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COASTAL PLAIN

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COASTAL PLAIN CRETACEOUS TO RECENT Cretaceous History of North America The Cretaceous was a time of high sea level and vast epicontinental seas. – PowerPoint PPT presentation

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Title: COASTAL PLAIN


1
COASTAL PLAIN
  • CRETACEOUS TO RECENT

2
Cretaceous History of North America
  • The Cretaceous was a time of high sea level and
    vast epicontinental seas.
  • The most prominent feature in North America
    during the Cretaceous, was the shallow
    epicontinental sea that flooded much of the
    western interior of the continent, from the Gulf
    of Mexico to the Arctic Ocean, as well as the
    Atlantic and Gulf Coastal Plains.

3
CretaceousPaleogeography
4
Cretaceous Chalk
  • Chalk, a white, fine-grained variety of limestone
    composed of microscopic shells (called
    coccoliths) of golden-brown algae, was deposited
    in many places around the world during the
    Cretaceous.
  • The word Cretaceous is derived from the Latin
    word for chalk, creta.

5
Atlantic Coastal Plain
  • The Atlantic Coastal Plain began to subside (or
    sink) early in Cretaceous time.
  • Marine and deltaic sediments accumulated,
    gradually building a wedge of sediments that
    thickened seaward.
  • Most of the Cretaceous sediment in this area was
    deposited on the present-day continental shelf.

6
Atlantic Coastal Plain
7
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8
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9
Late Cretaceous Units
  • POTOMAC FORMATION - (early and late Cretaceous) -
    A moderately well sorted and cross-bedded, quartz
    sand with quartz and quartzite pebbles deposited
    in fluvial environments.
  • The Potomac Formation is the basal sequence of
    the Cretaceous system in southern and central New
    Jersey (it is not recognized beneath the lower
    Raritan Formation in the bay area).
  • The thickness is reported in the range of 250 to
    800 feet.

10
Late Cretaceous Units
  • RARITAN FORMATION - (Cenomanian, Cretaceous) - In
    the Raritan Bay region the Raritan Formation
    unconformably overlies Newark Basin and older
    rocks, representing the beginning of a series of
    major transgressions and regressions of the seas
    during Cretaceous time.
  • The Raritan consists of clay, sand, lignite, and
    gravels representing progradational alluvial
    plain, coastal and neashore marine environments.
  • Very well exposed in unglaciated regions around
    the western end of Raritan Bay.
  • Subdivided units include the Raritan Fire Clay,
    Farrington Sand Member, Woodbridge Clay Member,
    Sayreville Sand Member, and South Amboy Fire Clay
    Member (oldest to youngest, respectively).
  • The Sayerville Sand Member is famous for its
    amber-bearing lignite lenses, insect remains,
    fossil wood and leaves, and pyrite nodules.
  • The Sayreville fossil beds have yielded an
    astonishing amount of information about life in
    the Late Cretaceous.

11
Sayreville/Kennedy Park
12
Amber in the Raritan Formation
The Sayreville Clay Member of the Raritan
Formation yields amber form scattered lignite
horizons. The amber is not of consistently high
quality like other amber-bearing regions of the
world. However, it is one of the older
amber-bearing deposits, and the amber frequently
contains insects (mostly gnat-like insects).
13
Late Cretaceous Units
  • MAGOTHY FORMATION - (Coniacian and Santonian,
    Cretaceous) - Unconformably overlies the Raritan
    Formation.
  • The Magothy Formation is beneath Quaternary
    glacial cover throughout most of Long Island, the
    south shore of Staten Island, and is fairly well
    exposed in small outcrops and excavations around
    Raritan Bay.
  • The Magothy is subdivided into units the
    Oldbridge Sand Member, the Amboy Stoneware Clay
    Member, and Cliffwood Beach Member (oldest to
    youngest, respectively).
  • The Magothy represents nearshore and alluvial
    depositional environments, similar to the Raritan
    Formation.
  • The thickness ranges between 10 and 200 feet.

14
Late Cretaceous Units
  • MERCHANTVILLE FORMATION - (late Santonian to
    early Campanian, Cretaceous) - Conformably
    overlies the Magothy Formation and consists of
    mixed sand and clay units representing nearshore
    and shallow marine depositional environments.
  • It is poorly exposed around the southern side of
    Raritan Bay.
  • It interfingers with the overlying Woodbury Clay.
  • The thickness of the unit measures between 20 and
    100 feet.

15
Late Cretaceous Units
  • WOODBURY SHALE - (early Campanian, Cretaceous) -
    Dark gray clay mud of the Woodbury Clay is
    exposed in excavations and along the shore of
    Raritan Bay near Cheesequake State Park, NJ.
  • The gray carbonaceous shale contains pyrite and
    bioturbation features of a marine or lagoonal
    environment.

16
Late Cretaceous Units
  • ENGLISHTOWN FORMATION - (early Campanian,
    Cretaceous) - The Englishtown consists of clay,
    slit and sand which locally displays lamination,
    thin- to thick- bedding, and cross
    stratification.
  • Fossils are generally scarce. Locally the unit
    contains lignite beach-type sand deposits.
  • The upper-most bed display bioturbation with
    burrows locally filled with glauconitic quartz
    sand from the unconformable overlying
    Marshalltown Formation.
  • The formation ranges from 20 to 150 feet in
    thickness.

17
Late Cretaceous Units
  • MARSHALLTOWN FORMATION - (middle Campanian,
    Cretaceous) - The Marshalltown consists of
    greenish-gray massive quartz-rich, glauconitic
    sand, silt and dark, micaceous clay.
  • Pyrite and siderite concretions, some displaying
    evidence of boring and reworking, are abundant at
    the base of the unit.
  • Other than traces of lignite and bioturbation,
    fossils are scarce in the unit.
  • The thickness of the formation is between 15 to
    20 feet.

18
Late Cretaceous Units
  • WENONAH FORMATION - (late Campanian, Cretaceous)
    - The Wenonah consists of micaceous quartz and
    silt and is rich in organic material (mostly
    silt-sized lignite fragments) and pyrite (in very
    fresh exposures).
  • The unit ranges in thickness from 35 to 55 feet
    along Raritan Bay, inland the upper part of the
    unit is exposed intermittently along creek banks.
  • Phosphatic nodules, siderite concretions filling
    bioturbation structures, and thin sand beds are
    common near the top of the unit.
  • Sharks teeth and fossil shell molds are common
    along with bone fragments and teeth of fish,
    reptiles, and swimming dinosaurs near the top of
    the unit.
  • Sedimentation patterns reflect storm-dominated
    depositional patterns on a shallow shelf
    environment.
  • The thickness of the formation measures in the
    range of 70 to 100 feet.

19
Fossils of the Wenonah Formation
A - D. sharks teeth (an excellent guide to
identifying sharks teeth is Bretton W. Kent,
(1994), Fossil Sharks of the Chesapeake Bay
Region. Columbia, MD Egan Rees Boyer, Inc.,
146 p.) E. sawfish teeth F. large fish scales
G. vertebrae, probably shark H. molds of
pelecypods (Cardium wenonah) and gastropods
(Lunatia halli I. Coral. (An exceptional
publication of fossil descriptions with plates
is Horace G. Richards, etal., The Cretaceous
Fossils of New Jersey, Part 1 (1958) and Part 2
(1962) Trenton, NJ Department of Conservation
and Economic Development.)
20
Late Cretaceous Units
  • MT. LAUREL FORMATION - (latest Campanian,
    Cretaceous) - The Mt. Laural is very similar in
    appearance and composition to the underlying
    Wenonah with the exception that it contains
    abundant micaceous, glauconitic sand which is
    locally cross-bedded.
  • The unit contains an abundance of phosphatic
    peletal material and bioturbation features
    siderite concretions commonly fill burrows.
  • The unit is about 25 feet thick near Sandy Hook
    but pinches out landward over a distance of
    several miles beneath an unconformity beneath the
    overlying Navesink Formation.
  • The boundary between the underlying Wenonah is
    undifferentiated in most areas east of the
    coastal area. Common Mt. Laurel and Wenonah
    fossils include sharks teeth and bone, shell
    molds, etc.

21
Late Cretaceous Units
  • NAVESINK FORMATION - (early Maastrichtian,
    Cretaceous) - The Navesink consists of peloidal
    glauconitic marl and sand that is locally thick
    bedded or crossbedded, and is locally clay-rich.
  • Fossils are very abundant in some areas.
  • Carbonaceous matter and phosphatic material,
    especially at the base. Mollusk fossils are
    abundant in the lower and middle portions of the
    unit.
  • Common Navesink fossils include Belemnitella
    americana, Expgyra costata, Expgyra cancellata,
    Pyncnodont sp., Ostrea falcata, Ostrea
    mesenterica, Choristothyris plicata, and many
    others. (An small collection of Navesink fossils
    is on diplay at the visitor's center at Poricy
    Park, Monmouth County, NJ).
  • The fossils occur in concentrated horizons within
    the unit. The fauna suggest a marine shelf
    environment.
  • It ranges in thickness between 65 to 45 feet
    throughout the Atlantic Highlands region.

22
Fossils of the Navesink Formation
Mollusks A-BExogyra cancellata, C Pyncnodont
mutabilis, D Belemnitella americana, E
Spondylus gregalis, F Ostrea mesenterica, G
Ostrea falcata Braciopod H. Choristothyris
pilcata
23
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24
Late Cretaceous Units
  • REDBANK FORMATION - (Maastrichtian, Cretaceous) -
    The Redbank Formation consists of gray to red
    sand deposited in nearshore environments.
  • Subaerial exposure at the end of "Redbank time"
    resulted in the leaching of shell material and
    the alteration of glauconite to limonite (hence
    the red color).
  • A lower brownish- black micaceous sand unit is
    called the Sandy Hook Member and displays
    abundant concretions in bioturbated horizons and
    has been described as locally fossiliferous.
  • The upper Shrewsbury Member is yellow to
    orange-gray sand. The unit is a approximately 120
    feet thick near Sandy Hook along the valley of
    the Navesink and Shrewsbury rivers, but grows
    progressively thinner until it eventually pinches
    out landward.

25
Late Cretaceous Units
  • TILTON FORMATION - (late Maastrichtian,
    Cretaceous) - The Tilton is a massive "olive to
    evergreen" green glauconitic quartz sand which is
    locally clay-rich and silty.
  • The unit displays an abundance of iron-staining
    and locally bears limonite and hematite crusts
    and concretions.
  • Locally glauconite constitutes as much as 80 (or
    more) of the sand, making portions of the
    formation an economic greensand in the central
    Coastal Plain.
  • Fossils, mostly poorly preserved molds and casts
    of pelecypods, Camptonectes, are common, whereas
    a richer marine fauna occurs further southward in
    central New Jersey.
  • The unit displays heavy bioturbation. The
    formation is in the range of 20 to 25 feet thick.

26
The Cenozoic Era
  • 65.5 million years ago to the present
  • Name "Cenozoic" "new life" or "recent life"

27
Periods of the Cenozoic Era
  • The Cenozoic Era consists of two periods
  • Older Paleogene Period
  • Younger Neogene Period
  • The Paris Basin is the type area for most of the
    epochs of the Cenozoic. There is a major
    unconformity in the basin that was chosen as the
    boundary between the Paleogene and the Neogene.

28
Periods of the Cenozoic Era
  • Until 2003, the two periods in the Cenozoic Era
    were the Tertiary and Quaternary Periods. You
    will see these terms on older maps and in older
    publications.
  • In 2003, the International Commission on
    Stratigraphy revised the nomenclature, dropping
    the terms Tertiary and Quaternary. The two
    periods of the Cenozoic Era are officially
    recognized as the Paleogene and the Neogene.

29
Cenozoic Time Chart
30
Paleogeography and Plate Tectonics
  • During the Cenozoic, the Atlantic and Indian
    Oceans widened, and the continents moved to their
    current positions.
  • Half of the present ocean crust has formed at the
    mid-ocean ridges since the beginning of the
    Cenozoic.

31
Tectonic and Paleographic Changes and Their
Effects on Climate
  • The Panama land bridge blocked the westward flow
    of the North Atlantic Current. The current was
    deflected to the north (turning to the right, as
    a result of the Coriolis Effect), and formed the
    Gulf Stream.
  • The Gulf Stream transported warm water northward
    and resulted in bringing warmer climates to
    northwestern Europe.
  • Gulf Stream also supplied warm, moist air toward
    the North Pole, which would ultimately result in
    precipitation which helped build the glacial ice
    sheets.

32
Important continental breakups
  • North Atlantic rift separated Greenland from
    Scandinavia
  • Australia separated from Antarctica. Circumpolar
    currents isolated Antarctica from warmer waters.
    Led to cooling of Antarctica.
  • Cold, dense ocean waters around Antarctica
    drifted northward along ocean floor, contributing
    to global cooling and the Ice Age.
  • Rifting occurred between Africa and Arabia,
    forming the Red Sea and the Gulf of Aden.

33
North America During the Paleogene
  • The Paleogene is dominated by
  • The deposition of marine sediments in eastern and
    southeastern North America

34
Paleogene Period
35
Eastern and Southeastern North America
  • Ridges and valleys of the Appalachian Mountains
    were carved by erosion.
  • As erosion proceeded, gentle isostatic uplift
    occurred. This stimulated more erosion, as
    streams cut downward.

36
Eastern and Southeastern North America
  • Uplift in the eroding Appalachians was coupled
    with downward tilting and deposition of sediments
    on the Atlantic Coastal Plain and continental
    shelf.
  • Sediments thicken seaward forming a clastic
    wedge.

37
Eastern and Southeastern North America
  • Eight marine transgressions and regressions are
    recorded in Cenozoic sediments on the Atlantic
    and Gulf Coastal Plains.
  • Carbonate sediments accumulated in Florida where
    less terrigenous clastic sediment was available.

38
Tertiary Units
  • HORNERSTOWN FORMATION - (Danian, early Paleocene)
    - A drastic change in fauna is represent at the
    base of the Hornerstown in New Jersey.
  • This is a reflection of both a mass extinction
    even as well as a hiatus in deposition.
  • The formation is lithologically similar to the
    Tilton consisting of a green glauconitic quartz
    sand.
  • Cretaceous fossils have been noted reworked
    upward into the basal units.
  • Fossil in the Hornerstown include gastropods,
    pelecypods, and other vertebrate bone material.
    The unit displays heavy bioturbation.

39
Tertiary Units
  • VINCETOWN FORMATION - (Paleocene to Eocene) - The
    Vincetown consists of quartz sand with phosphatic
    pellets and glauconite ranging form nearly trace
    to nearly 100 in some beds (glauconite being
    most abundant at the base of the unit where it
    appears gradational with the underlying
    Hornerstown).
  • Near the shore fossils are absent, however, the
    unit displays bioturbation structures.
  • Elsewhere on the Coastal Plain it is extremely
    fossiliferous containing abundant foraminifera,
    bryozoa, and a prominent basal shell bed
    containing Oleneothyris harlani, Gryphaea
    dissimilaris, and bone fragments. Thickness is in
    the range of 50 to 100 feet.

40
Tertiary Units
  • MANASQUAN FORMATION - (Eocene) - This unit is
    missing in the Atlantic Highlands region,
    however, it crops out along creek bottoms
    southward along the Jersey Shore.
  • It consists of a mixed shaley and sandy marl with
    abundant apatite pellets and siderite
    concretions, with fossils rare or absent.
  • Thickness (including Shark River) in the range of
    50 to 200 feet.

41
Tertiary Units
  • SHARK RIVER FORMATION - (Eocene) - This unit is
    also missing beneath the Cohansey Sand in the
    Atlantic Highlands region, however, it crops out
    along the creek banks of the Shark River (as the
    name applies) and contains sharks teeth.
  • The unit consist of a sandy, carbonaceous
    glauconitic marl and quartz sand.
  • It lies conformably on the Manasquan below. Some
    researchers do not differentiate Shark River from
    the underlying Manasquan Formation.

42
Tertiary Units
  • KIRKWOOD FORMATION - (middle Miocene) - The
    Kirkwood Formation is missing from the Atlantic
    Highlands section beneath the Cohansey Sand.
  • Further south the formation consists of a clayey
    to silty mudrock, massive sand, and thin pebble
    lenses deposited in a sublittoral to nearshore
    environments.
  • The unit is equivalent to the Calvert, Choptank,
    and St. Marys River formations in Maryland and
    Virginia.
  • The sparse occurrence of Calvert cliffs fauna in
    beach pebbles suggest that the Kirkwood-equivalent
    strata on the continental shelf is
    fossiliferous. (This unit has been suggested as
    time equivalent to the formation of the late
    Tertiary Schooley Peneplane throughout the
    mountainous Appalachian region.)
  • The bottom of the Kirkwood sits unconformably in
    top of older Tertiary units. The thickness is in
    the range of 100 to 300 feet in the Pine Barrens
    region.

43
Tertiary Units
  • COHANSEY SAND - (late Miocene to early Pliocene)
    - The formation consists of medium to
    coarse-grained arkosic quartz sand (well
    stratified and cross-bedded), with thin clay
    lenses and quartz and quartzite pebble
    conglomerate.
  • The unit represents a range of sedimentary
    environments ranging from fluvial to transitional
    marine environments (swamps, deltas, lagoons,
    beach sand, and shallow open marine shelf).
  • Sediments at the base of the Cohansey appear to
    fill broad fluvial channels carved downward into
    the underlying formations (down to the Tilton in
    the Atlantic Highlands region).

44
Tertiary Units
  • COHANSEY SAND
  • Many beds within the unit are heavily cemented by
    iron these ironstone sand and gravel depositons
    form a resistant hilltop caprock in the Highlands
    region.
  • The Cohansey represents most of the surface
    deposits throughout the New Jersey Coastal Plain
    and is well exposed on hills and roadcut and sand
    pits throughout the Pine Barrens region.
  • All fossil material appears to be leached out of
    the Cohansey (possibly by processes similar to
    the acid waters and bog-iron formation currently
    active in the Pine Barrens region.
  • The unit ranges in thickness from a several
    meters on hilltops to more than 150 feet on the
    western side of the coastal plain.

45
Tertiary Units
  • BEACON HILL FORMATION - (Pliocene?) - An
    iron-stained sandy quartz and quartzite-rich
    gravel deposit on top of the highest hill in
    Monmouth County, NJ (373 feet) probably
    represents a Pliocene fluvial gravel equivalent
    to late deposition the Cohansey Formation.
  • The Beacon Hill caps Apple Pie Hill and other
    small hills in the Pine Barrens region.

46
Quaternary and Holocene Deposits
  • BRIDGETOWN FORMATION - (early Pleistocene?) - The
    precise age of the Bridgetown Formation is
    unclear, however, it consists of a deeply
    weathered mix of silt, sand, and gravel and
    represents fluvial environments.
  • The Bridgetown probably represents sedimentation
    during an earlier, pre-Wisconsin interglacial
    stage. (Isphording Lodding, (1969) state that
    the Bridgetown and Pensauken formations are
    virtually indistinguishable along the coastal
    areas. Both units lack fossils.)

47
Quaternary and Holocene Deposits
  • PENSAUKEN FORMATION - (Late Pleistocene) -
    Wisconsin till unconformably overlies this unit
    that crops out along a trend from Staten Island
    to Trenton, NJ and southward along the Delaware
    River valley.
  • The unit consist of mixed detritus (eroded from
    older glacial material and exposed Coastal Plain
    formations) that was deposited in fluvial flood
    plain environments.
  • The existence of the Pensauken formation suggest
    that, for a time, the major drainage from the
    pre-Wisconsin glaciers was southward from the New
    York area toward Trenton into the Delaware River
    drainage.
  • Pedogenic weathering of the sediments suggest
    that it was deposited during a warm interglacial
    period.

48
Quaternary and Holocene Deposits
  • CAPE MAY FORMATION - (Late Pleistocene to
    Holocene) - The Cape May formation consists of
    surficial silts, sands and quartz-rich gravels
    along the coastal region of New Jersey and
    represents coastal beach and barrier sand
    deposits and back bay estuarine deposits.
  • The source of the sand is mostly from the
    Delaware River drainage supplemented by shelf
    sands and longshore drift sand from the
    Mid-Atlantic region.
  • The progessive reworking of Cape May deposits is
    the source of much sand on the New Jersey coast.

49
Quaternary and Holocene Deposits
  • COLUMBIANA GROUP (early to late Quaternary)
    consists of three named units - the Pensauken,
    Bridgetown, and Cape May formations (oldest to
    youngest, respectively) - each represents
    different depositional environments throughout
    the region.
  • The Gardeners Clay is probably a marine
    equivalent to the Pensauken Formation. Active
    research in the region will no doubt refine the
    correlation problems between Pleistocene and
    Holocene sedimentary deposits as investigations
    proceed on glacial deposits, and lacustrine,
    swamp, terrestrial, fluvial, estuary, nearshore
    and marine shelf deposits in the Bight region.

50
Quaternary and Holocene Deposits
  • GARDENERS CLAY - This poorly consolidated clay
    underlies Wisconsin Age glacial deposits
    throughout southern Long Island and has been
    interpreted as occurring beneath the modern
    barrier spit of Sandy Hook.
  • The Gardeners Clay contains a rich estuarine
    fauna with abundant foraminifera. The unit
    probably represents high-standing seas between
    advances of the latest Pleistocene (Wisconsin)
    glacier.

51
Quaternary and Holocene Deposits
  • WISCONSIN GLACIAL TILL - Wisconsin glacial
    deposits are apparent everywhere throughout Long
    Island, across northern Staten Island and in
    northern New Jersey.
  • Glacial till consists of unstratified mix of
    clay, silt and sand with a mix of rock material
    ranging from pebbles to giant boulders (derived
    from all rock source areas ranging from Manhattan
    to Central Quebec).
  • The terminal moraine extends across central New
    Jersey along a sinuous line from the vicinity of
    Perth Amboy to around the Delaware Water Gap on
    the western side of the state.
  • Outwash sand and gravel deposits (altered by
    soil-forming processes) cover much of southern
    Long Island, southern Staten Island and areas
    south of the terminal moraine in New Jersey.
  • Varved lake clays and swamp peat cover areas
    flooded by lakes.

52
Quaternary and Holocene Deposits
  • HOLOCENE DEPOSITS - The modern beach and barrier
    islands around the New York Bight represent
    reworked sand material that began accumulating
    during a slow-down in sea level rise that began
    about 3-4,000 years ago.
  • These modern coastal deposits overly older
    Holocene estuarine and fluvial sediments
    deposited behind barriers that developed during a
    period ranging from 12,000 to about 7,000 years
    ago. (These old barrier deposits are partially
    eroded and/or buried by younger sediments.
  • These barriers existed anywhere from 2 to 20
    kilometers seaward of the current shoreline when
    sea level was approximately 20 to 40 meters
    lower.
  • On the continental shelf these ancient barriers
    are currently supplying sediment to offshore sand
    ridges.
  • Sand along the Hudson River and on Staten Island
    displays an abundance of angular feldspar and
    lithic fragments indicative of fluvial
    sedimentation in the harbor region when sea level
    was lower.
  • Modern anthropogenic sediments and human activity
    has modified nearly all coastal and nearshore
    marine sedimentary environments.

53
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54
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55
Cenozoic Paleoclimates
56
Global Surface Cooling
  • There was a 10o C (18o F) temperature drop at end
    of Cretaceous Period.
  • Several warming trends occurred in the late
    Paleocene and Eocene, as indicated by
  • Fossils of palm trees and crocodiles in
    Minnesota, Germany, and near London.
  • Fossils of trees from temperate zones in Alaska,
    Norway and Greenland.
  • Coral reefs in latitudes 10-20o closer to the
    poles than at present.

57
Antarctica in the Paleogene
  • The climate was semitropical and mild in
    Antarctica during the Paleogene, as indicated by
    fossil spores and pollen, despite the fact that
    it sat on the South Pole.
  • Before Antarctica separated from Australia, it
    was warmed by currents moving southward from more
    equatorial latitudes.

58
  • Australia began to separate from Antarctica in
    the early Eocene, about 55 m.y. ago.
  • After separation, circumpolar currents developed
    around Antarctica, cutting it off from equatorial
    currents.
  • This resulted in temperature decrease and glacial
    conditions over Antarctica.

59
Global Surface Cooling
  • Temperatures dropped by about 8-13o C (roughly
    22o F) near the Eocene-Oligocene boundary, as
    indicated by isotope data from brachiopods from
    New Zealand.
  • Antarctic sea ice began to form by 38 m.y. ago.
  • Greenhouse conditions were replaced by icehouse
    conditions.

60
Worldwide cooling resulted in
  • First Cenozoic widespread growth of glaciers in
    Antarctica about 38-22 m.y. ago.
  • Global sea level dropped by about 50 m in the
    Early Oligocene, as glaciers formed.
  • Cold, dense polar water flowed northward across
    ocean bottom.
  • Upwelling of cold bottom waters affected world
    climate.

61
  • Decrease in diversity and extinctions of many
  • marine molluscs
  • planktonic and benthonic foraminifera
  • ostracodes
  • Extinctions were earlier and more severe at
    higher latitudes.
  • Reefs shifted toward the equator.
  • Calcarous biogenic deep sea sediments
    (foraminiferal ooze) shifted toward the equator
    and were replaced by siliceous biogenic sediments
    (diatom and/or radiolarian ooze) at higher
    latitudes.

62
  • Changes in pollen indicate long term cooling and
    drying.
  • Temperate and tropical forests shifted toward the
    equator.
  • Grasslands expanded.
  • Rainforests became confined to tropical,
    equatorial areas.
  • Glaciation occurred in other areas in Pliocene
    (and younger) deposits - Sierra Nevada, Iceland,
    South America, and Russia.

63
Antarctic Bottom Waters
  • The cold waters around Antarctica were dense, and
    sank to the ocean floor around Antarctica. (Cold
    water is denser than warmer water.)
  • Cold, dense ocean-floor waters moved downward and
    outward, away from Antarctica.
  • The northward movement of cold dense waters
    contributed to cool conditions during the late
    Eocene and early Oligocene, and ultimately led to
    the Pleistocene Ice Age.

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The Pleistocene
  • The Pleistocene began 1.8 m.y. ago.
  • The most extensive glaciations began about 1
    m.y. ago.
  • The end of the Pleistocene is when the ice sheets
    melted to approximately their current extent.
  • The Pleistocene-Holocene boundary is placed
    between about 12,000 and 11,000 years ago, at the
    midpoint of the warming of the oceans.
  • This coincides with a rise in sea level.

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The Pleistocene Ice Age
  • The Pleistocene is significant as the time in
    which humans evolved.
  • More than 40 million km3 of snow and ice covered
    about 1/3 of Earth's land area.
  • Continental glaciers covered much of North
    America and Europe.
  • Alpine glaciers covered parts of the Cordilleran
    Mountain range in western North America, the
    Alps, and other mountain ranges of Europe.

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  • Pleistocene continental glaciers in the Northern
    Hemisphere

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As a result of the Ice Age
  • Climatic zones in the Northern Hemisphere were
    shifted southward.
  • Arctic conditions prevailed across Europe and the
    U.S.
  • Sea level dropped as much as 75 m (225 ft) and
    the shoreline shifted seaward, exposing the
    continental shelves as dry land.
  • Streams cut deep canyons into the continental
    shelves and on land.

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  • Land bridges existed and led to migrations of
    mammals, including humans
  • Across the Bering Sea between Siberia and Alaska
  • Between Australia and Indonesia
  • British Isles were attached to Europe
  • The land was sculpted by glaciers in Europe and
    North America.
  • U-shaped valleys formed in mountainous areas

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  • Rainfall increased at lower latitudes.
  • Large lakes formed in the Basin and Range
    Province.
  • Lake Bonneville in Utah covered more than 50,000
    km2 and was about 1000 ft deep in places.
  • The Great Salt Lake is a small remnant of
    Pleistocene Lake Bonneville.
  • The Bonneville salt flats were formed as the lake
    evaporated.

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  • Winds coming off glaciers blew sediment southward
    forming löess deposits (Missouri River area,
    central Europe, northern China)
  • Parts of northern and eastern Africa that are
    currently arid had abundant water and were
    fertile and populated by nomadic tribes.
  • Nomadic tribes hunted along the edges of the
    continental glaciers. Wild game was abundant,
    furs provided warm clothing, and there were less
    problems with spoiled meat in the cold
    temperatures.

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  • Formation of the Great Lakes (depressions scoured
    by glaciers and flanked by moraines)
  • Formation of Cape Cod, MA - a moraine
  • Formation of Long Island, NY - a terminal moraine
  • Formation of Niagara Falls
  • Formation of large ice-dammed lakes, including
    Lake Missoula which drained catastrophically,
    forming the channeled scablands
  • Formation of hummocky topography and Pleistocene
    sand dunes

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  • Weight of the ice depressed the continental crust
    to as much as 200-300 m downward.
  • Uplift (isostatic rebound) after ice melted.
    Coastal features are now elevated high above sea
    level.

Map illustrating post-glacial uplift in North
America.
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  • Names of the "traditional" glacial and
    interglacial stages in North America
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