Late Paleozoic Earth History

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Late Paleozoic Earth History

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Title: Late Paleozoic Earth History

1
Chapter 11
Late Paleozoic Earth History
2
Tully Monster

Tullimonstrum gregarium, also known as the Tully
Monster, is Illinoiss official state fossil
Specimen from Pennsylvanian rocks, Mazon Creek
Locality, Illinois

Reconstruction of the Tully Monster
about 30 cm long

3
Mazon Creek Fossils

Approximately 300 million years ago
in the region of present-day Illinois,
sluggish rivers flowed southwestward through
swamps,
and built large deltas that extended outward into
a subtropical shallow sea
These rivers deposited high quantities of mud
that entombed many of the plants and animals
living in the area
Rapid burial
and the formation of ironstone concretions
preserved many of the plants and animals of the
area

4
Exceptional Preservation

The resulting fossils,
known as the Mazon Creek fossils
for the area in northeastern Illinois
where most specimens are found,
provide us with significant insights about the
soft-part anatomy of the region's biota
Because of the exceptional preservation of this
ancient biota,
Mazon Creek fossils are known throughout the
world
and many museums have extensive collections from
the area

5
Pennsylvanian Delta Organisms

During Pennsylvanian time, two major habitats
existed in northeastern Illinois
One was a swampy forested lowland of the
subaerial delta,
and the other was the shallow marine environment
of the actively prograding delta
Living in the warm, shallow waters
of the delta front were numerous
cnidarians,
mollusks,
echinoderms,

arthropods,
worms,
and fish

6
Swampy Lowlands

The swampy lowlands surrounding the delta were
home to more than 400 plant species,
numerous insects and spiders,
and other animals such as
scorpions and amphibians
In the ponds, lakes, and rivers were many
fish, shrimp, and ostracods
Almost all of the plants were
seedless vascular plants,
typical of the kinds that lived in the
coal-forming swamps
during the Pennsylvanian Period

7
Tully Monster

One of the more interesting Mazon Creek fossils
is the Tully Monster,
which is not only unique to Illinois,
but also is its official state fossil
Named for Francis Tully,
who first discovered it in 1958,
Tullimonstrum gregarium
was a small
up to 30 cm long
soft-bodied animal that lived in the warm,
shallow seas
covering Illinois about 300 million years ago

8
Tully Monster

The Tully Monster had a relatively long proboscis
that contained a "claw" with small teeth in it
The round-to-oval shaped body was segmented
and contained a cross-bar,
whose ends were swollen,
and are interpreted by some to be the animals
sense organs
The tail had two horizontal fins
It probably swam like an eel
with most of the undulatory movement occurring
behind the two sense organs

9
Tully Monster

There presently is no consensus
as to what phylum the Tully Monster belongs
or to what animals it might be related

10
Late Paleozoic Paleogeography

The Late Paleozoic was a time of
evolutionary innovations,
continental collisions,
mountain building,
fluctuating seas levels,
and varied climates
Coals, evaporites, and tillites
testify to the variety of climatic conditions
experienced by the different continents during
the Late Paleozoic

11
Gondwana Continental Glaciers

Major glacial-interglacial intervals
occurred throughout much of Gondwana
as it continued moving over the South Pole
during the Late Mississippian to Early Permian
The growth and retreat of continental glaciers
during this time
profoundly affected the world's biota
as well as contributing to global sea level
changes

12
Continental Collisions

Collisions between continents
not only led to the formation of the
supercontinent Pangaea
by the end of the Permian,
but resulted in mountain building
that strongly influenced oceanic and atmospheric
circulation patterns
By the end of the Paleozoic,
widespread arid and semiarid conditions prevailed
over much of Pangaea

13
The Devonian Period

During the Silurian,
Laurentia and Baltica collided along a convergent
plate boundary
to form the larger continent of Laurasia
This collision,
which closed the northern Iapetus Ocean,
is marked by the Caledonian orogeny
During the Devonian,
as the southern Iapetus Ocean narrowed
between Laurasia and Gondwana,
mountain building continued along the eastern
margin of Laurasia
with the Acadian orogeny

14
Paleogeography of the World

For the Late Devonian Period

15
Paleogeography of the World

For the Early Carboniferous Period

16
Paleogeography of the World

For the Late Carboniferous Period

17
Paleogeography of the World

For the Late Permian Period

18
Reddish Fluvial Sediments

The erosion of the resulting highlands
provided vast amounts of reddish fluvial
sediments
that covered large areas of northern Europe
Old Red Sandstone
and eastern North America
the Catskill Delta

19
Collision of Laurentia and Baltica

Other Devonian tectonic events include,
the Cordilleran Antler orogeny,
the Ellesmere orogeny along the northern margin
of Laurentia
which may reflect the collision of Laurentia with
Siberia
and the change from a passive continental margin
to an active convergent plate boundary
in the Uralian mobile belt of eastern Baltica

20
Uniform Global Climate

The distribution of
reefs,
evaporites,
and red beds,
as well as the existence of similar floras
throughout the world,
suggests a rather uniform global climate during
the Devonian Period

21
The Carboniferous Period

During the Carboniferous Period
southern Gondwana moved over the South Pole,
resulting in extensive continental glaciation
The advance and retreat of these glaciers
produced global changes in sea level
that affected sedimentation pattern on the
cratons
As Gondwana continued moving northward,
it first collided with Laurasia
during the Early Carboniferous
and continued suturing with it during the rest of
the Carboniferous

22
Gondwana/Laurasia Collision

Because Gondwana rotated clockwise relative to
Laurasia,
deformation of the two continents generally
progressed in a northeast-to-southwest direction
along
the Hercynian,
Appalachian,
and Ouachita mobile belts
The final phase of collision between Gondwana and
Laurasia
is indicated by the Ouachita Mountains of
Oklahoma
which were formed by thrusting
during the Late Carboniferous and Early Permian

23
Pangaea Began Taking Shape

Elsewhere, Siberia collided with Kazakhstania
and moved toward the Uralian margin of Laurasia
(Baltica),
colliding with it during the Early Permian
By the end of the Carboniferous,
the various continental landmasses were fairly
close together
as Pangaea began taking shape

24
Coal Basins in Equatorial Zone

The Carboniferous coal basins of
eastern North America,
western Europe,
and the Donets Basin of Ukraine
all lay in the equatorial zone,
where rainfall was high and temperatures were
consistently warm
The absence of strong seasonal growth rings
in fossil plants from these coal basins
is indicative of such a climate

25
Fossil Plants of Siberia

The fossil plants found in the coals of Siberia,
however, show well-developed growth rings,
signifying seasonal growth
with abundant rainfall
and distinct seasons
such as occur in the temperate zones
at latitudes 40 degrees to 60 degrees north

26
Continental Ice Sheets

Glacial condition
and the movement of large continental ice sheets
in the high southern latitudes
are indicated by widespread tillites
and glacial striations in southern Gondwana
These ice sheets spread toward the equator and,
at their maximum growth,
extended well into the middle temperate latitudes

27
The Permian Period

The assembly of Pangaea
was essentially completed during the Permian
as a result of the many continental collisions
that began during the Carboniferous
Although geologists generally agree
on the configuration and locations
of the western half of the supercontinent,
no consensus exists
on the number or configuration of the various
terranes
and continental blocks that composed the eastern
half of Pangaea

28
Pangaea Surrounded

Regardless of the exact configuration
of the eastern portion of Pangaea,
geologists know that the supercontinent
was surrounded by various subduction zones
and moved steadily northward during the Permian
Furthermore, an enormous single ocean,
Panthalassa,
surrounded Pangaea and
spanned Earth from pole to pole

29
Climatic Consequences

The formation of a single large landmass
had climatic consequences for the continent
Terrestrial Permian sediments indicate
that arid and semiarid conditions were widespread
over Pangaea
The mountain ranges produced by
the Hercynian, Alleghenian, and Ouachita
orogenies
were high enough to create rain shadows
that blocked the moist, subtropical, easterly
winds
much as the southern Andes Mountains do in
western South America today

30
Mountains Influenced Climate

The mountains influence produced very dry
conditions in North America and Europe,
as evident from the extensive
Permian red beds and evaporites
found in western North America, central Europe,
and parts of Russia
Permian coals,
indicative of abundant rainfall,
were mostly limited to the northern temperate
belts
latitude 40 degrees to 60 degrees north
while the last remnants of the Carboniferous ice
sheets retreated

31
Late Paleozoic History of North America

The Late Paleozoic cratonic history of North
America included periods
of extensive shallow-marine carbonate deposition
and large coal-forming swamps
as well as dry, evaporite-forming terrestrial
conditions
Cratonic events largely resulted from changes in
sea level because of
Gondwanan glaciation
and tectonic events related to the joining of
Pangaea

32
Mountain Building

Mountain building
that began with the Ordovician Taconic orogeny
continued with the
Caledonian,
Acadian,
Alleghenian,
and Ouachita orogenies
These orogenies were part of the global tectonic
process
that resulted in the formation of Pangaea by the
end of the Paleozoic Era

33
The Kaskaskia Sequence

The boundary between
the Tippecanoe sequence
and the overlying Kaskaskia sequence
Middle Devonian-Late Mississippian
is marked by a major unconformity
As the Kaskaskia Sea transgressed
over the low-relief landscape of the craton,
the majority of the basal beds deposited
consisted of clean, well-sorted quartz sandstones

34
Oriskany Sandstone

A good example is the Oriskany Sandstone
of New York and Pennsylvania
and its lateral equivalents
The Oriskany Sandstone,
like the basal Tippecanoe St. Peter Sandstone,
is an important glass sand
as well as a good gas-reservoir rock

35
Basal Kaskaskia Sandstones

Extent of the basal units of the Kaskaskia
sequence in the eastern and north-central
United States

36
Source Areas

The source areas for the basal Kaskaskia
sandstones
were primarily the eroding highlands of the
Appalachian mobile belt area,
exhumed Cambrian and Ordovician sandstones
cropping out along the flanks of the Ozark Dome,
and exposures of the Canadian Shield in the
Wisconsin area

37
Devonian Period

Paleogeography of North America during the
Devonian Period

38
Sediment Sources

The earlier Silurian carbonate beds
below the Tippecanoe-Kaskaskia unconformity
lacked Kaskaskia-like sands
The absence of such sands indicates
that the source areas for the basal Kaskaskia
had still been submerged and not yet exposed at
the time the Tippecanoe sequence was deposited
Stratigraphic studies indicate
that these source areas were uplifted
and the Tippecanoe carbonates removed by erosion
prior to the Kaskaskia transgression

39
Kaskaskian Rocks

Kaskaskian basal rocks
elsewhere on the craton
consist of carbonates
that are frequently difficult to differentiate
from the underlying Tippecanoe carbonates
unless they are fossiliferous
The majority of Kaskaskian rocks are
carbonates, including reefs, and associated
evaporite deposits
except for widespread Upper Devonian and Lower
Mississippian black shales

40
Other Parts of the World

In many other parts of the world, such as
southern England,
Belgium,
Central Europe,
Australia,
and Russia,
the Middle and early Late Devonian epochs were
times of major reef building

41
Reef Development in Western Canada

The Middle and Late Devonian-age reefs of western
Canada
contain large reserves of petroleum
and have been widely studied from outcrops and in
the subsurface
These reefs began forming
as the Kaskaskia Sea transgressed southward
into western Canada

42
Middle Devonian Reefs and Evaporites

By the end of the Middle Devonian,
the reefs had coalesced into a large barrier-reef
system
that restricted the flow of oceanic water into
the back-reef platform,
thus creating conditions for evaporite
precipitation
In the back-reef area, up to 300 m of evaporites
were precipitated in much the same way as in the
Michigan Basin during the Silurian

43
Devonian Reef Complex

Reconstruction of the extensive Devonian Reef
complex of western Canada

These reefs controlled the regional facies of the
Devonian epeiric seas

44
Potash from Evaporites

More than half of the world's potash,
which is used in fertilizers,
comes from these Devonian evaporites
By the middle of the Late Devonian,
reef growth stopped in the western Canada region,
although nonreef carbonate deposition continued

45
Black Shales

In North America, many areas of
carbonate-evaporite deposition
gave way to a greater proportion of shales
and coarser detrital rocks
beginning in the Middle Devonian and continuing
into the Late Devonian
This change to detrital deposition
resulted from the formation of new source areas
brought on by the mountain-building activity
associated with the Acadian orogeny in North
America

46
Increased Detrital Deposition

Deposition of black shales
was brought on by the the Acadian orogeny

47
Widespread Black Shales

As the Devonian Period ended,
a conspicuous change in sedimentation took place
over the North American craton
with the appearance of widespread black shales
These Upper Devonian-Lower Mississippian black
shales are typically
noncalcareous,
thinly bedded,
and usually less than 10 m thick

48
Extent of Black Shales

The extent of the upper Devonian and Lower
Mississippian Chattanooga Shale and its
equivalent units
such as the Antrim Shale and the Albany Shale

49
New Albany Shale

Upper Devonian New Albany Shale,
Button Mold Knob Quarry, Kentucky

50
Dating Black Shales

Because most black shales lack body fossils,
they are difficult to date and correlate
However, microfossils, such as
conodonts
microscopic animals
acritarchs
microscopic algae
or plant spores
indicate that the lower beds are Late Devonian,
and the upper beds are Early Mississippian in age

51
Origin Debated

Although the origin of these extensive black
shales is still being debated,
the essential features required to produced them
include
undisturbed anaerobic bottom water,
a reduced supply of coarser detrital sediment,
and high organic productivity in the overlying
oxygenated waters
High productivity in the surface waters leads to
a shower of organic material,
which decomposes on the undisturbed seafloor
and depletes the dissolved oxygen at the
sediment-water interface

52
Puzzling Origin

The wide extent in North America
of such apparently shallow-water black shales
remains puzzling
Nonetheless, these shales
are rich in uranium
and are an important source rock of oil and gas
in the Appalachian region

53
The Late Kaskaskia

Following deposition of the black shales,
carbonate sedimentation on the craton dominated
the remainder of the Mississippian Period
During this time, a variety of carbonate
sediments was deposited in the epeiric seas
as indicated by the extensive deposits of
crinoidal limestones
rich in crinoid fragments
oolitic limestones,
and various other limestones and dolostones

54
Mississippian Period

Paleogeography of North America during the
Mississippian Period

55
Mississippian Carbonates

These Mississippian carbonates display
cross-bedding, ripple marks, and well-sorted
fossil fragments,
all of which are indicative of a shallow-water
environment
Analogous features can be observed on the
present-day Bahama Banks
In addition, numerous small organic reefs
occurred throughout the craton during the
Mississippian
These were all much smaller than the large
barrier-reef complexes
that dominated the earlier Paleozoic seas

56
Regression of the Kaskaskia Sea

During the Late Mississippian regression
of the Kaskaskia Sea from the craton,
carbonate deposition was replaced
by vast quantities of detrital sediments
The resulting sandstones,
particularly in the Illinois Basin,
have been studied in great detail
because they are excellent petroleum reservoirs

57
Cratonwide Unconformity

Prior to the end of the Mississippian,
the epeiric sea had retreated
to the craton margin,
once again exposing the craton
to widespread weathering and erosion
This resulted in a cratonwide unconformity
when the Absaroka Sea began transgressing
back over the craton

58
The Absaroka Sequence

The Absaroka sequence
includes rocks deposited
during the Pennsylvanian
through Early Jurassic
At this point, we will only discuss the Paleozoic
rocks of the Absaroka sequence
The extensive unconformity
separating the Kaskaskia and Absaroka sequences
essentially divides the strata
into the North American
Mississippian and Pennsylvanian systems

59
Mississippian and Pennsylvanian Versus
Carboniferous

The Mississippian and Pennsylvanian systems of
North America
are equivalent to the European Lower and Upper
Carboniferous systems
Mississippian Lower Carboniferous
Pennsylvanian Upper Carboniferous

60
Absaroka Rocks

The rocks of the Absaroka sequence
are not only different from those of the
Kaskaskia sequence,
but they are also the result of different
tectonic regimes
The lowermost sediments of the Absaroka sequence
are confined to the margins of the craton

61
Lowermost Absaroka

These lowermost deposits
are generally thickest in the east and southeast,
near the emerging highlands of the Appalachian
and Ouachita mobile belts,
and thin westward onto the craton
The lithologies also reveal lateral changes
from nonmarine detrital rocks and coals in the
east,
through transitional marine-nonmarine beds,
to largely marine detrital rocks and limestones
farther west

62
Pennsylvanian Period

Paleogeography of North America during the
Pennsylvanian Period

63
What Are Cyclothems?

A cyclical pattern of alternating marine and
nonmarine strata
is one of the characteristic features of
Pennsylvanian rocks
Such rhythmically repetitive sedimentary
sequences are known as cyclothems
They result from repeated alternations
of marine
and nonmarine environments,
usually in areas of low relief

64
Delicate Interplay

Though seemingly simple,
cyclothems reflect a delicate interplay between
nonmarine deltaic environments
shallow-marine interdeltaic environments
and shelf environments
For example,
a typical coal-bearing cyclothem from the
Illinois Basin contains
nonmarine units,
capped by a coal unit
and overlain by marine units

65
Nonmarine Units of a Cyclothem

The initial units represent
deltaic deposits
and fluvial deposits
Above them is an underclay
that frequently contains roots from the plants
and trees
that comprise the overlying coal
The coal bed
results from accumulations of plant material
and is overlain by marine units

66
Cyclothem

Columnar section of a complete cyclothem

67
Pennsylvanian Coal Bed

Pennsylvanian coal bed, West Virginia
part of a cyclothem

68
Coal-Forming Swamp

Reconstruction of the environment of a
Pennsylvanian coal-forming swamp

69
The Okefenokee Swamp

in Georgia, is a modern coal-forming environment,

similar to those occurring during the
Pennsylvanian Period
70
Marine Units of a Cyclothem

Next the marine units consist of alternating
limestones and shales,
usually with an abundant marine invertebrate
fauna
The marine cycle ends with an erosion surface
A new cyclothem begins with a nonmarine deltaic
sandstone
All the beds illustrated in the idealized
cyclothems are not always preserved because of
abrupt changes from marine to nonmarine
conditions
or removal of some units by erosion

71
Cyclothem
72
Why Are Cyclothems Important?

Cyclothems represent
transgressive
and regressive sequences
with an erosional surface separating one
cyclothem from another
Thus, an idealized cyclothem
passes upward from fluvial-deltaic deposits,
through coals,
to detrital shallow-water marine sediments,
and finally to limestones typical of an open
marine environment

73
Modern Analogues

Such places as
the Mississippi delta,
the Okefenokee Swamp, Georgia
the Florida Everglades,
and the Dutch lowlands
represent modern coal forming environments
similar to those that existed during the
Pennsylvanian Period
By studying these modern analogues,
geologists can make reasonable deductions
about conditions existing in the geologic past

74
Sea Level Changes

The Pennsylvanian coal swamps
must have been large lowland areas neighboring
the sea
In such cases,
a very slight rise in sea level
would have flooded large areas,
while slight drops
would have exposed large areas,
resulting in alternating marine and nonmarine
environments
The same result could have been caused by
rising sea level and progradation of a large
delta, such as occurs today in Louisiana

75
Explaining Cyclicity

Such regularity and cyclicity in sedimentation
over a large area requires an explanation
In most cases, local cyclothems of limited extent
can be explained for
by rapid but slight changes in sea level
in a swamp-delta complex of low relief near the
sea
such as progradation or by localized crustal
movement
Explaining widespread cyclothems is more difficult

76
Favored Hypothesis

The hypothesis currently favored
by most geologists
for explaining widespread cyclothems
is a rise and fall of sea level
related to advances and retreats of Gondwanan
continental glaciers
When the Gondwanan ice sheets advanced,
sea level dropped,
and when they melted,
sea level rose
Late Paleozoic cyclothem activity on all cratons
closely corresponds to Gondwana
glacial-interglacial cycles

77
Cratonic Uplift

Recall that cratons are stable areas,
and when they do experience deformation, it is
usually mild
The Pennsylvanian Period, however, was a time of
unusually severe cratonic deformation,
resulting in uplifts of sufficient magnitude to
expose Precambrian basement rocks
In addition to newly formed highlands and basins,
many previously formed arches and domes,
such as the Cincinnati Arch, Nashville Dome, and
Ozark Dome,
were also reactivated

78
Ancestral Rockies

During the Pennsylvanian Period,
the area of greatest deformation occurred in the
southwestern part of the North American craton
where a series of fault-bounded uplifted blocks
formed the Ancestral Rockies
Uplift of these mountains,
some of which were elevated more than 2 km along
near-vertical faults,
resulted in the erosion of the overlying
Paleozoic sediments
and exposure of the Precambrian igneous and
metamorphic basement rocks

79
Pennsylvanian Highlands

Location of the principal Pennsylvanian highland
areas and basins of the southwestern part of the
craton

80
Ancestral Rockies

Block diagram of the Ancestral Rockies, which
were elevated by faulting during the
Pennsylvanian Period

Erosion of these mountains produced
coarse red sediments
that were deposited in the adjacent basins

81
Red Basin Sediment

As the Ancestral Rocky mountains eroded,
tremendous quantities of
coarse, red arkosic sand and conglomerate
were deposited in the surrounding basins
These sediments are preserved in many areas
including the rocks of the Garden of the Gods
near Colorado Springs
and at the Red Rocks Amphitheater near Morrison,
Colorado

82
Garden of the Gods

Storm-sky view of Garden of the Gods from Near
Hidden Inn, Colorado Springs, Colorado

83
Intracratonic Mountain Ranges

Intracratonic mountain ranges are unusual,
and their cause has long been debated
It is thought that the collision of Gondwana with
Laurasia along the Ouachita mobile belt
produced great stresses in the southwestern
region of the North American craton
These crustal stresses were relieved by faulting
that resulted in uplift of cratonic blocks
and downwarp of adjacent basins,
forming a series of ranges and basins

84
The Middle Absaroka

More Evaporite Deposits and Reefs
While the various intracratonic basins
were filling with sediment
during the Late Pennsylvanian,
the epeiric sea slowly began retreating from the
craton
During the Early Permian,
the Absaroka Sea occupied a narrow region
from Nebraska through west Texas

85
Permian Period

Paleogeography of North America during the
Permian Period

86
Middle Permian Absaroka Sea

By the Middle Permian,
the sea had retreated to west Texas
and southern New Mexico
The thick evaporite deposits
in Kansas and Oklahoma
show the restricted nature of the Absaroka Sea
during the Early and Middle Permian
and its southwestward retreat from the central
craton

87
Restricted Absaroka Sea

During the Middle and Late Permian,
the Absaroka Sea was restricted to
west Texas and southern New Mexico,
forming an interrelated complex of
lagoonal environments,
reef environments,
and open-shelf environments
Three basins separated by two submerged platforms
formed in this area during the Permian

88
Permian Reefs and Basins

Location of the west Texas Permian basins and
surrounding reefs

89
Massive Reefs

Massive reefs grew around the basin margins
while limestones, evaporites, and red beds were
deposited
in the lagoonal areas behind the reefs
As the barrier reefs grew and the passageways
between the basins became more restricted,
Late Permian evaporites gradually filled the
individual basins

90
Capitan Limestone Reef Reconstruction

Reconstruction of the Middle Permian Capitan
Limestone reef environment
Shown are brachiopods, corals, bryozoans and
large glass sponges

91
Capitan Limestone

Spectacular deposits representing the geologic
history of this region
can be seen today in the Guadalupe Mountains of
Texas and New Mexico
where the Capitan Limestone forms the caprock of
these mountains
These reefs have been extensively studied
because of the tremendous oil production that
comes from this region
By the end of the Permian Period,
the Absaroka Sea had retreated from the craton
exposing continental red beds
over most of the southwestern and eastern region

92
Late Paleozoic Mobile Belts

Having examined the Kaskaskia and Absarokian
history of the craton,
we now turn our attention to the orogenic
activity in the mobile belts
The mountain building that occurred during this
time
profoundly influenced the climatic and
sedimentary history of the craton
In addition it was part
of the global tectonic regime that formed Pangaea

93
Cordilleran Mobile Belt

During the Neoproterozoic and Early Paleozoic,
the Cordilleran area was a passive continental
margin
along which extensive continental shelf sediments
were deposited
Thick sections of marine sediments
graded laterally into thin cratonic units
as the Sauk Sea transgressed onto the craton
Beginning in the Middle Paleozoic,
an island arc formed off the western margin of
the craton

94
Antler orogeny

A collision between
this eastward-moving island arc
and the western border of the craton
took place during the Late Devonian and Early
Mississippian,
resulting in a highland area
This orogenic event,
the Antler orogeny,
was caused by subduction
and resulted in the closing of the narrow ocean
basin
that separated the island arc from the craton

95
Antler Highlands

Reconstruction of the Cordilleran mobile belt
during the Early Mississippian

in which deep-water continental slope deposits

were thrust eastward
over shallow-water continental shelf carbonates
forming the Antler Highlands

96
Erosion of the Antler Highlands

Erosion of the resulting Antler Highlands
produced large quantities of sediment
that were deposited to the east in the epeiric
sea covering the craton
and to the west in the deep sea

97
Major Tectonic Activity

The Antler orogeny was the first in a series
of orogenic events to affect the Cordilleran
mobile belt
During the Mesozoic and Cenozoic,
this area was the site of major tectonic activity
caused by oceanic-continental convergence
and accretion of various terranes

98
Ouachita Mobile Belt

The Ouachita mobile belt
extends for approximately 2100 km
from the subsurface of Mississippi
to the Marathon region of Texas
Approximately 80 of the former mobile belt
is buried beneath a Mesozoic and Cenozoic
sedimentary cover
The two major exposed areas in this region are
the Ouachita Mountains of Oklahoma and Arkansas
and the Marathon Mountains of Texas

99
Beginning of the Ouachita Orogeny

During the Neoproterozoic to Early Mississippian,
shallow-water detrital and carbonate sediments
were deposited on a broad continental shelf,
while in the deeper-water portion of the
adjoining mobile belt,
bedded cherts and shales were accumulating
Beginning in the Mississippian Period,
the rate of sedimentation increased dramatically
as the region changed from a passive continental
margin to an active convergent plate boundary,
marking the beginning of the Ouachita orogeny

100
Ouachita Mobile Belt

Plate Tectonic model for the deformation of the
Ouachita mobile belt
Depositional environment prior to the beginning
of orogenic activity

101
Ouachita Mobile Belt

Incipient continental collision between
North America and Gondwana began during
the Mississippian Period.

102
Ouachita Mobile Belt

Continental collision continued during the
Pennsylvanian and Permian periods

103
Gondwana/Laurasia Collision

Thrusting of sediments continued
throughout the Pennsylvanian and Early Permian
as a result of the compressive forces generated
along the zone of subduction
as Gondwana collided with Laurasia
The collision of Gondwana and Laurasia
is marked by the formation of a large mountain
range,
most of which was eroded during the Mesozoic Era
Only the rejuvenated Ouachita and Marathon
Mountains remain of this once lofty mountain range

104
Three Continuous Mobile Belts

The Ouachita deformation
was part of the general worldwide tectonic
activity
that occurred when Gondwana united with Laurasia
Three mobile belts
the Hercynian,
Appalachian,
and Ouachita
were continuous, and marked the southern boundary
of Laurasia

105
Complex Tectonic Activity

The tectonic activity that resulted in the uplift
in the Ouachita mobile belt was very complex
and involved not only the collision of Laurasia
and Gondwana
but also several microplates and terranes between
the continents
that eventually became part of Central America
The compressive forces impinging on the Ouachita
mobile belt
also affected the craton
by causing broad uplift of the southwestern part
of North America

106
Appalachian Mobile Belt

Caledonian Orogeny
The Caledonian mobile belt extends
along the western border of Baltica
and includes the present-day countries of
Scotland, Ireland, and Norway
During the Middle Ordovician,
subduction along the boundary
between the Iapetus plate and Baltica began,
forming a mirror image of the convergent plate
boundary
off the east coast of Laurentia (North America)

107
Caledonian Orogeny

The culmination of the Caledonian orogeny
occurred during the Late Silurian and Early
Devonian
with the formation of a mountain range
along the western margin of Baltica

108
Acadian Orogeny

The third Paleozoic orogeny to affect Laurentia
and Baltica
began during the Late Silurian
and concluded at the end of the Devonian Period
The Acadian orogeny affected the Appalachian
mobile belt
from Newfoundland to Pennsylvania
as sedimentary rocks
were folded and thrust against the craton

109
Acadian Zone of Collision

As with the preceding Taconic and Caledonian
orogenies,
the Acadian orogeny occurred along
an oceanic-continental convergent plate boundary
As the northern Iapetus Ocean continued to close
during the Devonian,
the plate carrying Baltica
finally collided with Laurentia,
forming a continental-continental convergent
plate boundary along the zone of collision

110
Increased Metamorphic and Igneous Activity

As the increased metamorphic and igneous activity
indicates,
the Acadian orogeny was more intense
and of longer duration
than the Taconic orogeny
Radiometric dates
from the metamorphic and igneous rocks
associated with the Acadian orogeny
cluster between 360 and 410 million years ago

111
Folding and Thrusting

Jjust as with the Taconic orogeny,
deep-water sediments
were folded and thrust northwestward,
producing angular unconformities
separating Upper Silurian from Mississippian rocks

112
Catskill Delta

Weathering and erosion of the Acadian Highlands
produced the Catskill Delta,
a thick clastic wedge
named for the Catskill Mountains
in upstate New York
where it is well exposed
The Catskill Delta, composed of
red, coarse conglomerates, sandstones, and
shales,
contains nearly three times as much sediment as
the Queenston Delta

113
Catskill Delta Clastic Wedge

Area of collision between Laurentia and Baltica

The Catskill Delta clastic wedge

and the Old Red Sand-stone
are bilaterally symmetrical
and derived their sediments
from the Acadian and Caledonian Highlands

114
Devonian Rocks of New York

The Devonian rocks of New York are among the best
studied on the continent
A cross section of the Devonian strata
clearly reflects an eastern source for the
Catskill facies
from the Acadian Highlands
These clastic rocks can be traced
from eastern Pennsylvania,
where the coarse clastics are approximately 3 km
thick,
to Ohio,
where the deltaic facies are only about 100 m
thick
and consist of cratonic shales and carbonates

115
Catskill Delta Red Beds

The red beds of the Catskill Delta
derive their color from the hematite found in the
sediments
Plant fossils and oxidation of the hematite
indicate
that the beds were deposited in a continental
environment

116
The Old Red Sandstone

The red beds of the Catskill Delta
have a European counterpart
in the Devonian Old Red Sandstone
of the British Isles
The Old Red Sandstone,
just like its North American Catskill
counterpart,
contains numerous fossils of
freshwater fish,
early amphibians,
and land plants

117
Old Red Sandstone

The Old Red Sandstone

is the counterpart to the Catskill Delta clastic
wedge

118
Red Beds Traced North

By the end of the Devonian Period,
Baltica and Laurentia were sutured together,
forming Laurasia
The red beds of the Catskill Delta
can be traced north,
through Canada and Greenland,
to the Old Red Sandstone of the British Isles
and into Northern Europe
These beds were deposited
in similar environments
along the flanks of developing mountain chains
formed at convergent plate boundaries

119
Closing of the Iapetus Ocean

The Taconic, Caledonian, and Acadian orogenies
were all part of the same orogenic event
related to the closing of the Iapetus Ocean
This event began
with paired oceanic-continental convergent plate
boundaries
during the Taconic and Caledonian orogenies
and culminated
along a continental-continental plate boundary
during the Acadian orogeny
as Laurentia and Baltica became sutured

120
Hercynian-Alleghenian Orogeny

Following this,
the Hercynian-Alleghenian orogeny began,
followed by orogenic activity
in the Ouachita mobile belt
The Hercynian mobile belt
of southern Europe
and the Appalachian and Ouachita mobile belts
of North America
mark the zone along which Europe
as part of Laurasia
collided with Gondwana

121
Eastern Laurasia Collided with Gondwana

While Gondwana and southern Laurasia collided
during the Pennsylvanian and Permian
in the area of the Ouachita mobile belt,
eastern Laurasia
Europe and southeastern North America
joined together with Gondwana
Africa
as part of the Hercynian-Alleghenian orogeny

122
Pangaea

These three Late Paleozoic orogenies
Hercynian,
Alleghenian,
and Ouachita
represent the final joining of Laurasia and
Gondwana
into the supercontinent Pangaea
during the Permian

123
The Role of Microplates and Terranes in the
Formation of Pangaea

We have discussed the geologic history
of the mobile belts
bordering the Paleozoic continents
in terms of subduction along convergent plate
boundaries
However, accretion along the continental margins
is more complicated than the somewhat simple,
large-scale plate interactions discussed here

124
Terranes or Microplates

Geologists now recognize
that numerous terranes or microplates existed
during the Paleozoic
and were involved in the orogenic events
that occurred during the time
We have been concerned only
with the six major Paleozoic continents
However, microplates of varying size
were present during the Paleozoic
and participated in the formation of Pangaea

125
Avalonia

For example, the microcontinent of Avalonia
is composed of
some coastal parts of New England,
southern New Brunswick,
much of Nova Scotia,
the Avalon Peninsula of eastern Newfoundland,
southeastern Ireland,
Wales,
England,
and parts of Belgium and Northern France

126
A Separate Continent

The Avalon microcontinent
existed as a separate continent
during the Ordovician
and began to collide with Baltica
during the Late Ordovician-Early Silurian
and then with Laurentia
as part of Baltica
during the Silurian

127
Numerous Microplates

Other terranes and microplates include
Iberia-Armorica (southern France, Sardinia,
Iberian peninsula)
Perunica (Bohemia)
numerous Alpine fragments
Microplates usually developed their own unique
faunal and floral assemblages

128
The Basic History Remains the Same

Thus, while the basic history
of the formation of Pangaea during the Paleozoic
remains the same,
geologists now realize that microplates and
terranes also played an important role
Furthermore, the recognition of terranes
within mobile belts helps explain
some previously anomalous geologic situations

129
Late Paleozoic Mineral Resources

Late Paleozoic-age rocks contain
a variety of important mineral resources
including energy resources
and metallic and nonmetallic mineral deposits
Petroleum and natural gas
are recovered in commercial quantities
from rocks ranging
from the Devonian through Permian

130
Hydrocarbons

Devonian-age rocks in
the Michigan Basin,
Illinois Basin,
and the Williston Basin of Montana, South Dakota,
and adjacent parts of Alberta, Canada,
have yielded considerable amounts of hydrocarbons
Permian reefs and other strata in the western
United States, particularly Texas,
have also been prolific producers

131
Permian-Age Coal Beds

Although Permian-age coal beds
are known from several areas including Asia,
Africa, and Australia,
much of the coal in North America and Europe
comes from Pennsylvanian deposits
Late Carboniferous
Large areas in the Appalachian region and the
Midwestern United States
are underlain by vast coal deposits
formed from the lush vegetation
that flourished in Pennsylvanian coal-forming
swamps

132
U.S. Coal Deposits

The age of the coals in the midwestern states and
the

Appalachian region are mostly Pennsyl-vanian
whereas those in the west are mostly Cretaceous
and Cenozoic

133
Bituminous Coal

Much of the coal is characterized as bituminous
coal
which contains about 80 carbon
It is a dense, black coal
that has been so thoroughly altered
that plant remains can be seen only rarely
Bituminous coal is used to make coke,
a hard gray substance made up of the fused ash
Coke is used to fire blast furnaces during the
production of steel

134
Anthracite

Some of the Pennsylvanian coal from North America
is anthracite,
a metamorphic type of coal
containing up to 98 carbon
Most anthracite is in the Appalachian region
It is an especially desirable type of coal
because it burns with a smokeless flame
and it yields more heat per unit volume
than other types of coal
Unfortunately, it is the least common type
so that much of the coal used in the U.S. is
bituminous

135
Evaporite and Gas

A variety of Late Paleozoic-age evaporite
deposits are important nonmetallic mineral
resources
The Zechstein evaporites of Europe extend
from Great Britain across the North Sea and into
Denmark, the Netherlands, Germany and eastern
Poland and Lithuania
Besides the evaporites themselves,
Zechstein deposits form the caprock
for the large reservoirs of the gas fields of the
Netherlands
and parts of the North Sea region

136
More Nonmetal Resources

Other important evaporite mineral resources
include
those of the Permian Delaware Basin of west Texas
and New Mexico
and Devonian evaporites in the Elk Point basin of
Canada
In Michigan, gypsum is mined and used in the
construction of sheetrock
The majority of the silica sand
mined in the United States comes from east of the
Mississippi River
and much of this comes from Late Paleozoic-age
rocks

137
Silica Sand

Silica sand from
the Devonian Ridgely Formation is mined in West
Virginia, Maryland, and Pennsylvania
and the Devonian Sylvania Sandstone is mined near
Toledo, Ohio
Recall that silica sand is used
in the manufacture of glass
for refractory bricks in blast furnaces
for molds for casting aluminum, iron, and copper
alloys
and for a variety of other uses

138
Limestones

Late Paleozoic-age limestones
from many areas in North America
are used in the manufacture of cement
Limestone
is also mined and used
in blast furnaces
when steel is produced

139
Metallic Minerals

Metallic mineral resources including
tin, copper, gold, and silver
are also known from Late Paleozoic-age rocks
especially those that have been deformed during
mountain building
Although the precise origin of the Missouri lead
and zinc deposits remains unresolved
much of the ores of these metals come from
Mississippian-age rocks
In fact, mines in Missouri account for a
substantial amount of all domestic production of
lead ores

140
Summary