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Chapter 11 . Late Paleozoic Earth History. Tully Monster. Tullimonstrum gregarium , also known as the Tully Monster, is Illinois’s official state fossil Specimen from Pennsylvanian rocks, Mazon Creek Locality, Illinois. Reconstruction of the Tully Monster about 30 cm long.

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Chapter 11

Late Paleozoic Earth History


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Tully Monster

  • Tullimonstrum gregarium, also known as the Tully Monster, is Illinois’s official state fossil

    • Specimen from Pennsylvanian rocks, Mazon Creek Locality, Illinois

  • Reconstruction of the Tully Monster

    • about 30 cm long


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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


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Exceptional Preservation

  • The resulting fossils,

    • known as the Mazon Creek fossils

      • for the area in northeastern Illinois

      • where most specimens are found,

    • provide us with significant insights about the soft-part anatomy of the region's biota

  • Because of the exceptional preservation of this ancient biota,

    • Mazon Creek fossils are known throughout the world

    • and many museums have extensive collections from the area


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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


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Swampy Lowlands

  • The swampy lowlands surrounding the delta were home to more than 400 plant species,

    • numerous insects and spiders,

    • and other animals such as

      • scorpions and amphibians

    • In the ponds, lakes, and rivers were many

      • fish, shrimp, and ostracods

    • Almost all of the plants were

      • seedless vascular plants,

      • typical of the kinds that lived in the coal-forming swamps

      • during the Pennsylvanian Period


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Tully Monster

  • One of the more interesting Mazon Creek fossils is the Tully Monster,

    • which is not only unique to Illinois,

    • but also is its official state fossil

  • Named for Francis Tully,

    • who first discovered it in 1958,

    • Tullimonstrum gregarium

    • was a small

      • up to 30 cm long

    • soft-bodied animal that lived in the warm, shallow seas

    • covering Illinois about 300 million years ago


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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


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Tully Monster

  • There presently is no consensus

    • as to what phylum the Tully Monster belongs

    • or to what animals it might be related


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Late Paleozoic Paleogeography

  • The Late Paleozoic was a time of

    • evolutionary innovations,

    • continental collisions,

    • mountain building,

    • fluctuating seas levels,

    • and varied climates

  • Coals, evaporites, and tillites

    • testify to the variety of climatic conditions

    • experienced by the different continents during the Late Paleozoic


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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


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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


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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


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Paleogeography of the World

  • For the Late Devonian Period


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Paleogeography of the World

  • For the Early Carboniferous Period


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Paleogeography of the World

  • For the Late Carboniferous Period


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Paleogeography of the World

  • For the Late Permian Period


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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


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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


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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


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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


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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


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Pangaea Began Taking Shape

  • Elsewhere, Siberia collided with Kazakhstania

    • and moved toward the Uralian margin of Laurasia (Baltica),

    • colliding with it during the Early Permian

  • By the end of the Carboniferous,

    • the various continental landmasses were fairly close together

    • as Pangaea began taking shape


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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


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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


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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


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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


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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


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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


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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


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Late Paleozoic History of North America

  • The Late Paleozoic cratonic history of North America included periods

    • of extensive shallow-marine carbonate deposition

    • and large coal-forming swamps

    • as well as dry, evaporite-forming terrestrial conditions

  • Cratonic events largely resulted from changes in sea level because of

    • Gondwanan glaciation

    • and tectonic events related to the joining of Pangaea


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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


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The Kaskaskia Sequence

  • The boundary between

    • the Tippecanoe sequence

    • and the overlying Kaskaskia sequence

      • Middle Devonian-Late Mississippian

    • is marked by a major unconformity

  • As the Kaskaskia Sea transgressed

    • over the low-relief landscape of the craton,

    • the majority of the basal beds deposited

      • consisted of clean, well-sorted quartz sandstones


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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


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Basal Kaskaskia Sandstones

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


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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


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Devonian Period

  • Paleogeography of North America during the Devonian Period


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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


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    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


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    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


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    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


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    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


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    Devonian Reef Complex

    • Reconstruction of the extensive Devonian Reef complex of western Canada

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


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    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


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    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


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    Increased Detrital Deposition

    • Deposition of black shales

    • was brought on by the the Acadian orogeny


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    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


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    Extent of Black Shales

    • The extent of the upper Devonian and Lower Mississippian Chattanooga Shale and its equivalent units

    • such as the Antrim Shale and the Albany Shale


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    New Albany Shale

    • Upper Devonian New Albany Shale,

    • Button Mold Knob Quarry, Kentucky


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    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


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    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


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    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


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    The Late Kaskaskia

    • Following deposition of the black shales,

      • carbonate sedimentation on the craton dominated the remainder of the Mississippian Period

    • During this time, a variety of carbonate sediments was deposited in the epeiric seas

      • as indicated by the extensive deposits of

      • crinoidal limestones

        • rich in crinoid fragments

      • oolitic limestones,

      • and various other limestones and dolostones


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    Mississippian Period

    • Paleogeography of North America during the Mississippian Period


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    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


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    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


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    Cratonwide Unconformity

    • Prior to the end of the Mississippian,

      • the epeiric sea had retreated

        • to the craton margin,

      • once again exposing the craton

      • to widespread weathering and erosion

    • This resulted in a cratonwide unconformity

      • when the Absaroka Sea began transgressing

      • back over the craton


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    The Absaroka Sequence

    • The Absaroka sequence

      • includes rocks deposited

        • during the Pennsylvanian

        • through Early Jurassic

      • At this point, we will only discuss the Paleozoic rocks of the Absaroka sequence

    • The extensive unconformity

      • separating the Kaskaskia and Absaroka sequences

      • essentially divides the strata

      • into the North American

      • Mississippian and Pennsylvanian systems


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    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


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    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


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    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


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    Pennsylvanian Period

    • Paleogeography of North America during the Pennsylvanian Period


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    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


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    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


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    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


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    Cyclothem

    • Columnar section of a complete cyclothem


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    Pennsylvanian Coal Bed

    • Pennsylvanian coal bed, West Virginia

    • part of a cyclothem


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    Coal-Forming Swamp

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


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    The Okefenokee Swamp

    • similar to those occurring during the Pennsylvanian Period

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


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    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



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    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


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    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


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    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


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    Explaining Cyclicity

    • Such regularity and cyclicity in sedimentation

      • over a large area requires an explanation

    • In most cases, local cyclothems of limited extent can be explained for

      • by rapid but slight changes in sea level

      • in a swamp-delta complex of low relief near the sea

      • such as progradation or by localized crustal movement

    • Explaining widespread cyclothems is more difficult


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    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


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    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


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    Ancestral Rockies

    • During the Pennsylvanian Period,

      • the area of greatest deformation occurred in the southwestern part of the North American craton

      • where a series of fault-bounded uplifted blocks formed the Ancestral Rockies

    • Uplift of these mountains,

      • some of which were elevated more than 2 km along near-vertical faults,

      • resulted in the erosion of the overlying Paleozoic sediments

      • and exposure of the Precambrian igneous and metamorphic basement rocks


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    Pennsylvanian Highlands

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


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    Ancestral Rockies

    • Erosion of these mountains produced

    • coarse red sediments

    • that were deposited in the adjacent basins

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


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    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


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    Garden of the Gods

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


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    Intracratonic Mountain Ranges

    • Intracratonic mountain ranges are unusual,

      • and their cause has long been debated

      • It is thought that the collision of Gondwana with Laurasia along the Ouachita mobile belt

      • produced great stresses in the southwestern region of the North American craton

    • These crustal stresses were relieved by faulting

      • that resulted in uplift of cratonic blocks

      • and downwarp of adjacent basins,

      • forming a series of ranges and basins


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    The Middle Absaroka

    More Evaporite Deposits and Reefs

    • While the various intracratonic basins

      • were filling with sediment

        • during the Late Pennsylvanian,

      • the epeiric sea slowly began retreating from the craton

    • During the Early Permian,

      • the Absaroka Sea occupied a narrow region

      • from Nebraska through west Texas


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    Permian Period

    • Paleogeography of North America during the Permian Period


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    Middle Permian Absaroka Sea

    • By the Middle Permian,

      • the sea had retreated to west Texas

      • and southern New Mexico

    • The thick evaporite deposits

      • in Kansas and Oklahoma

      • show the restricted nature of the Absaroka Sea

        • during the Early and Middle Permian

      • and its southwestward retreat from the central craton


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    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


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    Permian Reefs and Basins

    • Location of the west Texas Permian basins and surrounding reefs


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    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


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    Capitan Limestone Reef Reconstruction

    • Reconstruction of the Middle Permian Capitan Limestone reef environment

    • Shown are brachiopods, corals, bryozoans and large glass sponges


    Capitan limestone l.jpg
    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


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    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


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    Cordilleran Mobile Belt

    • During the Neoproterozoic and Early Paleozoic,

      • the Cordilleran area was a passive continental margin

      • along which extensive continental shelf sediments were deposited

    • Thick sections of marine sediments

      • graded laterally into thin cratonic units

      • as the Sauk Sea transgressed onto the craton

    • Beginning in the Middle Paleozoic,

      • an island arc formed off the western margin of the craton


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    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


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    Antler Highlands

    • in which deep-water continental slope deposits

    • Reconstruction of the Cordilleran mobile belt during the Early Mississippian

    • were thrust eastward

    • over shallow-water continental shelf carbonates

    • forming the Antler Highlands


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    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


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    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


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    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


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    Beginning of the Ouachita Orogeny

    • During the Neoproterozoic to Early Mississippian,

      • shallow-water detrital and carbonate sediments

      • were deposited on a broad continental shelf,

      • while in the deeper-water portion of the adjoining mobile belt,

      • bedded cherts and shales were accumulating

    • Beginning in the Mississippian Period,

      • the rate of sedimentation increased dramatically

      • as the region changed from a passive continental margin to an active convergent plate boundary,

      • marking the beginning of the Ouachita orogeny


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    Ouachita Mobile Belt

    • Plate Tectonic model for the deformation of the Ouachita mobile belt

    • Depositional environment prior to the beginning of orogenic activity


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    Ouachita Mobile Belt

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


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    Ouachita Mobile Belt

    • Continental collision continued during the Pennsylvanian and Permian periods


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    Gondwana/Laurasia Collision

    • Thrusting of sediments continued

      • throughout the Pennsylvanian and Early Permian

      • as a result of the compressive forces generated

      • along the zone of subduction

      • as Gondwana collided with Laurasia

    • The collision of Gondwana and Laurasia

      • is marked by the formation of a large mountain range,

      • most of which was eroded during the Mesozoic Era

    • Only the rejuvenated Ouachita and Marathon Mountains remain of this once lofty mountain range


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    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


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    Complex Tectonic Activity

    • The tectonic activity that resulted in the uplift

      • in the Ouachita mobile belt was very complex

        • and involved not only the collision of Laurasia and Gondwana

        • but also several microplates and terranes between the continents

        • that eventually became part of Central America

    • The compressive forces impinging on the Ouachita mobile belt

      • also affected the craton

      • by causing broad uplift of the southwestern part of North America


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    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)


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    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


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    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


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    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


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    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


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    Folding and Thrusting

    • Jjust as with the Taconic orogeny,

      • deep-water sediments

      • were folded and thrust northwestward,

      • producing angular unconformities

      • separating Upper Silurian from Mississippian rocks


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    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


    Catskill delta clastic wedge l.jpg
    Catskill Delta Clastic Wedge

    • The Catskill Delta clastic wedge

    • and the Old Red Sand-stone

    • are bilaterally symmetrical

    • and derived their sediments

    • from the Acadian and Caledonian Highlands

    • Area of collision between Laurentia and Baltica


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    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


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    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


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    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


    Old red sandstone l.jpg
    Old Red Sandstone

    • is the counterpart to the Catskill Delta clastic wedge

    • The Old Red Sandstone


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    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


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    Closing of the Iapetus Ocean

    • The Taconic, Caledonian, and Acadian orogenies

      • were all part of the same orogenic event

      • related to the closing of the Iapetus Ocean

    • This event began

      • with paired oceanic-continental convergent plate boundaries

      • during the Taconic and Caledonian orogenies

    • and culminated

      • along a continental-continental plate boundary

      • during the Acadian orogeny

      • as Laurentia and Baltica became sutured


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    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


    Eastern laurasia collided with gondwana l.jpg
    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


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    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


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    The Role of Microplates and Terranes in the Formation of Pangaea

    • We have discussed the geologic history

      • of the mobile belts

      • bordering the Paleozoic continents

      • in terms of subduction along convergent plate boundaries

    • However, accretion along the continental margins

      • is more complicated than the somewhat simple,

      • large-scale plate interactions discussed here


    Terranes or microplates l.jpg
    Terranes or Microplates Pangaea

    • Geologists now recognize

      • that numerous terranes or microplates existed

      • during the Paleozoic

      • and were involved in the orogenic events

      • that occurred during the time

    • We have been concerned only

      • with the six major Paleozoic continents

    • However, microplates of varying size

      • were present during the Paleozoic

      • and participated in the formation of Pangaea


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    Avalonia Pangaea

    • For example, the microcontinent of Avalonia

      • is composed of

      • some coastal parts of New England,

      • southern New Brunswick,

      • much of Nova Scotia,

      • the Avalon Peninsula of eastern Newfoundland,

      • southeastern Ireland,

      • Wales,

      • England,

      • and parts of Belgium and Northern France


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    A Separate Continent Pangaea

    • The Avalon microcontinent

      • existed as a separate continent

      • during the Ordovician

      • and began to collide with Baltica

        • during the Late Ordovician-Early Silurian

      • and then with Laurentia

        • as part of Baltica

        • during the Silurian


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    Numerous Microplates Pangaea

    • Other terranes and microplates include

      • Iberia-Armorica (southern France, Sardinia, Iberian peninsula)

      • Perunica (Bohemia)

      • numerous Alpine fragments

    • Microplates usually developed their own unique faunal and floral assemblages


    The basic history remains the same l.jpg
    The Basic History PangaeaRemains the Same

    • Thus, while the basic history

      • of the formation of Pangaea during the Paleozoic remains the same,

      • geologists now realize that microplates and terranes also played an important role

    • Furthermore, the recognition of terranes

      • within mobile belts helps explain

      • some previously anomalous geologic situations


    Late paleozoic mineral resources l.jpg
    Late Paleozoic PangaeaMineral 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


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    Hydrocarbons Pangaea

    • 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


    Permian age coal beds l.jpg
    Permian-Age Coal Beds Pangaea

    • Although Permian-age coal beds

      • are known from several areas including Asia, Africa, and Australia,

      • much of the coal in North America and Europe comes from Pennsylvanian deposits

        • Late Carboniferous

    • Large areas in the Appalachian region and the Midwestern United States

      • are underlain by vast coal deposits

      • formed from the lush vegetation

      • that flourished in Pennsylvanian coal-forming swamps


    U s coal deposits l.jpg
    U.S. Coal Deposits Pangaea

    • Appalachian region are mostly Pennsyl-vanian

    • whereas those in the west are mostly Cretaceous and Cenozoic

    • The age of the coals in the midwestern states and the


    Bituminous coal l.jpg
    Bituminous Coal Pangaea

    • 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


    Anthracite l.jpg
    Anthracite Pangaea

    • 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


    Evaporite and gas l.jpg
    Evaporite and Gas Pangaea

    • 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


    More nonmetal resources l.jpg
    More Nonmetal Resources Pangaea

    • Other important evaporite mineral resources include

      • those of the Permian Delaware Basin of west Texas and New Mexico

      • and Devonian evaporites in the Elk Point basin of Canada

    • In Michigan, gypsum is mined and used in the construction of sheetrock

    • The majority of the silica sand

      • mined in the United States comes from east of the Mississippi River

      • and much of this comes from Late Paleozoic-age rocks


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    Silica Sand Pangaea

    • Silica sand from

      • the Devonian Ridgely Formation is mined in West Virginia, Maryland, and Pennsylvania

      • and the Devonian Sylvania Sandstone is mined near Toledo, Ohio

    • Recall that silica sand is used

      • in the manufacture of glass

      • for refractory bricks in blast furnaces

      • for molds for casting aluminum, iron, and copper alloys

      • and for a variety of other uses


    Limestones l.jpg
    Limestones Pangaea

    • 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


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    Metallic Minerals Pangaea

    • 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


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    Summary Pangaea

    • 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

      • along low-lying craton margins


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    Summary Pangaea

    • Laurasia and Gondwana underwent a series

      • of collisions beginning in the Carboniferous

    • During the Permian, the formation

      • of Pangaea was completed

    • Surrounding the supercontinent

      • was a global ocean, Panthalassa

    • The Late Paleozoic history of the North American craton

      • can be deciphered from the rocks

      • of the Kaskaskia and Absaroka sequences


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    Summary Pangaea

    • The basal beds of the Kaskaskia sequence

      • that were deposited on the exposed Tippecanoe surface

      • consisted of either sandstones,

        • derived from the eroding Taconic Highlands,

      • or carbonate rocks

    • Most of the Kaskaskia sequence

      • is dominated by carbonates and associated evaporites


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    Summary Pangaea

    • The Devonian Period was a time of major reef building

      • in western Canada, southern England, Belgium, Australia, and Russia

    • Widespread black shales

      • were deposited over large areas of the craton

      • during the Late Devonian and Early Mississippian

    • The Mississippian Period was dominated for the most part by carbonate deposition


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    Summary Pangaea

    • Transgressions and regressions

      • over the low-lying North American craton,

        • probably caused by advancing and retreating Gondwanan ice sheets,

      • resulted in cyclothems

      • and the formation of coals

      • during the Pennsylvania Period


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    Summary Pangaea

    • Cratonic mountain building

      • specifically the Ancestral Rockies

      • occurred during the Pennsylvanian Period,

      • and resulted in thick nonmarine detrital rocks

      • and evaporites being deposited in the intervening basins

    • By the Early Permian,

      • the Absaroka Sea occupied a narrow zone of the south-central craton

      • Here, several large reefs and associated evaporites developed


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    Summary Pangaea

    • By the end of the Permian Period, the Absaroka Sea had retreated from the craton

    • The Cordilleran mobile belt was the site of the Antler orogeny,

      • a minor Devonian orogeny

      • during which deep-water sediments were thrust eastward over shallow-water sediments

    • During the Pennsylvanian and Early Permian,

      • mountain building occurred in the Ouachita mobile belt


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    Summary Pangaea

    • Ouachita tectonic activity

      • was partly responsible for the cratonic uplift

      • taking place in the southwest

      • resulting in the Ancestral Rockies

    • The Caledonian, Acadian, Hercynian, and Alleghenian orogenies

      • were all part of the global tectonic activity

      • that resulted in the assembly of Pangaea


    Summary148 l.jpg
    Summary Pangaea

    • During the Paleozoic Era,

      • numerous terranes, such as Avalonia, existed

      • and played an important role in the formation of Pangaea

    • Late Paleozoic-age rocks contain a variety of mineral resources

      • including petroleum, coal, evaporites,

      • silica sand, lead, zinc,

      • and other metallic deposits


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