Transcript The Cenozoic: The Tertiary

The Cenozoic: The Tertiary
Tertiary or Paleogene & Neogene
Tertiary: G. Arduino (1760)
Paleogene: K.F. Naumann (1866)
Neogene: R. Hornes (1835)
The Epochs of the Cenozoic
• Proposed by Charles Lyell in 1833
• Based on the work by Cuvier and Brongniart;
description of fossils from the Paris Basin
• Fossil description based on relative ratios of
living vs. extinct species
• Originally 4 epochs, Eocene, Miocene, Pliocene
and Pleistocene and Recent (Holocene)
• Later the Oligocene was recognized between
the Eocene and Miocene and Paleocene before
Eocene
Eocene Paleogeography
(50+/-5 my)
The Earth Today
Red Sea Rift
Formed 30 my
Oligocene
Cenozoic Regional Events: East
Coast
• Appalachians reduced to a peneplain
(Schooley Peneplain) by Paleocene
• Only monadnocks [low domal
structures](Stone Mountain) remain
• Several episodes of uplift and renewed
erosion of Appalachians (Miocene)
• Thick sequence of Carbonate deposition in
Florida-Bahamas platform
Florida-Bahamas Carbonate Bank
Cenozoic Regional Events
• Gulf Coast: Continued clastic
deposition (marginal marine and fluvial)
up to 40,000 ft vs. 20,000 in the Atlantic
coastal plain
Gulf Coast Accumulation of Tertiary Sediments
Cenozoic Regional Events:
Western North America
• Paleogene: Laramide Orogeny: volcanic
belts and fold and thrust belts to the east
(deformed most strata of the Cretaceous
seaway)
• Central W. US Colorado Plateau is quiet
• East of CO Plateau, basement uplifts
continue to form Rocky Mts.
Cenozoic Regional Events:
Western North America
• Neogene: Miocene Subduction creates
Cascade Range
• Faulting and mountain building in California
• Development of San Andreas Fault
• Initiation of Basin and Range topography>
Extentional, pull-aparts
• Columbia Plateau forms -massive fissure
eruptions of basaltic lava 500,000km2; 2800m
thick
• Uplift of Colorado Plateau (Grand Canyon),
Rocky Mts. and Sierra Nevada
Cenozoic Basins of the
Western Us
Eocene erosional detritus
and stream discharge filled
basins and formed extensive
shallow water lakes
One notable lake was the
Green River Fm. A series
of lacustrine deposits 600 m
of freshwater limestones and
shales (varves) 6.5 my of
deposition was 0.1mm/yr or
9.2cm/1000 yrs
Very well presrved fish,
insects and plants
Oil shales> petroleum reserve
Interaction of Pacific, Farallon and North American Plates >
Transform Boundary
Grand Tetons: Normal Fault uplift with displacement
of over 6000m
Extentional Tectonics
Pull-aparts
Columbia Plateau: Eruption of basaltic lava buried
500,000km2 under
2800m
Cenozoic Life
• Diversity of Scleractinian Coral Reefs
• Molluscs
– Multi-tiered suspension & deposit feeders
• Diversity of Planktic Organisms
– Forams as Index Fossils
• Fish
• Birds
DIATOMS
FORAMINIFERS
GREEN RIVER FORMATION
Teleost Fishes- Ray-Fin Fishes
20,000 species
Teleost
Oligocene Tuffs near Florissant Colorado
Late Eocene-Early Oligocene volcanic activity in the area around
Yellowstone National Park >> White River Fm., famous for mammals
in flood deposits with ash beds seen in the Badlands National Park of
South Dakota
Diatryma stood 2m
Most primitive birds are large
flightless ones
In the Cenozoic South American
Predatory birds were important
Birds: 27 orders of modern birds
Land and Water Birds
Cenozoic Life
• Advent of Mammals
– Archaic Mammals> Paleogene
– Modern Mammals> Neogene
• Diversity of Mammals
– Marsupial > earliest > pouched
– Placental > Advanced > direct birth
• Carnivores
• Ungulates > Hoofed Herbivores, Most abundant and
diversified (primitive)
– Perissodactyles (odd-toed)> horse, rhino
– Artiodactyles (even-toed, cloven hoofed)> cattle, pigs,
sheep, goats, deer, antelope
Marsupial vs Placental Mammals
Evolution of the Horse
Hyracotherium ancestral horse, ancestor of all perissodactyls, small
4, 3 toed animal to Equus, large complex enamel molars, one toe
The Pleistocene
• Pleistocene, the time period that spanned from 1.8
million to ~10,000 years ago.
• Pleistocene biotas were extremely close to modern ones
— many genera and even species of Pleistocene
conifers, mosses, flowering plants, insects, mollusks,
birds, mammals, and others survive to this day.
• Pleistocene was also characterized by the presence of
distinctive large land mammals and birds.
• Mammoths and their cousins the mastodons, longhorned
bison, sabre-toothed cats, giant ground sloths, and many
other large mammals characterized Pleistocene habitats
in North America, Asia, and Europe.
• Native horses and camels galloped across the plains of
North America. Great teratorn birds with 25-foot
wingspans stalked prey.
Mammoths had ridged molars, primarily for grazing on grasses, mastodon molars
had blunt, cone-shaped cusps for browsing on trees and shrubs. Mastodons were
smaller than mammoths,, and their tusks were straighter and more parallel.
Mastodons were about the size of modern elephants
Primates and Human Evolution
• Primates, meaning first
• Hominids, Family Hominidae, upright posture
• The Order Primates is one of the longest
surviving (Eocene) and generalized group of
mammals
• 2 suborders
– Prosimii and Anthropoidea
• Superfamily Homonoidea (3 Families; includes
chimps, gorillas, orangutans and humans)
Primate Evolution
• As a result of the change in climate and
vegetation, adaptive radiation occurred
among the Old World primates.
• During the late Miocene, primates
appeared that gave rise to the pongids
(orangutan, chimpanzee, and gorilla) and
the hominids (human family).
• A new group, the dryomorphs (formerly
dryopithecines) appeared in the Miocene.
Australopithicines
• Australopithecus africanus was discovered in
1924 by Raymond Dart in South Africa. Since
then, many specimens have been discovered in
East Africa, particularly in Olduvai Gorge by
Mary and Louis Leakey.
• East African fossil sites have yielded hundreds
of hominid bones, documenting human evolution
over the past 4 million years.
• Interbedded volcanic ash allows radiometric
dating of the hominid fossils.
Australopithecus africanus
• Australopithecus africanus skull replica. The
original of this replica was discovered by Robert
Broom in Sterkfontein, Transvaal, South Africa in
1947. 2.5 million years old.
"Lucy"
Australopithecus afarensis
• Discovered by Donald
Johanson in 1974 and
nicknamed "Lucy".
• Lucy was an erect-walking
hominid in East Africa about 3.5
million years ago. Posture is
determined from analysis of
pelvic and leg bones.
Hominids
• During the Pleistocene the hominid
tendency to increase brain size and hence
intelligence continued.
• Homo erectus, Homo neanderthalis, and
finally modern man (Homo sapiens)
succeeded each other in time (although
modern man and neanderthals lived
alongside each other in Europe for a short
period
The Earliest Humans
• Fossil evidence from along the Omo River in
southern Ethiopia shows that modern humans,
Homo sapiens, lived in Africa as much as
195,000 years ago, according to an article
published in February 2005
• Previously, modern humans were thought to
have appeared in Africa about 160,000 years
ago
• Humans appeared in Africa many thousands of
years before our species appeared on any other
continent
The Quaternary
• The Pleistocene 1.8 Ma-10,000Ka
– The term Pleistocene ("most recent") was
coined by Charles Lyell in 1839, on the basis
of a section of type strata in eastern
Sicily, according to the proportion of extinct to
living species of mollusk shells in the
sediment.
– Strata with 90 to 100% present day species
were designated Pleistocene.
• The Holocene 10,000 Ka- Present
Mt. St. Helens eruption
May 18, 2000
Cascade Range>> Subduction Zone (trench)
Columbia Plateau and
Cascade Range Volcanism
• West of the Columbia
Plateau, more viscous
lava produced the
volcanoes of the Cascade
Range.
• Volcanism is caused by
the North American plate
overriding the Juan de
Fuca plate in the eastern
Pacific.
Volcanoes of the Cascade Range
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•
•
•
•
•
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Mt. St. Helens
Mt. Rainier
Mt. Adams
Mt. Hood
Mt. Jefferson
Mt. Lassen
Mt. Shasta
Mt. Rainier
• Mt. Rainier is
considered to be the
most dangerous
volcano in the range.
• Major eruption about
2000 years ago, and
minor eruptions in
1800's.
Crater Lake
Crater Lake, Oregon formed from the
eruption and collapse of Mt. Mazama in
the Cascade Range about 6000 years
ago.
Origin of
Crater
Lake
In the last 30 years evidence from deep sea drilling has shown that about 25 million
years ago the earth's climate began to cool and the polar ice caps began to expand
steadily. The cause of this slow change in global environment is still unknown but
adjustment of atmospheric chemistry, possibly due to increasing volcanic activity may
have been the trigger. Volcanic dust in the upper atmosphere and the chemical
changes wrought by massive releases of sulfur dioxide from certain volcanoes can
cause large climatic changes.
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.
Worldwide cooling resulted in:
1. First Cenozoic widespread growth of glaciers in
Antarctica about 38-22 m.y. ago.
2. Global sea level dropped by about 50 m in the
Early Oligocene, as glaciers formed.
3. Cold, dense polar water flowed northward
across ocean bottom.
4. Upwelling of cold bottom waters affected world
climate.
5. Decrease in diversity and extinctions of many:
– marine molluscs
– planktonic and benthonic foraminifera
– ostracodes
6. Extinctions were earlier and more severe at
higher latitudes.
7. Reefs shifted toward the equator.
8. 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.
9. 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.
10. Glaciation occurred in other areas in Pliocene
(and younger) deposits - Sierra Nevada,
Iceland, South America, and Russia.
http://www.museum.state.il.us/exhibits/ice_ages/images/laurentide.mpg
Pleistocene Glaciations
30% of Earth’s surface
covered by glaciers
Glacial Erratic. Lopez Island, Washington
This granitic boulder is a long way from the nearest possible source area--too
far to be carried by anything other than ice.
Willow Lake and moraines on south flank of the Wind River Mtns, 9 miles NNW of Pinedale,
WY. View to the northeast. Note one or more recessional moraines and the different
morphological ages of the lateral moraines (i.e. pitted or smooth). Outwash channel in
foreground. (14Apr66) Lou Maher
Glacial Lake Missoula (ice dam 800 m high) 500 km3 water
Okanogan Glacier lobe dammed Columbia River, deflected flood waters
flood waters spilled across southeastern Washington, stripped off loess, created giant
ripples most floods occurred after [14C ] 19 ka 13 floods were after 13 ka, two > 6 X 106
m3/s (Benito O'Connor, 2004)
Advance of the Ice Sheets
• The Late Pliocene and Pleistocene had strong,
rapid, climatic fluctuations.
• Ice ages are characterized by glacial expansions
separated by warmer interglacial intervals.
• Before the mid-1970's, the Pleistocene was
divided into four glacial stages with intervening
warmer interglacial stages.
• More recent investigations have shown that
there may have been as many as 30 glacial
advances over the past 3 million years (roughly
every 100,000 years.)
Milankovitch Cycles
• The overriding controls in climate that has occurred during
the Quaternary are three predominant characteristics of the
earth's astronomical position relative to the sun, which vary
cyclically over time on different wavelengths
• This theory, first adequately proposed by a Serbian
mathematician, Milutin Milankovitch, who spent over 30
years perfecting it -publishing detailed accounts in the
1930s and 40s.
• It is these astronomical variables that have been forcing our
climate during the Quaternary and the sudden reversals in
trend and the step like pattern is the product of vast positive
and negative feedback systems operating in the climate
system.
• The effect of these climatic changes is spatially dissimilar
(i.e. in different parts of the World the climate has reacted
differently -perhaps becoming wetter or drier rather than
colder and warmer) and also their periodicity has altered
over time during the Quaternary.
Milankovitch Cycles
• In northwestern Europe the last 750,000 years
have been characterised by long periods
(c.100,000 years) of cold climates interspersed
with shorter periods (c.10-15,000 years) of
warmer conditions.
• Viewed against current fears of global warming
(currently believed to have been less than 1oC in
the last 100 years) then it gives us a chilling
insight into the actual geological evidence which
suggests that over 90% of the last 750ka has
been very cold at our latitude (with mean annual
air temperatures dropping well below zero).
• It is thought by some that any trend in global
warming will be easily outweighed by much
more important overlying trends and climatic
feedback systems.
Milankovitch Cycles
1. Precession - Earth's axis wobbles or moves in a
circle like a spinning top over 26,000 years,
affecting the amount of solar radiation received
at the poles.
Milankovitch Cycles
2. Orbital eccentricity - Earth's orbit around the Sun
changes from more circular to more elliptical by
about 2% over about 100,000 years, moving the
Earth closer to or farther from the Sun, and
varying the amount of solar radiation received by
the Earth.
Milankovitch Cycles
3. Angle of tilt of Earth's axis currently about 23.5o, this
tilt angle causes the
seasons.
Tilt angle varies from about
21.5o - 24.5o over about
41,000 years, changing
length of days and amount
of solar radiation received
at the poles.
The Little Ice Age
• Cold spells recurred periodically into the
Holocene.
• The “Little Ice Age” lasted from 1540 – 1890.
Temperatures were several degrees cooler than
today.
• Loss of harvests, famine, food riots, and warfare
in Europe.
• Cold conditions correlate with periods of low
sunspot activity.
• A time of extremely low sunspot activity from
1645 -1715 is known as the Maunder Minimum.
The Little Ice Age – cont’d
• Heightened volcanic activity occurred during the
Little Ice Age.
• Volcanic ash and aerosols in the atmosphere
caused temperatures to drop by blocking out
incoming solar radiation.
• The eruption of Mount Tambora in Indonesia in
1815 was followed by the “Year Without A
Summer”.
• Frost and snow were reported during June and
July of 1816 in New England and Northern
Europe.
End of the Little Ice Age
• Human-induced warming may be the
reason for the end of the “Little Ice Age”.
• Greenhouse gases associated with the
Industrial Revolution are the major factors
influencing global warming and climate
change today.