1. Early Paleozoic Earth History
Chapter 10
Early Paleozoic Earth History

2. The First Geologic Map William Smith,
a canal builder, published the first geologic map
on August 1, 1815

3. The First Geologic Map Five of the six geologic Paleozoic systems
Cambrian, Ordovician, Silurian, Devonian, and Carboniferous
We use the same basic geologic principles to interpret the geology of the Paleozoic Era

4. Cratons and Mobile Belts
Pannotia supercontinent began broke apart during the latest Proterozoic
By the beginning of the Paleozoic Era,
six major continents were present
Each continent can be divided
into two major components
a craton
and one or more mobile belts

5. Continental Architecture
Cratons typically consist of two parts
a shield
and a platform

6. Platforms
Extending outward from the shields are buried Precambrian rocks
The sediments over the platforms were deposited in widespread shallow seas

7. Paleozoic North America
Platform

8. Epeiric Seas The transgressing and regressing shallow seas
called epeiric seas
common feature of most Paleozoic cratons

9. Mobile Belts
Mobile belts are elongated areas of mountain building activity
They are located along the margins of continents
where sediments are deposited in the relatively shallow waters of the continental shelf
and the deeper waters at the base of the continental slope
During plate convergence along these margins,
the sediments are deformed
and intruded by magma
creating mountain ranges

10. Four Mobile Belts Four mobile belts formed around the margin
of the North American craton during the Paleozoic
Franklin mobile belt
Cordilleran mobile belt
Ouachita mobile belt
Appalachian mobile belt

11. Paleozoic North America
Mobil belts

12. Paleogeographic Maps Geologists use to construct paleogeographic maps
paleoclimatic data
paleomagnetic data
paleontologic data
sedimentologic data
stratigraphic data
tectonic data
to construct paleogeographic maps
which are interpretations of the geography of an area for a particular time in the geologic past

13. Paleozoic paleogeography
The paleogeographic history
of the Paleozoic Era is not as precisely known
as for the Mesozoic and Cenozoic eras
in part because the magnetic anomaly patterns
preserved in the oceanic crust
was subducted during the formation of Pangaea
Paleozoic paleogeographic reconstructions
are therefore based primarily on
structural relationships
climate-sensitive sediments such as red beds, evaporates, and coals
as well as the distribution of plants and animals

14. Six Major Paleozoic Continents
Baltica - Russia west of the Ural Mountains and the major part of northern Europe
China - a complex area consisting of at least three Paleozoic continents that were not widely separated and are here considered to include China, Indochina, and the Malay Peninsula
Gondwana - Africa, Antarctica, Australia, Florida, India, Madagascar, and parts of the Middle East and southern Europe

15. Six Major Paleozoic Continents
Kazakhstan - a triangular continent centered on Kazakhstan, but considered by some to be an extension of the Paleozoic Siberian continent
Laurentia - most of present North America, Greenland, northwestern Ireland, and Scotland
and Siberia - Russia east of the Ural Mountains and Asia north of Kazakhstan and south Mongolia

16. Paleogeography of the World
For the Late Cambrian Period

17. Paleogeography of the World
For the Late Ordovician Period

18. Paleogeography of the World
For the Middle Silurian Period

19. Early Paleozoic Global History
In contrast to today's global geography,
six major continents
dispersed at low tropical latitudes
polar regions were mostly ice free
By the Late Cambrian,
epeiric seas had covered most areas of
Laurentia, Baltica, Siberia, Kazakhstania, China,

20. Ordovician and Silurian Periods
Gondwana moved southward during the Ordovician and began to cross the South Pole
as indicated by Upper Ordovician tillites found today in the Sahara Desert
In contrast to Laurentia’s passive margin in the Cambrian,
an active convergent plate boundary formed along its eastern margin during the Ordovician
as indicated by the Late Ordovician Taconic orogeny that occurred in New England

21. Silurian Period Baltica moved northwestward relative
to Laurentia and collided with it
to form the larger continent of Laurasia
This collision closed the northern Iapetus Ocean
Siberia and Kazakhstania moved from
a southern equatorial position during the Cambrian
to north temperate latitudes
by the end of the Silurian Period

22. Early Paleozoic Evolution of North America
The geologic history of the North American craton may be divide into two parts
the first dealing comings and goings of epeiric seas
the second dealing with the mobile belts
In 1963, American geologist Laurence Sloss proposed that the sedimentary-rock record of North America could be subdivided into six cratonic sequences

23. Cratonic Sequences of N. America
White areas represent sequences of rocks
That are separated by large-scale uncon-formities shown in brown
Appa-lachian oro-genies
Cordilleran orogenies

24. Cratonic Sequence A cratonic sequence is
a large-scale lithostratigraphic unit
greater than supergroup
representing a major transgressive-regressive cycle
bounded by craton-wide unconformities
The six unconformities extend across
the various sedimentary basins of the North American craton
and into the mobile belts along the cratonic margin

25. The Sauk Sequence Rocks of the Sauk Sequence
during the Late Proterozoic-Early Ordovician
record the first major transgression onto the North American craton
Deposition of marine sediments
during the Late Proterozoic and Early Cambrian
was limited to the passive shelf areas of the
Appalachian and Cordilleran borders of the craton
The craton itself was above sea level
and experiencing extensive weathering and erosion

26. Cratonic Sequences of N. America
White areas = sequences of rocks
Brown areas = large-scale uncon-formities
Sauk sequence

27. The Sauk Sequence Because North America was located
in a tropical climate at this time
but there is no evidence of any terrestrial vegetation,
weathering and erosion of the exposed
Precambrian basement rocks must have proceeded rapidly
During the Middle Cambrian,
the transgressive phase of the Sauk
began with epeiric seas encroaching over the craton

28. Transcontinental Arch
By the Late Cambrian,
the Sauk Sea had covered most of North America,
leaving above sea level only
a portion of the Canadian Shield
and a few large islands
These islands,
collectively named the Transcontinental Arch,
extended from New Mexico
to Minnesota and the Lake Superior region

29. Cambrian Paleogeography of North America
During this time North America straddled the equator
Trans-continental Arch

30. The Sauk Sediments The sediments deposited The only difference
on both the craton
and along the shelf area of the craton margin
show abundant evidence of shallow-water deposition
The only difference
between the shelf and craton deposits
is that the shelf deposits are thicker

31. Sauk Carbonates Many of the carbonates are
bioclastic
composed of fragments of organic remains
contain stromatolites,
or have oolitic textures
contain small, spherical calcium carbonate grains
Such sedimentary structures and textures
indicate shallow-water deposition

32. A Transgressive Facies Model
Recall that facies are sediments
that represent a particular environment
During a transgression, the coarse (sandstone),
fine (shale) and carbonate (limestone) facies
migrate in a landward direction

33. Cambrian Transgression
Cambrian strata exposed in the Grand Canyon
The three formations exposed
along the Bright Angel Trail, Grand Canyon Arizona

34. Transgression The Tapeats sediments
are clean, well-sorted sands
of the type one would find on a beach today
As the transgression continued into the Middle Cambrian,
muds of the Bright Angle Shale
were deposited over the older Tapeats Sandstone

35. Time Transgressive Formations
Faunal analysis of the Bright Angel Shale indicates
that it is Early Cambrian in age in California
and Middle Cambrian in age in the Grand Canyon region,
thus illustrating the time-transgres- sive nature of formations and facies
younger shale
older shale

36. Cambrian Transgression
Cambrian strata exposed in the Grand Canyon
Observe the time transgressive nature of the three formations
The three formations exposed
along the Bright Angel Trail, Grand Canyon Arizona

37. Same Facies Relationship
By the end of Sauk time, much of the craton
was submerged beneath a warm, equatorial epeiric sea

38. Cambrian Facies
Block diagram from the craton interior to the Appalachian mobile belt margin
showing 3 major Cambrian facies
and the time transgressive nature of the units
The carbonate facies developed progressively
due to submergence of the detrital source areas by the advancing Sauk Sea

39. Upper Cambrian Sandstone
Outcrop of cross-bedded Upper Cambrian sandstone in the Dells area of Wisconsin

40. Regression and Unconformity
During the Early Ordovician, the Sauk Sea regressed.
The rocks exposed were predominately
limestones and dolostones
that experienced deep and extensive erosion
The resulting craton-wide unconformity
marks the boundary between the Sauk
and Tippecanoe sequences

41. Ordovician Period Paleo-geography of North America The continent
showing change in the position of the the equator
The continent
was rotating counter-clockwise

42. Cratonic Sequences of N. America
White areas = sequences of rocks
brown areas = large-scale uncon-formities
Regression
Tippecanoe sequence

43. The Tippecanoe Sequence
A transgressing sea deposited the Tippecanoe sequence over most of the craton
Middle Ordovician-Early Devonian
The Tippecanoe basal rock is the St. Peter Sandstone,
an almost pure quartz sandstone
occurs throughout much of the mid-continent
resulted from numerous cycles of weathering
and erosion of Proterozoic and Cambrian sandstones
deposited during the Sauk transgression

44. Transgression of the Tippecanoe Sea
Resulted in the deposition of
the St. Peter Sandstone
Middle Ordovician
over a large area of the craton

45. St. Peter Sandstone
Outcrop of St. Peter Sandstone in Governor Dodge State Park, Wisconsin

46. The Tippecanoe Sequence
The Tippecanoe basal sandstones were followed by widespread carbonate deposition
The limestones were generally the result of deposition
by calcium carbonate- secreting organisms such as
corals,
brachiopods,
stromatoporoids,
and bryozoans

47. Tippecanoe Reefs and Evaporites
Organic reefs are limestone structures
constructed by living organisms
Reefs appear to have occupied
the same ecological niche in the geological past

48. Modern Reef Requirements
Present-day reefs
grow between 30 degrees N and S of equator
Reefs require
warm, clear, shallow water of normal salinity for optimal growth

49. Present-Day Reef Community
with reef-building organisms

50. Reef Environments
Block diagram of a reef showing the various environments within the reef complex

51. Barrier Reefs Reefs create and maintain a steep seaward front
typically long linear masses forming a barrier between
a shallow platform
a deep marine basin
Reefs create and maintain a steep seaward front
that absorbs incoming wave energy
As skeletal material breaks off
from the reef front,
it accumulates along a fore-reef slope

52. Barrier Reef
Barrier Reef
Fore-reef slope

53. The Lagoon The lagoon area is a low-energy,
quiet water zone where fragile,
sediment-trapping organisms thrive
The lagoon area can also become the site
of evaporitic deposits
when circulation to the open sea is cut off
Modern examples of barrier reef systems
are the Florida Keys, Bahama Islands,
and Great Barrier Reef of Australia

54. Ancient Reefs Reefs have been common features since the Cambrian
The first skeletal builders of reef-like structures
were archaeocyathids

55. Stromatoporoid-Coral Reefs
Beginning in the Middle Ordovician,
stromatoporoid-coral reefs became common
similar reefs throughout the rest of the Phanerozoic Eon

56. Michigan Basin Evaporites
a broad, circular basin surrounded by large barrier reefs
Reef growth caused restricted circulation
and precipitation of Silurian evaporates within Upper Tippecanoe sequence of the basin

57. Silurian Period
Paleogeography of North America during the Silurian Period
Reefs developed in the Michigan, Ohio, and Indiana-Illinois-Kentucky areas

58. Northern Michigan Basin
Northern Michigan Basin sediments during the Silurian Period

59. Stromatoporoid Reef Facies
Stromato-poroid barrier-reef facies of the Michigan Basin

60. Evaporite
Evaporite facies

61. Carbonate Facies
Carbonate Facies

62. Silled Basin Model
Silled Basin Model for evaporite sedimentation by direct precipitation from seawater
Vertical scale is greatly exaggerated

63. Basin Brines
Because North America was still near the equator during the Silurian Period,
temperatures were probably high

64. Order of Precipitation
calcium carbonate first,
followed by gypsum
and lastly halite

65. Reefs in a Highly Saline Environ-ment?
Organisms constructing reefs could not have lived in such a highly saline environ-ment

66. The End of the Tippecanoe Sequence
During this regression,
marine deposition was initially restricted to
a few interconnected cratonic basins
By the Early Devonian,
the regressing Tippecanoe Sea retreated to the craton margin
exposed an extensive lowland topography

67. The Appalachian Mobile Belt
the first Phanerozoic orogeny
began during the Middle Ordovician

68. Mountain Building part of the global tectonic regime
that sutured the continents together,
forming Pangaea by the end of the Paleozoic
The Appalachian region
throughout Sauk time,
was a broad, passive, continental margin

69. Iapetus Ocean During this time,
the Iapetus Ocean was widening
along a divergent plate boundary
the Appalachian mobile belt was born with the onset of subduction of the Iapetus plate beneath Laurentia

70. Appalachian Mobile Belt
Evolution of the Appalachian mobile belt
Late Proterozoic opening of Iapetus Ocean
with passive continen-tal margins
and large carbon-ate plat-forms

71. The Taconic Orogeny The resulting Taconic orogeny,
named after present-day Taconic Mountains of
eastern New York,
central Massachusetts,
and Vermont

72. Shallow-Water Deposition
The Appalachian mobile belt
can be divided into two depositional environments
The first is the extensive,
shallow-water carbonate platform
that formed the broad eastern continental shelf
and stretched from Newfoundland to Alabama
Formed during the Sauk Sea transgression

73. Deep-Water Deposits
Replaced by deep-water deposits (second depositional environment) during middle Ordovician characterized by
thinly bedded black shales,
graded beds,
coarse sandstones,
graywackes,
and associated volcanics
This suite of sediments marks the onset
of mountain building, the Taconic orogeny

74. Sediment Source Sediment shed from the Taconic Highlands
and associated volcanoes
The subduction of the Iapetus plate beneath Laurentia
resulted in volcanism and downwarping of the carbonate platform

75. Appalachian Mobile Belt
Middle Ordovician transition to convergence resulted in orogenic activity

76. Orogeny Timing
Other evidence in the area from present-day Georgia to Newfoundland includes
volcanic activity in the form of deep-sea lava flows,
volcanic ash layers,
and intrusive bodies
These igneous rocks show a clustering
of radiometric ages between 440 to 480 million years ago
In addition, regional metamorphism
coincides with the radiometric dates

77. Queenston Delta Clastic Wedge
The clastic wedge resulting from the erosion
of the Taconic Highlands
referred to as the Queenston Delta

78. Queenston Delta Clastic Wedge
Taconic Highlands
consists of thick, coarse-grained detrital sediments nearest the highlands
and thins laterally into finer-grained sediments on the craton

79. A European Orogeny As the Iapetus Ocean narrowed and closed,
another orogeny also occurred in Europe during the Silurian (Caledonian Orogeny)

80. Caledonian Orogeny
The transition to convergence resulted in orogenic activity in North America and Europe
Caledonian Orogeny
was a mirror image of the Taconic Orogeny

81. Early Paleozoic Mineral Resources
Early Paleozoic-age rocks contain a variety
of important mineral resources, including
sand and gravel for construction,
building stone,
and limestone used in the manufacture of cement
An Important sources of industrial or silica sand is
the Middle Ordovician St. Peter Sandstone

82. Salt and Oil Thick deposits of Silurian evaporites,
mostly rock salt (NaCl)
and rock gypsum (CaSO4•H2O) altered to rock anhydrite (CaSO4)
and are important sources of various salts
In addition, barrier and pinnacle reefs
are reservoirs for oil and gas in Michigan and Ohio

83. Summary Six major continents existed
at the beginning of the Paleozoic Era
four of them were located near the paleo-equator
During the Early Paleozoic — Cambrian-Silurian
Laurentia was moving northward
and Gondwana moved to a south polar location,
as indicated by tillite deposits

84. Summary Most continents consisted of two major components
a relatively stable craton over which epeiric seas transgressed and regressed,
surrounded by mobile belts in which mountain building took place
The geologic history of North America
can be divided into cratonic sequences
that reflect cratonwide transgressions and regressions

85. Summary The Sauk Sea was the first major transgression onto the craton
At its maximum, it covered the craton
except for parts of the Canadian Shield
and the Transcontinental Arch,
a series of large northeast-southwest trending islands
The Tippecanoe sequence began with
deposition of an extensive sandstone over
the exposed and eroded Sauk landscape

86. Summary During Tippecanoe time, In addition, large barrier reefs
extensive carbonate deposition took place
In addition, large barrier reefs
enclosed basins,
and resulted in evaporite deposition within these basins
The eastern edge of North America
was a stable carbonate platform during Sauk time

87. Summary During Tippecanoe time The newly formed Taconic Highlands
an oceanic-continental convergent plate boundary formed,
resulting in the Taconic orogeny,
the first of several orogenies to affect the Appalachian mobile belt
The newly formed Taconic Highlands
shed sediments into the western epeiric sea
producing the Queenston Delta, a clastic wedge

88. Summary
Early Paleozoic-age rocks contain a variety of mineral resources including
building stone,
limestone for cement,
silica sand,
hydrocarbons,
evaporites
and iron ores