CHAPTER 10—EARLY PALEOZOIC EVENTS
CHAPTER OVERVIEW
Phanerozoic rocks are more accessible, less altered, and more fossiliferous than rocks of the earlier eons
and therefore they give us a more complete picture of Earth’s history. The eon we call Phanerozoic is
divided into Paleozoic (“ancient life”), Mesozoic (“middle life”), and Cenozoic (“recent life”). This chapter
looks specifically at Early Paleozoic and specifically the oldest three geologic periods: Cambrian,
Ordovician, and Silurian. These three periods together lasted about 126 million years. The geologic
history of the Paleozoic is characterized by long periods of sedimentation, and punctuated by intervals of
mountain building. In North America, the mountain-building events are called Taconic, Acadian, and
Allegheny.
During Late Neoproterozoic, the supercontinent Rodina broke up into six large continents and several
smaller microcontinents. As these continents drifted, ocean tracts opened and closed and subduction
zones developed that led to multiple thrust faults and orogenies. There was relatively little activity on the
interior of the continents with the site of intense deformation, igneous activity, and earthquakes at the
orogenic belts. Fossils of carbonate secreting marine organisms indicate that shallow seas were common
throughout much of the Earth during this time interval. The chapter discusses the transgression of major
seas that led to a variety of deposits. These sequences of transgression and regression of the seas are
named Sauk, Tippecanoe, Kaskaskia, and Absaroka. Each of these is described in detail. With no
evidence of compressional deformation, it is clear that western North America was a passive margin
during the early Paleozoic. Orogenic activity was more or less continuous at one place or another during
Silurian and Devonian.
While generally warm conditions dominated Laurentia during Early Paleozoic, there were some time
intervals of aridity. Extensive glacial deposits suggest frigid conditions in the region of today’s Sahara
Desert. Other factors that affected the climate included shorter days, stronger tidal effects, and the
absence of vascular plants.
LEARNING OBJECTIVES
By reading and completing information within this chapter, you should gain an understanding of the
following concepts:






Describe the breakup of the supercontinent Rodina, including the resulting land masses
and their locations.
Discuss the continental framework of Early Paleozoic using the events of the more
stable interiors. Consider the terms craton, platform, dome, basin, and orogenic belt.
Explain the approximate duration of the Sauk, Tippecanoe, Kaskaskia, and Absaroka
sequences and how they correspond to Paleozoic orogenic events.
Describe the events in the Cordillera including any deformational activities.
Discuss dynamic events in eastern North America including deposition and the
development of the Taconic Orogeny.
Discuss aspects of Early Paleozoic climates including indicators such as glacial
deposits, evaporites, fossiliferous limestones, extensive reefs, massive limestone
deposits, etc.
CHAPTER OUTLINE
I.
Dance of the Continents
II.
Some Regions Tranquil, Others Active
A. The Stable Interior
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
B. Orogenic Belts
III.
Identifying the Base of the Cambrian
IV.
Early Paleozoic Events
V.
Cratonic Sequences: the Seas Come In, the Seas Go Out
VI.
The Sauk and Tippecanoe Sequences
A. The First Major Transgression
B. Islands in the Inland Sea
C. Cambrian Rocks in the Southwest: A Transgressive Succession
D. The Second Transgression
E. Evaporites Mark the Sea’s “Last Stand”
VII.
Way Out West: Events in the Cordillera
A. In the Beginning, a Passive Margin
B. Early Paleozoic Rocks
C. Orogeny Begins
VIII.
Deposition in the Far North
IX.
Dynamic Events in the East
A. Taconic Orogeny
1. Northern Appalachian Region
2. Southern Appalachian Region
X.
The Caledonian Orogenic Belt
A. Ocean Expansion
B. Ocean Contraction
XI.
Aspects of Early Paleozoic Climate
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
KEY TERMS (pages given in parentheses)
Absaroka Sequence (283): A sequence of Permian-Pennsylvanian sediments bounded both above and
below by a regional unconformity and providing a record an episode of marine transgression over an
eroded surface, full flood level of inundation, and regression from the craton.
Acadian Orogeny (277): An episode of mountain building in the northern Appalachians during the
Devonian Period.
Alleghenian orogenic belt (277): The belt of rocks formed by mountain building tectonics of the
Allegheny Orogeny in North America.
Allegheny Orogeny (277): Late Paleozoic episodes of mountain building along the present trend of the
Appalachian Mountains. Likely caused by the collision, occurring during Late Carboniferous, of northwest
Africa and the southern part of the Appalachian belt. The third of the orogenies that built the Appalachian
Mountains of North America.
barred basin (287): A basin which had its opening to the sea restricted by a raided sill (or possibly also
by a submerged bar).
bentonite (293): Bentonite is composed of clay minerals that are formed by the alteration of volcanic ash.
Cretaceous rocks of Wyoming and Colorado include extensive beds of this soft, plastic, light-colored
clayey rock.
Caledonian orogenic belt (296): An orogenic belt extending from Ireland and Scotland northwestward
through Scandinavia. Created by the Caledonian Orogeny during Early Paleozoic episode of mountain
building in Europe.
Caledonian Orogeny (277, 297): A major Early Paleozoic episode of mountain building affecting Europe,
which created an orogenic belt, the Caledonides, extending from Ireland and Scotland northwestward
through Scandinavia.
Cordillera (287): The region of North America that consists of the entire system of more-or-less parallel
mountain ranges that extend westward from the Rocky Mountains to the Pacific coast. It includes the
Rocky Mountains, Sierra Nevada, and Coast Ranges.
cratonic sequences (283): Repeated advances (transgressions) and retreats (regressions) of
epicontinental seas. The regressions exposed old seafloors to erosion, creating extensive unconformities
that mark the boundaries of each transgressive-regressive cycle of deposition.
graptolites (287): Extinct colonial marine invertebrates considered to be protochordates. Graptolites
range from the Late Cambrian to the Mississippian.
Hercynian orogeny (277): The belt of rocks formed by mountain building tectonics of the Hercynian
Orogeny in Europe.
Iapetus ocean (277): During Early Cambrian, rifts were forming between once firmly-adjoined land
masses. The ocean flooded into the broadening rift zones, one of which separated North America and
what is now northern Europe. The Paleozoic ocean is know as Iapetus.
Kaskaskia sequence (283): A sequence of Devonian-Mississippian sediments, bounded above and
below by regional unconformities and recording an episode of transgression followed by full flooding of a
large part of the craton and by subsequent regression.
orogenic belt (280): Belt of crustal compression, mountain building, and metamorphism.
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
Ouachita-Marathon trough (296): This trough extends across the southern margin of the North
American craton. Although over 1500 kilometers long, only about 300 kilometers of its folded strata are
exposed.
Ouachita orogenic belt (277): The belt of rocks formed by mountain building tectonics of the Ouachita
Orogeny in North America.
Queenston clastic wedge (286, 294): A clastic wedge of red beds shed westward from highlands
elevated in the course of the Taconic Orogeny.
Rheic Ocean (277): An ocean that began to form as the Iapetus began closing during Ordovician and
Silurian. Located north of Iapetus, between Laurentia and Africa.
Sauk sequence (283): A sequence of Upper Precambrian to Ordovician sediments bounded both above
and below by a regional unconformity and recording an episode of marine transgression, followed by full
flooding of a large part of the craton, and ending with a regression from the craton.
Taconic Orogeny (277, 291): A major episode of orogeny that affected the Appalachian region in
Ordovician time. The northern and Newfoundland Appalachians were the most severely deformed during
this orogeny.
Tippecanoe sequence (283): A sequence of Ordovician to Lower Devonian sediments bounded above
and below by regional unconformities and recording an episode of marine transgression, followed by full
flooding of a large region of the craton and subsequent regression.
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
MULTIPLE-CHOICE QUESTIONS
1.
The Paleozoic ocean that separated North America and what is now northern Europe when the
supercontinent Rodinia formed rifts that split the land mass was known as
a. Iapetus.
c. Proto-Pangea.
b. Mirovia.
d. Laurasia.
2.
The sequence of sediment deposition on the North American craton during Paleozoic, from oldest
to youngest, is
a. Sauk, Tippecanoe, Kaskaskia, Absaroka. c. Tippecanoe, Kaskaskia, Sauk, Absaroka.
b. Absaroka, Kaskaskia, Tippecanoe, Sauk. d. Sauk, Absaroka, Kaskaskia, Tippecanoe.
3.
A large-scale, lithostratigraphic unit that represents a major transgressive-regressive cycle and is
bounded by a regional unconformity is called a
a. platform.
c. cratonic sequence.
b. shield.
d. cyclothem.
4.
During Cambrian, the North American continent was
a. domed upward and experienced extensive erosion.
b. submerged beneath an epeiric sea except for the Transcontinental Arch region.
c. rifted apart along the present day Mississippi River region.
d. combined into a great supercontinent called Pangea.
5.
The lithology of the Tippecanoe sequence, from oldest to youngest, is
a. black shales, limestones, and sandstones. c. conglomerates, limestones, and dolomites.
b. sandstones, conglomerates, and limestones.d. limestones, dolomites, and evaporates.
6.
The first occurrence of shell-bearing multi-cellular animals was in what system?
a. Silurian
c. Devonian
b. Cambrian
d. Precambrian
7.
During Early Paleozoic the North American craton was bounded on four sides by orogenic belts.
They were
a. Ouachita, Cordilleran, Franklinian, and Caledonian.
b. Franklinian, Caledonian, Appalachian, and Cordilleran.
c. Caledonian, Michigonian, Appalachian, and Cordilleran.
d. Willistonian, Franklinian, Michigonian, and Caledonian.
8.
The boundary of the base of Cambrian rocks is marked by the lowest (oldest) occurrence of feeding
burrows of this trace fossil.
a. Arthropod (trilobite)
c. Porifera
b. Brachiopoda
d. Trichophycus
9.
A basin where evaporation produced heavy brines that sank to the bottom and were prevented from
escaping because of the sill or bar is called
a. the Cordilleran Region.
c. Sauk Deposition.
b. Barred Basin.
d. Appalachian Basin.
10. An extensive accumulation of mostly clastic sediments that are deposited in an area adjacent to an
uplifted region is called a(n)
a. depositional basin.
c. structural dome.
b. clastic wedge.
d. alluvial fan.
11.
During what geologic system were extensive evaporite minerals deposited in the Michigan Basin?
a. Proterozoic
c. Silurian
b. Cambrian
d. Ordovician
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Chapter 10—Early Paleozoic Events
12.
13.
The cratonic sequence of which the St. Peter Sandstone is a part
a. Sauk.
c. Kaskaskia.
b. Tippecanoe.
d. Absaroka.
The principle that postulates that sediments deposited during transgression (or regression) do not
necessarily correlate in geologic age throughout their areal extent is called
a. uniformitarianism.
c. the principle of original horizontality.
b. the principle of lateral continuity.
d. the principle of temporal transgression.
14.
In the Cordilleran region, the earliest deposits were sands, which graded westward into finer
clastics and carbonates. An excellent place to study this Sauk transgression is along the walls of
the
a. Niagara Escarpment.
c. St. Peter Sandstone.
b. Grand Canyon of the Colorado River.
d. Niagara Falls.
15.
Paleozoic rocks of the Ouachita Belt are noted for their
a. shelly facies.
c. large mineral content.
b. abundant supply.
d. unusually siliceous and cherty derived from
submarine weathering of ash.
16.
Ash beds, associated with the great volcanism that occurred during the rising of the Taconic ranges
have been weathered to a clay called
a. bentonite.
c. graptolites.
b. siliceous shales.
d. zircon.
17.
The most often associated fossil that contain stipes (branches) that is common in Ordovician dark
shales in Europe and North America are called
a. mollusks.
c. graptolites.
b. brachiopods.
d. peleypods.
18.
The break up of Neoproterozoic supercontinent Rodina produced Laurnetia which was composed
of North America and parts of all of the following except
a. Greenland.
c. North Western Ireland.
b. Scotland.
d. Africa.
19.
The six major continents derived from the breakup of Rodinia were
a. Laurentia, Baltica Kayalchstania, Siberia, China, and Gondwana.
b. Laurasia, Baltica, Kayalchstania, Siberia, China, and Gondwana.
c. Laurentia, Baltica, Kayalchstania, Siberia, China, and Gowganda.
d. Laurasia, Baltica, Kayalchstania, Siberia, China, and Gowganda.
20.
The eon we call Phanerozoic includes these three eras.
a. Proterozoic, Mesozoic, Cenozoic.
c. Paleozoic, Mesozoic, Cenozoic.
b. Proterozoic, Jurassic, Cenozoic.
d. Paleozoic, Jurassic, Cenozoic.
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
FILL IN THE BLANK
1.
This clastic wedge of red beds shed westward from highlands elevated during the Taconic Orogeny
and was called the
.
2.
A basin which had its opening to the sea restricted by a raised sill (or possibly by a submerged bar)
is called a
.
3.
The name of the orogeny where initial activity began during Early Ordovician and continued with
intense deformation through Middle and Late Ordovician is
.
4.
The St. Peter Sandstone, which is pure quartz and used in the manufacture of glass, was deposited
during which sequence of deposition?
5.
The Taconic and Acadian orogenies were the result of plate convergence associated with the
narrowing of the
Ocean.
6.
The closure of the Iapetus and crumpling of the Caledonian marine basin began in what time
period?
7.
The Caledonian Orogeny reached in climax during what two periods?
to
8.
The mobile belt that contains rocks that are well exposed not only in the British Isles but also across
northeastern Greenland and Spitzbergen is called the
9.
Clinton iron ore from the Silurian Clinton Group near Birmingham, Alabama is made mainly of what
oxide mineral?
.
10.
The shales noted for their rich content of fossil colonial organisms used to subdivide the Ordovician
and Silurian into biostratigraphic zones are called the
.
11.
The relatively stable part of a continent that consists of a Precambrian shield and the buried
extension of the shield known as the platform is called the
.
12.
One of the largest of the highland regions during Cambrian (Sauk sequence) that was a vast upland
area composed of previously formed Precambrian igneous and metamorphic rocks was called
13.
The classic example of Silurian strata exposed along the walls of a gorge where a river flows from
Lake Erie into Lake Ontario is called
.
14.
The effects of the Taconic orogeny are represented by remnants of an activity in the Taconic
mountains of New York in ash beds now weathered to clay is called
15.
.
.
In North America the mountain building events are called the _____________, ___________, and
________________ orogenies.
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
TRUE/FALSE
1.
The ocean formed during the rifting between North America and the remainder of the
Proterozoic craton was called Rodinia Ocean.
2.
The principle of temporal transgression stipulates that sediments deposited by
advancing or regressive seas are of correlative geologic age throughout their aerial
extent.
3.
The St. Peter Sandstone is characterized as a “mature” sandstone because of good
sorting and an abundance of well-rounded grains of stable minerals.
4.
The Sauk and Tippecanoe cratonic sequences record the transgressive-regressive
cycles of Early Paleozoic.
5.
The Iapetus ocean formed during Early Paleozoic as a response to the rifting of
Pangea.
6.
During Ordovician, extensive evaporite deposits were forming in the Michigan Basin.
7.
The Tippecanoe and Kaskaskia represent sequences of deposition on the North
American craton during Early Paleozoic.
8.
The Queenston Clastic Wedge was formed as a result of the Taconic orogeny.
9.
In North America the mountain-building events during Early Paleozoic are called the
Taconic, Acadian, and Allegheny orogenies.
10.
During Early Paleozoic, there were four large continents.
Chapter 10— Early Paleozoic Events
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Chapter 10—Early Paleozoic Events
ANSWER KEY
Multiple Choice
1. a
2. a
3. c
4. b
5. d
6. b
7. b
8. c
9. b
10. b
11. c
12. b
13. d
14. b
15. d
16. a
17. c
18. d
19. a
20. c
Fill Ins
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
Queenston clastic wedge
barred basin
Taconic Orogeny
Tippecanoe
Iapetus
Middle Ordovician
Late Siburian
Early Devonian
Caldonian Belt
hematite
Gaptolite facies
craton
Transcontinental Arch
bentonite
Taconic, Acadian,
Allegheny
Chapter 10— Early Paleozoic Events
© 2013 JOHN WILEY & SONS, INC. ALL RIGHTS RESERVED
True/False
1. F
2. F
3. T
4. T
5. F
6. F
7. F
8. T
9. T
10. F
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Chapter 10—Early Paleozoic Events
RESPONSES TO QUESTIONS ACCOMPANYING SELECTED FIGURES
FIGURE 10–4 (p. 279) Among the possibilities for your location, you might select beneath the Cordilleran
or Appalachian seaway, on lowlands of the Canadian Shield, beneath a shallow epicontinental sea, or on
an island along the Transcontinental Arch. The answer depends on where you live. If you do not know
where you are in relation to locations depicted on Figure 10-4, refer to a map of the U.S. and compare
with Figure 10-4.
FIGURE 10–12 (p. 285) The “fining-upward” sequence from sandstone (Tapeats Sandstone) to shale
(Bright Angel Shale) to limestone (Mauv Limestone) indicates a rise in sea level.
Chapter 10— Early Paleozoic Events
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