Early Paleozoic Earth History - PowerPoint PPT Presentation

About This Presentation

Early Paleozoic Earth History


Modern examples of barrier reef systems. are the Florida Keys, Bahama Islands, and Great Barrier Reef of Australia. The Lagoon ... – PowerPoint PPT presentation

Number of Views:307
Avg rating:3.0/5.0
Slides: 89
Provided by: ThomsonBr1
Learn more at: http://www.geol.lsu.edu


Transcript and Presenter's Notes

Title: Early Paleozoic Earth History

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
  • We use the same basic geologic principles to
    interpret the geology of the Paleozoic Era

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
  • Cratons typically consist of two parts
  • a shield
  • and a platform

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

Paleozoic North America
  • Platform

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

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 formed
  • around the margin
  • of the North American craton during the Paleozoic
  • Franklin mobile belt
  • Cordilleran mobile belt
  • Ouachita mobile belt
  • Appalachian mobile belt

Paleozoic North America
  • Mobil belts

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
  • 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
  • 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 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
  • For the Late Cambrian Period

Paleogeography of the World
  • For the Late Ordovician Period

Paleogeography of the World
  • For the Middle Silurian Period

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
  • 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 Laurentias passive margin in the
  • 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
  • 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
  • to north temperate latitudes
  • by the end of the Silurian Period

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
  • 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
  • White areas represent sequences of rocks
  • That are separated by large-scale uncon-formities
    shown in brown
  • Appa-lachian oro-genies
  • Cordilleran orogenies

Cratonic Sequence
  • A cratonic sequence is
  • a large-scale lithostratigraphic unit
  • greater than supergroup
  • representing a major transgressive-regressive
  • 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

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. America
  • White areas sequences of rocks
  • Brown areas large-scale uncon-formities
  • Sauk sequence

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

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
  • During this time North America straddled the
  • Trans-continental Arch

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
  • The only difference
  • between the shelf and craton deposits
  • is that the shelf deposits are thicker

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
  • 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 strata exposed in the Grand Canyon
  • The three formations exposed
  • along the Bright Angel Trail, Grand Canyon Arizona

  • 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
  • muds of the Bright Angle Shale
  • were deposited over the older Tapeats Sandstone

Time Transgressive Formations
  • Faunal analysis of the Bright Angel Shale
  • that it is Early Cambrian in age in California
  • and Middle Cambrian in age in the Grand Canyon
  • thus illustrating the time-transgres-sive nature
    of formations and facies

younger shale
older shale
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
  • By the end of Sauk time, much of the craton
  • was submerged beneath a warm, equatorial epeiric

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

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

Regression and Unconformity
  • During the Early Ordovician, the Sauk Sea
  • 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
  • Paleo-geography of North America
  • showing change in the position of the the equator
  • The continent
  • was rotating counter-clockwise

Cratonic Sequences of N. America
  • White areas sequences of rocks
  • brown areas large-scale uncon-formities
  • Regression
  • 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
  • an almost pure quartz sandstone
  • occurs throughout much of the mid-continent
  • resulted from numerous cycles of weathering
  • and erosion of Proterozoic and Cambrian
  • deposited during the Sauk transgression

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

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

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
  • 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
  • with reef-building organisms

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

Barrier Reefs
  • typically long linear masses forming a barrier
  • 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

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
  • Reefs have been common features since the
  • The first skeletal builders of reef-like
  • were archaeocyathids

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
  • 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 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 sediments during the
    Silurian Period

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

  • Evaporite facies

Carbonate Facies
  • Carbonate Facies

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

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

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

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
  • 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 first Phanerozoic orogeny
  • began during the Middle Ordovician

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
  • 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

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 resulting Taconic orogeny,
  • named after present-day Taconic Mountains of
  • eastern New York,
  • central Massachusetts,
  • and Vermont

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
  • 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 shed from
  • the Taconic Highlands
  • and associated volcanoes
  • The subduction of the Iapetus plate beneath
  • resulted in volcanism and downwarping of the
    carbonate platform

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

Orogeny Timing
  • Other evidence in the area from present-day
    Georgia to Newfoundland includes
  • volcanic activity in the form of deep-sea lava
  • 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
  • The clastic wedge resulting from the erosion
  • of the Taconic Highlands
  • referred to as the Queenston Delta

Queenston Delta Clastic Wedge
  • 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

A European Orogeny
  • As the Iapetus Ocean narrowed and closed,
  • another orogeny also occurred in Europe during
    the Silurian (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-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
  • the Middle Ordovician St. Peter Sandstone

Salt and Oil
  • Thick deposits of Silurian evaporites,
  • mostly rock salt (NaCl)
  • and rock gypsum (CaSO4H2O) 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

  • 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

  • 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

  • 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
  • The Tippecanoe sequence began with
  • deposition of an extensive sandstone over
  • the exposed and eroded Sauk landscape

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

  • During Tippecanoe time
  • an oceanic-continental convergent plate boundary
  • 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

  • Early Paleozoic-age rocks contain a variety of
    mineral resources including
  • building stone,
  • limestone for cement,
  • silica sand,
  • hydrocarbons,
  • evaporites
  • and iron ores
Write a Comment
User Comments (0)
About PowerShow.com