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Chapter 10. Early Paleozoic Earth History. The First Geologic Map. William Smith, a canal builder, published the first geologic map on August 1, 1815. The First Geologic Map. Five of the six geologic Paleozoic systems Cambrian, Ordovician, Silurian, Devonian, and Carboniferous

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Early Paleozoic Earth History


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Chapter 10

Early Paleozoic Earth History

the first geologic map
The First Geologic Map
  • William Smith,
    • a canal builder, published the first geologic map
    • on August 1, 1815
the first geologic map3
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
cratons and mobile belts
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
continental architecture
Continental Architecture
  • Cratons typically consist of two parts
    • a shield
    • and a platform
platforms
Platforms
  • Extending outward from the shields are buried Precambrian rocks
  • The sediments over the platforms were deposited in widespread shallow seas
epeiric seas
Epeiric Seas
  • The transgressing and regressing shallow seas
    • called epeiric seas
    • common feature of most Paleozoic cratons
mobile belts
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
four mobile belts
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
paleogeographic maps
Paleogeographic Maps
  • Geologists use
    • 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
paleozoic paleogeography
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
six major paleozoic continents
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
six major paleozoic continents15
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
paleogeography of the world
Paleogeography of the World
  • For the Late Cambrian Period
paleogeography of the world17
Paleogeography of the World
  • For the Late Ordovician Period
paleogeography of the world18
Paleogeography of the World
  • For the Middle Silurian Period
early paleozoic global history
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,
ordovician and silurian periods
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
silurian period
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
early paleozoic evolution of north america
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

cratonic sequences of n america
Cratonic Sequences of N. America
  • That are separated by large-scale uncon-formities shown in brown
  • White areas represent sequences of rocks

Appa-lachian oro-genies

Cordilleran orogenies

cratonic sequence
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
the sauk sequence
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
cratonic sequences of n america26
Cratonic Sequences of N. America
  • Brown areas = large-scale uncon-formities
  • White areas = sequences of rocks
  • Sauk sequence
the sauk sequence27
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
transcontinental arch
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
cambrian paleogeography of north america
Cambrian Paleogeography of North America
  • During this time North America straddled the equator
  • Trans-continental Arch
the sauk sediments
The Sauk Sediments
  • The sediments deposited
    • 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
sauk carbonates
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
a transgressive facies model
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
cambrian transgression
Cambrian Transgression
  • The three formations exposed
    • along the Bright Angel Trail, Grand Canyon Arizona
  • Cambrian strata exposed in the Grand Canyon
transgression
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
time transgressive formations
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

cambrian transgression36
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
same facies relationship
Same Facies Relationship
  • By the end of Sauk time, much of the craton
    • was submerged beneath a warm, equatorial epeiric sea
cambrian facies
Cambrian Facies
  • 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
  • Block diagram from the craton interior to the Appalachian mobile belt margin
upper cambrian sandstone
Upper Cambrian Sandstone
  • Outcrop of cross-bedded Upper Cambrian sandstone in the Dells area of Wisconsin
regression and unconformity
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
ordovician period
Ordovician Period
  • Paleo-geography of North America
    • showing change in the position of the the equator
  • The continent
    • was rotating counter-clockwise
cratonic sequences of n america42
Cratonic Sequences of N. America
  • brown areas = large-scale uncon-formities
  • White areas = sequences of rocks
  • Regression
  • Tippecanoe sequence
the tippecanoe sequence
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
transgression of the tippecanoe sea
Transgression of the Tippecanoe Sea
  • Resulted in the deposition of
  • the St. Peter Sandstone
    • Middle Ordovician
  • over a large area of the craton
st peter sandstone
St. Peter Sandstone
  • Outcrop of St. Peter Sandstone in Governor Dodge State Park, Wisconsin
the tippecanoe sequence46
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
tippecanoe reefs and evaporites
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
modern reef requirements
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
present day reef community
Present-Day Reef Community
  • with reef-building organisms
reef environments
Reef Environments
  • Block diagram of a reef showing the various environments within the reef complex
barrier reefs
Barrier Reefs
    • 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
barrier reef
Barrier Reef
  • Fore-reef slope
  • Barrier Reef
the lagoon
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
ancient reefs
Ancient Reefs
  • Reefs have been common features since the Cambrian
  • The first skeletal builders of reef-like structures
    • were archaeocyathids
stromatoporoid coral reefs
Stromatoporoid-Coral Reefs
  • Beginning in the Middle Ordovician,
    • stromatoporoid-coral reefs became common
    • similar reefs throughout the rest of the Phanerozoic Eon
michigan basin evaporites
Michigan Basin Evaporites
  • Michigan Basin
    • 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
silurian period57
Silurian Period
  • Paleogeography of North America during the Silurian Period
  • Reefs developed in the Michigan, Ohio, and Indiana-Illinois-Kentucky areas
northern michigan basin
Northern Michigan Basin
  • Northern Michigan Basin sediments during the Silurian Period
stromatoporoid reef facies
Stromatoporoid Reef Facies
  • Stromato-poroid barrier-reef facies of the Michigan Basin
evaporite
Evaporite
  • Evaporite facies
carbonate facies
Carbonate Facies
  • Carbonate Facies
silled basin model
Silled Basin Model
  • Silled Basin Model for evaporite sedimentation by direct precipitation from seawater
    • Vertical scale is greatly exaggerated
basin brines
Basin Brines
  • Because North America was still near the equator during the Silurian Period,
    • temperatures were probably high
order of precipitation
Order of Precipitation
  • calcium carbonate first,
  • followed by gypsum
  • and lastly halite
reefs in a highly saline environ ment
Reefs in a Highly Saline Environ-ment?
  • Organisms constructing reefs could not have lived in such a highly saline environ-ment
the end of the tippecanoe sequence
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
the appalachian mobile belt
The Appalachian Mobile Belt
  • the first Phanerozoic orogeny
    • began during the Middle Ordovician
mountain building
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
iapetus ocean
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
appalachian mobile belt
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
the taconic orogeny
The Taconic Orogeny
  • The resulting Taconic orogeny,
    • named after present-day Taconic Mountains of
      • eastern New York,
      • central Massachusetts,
      • and Vermont
shallow water deposition
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
deep water deposits
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
sediment source
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
appalachian mobile belt75
Appalachian Mobile Belt
  • Middle Ordovician transition to convergence resulted in orogenic activity
orogeny timing
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
queenston delta clastic wedge
Queenston Delta Clastic Wedge
  • The clastic wedge resulting from the erosion
    • of the Taconic Highlands
    • referred to as the Queenston Delta
queenston delta clastic wedge78
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
  • Queenston Delta clastic wedge
a european orogeny
A European Orogeny
  • As the Iapetus Ocean narrowed and closed,
    • another orogeny also occurred in Europe during the Silurian (Caledonian Orogeny)
caledonian orogeny
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
early paleozoic mineral resources
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
salt and oil
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
summary
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
summary84
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
summary85
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
summary86
Summary
  • During Tippecanoe time,
    • 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
summary87
Summary
  • During Tippecanoe time
    • 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
summary88
Summary
  • Early Paleozoic-age rocks contain a variety of mineral resources including
    • building stone,
    • limestone for cement,
    • silica sand,
    • hydrocarbons,
    • evaporites
    • and iron ores