Chapter 13 - The Cenozoic Era
Chapter Outline
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I. Overview of Cenozoic
A. Subdivision Schemes (m.y. = million years)
1. Two Periods (American scheme)
a. Tertiary: 65 to 1.8 m.y.
b. Quaternary: 1.8 to 0 m.y.
2. Three Periods (European Scheme)
a. Paleogene: 65 to 24 m.y.
b. Neogene: 24 to 2 m.y.
c. Quaternary: 2 to 0 m.y.
3. Epoch Subdivisions of Tertiary
a. Paleocene 65 to 58 m.y.
b. Eocene: 58 to 37 m.y.
c. Oligocene: 37 to 24 m.y.
d. Miocene: 24 to 5 m.y.
e. Pliocene: 5 to 2 m.y.
f. Pleistocene 2 to .01 m.y.
g. Holocene .01 to 0 m.y.
B. Plate Tectonics
1. Vast sea floor expansion
a. 50% of sea floor produced in last 65 m.y.
b. Most new sea floor in Atlantic and Indian Oceans
2. Significant westward movement of N. and S. America
a. San Andreas fault system produced
b. Andean trench deformed
c. Cascade Panamanian Andean volcanic chain developed
d. extensive west coast orogensis
3. Significant rifting
a. North Atlantic: Greenland split from Scandinavia
b. South Pacific: Australia split from Antarctica
c. Indian Ocean: Arabia split from Africa (creating Gulf of Aden and Red
Sea)
4. Significant Collisional Events
a. Africa Eurasia: Alps built
b. India Eurasia: Himalayas built
5. Cenozoic Characteristics
a. continents stood high: Transgressions limited
b. sharply defined climatic zones
c. cooling trend culminated in Pleistocene Ice Ages
II. Pre Pleistocene Cenozoic History
A. Eastern United States
1. Structural changes
a. broad gentle uplifts
b. east tilting of Atlantic Coastal Plain and shelf
c. subsiding platforms in Florida-Bahamas area
d. Late Tertiary uplift of Florida
2. Sedimentation and erosion
a. Appalachian plains? beveled by erosion
b. valley and ridge topography sculpted
c. coastal plain alluvial sedimentation
d. reworking by marine transgressions
e. corraline carbonates (2500 m) in Florida area
B. Gulf Coast
1. best stratigraphic record in N. America
2. 8 major cycles of transgression/regression
3. Paleocene transgression as far north as Illinois
4. common cyclilc sequence: Deltaic above offshore deposits
5. comprise seaward-thickening wedge of clastics
6. carbonates absent in region
C. Rocky Mountains and High Plains
1. Structural changes
a. Late Cretaceous Early Tertiary accretionary events account for major
structural features of western Cordillera
b. Miocene uplift and erosion exposed present topography (Rocky
Mountains)
c. Miocene uplift resulted in re-deposition of Early Tertiary sediments of
intermontane basins
d. Late Tertiary normal faults elevated the Teton Range (6000 m
displacement): Teton fault scarp is 2500 m high
2. Volcanic activity
a. Tertiary volcanic ash common throughout western U.S.
b. Late Eocene Oligocene explosive volcanism blanketed Yellowstone
Park area and San Juan Mountains with volcanic ash
c. Late Tertiary volcanics associated with uplift of Teton Range
d. Miocene volcanics and vein deposits: Cripple Creek, Colorado
3. Sedimentation
a. Paleocene (Fort Union Formation, 1800 m thick): Clatics in
intermontane basins (silt, sand, shale, coal, lignite)
b. Eocene lake deposits in intermontane basins (Green River Fm. in basins
between Wind River and Owl Creek mountains): 600 m fresh water
limestone and shale; seasonal varves; 6.5 m.y. record; insect, plant, fish
fossils, oil shales
c. Eocene stream deposits (Wasatch Fm.): intermontane basin fills, red
colors; fine upward from conglomerates to siltstones
d. Eocene Oligocene flood plain deposits (White River Fm.): Clays, silts,
and ash with extensive mammal accumulations in flood deposits
e. Oligocene lacustrine deposits filled with volcanic ash (Florissant beds):
Spectacular preservation of insects, leaves, fish, birds, spores, pollen
f. Miocene fluvial and lacustrine sedimentation (intermontane basins) and
piedmont plains (east of Rocky Mountains): Grasslands with camels,
horses, rhinoceroses, deer, other grazing animals; Great Plains developed;
spectacular erosional features
g. Pliocene flood plain deposits: Reflect cooler, drier conditions
D. Basin and Range Province: Nevada-Utah to Mexico
1. Structural history
a. Mesozoic overthrusting
b. Early Tertiary regional arch
c. Miocene-Holocene arch subsidence and normal faulting: North south
trending fault block mountains (horsts and grabens) developed by tensional
forces
2. Causes of Structural development: Four hypotheses
a. Subduction Hypothesis: Pacific spreading center active below region as
it was subducted
b. Oblique Shearing Hypothesis: Tension due to west coast shearing
c. Older Plate Hypothesis: Buoyant mass below region pressed against
base of crust in region
d. Rifting Hypothesis: Mantle convection is pulling apart region as in a rift
3. Sedimentation
a. Miocene evaporites in lakes
b. Miocene Holocene coarse clastic shed off mountains
c. Miocene Holocene clastics fill grabens
E. Colorado Plateau: An Enigma
1. Region of non folded, flat lying Paleozoic and Mesozoic rocks
a. crustal butress with deformation all around it
b. plateau raised repeatedly in Early to Middle Pliocene (5 to 10 m.y. ago)
2. Structure and volcanics: Steep faults are avenues for lava
3. Uplift and Erosion: Grand Canyon cut down 2600 m into crystalline
Precambrian rocks
F. Columbia Plateau and Cascades
1. Region built by two styles of volcanic activity
a. relatively quiet fissure eruptions covering ½ million km with 2800 m of
lava
b. explosive, violent volcanic mountain chains issuing lava, pyroclastics,
and ash clouds (nuee ardents)
2. Columbia Plateau: Late Tertiary and Quaternary basaltic fissure eruptions;
layered basalt
3. Cascades
a. volcanism due to melting of downgoing Juan de Fuca Plate
b. volcanism began 4 m.y. ago (Pliocene)
c. recent eruptions: Mt. St. Helens, WA 1980
d. other recent eruptions: Mt Lassen 1914 to 15; Mt. Ranier 2000 yr. ago
e. caldera producing eruption: Mt. Mazama exploded to form Crater Lake
Oregon
G. Sierra Nevada, western California, Alaska
1. Sierra Nevada mountains
a. Jurassic: Formed by plutonism in Nevadan orogeny
b. Cretaceous and Tertiary: eroded deeply
c. Pliocene-Pleistocene: rang uplift 4000 m along huge normal faults on east
side; range tilted west depressing the California trough on the west side.
d. Pliocene- Pleistocene: rejuvenated streams and the valley glaciers cut
present topography(e.g. Yosemite Park).
2. California west of sierra nevada mountains
a. Paleocene-Miocene: affected by subduction tectonics, deformation
volcanism
b. Miocene: Conversion to strike-slip (transform) fault tectonics cease
subduction in area
c. Miocene- Pliocene: Regression due to uplift
d. Miocene-present: Creation of submarine basins due fault movements;
clastic; chert; diatomics
Quaternary: Final regression from most western California marine basin
3. Alaska and arctic islands of Canada
a. Aleutian chain volcanics
b. Aleutian back-arc basin: Clastics with coal; spores and pollen indicate
warmer temperatures than now
c. Alaska and Canada: Clastics , pyroclastics lavas
4. West coast Tectonics
a. East-dipping subduction: Mesozoic and early tertiary orogenesis
b. Orogenic effects: Batholiths, compressional structures volcanism,
metamorphism, ore emplacement
c. Farallon Plate: Extensively melted (including spreading ridge); northern
segment = Juan de Fuca Plate; southern segment = Cocos Plate
d. Pacific Plate: Moving northeast prior to west-coast contact; therefore
strike-slip fault motion was assumed(Miocene)
e. Baja California split from Mexico: Pliocene (5 m.y. ago); moving north
on pacific plate
H. South America
1. Andean orogenic belt
a. Cretaceous: Deformation metamorphism, granite plutonism
b. Cenozoic: (especially Miocene): Folding and volcanism
c. Miocene- Pliocene: Highlands eroded
d. Late Pliocene: Renewed uplift; present-day relief
e. Cenozoic tectonics due to continual subduction of South pacific Plate
under western S. America
f. Cenozoic clastics she off Andes: Amazon and Orinoco basins or
intermontane rifts
I. Tethyan realm (Europe)
1. Eocene Deformation
a. Africa moves north towards Asia deforming Asia and creating Pyrenees
and atlas mountains
b. North movement converts to scissor-like closure: Beginning formation
of Alps
c. Flych deposition in basins: Dark marine shales immature sands chert
2. Pliocene deformation
a. enormous recumbent folds form and rise to form mountains from Tethys
marine sediments
b. compression forces folds to north on to Eurasia
c. thrust faults cut folds on undersides
d. Molasse deposits: Piedmont clastic wedge shed on north side of rising
Alps
3. Miocene deformation an sedimentation
a. glacial -induce sea level drop of 50m
b. tectonic restriction of inlet at straits of Gibraltar
c. factors above isolated the proto-Mediterranean from global sea;
evaporation 5.5 m.y. ago turned basin into an evaporic basin and eventually
a desert( like Death Valley, CA today)
4. Pliocene- Quaternary deformation
a. jura folds formed: Older rocks transported over molasse; from northern
front of Alps today
5. Similar age deformation: Appenes, Caucasus Carpathian and Himalayas
J. Tethyan Realm (India)
1. Paleocene-Oligocene: Folding, thrusting, granitic plutonism as ocean closed
between India and Eurasia
2. Miocene: Intensive orogenic episode; elongate tracts of sea floor folded and
thrust south onto India; northern trough of India formed(5000m continental
clastics)
3. Pliocene-Quaternary: Great elevation of plateaus and folded ranges; retreat
of marginal seas; continued collision of India-Eurasia; Himalayan Mountains thus
built
K. Northern Europe (France, Scotland, Ireland, Spitsbergen, Greenland, Baffin
Island)
1. Early Cenozoic lavas: Giant’s Causeway of Ireland; same age as Greenland
Europe split
2. Paleocene Eocene Oligocene: Repeated cyclic transgressions and
regressions into Europe
a. Oligocene: Greatest transgression
b. Flooding from North Sea toward SE
c. Paris Basin: Thick section above Cretaceous chalks
3. Miocene Holocene: Uplift prevented further transgressions
L. Mongolia and China
1. Himalayan epeirogenic uplifts
2. Swamp, lake, meandering stream deposits
3. Significant mammal fossils preserved
M. Africa
1. Northern region near Tethys: little deformation, flat lying rocks
2. Southern region: Emergent in Cenozoic
3. Eastern region: Cenozoic uplift and rifting
a. 3000 m of uplift in a broad arch
b. fracturing and normal faulting on arch crest
c. east African rift valleys formed
d. volcanic development in rifts (Mt. Kenya and Mt. Kilimanjaro)
e. elongate lakes formed in rifts
N. Western Pacific
1. Australia
a. stable in Cenozoic
b. peripheral basin sedimentation
c. coal bearing clastics in interior
d. southeastern border tectonics: Paleocene and Eocene volcanism;
associated with Antarctica Australia split (50 - 60 m.y.a.)
2. New Zealand
a. great volumes of andesites and basalts extruded; volcanism continues
today
b. vertical fault movement of 18,000 m on east side of north island (Alpine
Fault)
3. Aleutians, Japan, Philippines, Indonesia: Folding and volcanism associated
with subduction; continues today
O. Antarctica
1. Climate record from stratigraphy
a. Paleocene Oligocene: Mild, semitropical
b. Miocene Quarternary: Frigid conditions developed; polar cap grew
2. Pacific (west) side tectonics
a. immature marine clastics and volcanics
b. eastward subduction of Pacific Plate
III. Pleistocene and Holocene History (Earth’s most recent 2 m.y.)
A. Overview of Epochs
1. Time of Ice Ages
a. 40 million km3 snow and ice covered 1/3 Earth’s surface
b. Glacial terrains created
c. Climatic zones shifted southward
d. Arctic conditions in Europe, N. America
e. Intensive rain in lower latitudes
f. Human evolution and migrations
2. Tectonics and Volcanics
a. Volcanics of NM, AZ, IK, Mexico, Iceland, Spitsbergen, Pacific rim
b. Subduction zones active (western N. and S. America)
c. Crustal uplifts: Tetons, Sierra Nevadas, central and northern Rockys
d. Orogenic mountain building: Alps, Himalayas, and connecting ranges
3. Climatic Characteristics
a. glacial and interglacial intervals
b. ocean cooling events independent from glaciation
B. Pleistocene Holocene Chronology
1. Original concept of Pleistocene base (Lyell, 1839)
a. Marine strata young enough to contain 90 - 100% of presently living
mollusks as fossils
b. Lyell’s concept applied to marine strata in Italy, not worldwide
c. Non-marine record not well defined as a result
2. Modern concept: Pleistocene base = 1.8 m.y.a
a. 1.8 m.y. widely accepted date of base
b. 1.8 m.y. does not coincide with onset of glaciation; glaciation no a
synchronous event; oldest extensive glaciation = 1.0 m.y.
c. marine sediments: base is extinction (last occurrence) of discoasters
d. Continental deposits: Base is first occurrence of modern horse fossils
(Equus), elephants, etc.
3. Modern Concept: Holocene base
a. Base defined as level (age) of melting of ice sheets to approximately
their present position and sea level rise to near present level
b. Base defined as above 8000 yr. ago
c. Some geologists define base a midpoint in glacial retreat and sea level
rise
d. Base defined as above 11,000 - 12,000 y.r.ago
4. Independence from "Ice Age" concept
a. Pre 1975 concept: Pleistocene consisted of 4 glacial intervals and 3
interglacial intervals; Holocene was final interglacial interval
b. Post 1975 concept: Glacial intervals are not synchronous and more
than 4 occurred, therefore epochs independent of such constraints
c. Reasoning for above: Discovery of 30 intervals of severe cold over last
3 m.y.
5. Variables affecting Earth’s Climates over Time
a. atmospheric changes: Greenhouse versus icehouse
b. geographic and tectonic changes
c. oceanographic changes
d. astronomic changes: sunspot cycles, Milankovitch cycles, etc.
C. Terrestrial Stratigraphy of Pleistocene
1. Sedimentary deposits by environment (facies)
a. glacial (till): Terminal moraine, ground moraine
b. fluvial (stratified drift): Braided and meandering streams
c. lacustrine
2. Erosion surfaces
a. bedrock scour by ice
b. meltwater stream incision
c. meltwater flood (scablands)
3. Correlation and relative age determination requires mutually sustaining
criteria
a. degree of stream dissection of moraine
b. depth of oxidation of sediment layer
c. degree of chemical weathering of layer
d. fossil pollen as climatic indicators
e. varved clays in lake deposits
f. C14 dating of wood, bone, shell, peat (note: ½ lift = 5570 yr.)
D. Marine Stratigraphy of Pleistocene: Correlation Methods in Continuous Core
1. Oxygen isotope rations in calcareous planktonic foraminifers: Indicator of
water volume stored as ice in glaciers
a. O18 is heavier and is not evaporated as readily as O16, thus snow and
ice are enriched in O16
b. O18 / O16 ratios from cores plotted versus depth in core show
variations in ice volume (thus sea level) over time; also shows climate
changes
2. Relative abundance of foraminifera sensitive to temperature changes
a. Globorotalia menardii: tropical species associated with warm waters
b. Globorotalia truncatulinoides: coils right in warm water; coils left in
cold water
c. Background sedimentation rates and ages in core determined by C14
dating of foraminiferal tests
3. Remnant magnetism
a. depositional remnant magnetism may be correlated with known
geomagnetic time scale
b. age check by allied C14 dating
c. magnetism may be disturbed by bioturbation
E. Effects of Pleistocene Glaciation
1. Sea level drop: 75 m below today’s level at maximum
a. continental shelves as dry lands (forests, grassland, plains) inhabited by
humans
b. land bridges: British Isles-Europe, Siberia - Alaska
c. interglacial intervals inundated shelves and bridges; forced animal
migrations
2. Glacial physical effects
a. ice caused erosion
b. weight of ice depressed crust 200-300 m below pre-glacial level;
interglacial crustal rebound (as today); elevation of glacial coastlines
c. obliteration of river systems by continental glaciers
d. establishment of new glacial and interglacial river drainage basins
e. changes in stream gradient and sediment load in glacial versus
interglacial times; sea level affected base levels worldwide
f. continental lakes (Great Lakes of N. America) scoured in lowlands by
continental ice sheets
g. development of huge ice-dammed lakes of temporary nature; huge lake
bed deposits exist today (Lake Agassiz of N.D. MN. and Canada)
h. pluvial lakes formed: Thousands of large and small lakes formed in low
latitudes by excess rainfall in glacial intervals (dry during interglacials);
example: Lake Bonneville, site of salt flats and Great Salt Lake, UT today
i. glacial impoundment lakes: Impoundment floods created channeled
scablands (draining of glacial lake Missoula) resulted in flood of 2000 km3
water and severe erosion
j. soil erosion: Soil stripped off craton of Canada and transported south
k. loess blanket deposition: Dense, cold air flowing off glaciers blew fine
material from tills and drift to lower latitude areas(loess blankets of
Missouri River Valley)
F. Causes of Pleistocene Climates
1. Any theory must account for reasons why-
a. climates grew cooler from Middle Cenozoic to Pleistocene (long term
trend)
b. glacial interglacial intervals alternate (short term trends)
c. temperature and precipitation conditions mitigate to form proper
combination
d. many factors may be involved
2. Milankovitch Theory of Solar Radiation
a. Earth’s astronomical motion accounts for changes in amount of solar
energy received thus spawning glacial intervals
b. Earth’s axial tilt: Varies 22 to 24 degrees over 41,000 yr. period
(changes seasonal length of day and amount of solar energy at high
latitude)
c. Earth’s axial precession: Axis of rotation movers in circle with period
of 26,000 yr.
d. Earth’s orbital eccentricity: Varies by 2% with a period of 100,000 yr.
(thus earth is closer to sun at times)
e. Support for theory: Radiometric and oxygen isotope studies show
strong correlation to Milankovitch calculations, especially to role of
eccentricity at 100,000 yr. intervals over last 600,000 yr.
f. Criticism of theory: Why not operative over all of geological time?
3. Other factors affecting Milankovitch Climatic Change
a. Albedo (reflectivity of Earth): Currently 33% solar energy reflected
during this interglacial and sea level high stand; during extreme low sea
levels more continent would be exposed and albedo higher (thus lower
global temperatures); 8 degree C drop per 1% change
b. Cloud Ash Dust Absorption of solar energy
c. Greenhouse gas content (especially CO2); decrease CO2 = cooling,
increase = warming but cloud cover and excess precipitation may trigger
ice buildup
d. Oceanic effects: Northward deflection of Gulf Stream type currents
(e.g. 3.5 m.y.a. when Isthmus of Panama formed) would send warmth and
moisture to northern regions
e. Continental positions: Continents must be at or near poles or snow will
fall in ocean and melt
4. Milankovitch predictions of future
a. 20,000 cooling trend going into next glacial
b. unknown factors: CO2 and other atmospheric changes by humans
G. Cenozoic Climatic Evidence
1. Worldwide cooling : Early Cenozoic to present
2. Late Paleocene and Eocene: Temporary warming indicated by plants and
animal fossils at high latitudes (palms, coral reefs, crocodiles); ice cap
begins in Antarctica
3. Oligocene: Resumed cooling trend (displaced reefs and forests to south)
4. Miocene: Brief warming, then cooler; glaciation in Antarctica
5. Pliocene: Mountain glaciers in Sierra Nevada (CA), Iceland, S. America
(Andes), Russia
IV. Mineral Resources of Cenozoic
A. hydrocarbons (oil and gas): Tertiary has most of all systems
1. Paleocene: North Sea and Libya?
2. Eocene: TX, LA, Iraq, Russia, Pakistan, Australia
3. Oligocene: Western Europe, Burma, CA, Gulf Coast U.S.
4. Miocene: All continents except Australia (especially Middle East, Gulf Coast
U.S. and CA)
B. Oil Shales: Eocene Green River Fm., western U.S.
C. Coal: Lignitic and subbituminous types (low sulfur)
1. Paleocene: ND, SD, WY, MT (largest fossil fuel deposits in U.S.)
2. Eocene: pacific coast U.S.
D. Metals
1. Placer gold (CA)
2. Manganese (Early Tertiary, Russia - 75% world’s supply)
3. Molybdenum (Climax, CO, 40% world’s supply)
4. Tertiary intrusives source for Cu, Zn Ag, Pb, Hg (western n. America,
Andes, Pacific orogenic belts)
E. non-metallic resources
1. Diatomite (silica): CA
2. Building stone and clay
3. Phosphates, sulfur, salt, gypsum
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