaland.
D) glaciers melted from Gondwanaland.

Question 22

The second phase of the great Ordovician mass extinction is associated with the disappearance of many fossil groups

A) that were adapted to warm conditions.
B) that were adapted to cool conditions.
C) at the level that marked the onset of marine transgression.
D) at the level that marked the onset of marine regression.

Question 23

During Late Cambrian and Early Ordovician, eastern North America (Laurentia) was a

A) tectonically active region, which had a subduction zone.
B) passive continental margin with vast carbonate shelves.
C) site of vast continental rifting and volcanism.
D) tectonically active region, which had extensive volcanic activity.

Question 24

During the great mass extinction of Late Ordovician, many bottom-dwelling species of __________ died out.

A) acritarchs
B) bryozoans
C) graptolites
D) nautiloids

Question 25

That the concentric layers within Ordovician ooids precipitated from seawater with a Mg:Ca ratio less than 2 is indicated by

A) concentric layers of aragonite around a nucleus.
B) elongate calcite crystals that radiate outward from the center.
C) a nucleus that may have been a pellet or small shell fragment.
D) spicules and other organic structures in the layers and nucleus.

Question 26

The movement of __________ toward the south pole is associated with the onset of __________ during Late Ordovician.

A) Baltica; global warming
B) Baltica; the spread of glaciers
C) Gondwanaland; the spread of glaciers
D) Gondwanaland; global warming

Question 27

The Taconic orogeny was the result of a collision between Laurentia and

A) Baltica.
B) both Baltica and Gondwanaland.
C) both Baltica and Gondwanaland, plus several islands.
D) both Gondwanaland and Siberia, plus exotic terranes.

Question 28

The development of a Late Ordovician ice sheet on Gondwanaland resulted in

A) global warming.
B) glacial melting.
C) global regression.
D) global transgression.

Question 29

At the top of the Cambrian Bonanza King Formation of Nevada, the trilobite __________ becomes extinct and the trilobite __________ appears.

A) Tricrepicephalus; Coosella
B) Kingstonia; Kormagnostus
C) Deiracephalus; Carinamala
D) Coosia; Carinamala

Question 30

Upper Ordovician sediments across much of Ohio and West Virginia consist of

A) molasse and flysch.
B) sandstones and mudstones.
C) limestones and dolostones.
D) dolostones and mudstones.