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 Pensylvanian rocks, Mazon Cree
  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 Maxon 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,
• including millipedes and centipedes, as well as
  spiders
• and other animals such as
• scorpions and amphibians
• In the ponds, lakes, and rivers were many
• fish, shrimp, and ostracodes
• 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
• its scientific name
• 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
Tully Monster

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

• Reconstruction of the Tully Monster
• about 30 cm long

11
Late Paleozoic Paleogeography

• The Late Paleozoic was a time of
• 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

12
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

13
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

14
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

15
Paleogeography of the World

• For the Late Devonian Period

16
Paleogeography of the World

• For the Early Carboniferous Period

17
Paleogeography of the World

• For the Late Carboniferous Period

18
Paleogeography of the World

• For the Late Permian Period

19
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

20
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
• These are probably related to the collision of
  Laurentia and Baltica

21
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

22
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

23
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

24
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
• The northwestern margin of China may have
• collided with the southwestern margin of Siberia
• during the Late Carboniferous
• By the end of the Carboniferous,
• the various continental landmasses were fairly
  close together
• as Pangaea began taking shape

25
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

26
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

27
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

28
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

29
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

30
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

31
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

32
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 due to
• Gondwanan glaciation
• and tectonic events related to the joining of
  Pangaea

33
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

34
The Kaskaskia Sequence

• The boundary between
• the Tippecanoe sequence (discussed previously)
• and the overlying Kaskaskia sequence
• Middle Devonian-Middle 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

35
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

36
Basal Kaskaskia Sandstones

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

37
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

38
Devonian Period

• Paleogeography of North America during the
  Devonian Period

39
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

40
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

41
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

42
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

43
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

44
Devonian Reef Complex

• Reconstruction of the extensive Devonian Reef
  complex of western Canada

• These reefs controlled the regional facies of the
  Devonian epeiric seas

45
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

46
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

47
Increased Detrital Deposition

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

48
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

49
Extent of Black Shales

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

50
New Albany Shale

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

51
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

52
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

53
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

54
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 were 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

55
Mississippian Period

• Paleogeography of North America during the
  Mississippian Period

56
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

57
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

58
Cratonwide Unconformity

• Prior to the end of the Mississippian,
• the Kaskaskia 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

59
The Absaroka Sequence

• The Absaroka sequence
• includes rocks deposited
• during the latest Mississippian
• 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

60
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

61
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

62
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

63
Pennsylvanian Period

• Paleogeography of North America during the
  Pennsylvanian Period

64
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

65
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

66
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

67
Cyclothem

• Columnar section of a complete cyclothem

68
Pennsylvanian Coal Bed

• Pennsylvanian coal bed, West Virginia
• part of a cyclothem

69
Coal-Forming Swamp

• Reconstruction of the environment of a
  Pennsylvanian coal-forming swamp

70
The Okefenokee Swamp

• in Georgia, is a modern coal-forming environment,

similar to those occurring during the
Pennsylvanian Period
71
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

72
Cyclothem

• Columnar section of a complete cyclothem

73
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

74
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

75
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

76
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
• a swamp-delta complex of low relief near the sea
• by
• rapid but slight changes in sea level
• or by localized crustal movement
• Explaining widespread cyclothems is more difficult

77
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

78
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

79
Ancestral Rockies

• During the Late Absaroka (Pennsylvania),
• 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

80
Pennsylvanian Highlands

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

81
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

82
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

83
Garden of the Gods

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

84
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
• 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

85
The Late Absaroka

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

86
Permian Period

• Paleogeography of North America during the
  Permian Period

87
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
• provide evidence of the restricted nature of the
  Absaroka Sea
• during the Early and Middle Permian
• and its southwestward retreat from the central
  craton

88
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

89
Permian Reefs and Basins

• Location of the west Texas Permian basins and
  surrounding reefs

90
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

91
Capitan Limestone Reef Reconstruction

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

92
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

93
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

94
Cordilleran Mobile Belt

• During the Late Proterozoic 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

95
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

96
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

97
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

98
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

99
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

100
Beginning of the Ouachita Orogeny

• During the Late Proterozoic 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

101
Ouachita Mobile Belt

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

102
Ouachita Mobile Belt

• Incipient continental collision between
  North America and Gondwana began during
  the Mississippian to Pennsylvanian

103
Ouachita Mobile Belt

• Continental collision continued during the
  Pennsylvanian Period

104
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 Ouchita and Marathon
  Mountains remain of this once lofty mountain range

105
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

106
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 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

107
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)

108
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

109
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

110
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

111
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

112
Folding and Thrusting

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

113
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

114
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

115
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

116
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

117
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

118
Old Red Sandstone

• Old Red Sandstone on one side
• and the Catskill Delta on the other

119
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

120
Closing of the Iapetus Ocean

• The Taconic, Caledonian, and Arcadian 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

121
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

122
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

123
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

124
What Role Did Microplates Play 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

125
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
• In this chapter and the previous one,
• 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

126
Avalonia

• For example, the small continent 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

127
A Separate Continent

• The Avalon microplate
• existed as a separate continent
• during the Ordovician
• and began to collide with Baltica
• during the Silurian
• and Laurentia
• as part of Baltica
• during the Devonian

128
Numerous Microplates

• Florida and parts of the eastern seaboard of
  North America
• make up the Piedmont microplate
• that was part of the larger Gondwana continent
• This microplate became sutured to Laurasia
• during the Pennsylvanian Period
• Numerous microplates occupied the region between
  Gondwana and Laurasia
• that eventually became part of Central America
• during the Pennsylvanian collision between these
  continents

129
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 also
  played an important role
• Furthermore, the recognition of terranes
• within mobile belts helps explain
• some previously anomalous geologic situations

130
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

131
Hydrocarbons

• For example, 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

132
Permian-Age Coal Beds

• Although Permian-age coal beds
• are known for 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

133
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 Tertiary

134
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

135
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

136
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

137
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 wallboard
• 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

138
Silica Sand

• For example, silica sand from
• the Devonian Ridgely Formation is mined in West
  Virginia, Maryland and Pennsylvania
• and the Devonian Sylvania Sandstone is mined near
  Detroit, Michigan
• 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

139
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

140
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

141
Summary

• During the Late Paleozoic, Baltica
• and Laurentia collided, forming Laurasia
• Siberia and Kazakhstania collided
• and finally were sutured to Laurasia
• Gondwana moved over the South Pole
• and experienced several glacial-interglacial
  periods,
• resulting in global sea level changes
• and transgressions and regressions