Transcript ppt

Formation of the Great Lakes
Part 2
The Precambrian Continued
History Channel Video
Chapter 2 in Grady
Chapter 2 in Greenberg
History of Life on Earth
Deep Time
4550 mya to present
era
eon
era
era
Precambrian Eon
 Hadean Era
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Geology
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Birth of solar system - 4.55 bya
Escaping gasses create early atmosphere
Earth’s core forms - 4.4 bya
Great oceans form
Oldest known rocks - 4.055bya
Biology
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First evidence of life - 3.85 bya
Precambrian Eon
 Archaean Era
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Geology
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Small continents form
Continents begin to shift
Biology
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Bacteria diversify -3.8 bya
First photosynthetic bacteria – 3.7bya
Oldest fossils – 3.5 bya
First Eukaryotes – 2.7 bya
Bacteria on land – 2.6
Great Lakes Basin in the
Precambrian
 Foundation for Great Lakes Basin (GLB) was
formed over 3 bya in Precambrian
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Canadian Shield
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Igneous rocks
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Exposed in northern and northwestern part of
GLB
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Extends below sedimentary rocks deposited in
the southern and eastern parts of GLB during
Paleozoic era
Precambrian
 Many of the oldest rocks found on earth today
are found in the Superior Upland, a part of
the Canadian Shield, the broad swath
Precambrian rocks that curves around
Hudson Bay.
 These rocks make up the "core" of the North
American continent.
Canadian Shield
 Canadian Shield Craton made up of three
geological provinces
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Superior Uplands Province
Southern Province
Grenville Province
 The Central Lowlands Province contains the
lower midwest USA region of the GLB. Bedrock
here is limestone
 Remnants of the rocks of these three
provinces form the deep basement of the
Great Lakes basin. Igneous basalt.
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Smooth, Grey to pinkish
Canadian Shield Rock
Canadian Shield
 Once Shield formed
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Middle of continent stable geologically
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Craton
Margins of continent very active
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Volcanism creating new land
Orogenies
Precambrian
 The Precambrian is actually a segment of
time that includes two eras, the Proterozoic
and the Archaean that span billions of years.
 The oldest rocks on earth formed during this
time, as well as the first continents, and the
earliest, simplest forms of life.
Cambrian
Archean
 3800 to 2500 mya
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The oldest rocks on earth are from this era
During the Archean, the cratons--the masses
of rock that make up the basic, initial structure
of continents--formed.
The crustal bodies that formed were smaller
than today's continents and are referred to as
protocontinents.
 Today, Archean-aged rocks are found in
areas such as the Superior Upland and the
Rocky Mountains.
Archean Era
 Major Events:
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The earth was pummeled with meteors.
Scientists believe that a huge impact tore
away a large chunk of the earth and trapped it
in orbit, forming the moon.
Seawater and an atmosphere developed.
The oceans became populated with algae,
bacteria, and colonies of microorganisms
known as stromatolites (first oxygen deposited
in atmosphere).
Great Lakes Basin in the
Precambrian
 Volcanism and sedimentary deposits were
the source of the rich mineral deposits found
in this region
 Early sedimentary and volcanic rocks were
folded and heated into complex structures.
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These were later eroded and, today, appear
as the gently rolling hills and small mountain
remnants of the Canadian Shield, which forms
the northern and northwestern portions of the
Great Lakes Basin.
Precambrian
 Other Precambrian rocks are found
throughout the continent, in places such as
the Adirondack Mountains, the Rocky
Mountains, the Llano Uplift, the Black Hills,
the Baraboo Range, and the Grand Canyon.
Great Lakes Basin in the Late
Precambrian
 Central North America experienced repeated
transgressions and regressions of shallow,
tropical seas during Paleozoic
 Large
areas of tropical coral reefs
 Seas deposited layers of materials that
became sedimentary rocks
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Limestone, shales, sandstone, gypsum
3 Domains of Life
3 Domains of Life
Kingdoms and Domains
 When Linnaeus developed his system of
classification, there were only two kingdoms,
Plants and Animals.
 But the use of the microscope led to the
discovery of new organisms and the
identification of differences in cells. A twokingdom system was no longer useful.
 Today the system of classification includes six
kingdoms.
Kingdoms and Domains
 5 Kingdom system (Whittaker 1969)
 Monera
- bacteria and cyanobacteria
 Protista - protozoa, algae, slime molds
 Fungi - molds, yeasts
 Plantae - plants
 Animalia - animals
Kingdoms and Domains
 Carl Woese - U. of Illinois
(1970’s-present)
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Studied gene sequences
of bacteria, archaea, and
eukaryotes
Found major
fundamental differences
Kingdoms and Domains
 6 Kingdom system (mid 1970’s)
 Split
Monera (or Prokaryotae) into:
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Eubacteria
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Archaea
 The
two groups differ biochemically and
genetically from each other
Six-Kingdom Classification
Kingdoms and Domains
 How are organism placed into their
kingdoms?
 Cell
type, complex or simple
 How
they obtain energy
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Autotroph
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Heterotroph
 The
number/types of cells in their body
Tree of Life
Fossil Record
 This is substantial, but does not provide a
complete evolutionary history.
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The fossil record usually tells us about abundant,
widespread organisms with hard shells or
skeletons.
Phylogeny has a biogeographic basis in
continental drift.
Moving continents isolate populations, allowing for
evolution to occur.
250 million years ago all continents were
connected as Pangaea.
Pangaea “broke” apart about 180 million years
ago.
Two Types of Cells
 Prokaryotes – cells without a nucleus, simple
cell structure
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Bacteria and Archaea
 Eukaryotes – cells have a nucleus which
contains the DNA, also have complex
structure
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Includes protozoa, algae, plants, fungi and
animals (including us)
Life in the Precambrian
 Archaean Era - 3800 to 2500 mya
 Oldest sedimentary rocks (3.8 BYA)
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First life appears ~3.6 bya
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Chemotrophic, anaerobic, asexual
Oldest fossils - 3.55 BYA
Prokaryotes dominate
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Few fossils
Eubacteria and Archaea
Cyanobacteria form extensive stromatolite
systems
Primitive Eukarya appear
Photosynthesis appears
How old are they?
 Oldest known fossil bacteria are about 2.8
billion years old
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Look like cyanobacteria suggesting ancient
origin for photosynthesis
Cyanobacteria fossils from stromatolites date
to 2.8 to 2.5 bya (maybe older)
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Filamentous strands of cells resembling modern
species of Oscillatoria or Lyngbya
Stromatolites still exist as living fossils
Floating
cyanobacterial mat
from a hot spring
Fossilized
cyanobacterial mat
Colonial chroococcalean cyanobacterium from the
Bitter Springs chert of central Australia, a site dating
to the Late Proterozoic, about 850 million years old.
Palaeolyngbya also
from the Bitter
Springs chert.
Living Lyngbya
First photosynthetic bacteria
 Early microbes thrive in an oxygen-free environment,
feeding on organic molecules like glucose and
producing energy by the process of fermentation.
 As populations grow and food supplies become
scarce, bacteria that can generate their own food and
energy evolve.
 Many of them use photosynthesis in which energy
radiated from the sun is converted into chemical
energy the organism can store and use.
 Photosynthesizing bacteria grow larger and
reproduce faster than their competitors.
Methanogenic
Archaea
1st Mass Extinction
Oldest Fossils
 Look like cyanobacteria
suggesting ancient origin for
photosynthesis
 Cyanobacteria fossils from
stromatolites date to 2.8 to
2.5 bya (maybe older)
 Filamentous strands of
cells resembling modern
species of Oscillatoria or
Lyngbya
 Stromatolites still exist as
living fossils
Fossil Oscillatoria
Living Oscillatoria
Fossil (left) and living
(upper right) Lyngbya
Stromatolites
 Layered mounds of calcareous material
between cyanobacterial cells.
 Following
slides show fossil
stromatolites
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Closest place to find these: Upper
Peninsula of Michigan
FOSSILS
Doing the backstroke among the stromatolites in
a tropical Precambrian sea
Stromatolites
Keweenaw Peninsula, Michigan
Michigan Stromatolites
Marquette County 2.1 to 2.2 bya
Michigan Stromatolites
Marquette County 2.1 to 2.2 bya
Kona Dolomite from Michigan
dated to over 2 billion years
old. Thought to be a
stromatolite.
Stromatolite Formation
 Many layers were produced as calcium
carbonate precipitated over the growing mat
of bacterial filaments.
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Photosynthesis by the cyanobacteria depleted
carbon dioxide in the surrounding water, initiating
precipitation of calcium carbonate.
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The minerals, along with grains of sediment
precipitating from the water, were then trapped
within the sticky layer of mucilage that surrounds
the cyanobacterial colonies, which then continued
to grow upwards through the sediment to form a
new layer.
Stromatolite Formation
 As
this process occured over and over
again, the layers of sediment were
created.
Stromatolite formation
still occurs today;
Shark Bay in western
Australia is well known
for the stromatolite
"turfs" rising along its
beaches.
Shallow, marine, low
latitude, hypersaline
environments. Also
found in the Bahamas.
Living Stromatolites Shark
Bay, Australia
Banded Iron Formations
 BIFs are another type of stromatolite
 Made from 1.8 to 2.5 billion years ago during peak of
cyanobacterial stromatolites
 Composed of alternating layers of iron-rich material
(commonly magnetite) and silica (chert)
Sedimentary Rock on ocean floor
 Red = iron oxide
 Black/gray layers chert – a metamorphic rock made
as silica replaces the calcium carbonate of
limestone.
 Found in Northern Michigan SEE FOSSIL
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Banded Iron-Formation
 Seasonal and/or biological
cycles resulted in
intervening periods when
iron or oxygen were not as
available
 The black layers are made
of chert (micro-crystalline
quartz) that was laid down
during these intervening
periods.
Banded Iron Formations
 By 1.9 bya, oxygen makes up about three
percent of the atmosphere's vital gases.
 This level later rose to present-day levels of
21 percent.
 As the supply of oxygen increased and
organisms increasingly tapped energy from it,
cells grew larger and divided more quickly.
Banded Iron Formations
 How they were made #1
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Large amounts of the soluble form of iron were
released from the Earth's interior into the
Archaean oceans. (reduced ferric iron)
Oxygen in the oceans would have oxidized
(rusted) this iron to form insoluble (ferrous)
iron oxide which precipitated and formed
layers of reddish sediment on the ocean floor.
The layers or banding is assumed to result
from cyclic peaks in oxygen production. It is
unclear whether these were seasonal or
followed some other cycle.
sis
Banded Iron Formations
 How they were made #2
 It
is also thought that bacteria may have
played a role in the formation of the
bands of precipitated iron.
 Certain bacteria can oxidize reduced
ferric iron to insoluble ferrous iron
Banded Iron Formations
 Economic significance
 Banded
iron formations (BIFs) are the
primary source of today's global iron ore
supply.
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600 trillion tons of iron ore present today, so we know
there was plenty of iron in Precambrian waters.
Bacteria are capable of precipitating a number of
other minerals including manganese and even gold
 These processes are being adapted to facilitate
mining of these minerals and removal of heavy
metal pollutants from soils
From The Great Lakes:
an Environmental Atlas
and Resource Book
Banded Iron Formations
 Alternating rust- and gray-colored bands in
BIF’s are evidence that:
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Oxygen was present in the ocean water as a
result of photosynthesis by cyanobacteria
Oxygen production fluctuated over time.
Don’t know cause of fluctuations
Red Beds
 Rusting of the Earth: 2.2-1.9 bya
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During peak of stromatolites
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As underwater chimneys called deep-sea vents
release dissolved iron into Precambrian waters,
oxygen is used up as quickly as it is produced.
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Once the iron supply is exhausted, however,
oxygen begins escaping the seas into the open air.
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Evidence of a buildup of atmospheric oxygen first
appears in rock layers 2.2-1.9 billion years old,
during which time most of the planet's exposed
surface rusts.
Red bed shale-sandstone sequence
near Kugluktuk, Nunavut, CA
Banded Iron
Formations
KARIJINI NATIONAL PARK Western Australia
FIRST MASS EXTINCTION
 As more and more cyanobacteria spread
across Earth, the oxygen waste they
produced through photosynthesis proved
toxic to most other microbes.
 In fact, only those sheltered in oxygen-poor
habitats like the murky depths and those with
genetic mutations that somehow enabled
them to tolerate oxygen survived.
 FIRST MASS EXTINCTION ON EARTH!
Cambrian
Paleoproterozoic (2500 to 1600 mya)
 Oxygen present in atmosphere so  Metabolism began diversification
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Earliest Proterozoic life was single-celled and
anaerobic – did not use oxygen
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Oxygen was toxic to these organisms – 1st max
extinction event!
Various ways to breakdown glucose anaerobically
Later, more complex single-celled aerobic life
evolved which used oxygen
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Use oxygen for the process of respiration
Paleoproterozoic (2500 to 1600 mya)
 Peak of stromatolites
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Cyanobacteria oxygenated the atmosphere
 Oxygen caused “Rusting of the Earth”
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Depletion of oceanic iron
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Combined with oxygen and precipitated as “rust”
Precipitated iron settled to the ocean floor
Iron found in Banded Iron Formations
Complex Single-celled Life
 Acritarchs
 Acid-resistant, organicwalled, micro-plankton
 Common Proterozoic
eukaryote fossils
 Represent encysted
"resting stage" of organism
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Resting cysts of algae
Egg cases of small
metazoans
Others are cysts of
unknown eukaryotes
Late Proterozoic Ice Age
 Occurred from 850 to 635 mya in the late Proterozoic
 Second, and possibly most severe glaciation in
earth’s history
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Glacial deposits are so widespread at this time that
geologists refer to it as “Snowball Earth".
 May have caused extinction of Acritarchs
 It has been suggested that the end of this cold period
was responsible for the subsequent Cambrian
Explosion, However, this theory is still controversial
 Formal name Varangian glaciation
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Named after an area in Norway
Precambrian Animals
650 to 544 mya
Ediacaran Fauna of Australia and
Newfoundland, CA
Soft Bodied Invertebrates
Life in the Late Proterozoic
 In the latest part of the Proterozoic (~ 600 mya), multi
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cellular, complex life is recorded in the fossil record.
Oldest fossils within Kingdom Animalia are Vendian
age 650 to 544 mya, and are found at nearly 30
locations around the world, and are most distinctive.
Fossils are preserved as thin impressions on bedding
surfaces of fine to medium-grained sedimentary rocks.
Organisms were very thin, lacked any minerallized hard
parts or well developed organs or organ systems, and
had a quilt-like outer surface.
Uncertainty about what groups of animals these fossils
might represent, and, if they were ancestral to the
animals that appeared in the late Cambrian.
Avalon Peninsula Newfoundland, CA
Ediacaran Biota
 Appeared immediately after the prolonged
period of global glaciations towards the end
of the Precambrian
 Extraordinary organisms:
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Discs
Fronds
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Segmented morphologies
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•Jellyfish
•Worm Tubes
 Locations
 Flinders Range (Ediacaran Hills), South Australia
 Avalon Zone of Newfoundland
 Nama Group in Namibia
Cyclomedusa
a jellyfish
Charnia masoni - no known
living descendants
Dickinsonia costata – early
relative of earthworms?
Trace fossils of primitive
worms
Precambrian Ocean – Ediacaran Fauna
620 to ~543 mya
Charnia
Cloudinia
Cyclomedusa
Dickinsonia
Parvancorina
Spriggina
Paleozoic Era
 With the coming of the Paleozoic Era, most of
central North America was flooded again and
again by marine seas, which were inhabited
by a multitude of life forms, including corals,
crinoids, brachiopods and mollusks.
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Transgressions and regressions of ocean
The seas deposited lime silts, clays, sand and
salts, which eventually consolidated into
limestone, shales, sandstone, halite and
gypsum.
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