Outline for Dr. Heaton's ESCI 103 class
Principles of Earth Science II
or Historical Geology
Textbook: Harold L. Levin, The Earth Through Time,
8th Edition
Chapter 2 – Early Geologists Tackle History’s Mysteries
Key Historical
Figures and their Contributions
Herodotus (450 B.C.) and later Leonardo da Vinci (1452‑1519)
Recognized fossils
as remnants of ancient life that lived where the fossils are found
Nicolaus Steno
(1638‑1687)
Principal of Superposition (higher
layers of rock are younger than lower layers)
Principal of Original Horizontality
(tilted layers of rock were formed horizontal)
Principal of Original Lateral
Continuity (rock layers are continuous over large areas)
Abraham Werner
(1749‑1817)
Neptunist (believed all rocks, including
basalt, precipitated out of the ocean)
James Hutton (1726‑1797)
Plutonist (believed that igneous rocks
formed from a liquid melt)
Proposed long geologic cycles (like a
heat engine) to explain origin of soil for farming
Father of Uniformitarianism (old earth,
gradual change, "present is the Key to the past")
Principal of Unconformities
(sedimentary discontinuities representing time hiatuses)
William
"Strata" Smith (1769‑1839)
Principal of Fossil Succession (using
fossils to correlate rock ages)
Mapped the rocks of
Georges Cuvier
(1769‑1832)
Famous anatomist, defender of
Catastrophism and mass extinction
Mapped the rocks of
Charles Lyell (1797‑1875)
Principal expounder of
Uniformitarianism, Gradualism, and a cyclic history of life
Principal of Cross‑cutting
Relations (dating of features by their effects on each other)
Principal of Inclusions (pieces of
older rock are encased within younger rock)
Charles Darwin
(1809‑1882)
Follower of Lyell, defender of
Uniformitarianism and Gradualism
Proposed Evolution by Natural Selection
to explain faunal succession
Proposed another evolutionary theory to
explain coral reefs
Lord Kelvin (1824‑1907)
Physicist who claimed that Lyell's
earth was an absurd perpetual motion machine
Claimed that the sun and the earth were
rapidly cooling from an original molten state
Calculated that the earth was too young
for
His ideas were negated with the
discovery (around 1900) of nuclear reactions
Key Historical
Issues
The age of the
earth and its features
Rapid catastrophic
change vs. slow gradual change
Time's arrow vs.
time's cycle
The ultimate cause
of things (natural or supernatural)
Historical science
requires different approaches than laboratory science
Detailed study of
modern processes, comparison with past features (Actualism)
Recognition of past
processes no longer operating today
Hypothesis testing,
multiple working hypotheses
Chapter 3 – Time and Geology
The Geologic
Time Scale: "type sections" named locally and later correlated
worldwide
Hierarchy of Eons, Eras, Periods,
Epochs, developed in early 1800's
Dates in years added in 1950's using
radiometric dating
Learn Eons, Eras,
Periods, Epochs of Cenozoic, and dates of era boundaries
Stratigraphy is the
science of correlating sedimentary rocks.
Geochronology is
the science of dating geologic events.
Adam Sedgwick‑‑named
Cambrian, used lithology as basis (bad for correlation)
Roderick Murchison‑‑named
Silurian, used fossils as basis (better method)
Charles Lyell‑‑named
epochs of Cenozoic based on percentage of modern species
Cambrian,
Ordovician, Silurian, Devonian: named for places and tribes in
Carboniferous:
named for the important coal deposits it bears in
Subdivided into Mississippian and
Pennsylvanian in
Permian: named for
the
Triassic: named for
the three-fold division of rocks of this age in
Jurassic: named for
the
Cretaceous: named
for the chalk deposits it contains throughout
Tertiary and
Quaternary: remnant names from the original "Primary, Secondary"
nomenclature
Paleogene and
Neogene: modern official periods of the Cenozoic Era
Classification & Hierarchy of
Sedimentary Units
Time Units Time‑Stratigraphic Units Rock Units
Eon = Eonothem
Era = Erathem
Period = System » Group
Epoch = Series » Formation
Age = Stage » Member
Chron = Zone
(chronozone)
Lithostratigraphy—using rock type as
the basis of correlation
Formations are based on
lithology (rock type) and can be "time transgressive"
They also cover a
limited geographic area and cannot be correlated worldwide
The trick is
relating stratigraphy (rock layers) with time (actual age)
Biostratigraphy—using fossils as
the basis of correlation
Fossil zones are the
stratigraphic ranges covered by index fossils (short-lived species)
Strategies for
aging events
Relative dating‑‑establishing
a sequence of events irrespective of time or duration
Examples: superposition, cross‑cutting
relations, fossil correlation, etc.
Absolute dating‑‑giving
a date (i.e. in years) to each past event
Requirements of a
natural clock
1) Irreversible,
non-cycling process
2) Constant or
uniformly changing rate
3) Measurable
initial condition
4) Measurable final
condition
Early (failed)
attempts at dating the earth
Rates of deposition
& rates of erosion (non‑uniform rate, but did show that the earth was
old)
Saltiness of the
ocean (involves a cycling process rather than cumulative process)
Heat flow from the
earth [Lord Kelvin] (failed to account for heat from radioactivity)
Radiometric dating
(works best with igneous rocks)
Atoms, nuclei,
protons, neutrons, atomic number, mass number, and isotopes (nuclides)
Radioactive decay,
parent isotope, daughter isotope
Types of decay:
Alpha, Beta, Gamma, Electron capture
Statistical
probability and the law of large numbers
The Half‑life
concept: the time required for half the unstable atoms to decay
Each radioisotope has its own half‑life
value which must be experimentally determined.
Isotopes useful in geology have very
long half‑lives because they are dating old events.
Isotopes most
useful in dating past events on earth
Uranium‑238 >>
Lead‑206 4.5 billion year half‑life Multiple α and ß decays
Uranium‑235 >>
Lead‑207 0.7 billion year half‑life Multiple α and ß decays
Potassium‑40 >>
Argon‑40 1.3 billion year Half‑life Electron capture
Rubidium‑87 >>
Strontium‑87 49 billion year half‑life ß decay
Carbon‑14 >>
Nitrogen‑14 5730 year half‑life ß decay
A closed system is
needed to maintain the components and predict the initial condition.
Blocking
temperature is the temperature below which a mineral becomes a closed system.
Isochrons are plots
from multiple samples that indicate potential problems with the dates.
Concordant dates:
similar results from multiple radioisotopes (always good)
Discordant dates:
inconsistent results from multiple radioisotopes (sometimes bad)
Know the assumed
initial conditions and what event is being dated with each method.
Know what
assumptions each dating method is based upon and any potential for error.
Know what type(s)
of decay is (are) involved with each method and the half‑life.
Other dating
techniques
Fission track
dating‑‑counting holes in minerals made by energetic decay products
Magnetostratigraphy‑‑the
record of reversals of the earth's magnetic field
Time‑parallel
surfaces: ash beds, tillites, magnetic reversals, fossil origins & extinctions
Relative and
absolute dating can be used in conjunction with one another to bracket true
ages.
Radiocarbon Dating
Carbon-14 is
generated in the atmosphere and cycles through the food chain with
Carbon-12/13.
When an organism
dies its Carbon-14 decays back to nitrogen and escapes into the atmosphere.
Comparing Carbon-14
to Carbon-12 & 13 in a sample tells you when the organism died.
Chapter 4 – Rocks and Minerals:
Documents that Record Earth’s History
Minerals (naturally
occurring solids, orderly atomic arrangement and chemical comp.)
Silicates
Framework silicates: quartz, feldspars
(orthoclase, plagioclase)
Sheet silicates: biotite, muscovite,
chlorite, clay minerals (kaolinite, talc)
Double chain silicates: amphiboles
(hornblende)
Single chain silicates: pyroxenes
(augite)
Orthosilicates (isolated tetrahedra):
olivine, garnet
Carbonates:
calcite, dolomite
Phosphates:
apatite, turquoise
Sulfates: gypsum,
barite
Sulfides: pyrite,
chalcopyrite, sphalerite, galena
Chlorites: halite,
fluorite
Oxides: hematite,
limonite, magnetite, corundum, ice
Native elements:
copper, gold, sulfur, graphite, diamond
Igneous Rocks (form from a
liquid melt, rocks in bold are most common)
Composition
Felsic: Granite/Rhyolite
Intermediate:
Diorite/Andesite
Mafic: Gabbro/Basalt
Ultramafic:
Peridotite/Komatiite
Texture
Plutonic (coarse‑grained,
intrusive): Granite, Diorite, Gabbro, Peridotite
Volcanic (fine‑grained,
extrusive): Rhyolite, Andesite, Basalt, Komatiite
Volcanic glass:
Obsidian, Pumice
Sedimentary Rocks (formed at earth's
surface from sedimentary particles, layered)
Clastic sediments‑‑made
from fragments of pre‑existing rocks (via erosion)
Conglomerate/Breccia,
Sandstone, Siltstone, Shale, Coal
Chemical sediments‑‑sediments
precipitated out of water (organic or inorganic)
Limestone (Chalk, Coquina, Oolitic
ls.), Dolostone, Chert, Rock salt, Rock gypsum
Lithification‑‑occurs
by the compaction and/or cementation of sediments
Sorting‑‑the
process by which similar clastic particles are collected together
Sedimentary
structures‑‑cross bedding, mud cracks, varves
Metamorphic Rocks (recrystallized in
the solid state)
Factors:
temperature, pressure, intergrannular fluids
Low vs. high grade
metamorphism‑‑indicated by index minerals, partial melting
Foliation‑‑planar
texture in rock running perpendicular to stress
Settings: burial
metamorphism, regional metamorphism, contact metamorphism
Sandstone >>> Quartzite (non‑foliated)
Limestone >>> Marble (non‑foliated)
Shale >>>
Slate >>> Phyllite
>>> Schist >>>
Gneiss (foliated)
Granite >>>
Gneiss (foliated)
Basalt >>>
Greenstone (non‑foliated)
Chapter 5 – The Sedimentary Archives
Tectonic Settings
Mountain Belts‑‑areas
of recent uplift from either collision or inflation by magma
Cratons‑‑non‑mountainous
portion of continents, eroded flat, very old
1) Shields: exposed
basement metamorphic complexes, often gneiss intruded by granite
2) Platforms: areas
with flat‑lying sedimentary rocks covering the basement complex
Environments of
Deposition
Marine Deposition (fine sediments,
clastic or biogenous/hydrogenous, great lateral uniformity)
Continental
Shelves: shallow water, abundant life, much sediment (much shale &
limestone)
Continental Slope:
unstable accumulation, erosional canyons formed by turbidity currents
Continental Rise:
turbidites form deep-sea fans at base of submarine canyons
Abyssal Plains:
slow sediment accumulation covers abyssal hills (very fine clays & oozes)
Transitional
Deposition (shoreline, high rates of deposition, clastic sediments from rivers)
Deltas: very thick
accumulations of lag gravels, channel sands, backswamp clays and coal
Beaches: longshore
drift, clean quartz & magnetite sand accumulation
Barrier
Island/Lagoon Sequences: sandstone and coal form in adjacent environments
Tidal Flats: muds
carried by tidal waters in areas of constantly‑changing shoreline
(Narrow linear
environments along coast, resultant rock units are often time‑transgressive)
(Thick
accumulations of sediments can form in shallow water because of subsidence)
Continental
Deposition (includes coarsest sediments, mixed local environments)
Meandering Rivers:
floodplains, point bars, lag gravels, backswamps, oxbow lakes
Braided Rivers:
thick & wide deposits of channel sands
Alluvial Fans/Playa
Lakes: coarse conglomerates interfingering with alkali muds
Sand Dunes:
crossbeded sands, indicates strong winds and lack of vegetation
Glaciers: tillite
(with striated cobbles), loess, associated lake & braided stream deposits
Catastrophic
Flooding: rare and distinct, scouring of bedrock, well sorted conglomerates
Features of
Sedimentary Rocks
Coloration
Black Coloration:
unoxidized organic carbon, FeS2, H2S (poor circulation,
organic deposition)
Red Coloration:
ferric (oxidized) iron (with evaporites indicate warm & arid conditions)
Can result from red source rock,
subaerial oxidation, or subsurface alteration
Texture
Particle size
(Wentworth scale), sorting, roundness/sphericity, grain orientation, matrix/cement
Sedimentary
Structures (features larger than grains)
Mud cracks:
intermittent wet and dry conditions
Cross-bedding:
planar (beach and dune deposits), trough (braided rivers sediments)
Ripple Marks:
symmetric (oscillating waves), asymmetric (stream or wind currents)
Graded Bedding:
fining upward (turbidity currents: coarse fraction settles first, fine fraction
last)
Geopetal
structures: indicate "up" direction during deposition (ripples, mud
cracks, foot prints)
Chapter 5 – The
Sedimentary Archives, cont.
Sandstones (indicate source
rock & distance of transportation [maturity])
Quartz Sandstone:
rounded quartz grains, other minerals weathered away (long transportation)
Arkose: >25%
feldspar (close proximity to granite or gneiss source rock)
Graywacke: poor
sorting, fine matrix (fast erosion or high volcanic input, active tectonic
areas)
Lithic Sandstone:
many rock fragments (deltaic coastal plains, short transportation)
Limestones (carbonates, form
in precipitation settings far from clastic sediment sources)
Can be composed of
shell fragments, tiny algae fragments, inorganic oöids, etc.
Carbonate Platforms
are broad shallow continental shelves dominated by carbonate deposition
During periods of
high sea level (Cambrian, Mississippian) carbonate deposition was extensive
Dolomite forms when
evaporating sea water develops high concentrations of magnesium
Shales (made of very fine
particles derived from erosion, mostly of clay minerals)
Clay minerals form
from the weathering of other minerals
These particles are
so small that they can be carried great distances suspended in water
Typical
Depositional Settings
Sandstone‑-in
deltas and beaches (nearest shore)
Shale‑‑near
shore where carried by local currents
Limestone‑‑farthest
from shore where clay particles are not present to dilute precipitates
Changes in Sea
Level
Transgression‑‑a
rise in sea level causing flooding ("transgression") of the land
Regression‑‑a
fall in sea level causing the exposure of previously drowned land
Transgression
sequences: unconformity (bottom), sandstone, shale, limestone (top)
Regression
sequences: limestone (bottom), shale, sandstone, unconformity (top)
Unconformities
Disconformity‑‑sedimentary
layers are parallel above and below the unconformity
Angular
unconformity‑‑sedimentary layers below meet the unconformity at an
angle
Nonconformity‑‑igneous
or metamorphic rocks underlie the unconformity
Chapter 6 – Life on Earth: What do Fossils Reveal?
Previous
assumption: special creation of fixed species, spontaneous regeneration, no
extinctions
Georges de Buffon
(1707 1788)
Defined the species concept, observed
that environments change species over time
Noted that characters are inherited in
all species, proposed a vague notion of evolution
Carolus Linnaeus
(1707‑1778)
Classified life hierarchically:
kingdom, phylum, class, order, family, genus, species
Jean Baptiste de
Lamarck (1744‑1829)
Believed in an automatic regeneration
of life (extinctions impossible)
Believed that life forms evolve with
the most complex species being the oldest
Proposed a mechanism for evolution: the
inheritance of acquired characters
Georges Cuvier
(1769‑1832)
Opposed the evolutionary ideas of
Buffon and Lamarck, believed in the fixity of species
Demonstrated the reality of extinction,
short‑lived "index fossils" useful time indicators
Louis Pasteur (1822‑1895)
Demonstrated that life can only arise
from existing life (no spontaneous generation)
Charles Darwin
(1809‑1882)
An excellent biological observer from
his youth, dabbled in medicine & the clergy
Converted to the notion of a very old
& uniformitarian earth by writings of Charles Lyell
Voyage of the Beagle (1831‑1836)
exposed him to fossils and to island biogeography
Set a whole new standard for the
collection of scientific specimens, meticulous researcher
Convinced of evolution (descent with
modification) of species by "natural selection"
Natural Selection
(adapted from socioeconomic theories by Adam Smith & Thomas Malthus)
Organisms produce far more offspring
than the environment can sustain
Offspring exhibit variation, and these
variations are heritable
Environmental factors
"select" which variants survive to produce the next generation
By sustained selective pressure a
species can be radically modified over time
A gradually changing earth (Lyell)
produces gradually changing species (
Evidences of
evolution (i.e. facts that evolution explains well)
Historic small‑scale changes
within species in nature (natural selection)
Historic large‑scale changes in
domesticated plants and animals (human selection)
Common body plans and biochemistry in
diverse organisms (homologies)
Common embryologic developmental stages
in all vertebrates
Rudimentary or "vestigial"
organs
Blatant imperfections (maladaptations)
and oddities with historical explanations
Biogeographic distributions (habitat
barriers, colonization factors, isolated populations)
The fossil record (the only true
documentation of evolution)
a) Linking fossils on the large scale (intermediate forms)
b) The dilemma of the fossil record at the species level
"Phyletic Gradualism" vs.
"Punctuated Equilibrium"
Genetics of Gregor
Mendel (1822‑1884)
Provided the long‑sought basis
for inheritance
At first seemed contradictory to
evolution because it limited possible variation
Eventually formed a foundation for
evolution via mutations and genetic recombination
Disorder of the genetic code (like a
jumbled computer program) suggestive of evolution
Inheritance of
Acquired Characters has some truth to it
Human culture is passed on in a
Lamarckian fashion
Immunities (via acquired antibodies,
not genes) are often inherited
Viral DNA and "jumping genes"
may sometimes be passed on to offspring
Know the definition
and examples of these terms
Divergent evolution‑‑a
single species giving rise to morphologically distinct species
Convergent
evolution‑‑distant species coming to look superficially alike
Iterative evolution‑‑one
lineage repeatedly giving rise to similar descendants
Adaptive radiation‑‑one
form quickly giving rise to many diverse descendants
Evolutionary trend‑‑a
long‑term evolutionary change in the same direction in a lineage
Sympatric
speciation‑‑a single population diverging into two different
species
Allopatric
speciation‑‑isolated populations of a species diverging to form
different species
Preadaptation‑‑a
body structure switching from one function to another
Neoteny‑‑a
juvenile trait being retained into adulthood
Microevolution‑‑small‑scale
changes in a lineage
Macroevolution‑‑development
of an entirely new body form or structure
Extinction‑‑the
termination of a lineage
Uses of Fossils
1) Learning about
ancient life to better understand our world (Paleobiology)
2) Geologic time
correlation (Biostratigraphy)
Index fossils (fossils with a short geologic
time range)
Biozones: range zones, assemblage
zones, concurrent range zones
The problem of reworked fossils
3) Environmental
indicators (Paleoecology)
Subdivisions of the marine and
terrestrial realms, habitats
Ecosystems, trophic levels, niches
4) Reconstructing
ancient geography (Paleobiogeography)
Dispersal (corridors, filter routes,
sweepstakes routes)
Body fossils‑‑bodily
remains of prehistoric organisms
Trace fossils‑‑tracks,
trails, burrows, etc. (Ichnology)
Types of
preservation‑‑permineralization, carbonization, etc.
Advantages for
preservation‑‑hard parts, rapid burial, etc.
The fossil record
(an accidental historical record) is a good but incomplete record of life
The Evolution/Creation Debate
Ideas Popular in Western Religions
God created the universe (primarily for Man) and is the
ultimate authority on all matters.
Prophets reveal God's will and purpose; past scripture
is a substituted for prophets today.
Argument from Design: the best proof of God's existence
is his creations (William Paley, 1802)
Deism: the world is a self‑running machine set in
motion by God (René Descartes, 1596‑1650)
Biblical Creationism: the world was created in 6 literal
days, a world-wide flood killed most life
The Fundamentals of Science
Observation and Experiment—collecting data from the
physical world itself to learn its history
Rational Thinking—careful evaluation, hypothesis
testing, theory generation (no higher authority)
Naturalism—the belief that all things have come about by
way of consistent natural laws
The Dethroning of God as Creator (finding explanations
for origins that don't invoke God)
1) Nebular Hypothesis of Laplace & Kant for the
origin of the solar system and the earth
2) Uniformitarian Geology of Hutton & Lyell for the
origin of the earth's rocks and features
3) Evolution by Natural Selection of Darwin &
Wallace for life on earth
The Genesis Account
1) God created heaven and earth and the various
"kinds" of life (Genesis 1:1‑2:7, Exodus 20:11)
2) The Fall of Adam brought death into the world
(Genesis 2:16‑17, 3:1‑24, I Cor. 15:21‑23)
3) The Flood of Noah killed off nearly all life on earth
(Genesis 6:5‑8:19)
Ways of Harmonizing Geological Observations with Genesis
1) Day-Age Theory: each "day" of Creation is
really a long geologic time period
2) Gap Theory: there was a long time gap between the
first two verses of Genesis
3) Creation Science: earth is ~6,000 years old, Noah's
Flood created the sedimentary rocks
Spectrum of Positions on Science and Religion
1) Atheistic Evolution: evolution is the only
explanation needed for life on earth
2) Theistic Evolution: evolution is true, but God guided
the process (Catholic viewpoint)
3) Day-Age & Gap Theories: evolution is false but
there were long geological ages
4) Creation Science: the earth is young, Noah's Flood
deposited most sedimentary rocks
The History and Nature of Creation Science
Originated with a Seventh Day Adventist named George
McCready Price (1870‑1963)
Price
differed from other creationists by attacking geology rather than biology.
Made popular to Protestants by Whitcomb & Morris' The
Genesis Flood (1963) & Jerry Falwell
Morris' Scientific Creationism presents
Creationism as a Science rather than a religion.
Science is
the modern way of knowing all truth, so even religion must be scientific.
Creationists
have tried (unsuccessfully) to get Creationism into the science classroom.
Creationism in Court
1) Tennessee Anti-Evolution Act (1925) prohibited the
teaching of evolution in public schools
Scopes
Monkey Trial at
2) Equal Time laws (equal time required for evolution
and Biblical view of origins)
These were
ruled unconstitutional at the outset because of Separation of Church and State.
3) Arkansas Balanced Treatment Act (1981) based on the
Evolution/Creation science distinction
Judge
Overton banned implementation of the law because of its obvious religious
basis.
Creationist Societies
Religion and Science Association (1935‑1937): All
camps represented, failed over disagreements
Deluge Geology Society (1938‑1947): Mostly
Adventists, all believers in Flood Geology
American Scientific Affiliation (1941‑present):
Gradually came to accept theistic evolution
Creation Research Society (1963‑present):
Membership requires M.S. and acceptance of a creed
Institute for Creation Research (1970‑present):
The center of modern creationism,
Creationist
Strategies
Attack evolution as
the cause of all social ills (crime, homosexuality, communism, etc.)
Attack evolutionary
science (intermediate fossils, geological sequences, radiometric dating)
Appeal to the
Second Law of Thermodynamics (argue that evolution violates that law)
Claim there are
only two possible models, so disproving one proves the other to be true
Tune arguments and
examples to education level of the audience
Use debate platform
to argue their case (Duane T. Gish is a prominent debating creationist)
Never propose a
comprehensive theory for opponents to evaluate and compare with their own
Is Creation Science
Really Scientific?
Creationists claim
it is because they appeal to scientific laws, observations, and principles to
support their theory. They also claim that evolution is as much a religion as
their position is. Their books contain mostly scientific arguments (mostly
trying to discredit scientific viewpoints).
Mainstream
scientists discount Creationism as a science because it begins with religious
conclusions and then only accepts the "evidence" that supports them
(they never test hypotheses and accept the results), and because most
creationist claims (young earth, world-wide flood, etc.) were proven false
(based on scientific observations) almost 200 years ago.
Most scientists,
philosophers, and legal experts see Creation Science as a political movement by
conservative Christian fundamentalists to advance their cause and oppose
atheism. However, about half of Americans believe the creationist position, and
a majority feels that both evolution and creation should be taught in the
public schools to expose students to both positions.
Intelligent Design:
a new brand of Creationism
Intelligent Design
proponents seek scientific evidence for the existence of God but do not make
any other conclusions (no claims about the age of the earth, the truth of
evolution, etc.). Most proponents are theistic evolutionists and other liberal
Christians rather than Fundamentalists.
Michael Behe:
argued that certain biochemical machines have Irreducible Complexity
William Dembski:
said random and non-random causes can be distinguished by Design Inference
Phillip Johnson:
Most traditional
scientists oppose Intelligent Design because 1) these arguments are just a
rehash of old ideas that were thoroughly addressed by Darwin and others long
ago, and 2) accepting these arguments leads nowhere because the
"intelligent designer" is not known well enough to apply as a
causality in any kind of scientific research study.
Other Comments on
the Conflict between Science and Religion
Science struggles
over the origin of life, whereas death needs no special explanation.
Religion needs no
explanation for the origin of life, but it struggles over the issue of death.
Humans used to view
all actions imposed on them as "Acts of God" (good weather, bad
weather, lightning, etc.), whereas now we attribute all such immediate actions
to natural causes. Only very big things are still sometimes attributed to God's
will (our origin, birth, and death).
Science is about
understanding cause and effect, discovering new phenomena, and revealing the
history of the universe. Prophets, scriptures, and psychics have not been
helpful in making scientific discoveries or breakthroughs, whereas exploration,
experiments, and brainstorming have been very helpful. It is therefore logical
to view supernatural sources of information as invalid or irrelevant.
Naturalism (the
idea that only natural causes can be accepted) is a philosophy, a procedural
strategy, and a religion (effectively atheism). It is therefore a murky legal
and political issue as to where good science ends and the religion of atheism
begins.
Chapter 7 – Plate Tectonics Underlies All Earth History
Paradox of thickest
sedimentary sequences being found in highest mountain belts
Early theories
sought a cause & effect relationship between the two (vertical tectonics)
Continental Drift theory of Alfred
Wegener (horizontal tectonics, focus on continents)
‑Geographic
fit of continents like puzzle pieces
‑Continuation
of geographic or stratigraphic features across widely‑spaced continents
Mountain ranges like
‑Sedimentary
sequences including lake deposits and tillites
Glacial‑striated rocks that are
paradoxical in their current positions
‑Odd
positioning of late Paleozoic climate indicators
Tillites and glacial striations near
the equator on
Thick coal deposits and trees without
annual growth rings in
Evaporite deposits in northern
Coral reefs in the
‑Strange
biographic patterns of Paleozoic fossils
Tropical Glossopteris flora
found on all Gondwana continents
Terrestrial reptile Lystrosaurus
found on all Gondwana continents
Freshwater reptile Mesosaurus
found only on
‑Strange
biogeographic patterns of modern animals (some false evidences)
Similar earthworms, lungfishes, and
flightless birds on Gondwana continents
Anteaters found on
Similar mammalian faunas on
The alternate
biographic theory of Land Bridges and why Wegener correctly rejected it
Bimodality of the
earth's crust (basaltic oceanic vs. granitic continental crust), isostatic balance
The failed search
for a mechanism to drive horizontal continental movements
Sea‑floor
Spreading concept of 1950's (ocean centered, based on knowledge
of seafloor)
Paleomagnetism:
Earth's magnetic field, remnant magnetism in basalt, apparent polar wandering
Parallel symmetric
magnetic stripes on the sea floor: the search for an explanation
The Vine/Matthews
hypothesis, Morley's manuscript rejected!
Plate Tectonics (a unifying theory
for geology, explaining all features of the earth's crust)
"Floating"
lithospheric plates of continental and/or oceanic crust moving horizontally
Plate movement
driven by convection currents in mantle, ridge push, slab pull
1) Divergent plate
boundaries: mid‑oceanic ridges and continental rifts
2) Transform plate
boundaries: transform faults, the
3) Convergent plate
boundaries: deep‑sea trenches, island arcs and andesitic mountains
a) Ocean/ocean collisions, b)
continent/ocean collisions, c) continent/continent collisions
Plate boundaries
site of mountain ranges, volcanos, and earthquake epicenters
Hot spot island
chains (
Allochthonous or
accreted terrains (
Origin of the
Earth's Crust
1) Oceanic crust is
formed from partial melting of the mantle below mid‑oceanic ridges.
2) Continental
crust is formed from partial melting of oceanic crust in subduction zones.
Continental crust with its lower
density will not subduct and therefore "lasts forever."
Chapter 8 – Earliest Earth: The Hadean and Archean Eons
Universe mostly
Hydrogen & Helium; Earth mostly Iron, Oxygen, Silicon, Magnesium
Heavy elements
created in supernova explosions, recycled into new solar systems
Origin of the solar
system: Solar nebula hypothesis of Kant and Laplace
The solar system began as a nebula of
hydrogen, helium, and a trace of heavier elements
Contraction caused spinning by
conservation of angular momentum
Contraction converted gravitational
potential energy to heat, igniting fusion in the sun
Planetesimals formed in nebula and
fused by gravity to form protoplanets
Solar winds blew the hydrogen and
helium off the inner (terrestrial) planets
The forming planets swept up most of
the excess debris in the solar system
Meteorites
Ordinary
chondrites: ferromagnesian silicates (like earth's mantle) & spherical
chondrules
Carbonaceous
chondrites: chondrites with 5% organic compounds, same composition as sun
Achondrites:
chondrites lacking chondrules
Iron meteorites:
crystals of iron‑nickel alloy (like earth's core)
Stony‑iron
meteorites: mixture of silicates and iron‑nickel
Radiometric age of
meteorites: up to 4.566 billion years
The Moon
Large for the size
of the planet it orbits, ¼ size of earth, 1/6 gravity of earth, no atmosphere
Theories of origin:
simultaneous creation with earth, separated from earth, captured by earth
Orbital and axial
cycles the same, so one side always faces earth
Cratered highlands
of anorthosite (4.6‑4.0 b.y. old), maria basins of basalt (3.8‑3.2
b.y. old)
Unconsolidated
lunar regolith ("soil") from impacts blankets the moon,
micrometeorites
The moon is a
museum of the solar system's early history, nothing to obliterate old features
Other Inner or
"Terrestrial" Planets
Mercury: similar to
earth's moon but without maria, close to sun
Venus: similar in
size to earth, thick carbon dioxide atmosphere, 475° surface temperature
Lack of oceans prevents incorporation
of carbon dioxide into carbonate rocks
Lack of liquid water prevents hydrologic
erosion
Continent‑like
highlands, large volcanoes, and rolling hills are present, so internally
(tectonically) Venus appears to be much like the earth
Mars: ½ the
diameter of earth, thin atmosphere, giant volcanoes
Winds create dust storms and create a
desert‑like landscape
Ice caps show presence of water,
evidence of past stream erosion, no oceans
Outer Planets or
Gas Giants
Jupiter: largest
planet in solar system, thick stormy atmosphere
Saturn: similar to
Jupiter, has prominent ring system
Uranus and Neptune
are smaller gas giants
Pluto and the moons
of the gas giants are similar to the terrestrial planets
Studying Earth's
interior
Density of the earth: 5.5 g/cm3
for whole earth, 2.8 g/cm3 for crustal rocks
Earth's magnetic field: requires iron
in motion
Seismic waves and their shadow zones
Primary waves: particles move
parallel to wave motion, circular shadow zone
Secondary waves: particles move
perpendicular to wave motion, ring shadow zone
Surface waves: particles move in
circles along surface of earth, local only
Mohorovicic
discontinuity: base of earth's crust, top of earth's mantle (5‑70 km deep)
Seismic low
velocity zone: partly molten region in upper mantle (100‑170 km deep)
Gutenberg
discontinuity: base of silicate mantle, top of metallic core (2900 km deep)
Inner Core: Solid iron and
nickel (intense pressure keeps it in the solid state)
Outer Core: Liquid iron and
nickel (intense heat keeps it in the liquid state)
Mantle: Ultramafic rocks
(peridotite and komatiite) composed of mafic minerals like olivine
Asthenosphere: partly molten low
velocity zone, source of magma, drives tectonic plates
Lithosphere: crust and mantle
above low velocity zone, moves in pieces called tectonic plates
Oceanic crust: thin (5‑12
km), dense (3.0 g/cm3), dark (basaltic), young (<200 M.Y.)
Continental crust: thick (35‑70
km), less dense (2.7 g/cm3), light (granitic), old (<4 B.Y.)
The earth probably
began as a uniform body but underwent differentiation into layers as gravity
pulled the densest components to the core and let the lightest components float
to the surface
Earth's Atmosphere
1) Hydrogen/helium
blown away by solar winds from young sun
2) Water/nitrogen/carbon
dioxide from volcanic outgassing and/or carbonaceous chondrites
3) Nitrogen/oxygen
from photochemical dissociation and photosynthesis (allowed ozone
layer)
Banded iron
formations exist from the second atmosphere, most over 3 B.Y. old
Red beds of oxidized iron
become abundant at about 1.8 B.Y. ago
Current atmosphere:
78% Nitrogen (N2), 21% Oxygen (O2), 1% Argon (Ar), 0.03%
CO2
Outgassing also
produced ocean water and carbonate/sulfate rocks (excess volatiles).
Carbon dioxide
& water vapor in atmosphere cause a warming "greenhouse" effect:
solar energy (visible light) enters atmosphere freely, but escaping energy
(infrared light) is held by the atmosphere and released slowly.
Origin of Life and
the Earliest Fossils
Conditions of the
primitive atmosphere and ocean very different from today
Urey and Miller
Experiment has produced amino acid chains inorganically
Proteins (long
amino acid chains) and nucleic acids necessary for life
Basis of life is
the ability to replicate (reproduce)
Experimental
microspheres formed of proteinoids resemble cells
Heterotrophs
probably developed first and consumed organic soup of early oceans
Autotrophs
developed the ability to derive energy from inorganic chemicals and from
sunlight
Anaerobic
respiration (fermentation) is an inefficient energy process
Aerobic respiration
(using oxygen) is much more efficient
Prokaryotic cells
vs. Eukaryotic cells and the Endosymbiotic Theory
The earliest
fossils: tiny cells, filaments, and stromatolites
Chapter 9 – The Proterozoic: Dawn of a More Modern World
Precambrian time: named by Sedgwick
for "basement" rocks and "pre‑fossil" strata
Turns out to
comprise 87% of earth history, to have a record of primitive life
Early
classification
Hadean Eon:
earliest (4.6‑4.0 B.Y.), no surviving rocks, probably many meteorite
impacts
Archean Eon: middle
(4.0‑2.5 B.Y.), highly metamorphosed rocks ("basement" of
continents)
Proterozoic Eon:
later (2.5‑0.5 B.Y.), early "non‑fossiliferous"
sedimentary rocks
Degree of
metamorphism turns out not to be a good measure of age, but eon names
still used
Classification of
Continental Areas
Mountain Belts‑‑areas
of recent uplift from either collision or inflation by magma
Mountain building events (orogenies)
are what lead to regional metamorphism
Cratons‑‑non‑mountainous
portion of continents, eroded flat, very old
1) Shields: exposed
basement metamorphic complexes, often gneiss intruded by granite
These are the deep roots of ancient
mountain belts exposed by long‑term erosion
Zones of uniform age represent various
old orogenies, are called Precambrian Provinces
Sometimes cut by failed rift systems
containing normal faults and basalt dikes and flows
2) Platforms: areas
with flat‑lying sedimentary rocks covering the basement complex
Origin of Oceanic
Crust
Mafic basalt
derived from ultramafic mantle in rift zones (divergent plate boundaries)
Replaced an assumed
original ultramafic crust, disrupted by mantle convection and meteorites
Origin of
Continental Crust
Formed slowly and
locally by partial melting of descending basalt slabs in subduction zones
These small, low‑density
felsic zones collided and grew to form mountainous continents
Subduction zones
along continental margins inflated them with additional felsic magma
Mountain belts take
at least half a billion years to erode flat to form cratons
Large continents
were present on earth by the late Archean (most basement rocks > 2.5 B.Y.)
Earth during the
Archean (different than today; uniformitarianism difficult to apply)
Shallow oceans
overlying thin, actively‑moving basaltic crust (early oceanic crust)
Small
protocontinents forming as island arcs, fusing by collisions to form continents
Continents
mountainous with small cratons and virtually no continental shelves
Back‑arc
structural basins filling with sediments and volcanics formed greenstone
belts
Greenstone belts
grade upward from ultramafic to felsic volcanic sediments, intruded by granite
Upper Sediments
sometimes contain unoxidized Banded Iron Formations (rich iron ore)
Earth during the
Proterozoic Eon
Transition to a
more modern tectonic style including large continental masses.
Large cratons had
formed via long-term erosion by the end of the Archean, allowing continental
shelves and epeiric seas (like modern
Tills in the
Gowganda Formation of Ontario indicate a period of early Proterozoic
glaciation.
Worldwide tills of
late Proterozoic age indicate world-wide glaciation 700‑800 M.Y.
ago. This may have resulted from a
accumulation of continents along the equator.
Proterozoic
sediments include both immature graywackes (from volcanic sediment) and mature
quartz sandstones (from weathering of granite and gneiss), indicating larger
and more stable continents. Limestones
with stromatolites (algal mats) are also present, showing that primitive
life was abundant in broad shallow seas.
Banded Iron Formations give way to red beds during the
Proterozoic, indicating the presence of free oxygen in the atmosphere.
Precambrian History
of Laurentia (proto
Most Precambrian
Provinces formed in the Archean and fused together by 1.9 B.Y. ago.
The Wopmay Orogeny
added another microcontinent to NW Laurentia about 1.8 B.Y. ago.
Continents collided
in Mazatzal Orogeny to form the first supercontinent about 1.4 B.Y. ago.
Large‑scale
rifting broke up this supercontinent 1.2 B.Y. ago (Keweenawan Rift a remnant).
A continent to the
SE collided with Laurentia in Grenville Orogeny about 0.9 B.Y. ago.
Laurentia was
mostly stable during late Proterozoic, leading to thick sedimentary
accumulation:
Belt Supergroup (
Grand Canyon Supergroup (exposed in
Animikie Group (
Other Continents
during the Precambrian
Gondwanaland formed during the
Proterozoic and was the world's largest continent.
The
The Tasman Orogenic
Belt of eastern
What is now
Life of the
Proterozoic
Stromatolites
become widespread and abundant in Proterozoic, due in part to continental
shelves
The origin of the
eukaryotic cell was the first great evolutionary event of the Proterozoic
Acritarchs seem to
represent planktonic algae in a resting phase with a hard cell wall
Ediacara Fauna: the first large
organisms, shaped like pancakes, ribbons, and threads
These sort‑bodied
organisms are preserved in sandstone because there were no scavengers
Glaessner
interpretation: Ediacaran species are primitive forms of modern animal phyla
Seilacher
interpretation: Ediacaran fauna is a separate, failed radiation of life
The origin of
animals (or any large organisms) and the problem of surface area to volume
ratio
Why be big?
Chapter 10 – Early Paleozoic Events
Plate Tectonic
Configuration in the Cambrian
Paleomagnetics
reveal orientation and latitude of continents but not longitude
Laurentia (proto
Other small
continents: Baltica (proto
The giant
Gondwanaland was at the equator but was headed south
The continents were
all close together but were moving apart after a late Proterozoic breakup
Vendian normal
faults and basalt intrusions around the continental margins demonstrate this
The Cambrian was a
quiet time tectonically: no continental collisions & little mountain
building
The Paleozoic Era
is marked by the opening then closing of the "
Sedimentary Rocks
of the Early Paleozoic
Four major
Paleozoic transgression/regression cycles in
1) Sauk (Cambrian/Ordovician)
2)
3) Kaskaskia (Devonian/Mississippian)
4) Absaroka (Pennsylvanian/Permian)
Low sea level is
indicated by widespread unconformities separating deposits of these cycles.
High sea level is
indicated by widespread marine sedimentation on the continent, especially
limestone (i.e. when water covers most of a continent, there is little exposed
land to produce clastic sediments and much shallow water for animals to live
& grow skeletons).
Arches‑‑high
areas that receive deposition only during the highest sea levels, prone to
erosion
Basins‑‑low
areas under nearly constant deposition that accumulate great thickness of
sediment
Aulacogens‑‑large
grabens from rifting that receive thick sedimentary deposition
Cambrian transgression
(base of Sauk Cycle) left a classic transgression sequence:
1) Unconformity (old erosional land
surface), 2) Sandstone, 3) Shale, 4) Limestone
The sea advanced
across the continent at about ½ an inch per year during the transgression
Cambrian rock
thicknesses: 5000 m in
Only a narrow
Transcontinental Arch was left above water (no deposition) by late Cambrian
This explains why
Cambrian rocks exist in western but not eastern South Dakota (Arch in
Sediments along
Transcontinental Arch are near‑shore facies (sandstones, e.g. Wisconsin
Dells)
The Arch may have
always been above water or experienced alternating deposition and
erosion
Basal sandstones
are derived from continental areas via river, wind, and beach transport
The lack of any
land plants during the Cambrian subjected sediments to constant transportation
Long periods of
current, wind, and wave action created very mature quartz sandstones
Different kinds of
ripple marks indicate final deposition by wind, rivers, or ocean waves
Overlying shales
formed from smaller rock fragments (mostly clay minerals) washed offshore
Most marine
invertebrates like warm, shallow (lighted & oxygenated), sediment‑free
ocean water
The abundance of
such conditions during the Cambrian must have helped early animals diversify
Most Cambrian
limestones are made up primarily of shell fragments (clastic limestones)
Warm, shallow, wave‑agitated
waters led to inorganic precipitation of some oolitic limestones
Sometimes the
inland seas became hypersaline from evaporation (leading to low animal
diversity)
The
The
The
The base of the
There is also a
very extensive black shale layer loaded with graptolites (graptolitic shale
facies).
Tectonic Events of
the Ordovician (Laurentia)
The
A huge volcanic
eruption left a meter‑thick ash layer over much of
Subduction‑related
vulcanism created an island arc (microcontinent) just south of Laurentia.
The collision of
this microcontinent with Laurentia caused the Taconic Orogeny (first of three
orogenies that formed the
The Taconic Orogeny
is the same as the Caledonian Orogeny of
(Modern analog of the
Taconic Orogeny are found in
Tectonic Events of
the Ordovician (Elsewhere)
Baltica and
Gondwanaland moved
south, with the present‑day
The resulting
lowering of global sea level helped cause the Late Ordovician mass extinction.
The closing of the
Cambrian seaways (
Chapter 11 – Late Paleozoic Events
Beginning the
Assembly of Pangea
Baltica and
Laurentia collided to form Laurussia (Acadian/Caledonian Orogeny, Devonian)
This uplifted the
northern
Thick clastic
wedges in
Transcontinental
arch still a highland in central
Island arc collided
with Laurentia (Nevada/Idaho region) in Antler Orogeny (Devonian)
Gondwanaland joined
Laurussia (Allegheny/Hercynian Orogeny, Pennsylvanian)
Kazakhstania,
Mississippian
Period in Laurussia
Acadian and
Continent‑wide
inland
Most caves in the
A late
Mississippian regression (of
Pennsylvanian
Period in Laurussia
Collision of
Gondwanaland with Laurussia formed Appalachian/Ozark/Ouachita Mountains
Transgression of
Regional uplifts
and basins in the western
In
Permian Period in
Laurussia
Uplift of
Appalachian/Ozark/Ouachita Mountains continued but finally ended in late
Permian
Subduction along
the western margin of the
The late Permian
was a time of very low sea level, much like today.
Chapter 12 – Life
of the Paleozoic
Tommotian Fauna: tiny shelly
fossils of the latest Proterozoic, prelude to Cambrian Explosion
Life of the
Cambrian
First complex animals
with hard skeletons, restricted to oceans, evolutionary rates very high
Dominated by
trilobites and other arthropods, inarticulate brachiopods, and weird
echinoderms
Sponges (Porifera)
are the simplest large animals, each cell being identical
Archaeocyathids
(cup animals) took over from stromatolites as the main structural reef formers
Burgess Shale Fauna (middle Cambrian)
shows there were many strange soft‑bodied creatures
Anomalocaris of the Burgess
Shale appears to have been the first big carnivore
Most of these
animals went extinct before the end of the Cambrian; trilobites were reduced
The Cambrian was a
time of experimentation with basic body forms.
The Ordovician was
a time of standardization and specialization.
Cambrian Fauna Ordovician/Paleozoic
Fauna
Anomalocaris (top carnivore) Eurypterids
(top carnivores)
Archaeocyathids
(reefs) Rugose
and tabulate corals (reefs)
Trilobites Bryozoans
(reefs)
Inarticulate
brachiopods (unhinged) Articulate
brachiopods (hinged)
Weird echinoderms Burrowing
bivalves
Weird Burgess Shale
creatures Crinoids
("sea lilies" with long stalks)
Graptolites
(floaters)
The first
vertebrates (jawless fishes called Ostracoderms) appeared in the Ordovician.
The land was still
completely barren during the Ordovician.
A mass extinction
in late Ordovician killed off many invertebrate families but no major groups.
The Paleozoic
Marine Fauna
Rugose and tabulate
corals, bryozoans, and stromatoporoids the main structural reef formers
Crinoids,
articulate brachiopods, and molluscs (gastropods, bivalves, cephalopods) also
common
Important shelled cephalopods:
nautiloids, ammonoids (goniatites and ceratites)
Graptolites and
conodonts are two hard‑to‑interpret animals that provide excellent
index fossils
Asteroids (star
fishes) and cephalopods were also important predators
The Origin of
Vertebrates
Pikaia of the Burgess
Shale is the first known chordate, similar to living Amphioxus
Vertebrae replaced
the notochord as main structure, myotomes (muscle blocks) cause propulsion
Disarticulated fish
scales are found in the late Cambrian
Ostracoderms are
armored jawless fishes of the early Paleozoic, like living lampreys &
hagfishes
Jaws formed as
modified gill arches, gave vertebrates predatory advantage
Four classes of
jawed fishes arose in Silurian/Devonian: Placoderms (armored fishes),
Chondrichthyes (cartilaginous fishes: sharks, skates, rays), Acanthodians
(spiny fishes), Osteichthyes (bony fishes: most modern fishes)
Two kinds of
osteichthyes developed: ray‑fin fishes (no lungs, most diverse) and lobe‑fin
fishes (lungfishes, coelacanths [like Latimeria], and rhipidistians
[gave rise to amphibians])
Devonian "age
of fishes," Ostracoderms and Placoderms gone by end of Devonian
The Invasion of the
Land
Living on land
requires a waterproof "skin" and structural support to resist force
of gravity
Green algae
(Chlorophytes) probably gave rise to land plants, though little similarity
exists
A vascular system
developed to distribute water from the ground and food from above ground
Simple psilophytes
appeared in Silurian, began stabilizing ground and forming soil
Devonian and
Carboniferous dominated by lycopods, sphenopsids, ferns (formed coal deposits)
The first seed
plants were the "seed ferns" (including Glossopteris) of the
late Carboniferous
Primitive
gymnosperms (ancestors of conifers) and ginkgoes arose in the Permian
Insects arose from
marine arthropods and became very large; many flying forms
The Origin of
Amphibians
Ichthyostega appeared in Devonian; shares limb structure, skull bone
structure, labyrinthodont teeth, and tail fin with rhipidistian fishes
Labyrinthodont
amphibians of late Paleozoic became large predators of fish and insects
Lepospondyls are
odd small amphibians of Paleozoic, some had boomerang‑shaped heads
Anthracosaurs developed
into reptiles
Major groups
classified by the structure of the vertebral centrum
The Origin of
Reptiles
Development of
amniotic egg (equivalent to seed in plants), complete divorce from water bodies
Major groups
classified by temporal openings in skull: anapsids (stem forms, turtles),
synapsids (mammal‑like reptiles, some with "sails"), diapsids
(includes lizards, snakes, dinosaurs)
Took over most
niches from amphibians by end of Paleozoic, synapsids particularly dominant
The Great Permian
Extinction
Complete extinction
of trilobites, rugose and tabulate corals, fusulinids, acanthodian fishes
Heavy losses by
brachiopods, bryozoans, crinoids, ammonoids, synapsid reptiles
Chapter 13 – Mesozoic Events
Breakup of Pangea
Gondwanaland
separated from Laurasia (
Gondwanaland and
Laurasia broke up from east to west, and the
Panthalassa shrunk
by subduction at its edges to produce the modern
Evidence of
Triassic rifting abundant in Newark Group of eastern
Normal faults,
alluvial fan redbeds (with dinosaur footprints), and basalt flows are common
The
The resulting salt domes of the
An island arc
collided with western
Many such
"displaced" or "accreted" or "exotic" terranes
exist from
Mountains formed by
these collisions shed large volumes of sediment to the continental interior
Further subduction
along the coast emplaced large batholiths of granite now exposed in the
Triassic Period in
An unconformity
exists almost everywhere between Permian and Triassic formations
The Triassic is
famous for continental (non‑marine) redbeds formed from eroding sediments
of the Appalachian and
The Moenkopi
Formation is a classic redbed shale/limestone in the
The overlying
Chinle Formation is famous for its plentiful petrified wood and uranium
deposits
Jurassic Period in
The Navajo
Sandstone of the
The
Sediments silted up
the
Cretaceous Period
in
An early Cretaceous
transgression formed a northern and southern sea that didn't meet
A late Cretaceous
transgression formed a continuous seaway north to south across the continent
Coal formed from
swamp deposits along the coasts of the sea, and dinosaurs were abundant
The interior
(including South Dakota) accumulated marine sediments from the sea, most
notably the Dakota Sandstone (sand of early transgression), the Niobrara Chalk
(similar in age & rock type to the White Cliffs of Dover in England), and
the Pierre Shale (famous for its ammonoid and marine reptile fossils as well as
bentonite deposits)
Mesozoic climates
were warm and equable, no glaciation anywhere
Continents were
separating but were still close together
Chapter 14 – Life
of the Mesozoic
Plant Life
New marine
phytoplankton: Coccolithoforids, Silicoflagellates, Diatoms
Gymnosperms (naked
seed plants) dominant on land: Cycads, Ginkgoes, Conifers
Angiosperms
(flowering plants, enclosed seeds) first appear in the Cretaceous
Invertebrates
Foraminifera
(unlike Paleozoic fusulinids) undergo adaptive radiation
Rudist bivalves
shaped like horn corals dominate many reefs
Scleractinian
corals dominate reefs in tropical waters of
Bivalves dominate
over brachiopods after Permian extinction
Ammonite ammonoids
with complex sutures make excellent Mesozoic index fossils
Belemnites were a
group of cephalopod molluscs with internal chamber skeletons
Echinoids (sea
urchins) join starfishes as prominent echinoderms
Terrestrial
Vertebrates (Mesozoic "Age of Reptiles")
Synapsid reptiles
decline in Triassic but give rise to mammals before disappearing
Therapsid/mammal
transition gradual, reptile jaw articulation bones become middle ear bones
Mammals develop
teeth with precise occlusion for chewing their food, teeth good index fossils
Mammals remain
small and inconspicuous (probably all nocturnal) during the Mesozoic
Diapsid reptiles,
especially archosaurs (ruling reptiles), take over all the big land niches
Thecodonts (early
archosaurs) were bipedal runners that gave rise to crocodilians, phytosaurs,
pterosaurs, saurischian and ornithischian dinosaurs, and birds
Saurischians
("lizard hip" dinosaurs) include the great carnivorous bipeds
(Theropods) like Tyrannosaurus and the gigantic quadrupeds (Sauropods)
like Apatosaurus
Ornithischians
("bird hip" dinosaurs) include the armored and bizarre dinosaurs like
Stegosaurus, Ankylosaurus, Triceratops, and the dome head
and duck bill dinosaurs
Triassic dinosaurs
were small, Jurassic dinosaurs included the giant sauropods (the largest land
animals of all time), and Cretaceous dinosaurs were the most diverse and
bizarre
The great dinosaur
controversy: were they warm or cold blooded, active or sluggish
Marine Reptiles
Ichthyosaurs were
the most fish‑like, totally aquatic, used live birth in the water
Placodonts were
clam crushers similar to modern walruses, lived only in Triassic
Plesiosaurs swam
with limbs as paddles, some had long necks, up to 40 feet long
Mosasaurs were
giant sea‑going varanid lizards of the Cretaceous
There were also
giant marine crocodiles and turtles
Avian Reptiles and
Birds
Pterosaurs were
primarily gliders, supported membrane on elongate little finger, includes
largest flyers with wingspan up to 50 feet, some had aerodynamic head crests
First bird Archaeopteryx
from the Jurassic Solenhofen Limestone of
True flight
developed three times in vertebrate history (pterosaurs, birds, bats), but each
group turned the vertebrate forelimb into a wing in a different way
The Great Terminal
Mesozoic Extinction
Complete extinction
of ammonoids, belemnites, rudist bivalves, dinosaurs, pterosaurs, ichthyosaurs,
plesiosaurs, and mosasaurs; big losses among other groups also
The asteroid impact
hypothesis of Alvarez (1980), or the return of catastrophism!
Evidence of impact:
iridium layer worldwide at K‑T boundary, shocked quartz, microtectites
The possibility of
periodic mass extinction: galactic cycle, planet X, Nemesis
Lingering
questions: Was extinction gradual or sudden, the cause earth‑based or
extraterrestrial?
Chapter 15 – Cenozoic Events
Cenozoic epochs
named by Lyell for percentage of modern marine genera
Tertiary/Quaternary
remnants from earliest subdivision; Paleogene/Neogene an alternate scheme
Gradual regression
of sea, inland seaway gone,
Active tectonics:
continents continue spreading, several north‑south collisions occur
Orogenies Forming
Modern
Nevadan (Jurassic
of California): mostly emplacement of granitic plutons, metamorphism
Sevier (Cretaceous
of Utah to
Laramide (Tertiary
of Arizona to
Basin and Range
rifting (Miocene to Recent of California to
Cause may have been
plate reconfiguration on
Tertiary lakes
formed in intermontane basins (
Tertiary
terrestrial sediments of western
Giant volcanic ash
falls covered the western
Colorado Plateau a
raised but undeformed region between Basin and Range Faults
Columbia Plateau
and Snake River Plain covered by thick Basalt Flows
Active vulcanism
continues in
The Closing of the
Later
Rifting has opened
the
The
Glaciation began in
the Miocene on
Glaciation
increased in the Pliocene but expanded dramatically in the Pleistocene.
The Pleistocene
Epoch is named for the great Ice Age in
Originally four
glacial intervals were recognized: Nebraskan, Kansan, Illinoian, Wisconsinan.
It is now known
that there were dozens of glacial intervals with interglacials between them.
Effects of the Ice
Age
Cycles of
glaciation, separated by interglacials, modified the higher latitudes.
Laurentide and
Cordilleran Ice Sheets covered
Tillites cover
northern
Sea level dropped
during glacials, making the
River systems were
deranged,
Valley glaciers formed
as far south as
Pluvial lakes
formed in
Plant zones were
driven far south of their current ranges then returned north again.
Coastal Zones of
the
Glacial Erosion‑‑many
fjords and islands with hard bedrock (coast of
Glacial Deposition‑‑peninsulas
and islands made of glacial till (
Estuaries‑‑drowned
river valleys cut by glacial runoff (
Barrier islands
& lagoons‑‑stable coasts south of glacially‑effected
areas (
Possible Causes of
the Ice Age
Long‑term
global cooling may have occurred due to changes in continental positions that
altered the flow of ocean currents (oceans now connected only around the south
pole).
Individual Ice Ages
may be controlled by Milankovitch Cycles or by natural glacial cycles.
The earth's
reflectivity (albedo) may have been a positive feedback for formation of
glaciers.
Cold high pressure
centers and inundation by sea water may have been negative feedbacks.
The Holocene may be
only an interglacial stage!
The Ice Age and
Life
The Ice Age was a
cool and wet time, and plant and animal life was abundant and diverse.
Extinction of
giants at end of Pleistocene in
Climatic change and
human hunting are competing theoretical causes of the extinction.
Chapter 16 – Life of the Cenozoic
Marine
invertebrates (except ammonoids) and protozoans continue much as in the
Mesozoic.
Angiosperms
(flowering plants) dominate flora; origin of grasses and grasslands in Miocene
Insects diversify
together with angiosperms in symbiotic relationships.
Rodents, songbirds,
frogs, and bats diversify as seed and insect eaters.
Carnivorous
mammals, birds, and snakes diversify as predators of rodents, frogs, and
songbirds.
Endothermic mammals
and birds are the great success stories of the Cenozoic.
Birds
Birds originated in
the Jurassic from thecodonts or theropod dinosaurs, Archaeopteryx
Birds became the
most successful and diverse group of flyers ever, especially song birds.
Birds became successful
predators of fish, shellfish, reptiles & mammals; Penguins fly in water.
Ratites are
flightless herbivorous birds; Diatryma was a giant Eocene carnivorous
bird.
The fossil record
of birds is poor because of their thin bones and lack of teeth.
Mammals
Mammals originated
from synapsid (mammal‑like) reptiles in the Triassic Period.
Mammals remained
small & nocturnal during the Mesozoic, diversified after the dinosaurs
died.
Mammals have one
lower jaw bone, three middle ear bones, and precise tooth occlusion.
Mammal fossils are
scarce in the Mesozoic but very plentiful in the Cenozoic.
Multituberculates
were rodent‑like mammals with a huge tooth that survived into the
Oligocene.
Monotremes
(platypus & echidna) are living egg‑laying mammals of the
Eupantotheres gave
rise to marsupial (pouched) and placental mammals in the Cretaceous.
Marsupials
originated in
They thrived in
The opossum was the only marsupial
successful at invading
Australian marsupials are now
threatened by competition with invading placentals.
Placentals
originated in
Edentates (sloths, anteaters,
armadillos) made it to
Caviamorph rodents & monkeys
somehow got to
Mammals are
excellent evolutionary examples of variations on a theme.
Shrews are the most similar to the
original placental mammals of the Cretaceous.
Bats are similar to shrews except for
the elongate fingers with a flying membrane.
Rodents retain a primitive skeleton but
undergo huge variations in tooth morphology.
Primates remain primitive except for
grasping digits and an enlarged brain.
Creodonts and carnivores elongate the
feet and develop shearing teeth.
Whales loose the pelvic girdle and
develop a horizontal fluke for swimming.
Artiodactyls (camels, deer, cattle) walk
high on two toes, have high crescent‑shaped teeth
Perissodactyls (horses, rhinos) walk
high on three or one toe(s), have high‑crowned teeth.
Proboscidians (elephants, mastodons)
have pillar‑like limbs, sequential tooth eruption.
The earliest large
mammals (titanotheres, giant rhinos) went extinct; iterative evolution
The Ice Age was a
cool and wet time, and plant and animal life was abundant and diverse.
Extinction of
giants at end of Pleistocene in
Climatic change and
human hunting are competing theoretical causes of the extinction.
Chapter 17 – Human Origins
Order Primates
Suborder Prosimii
Superfamily Tupaioidea (tree
shrews)
Superfamily Lemuroidea
(lemurs)
Superfamily Lorisoidea (bush
babies)
Superfamily Tarsioidea
(tarsiers)
Suborder Anthropoidea
Superfamily Ceboidea (South
American monkeys, prehensile tail)
Superfamily Cercopithecoidea
(African Monkeys)
Superfamily Hominoidea
Family Hylobatidae
(gibbons, siamangs)
Family Pongidae
(orangutans, chimps, gorillas)
Family Hominidae
(humans)
Primate
specializations include shortened face, forward‑facing eyes, enlarged
brain, long limbs, and grasping hand with opposable thumb. Otherwise primates are unspecialized.
Early primate
adaptations are attributable to living in trees and catching insects by hand.
Earliest primate Purgatorius
from Cretaceous Hell Creek Formation of Montana
Prosimians diversified
in
Cooling
temperatures reduced their range to southern
Monkeys reached
Apes arose in the
Miocene of Africa as grasslands developed there, have 5‑cusp molars.
Early Miocene:
Dryomorphs (large canines,
Middle Miocene:
Ramapithecines (small canines, very diverse)
Late Miocene/Early
Pliocene: poor fossil record
It was long
believed that Ramapithecus was the first human and that the human/ape
split occurred at least 15 M.Y. ago. DNA
and protein similarities, however, suggested a mere 5 M.Y. ago split with man,
chimp, and gorilla being equally similar.
Discovery of more skeletal material revealed that Ramapithecus is
an orangutan. Earliest fossil humans are
middle Pliocene
Hominid species Age Brain size Height
Australopithecus afarensis 4.0‑3.0 M.Y. 380‑450 cc 1.2 m ("Lucy," fully bipedal)
Australopithecus africanus 3.0‑2.5 M.Y. 380‑450 cc 1.4 m
Australopithecus robustus 1.9‑1.6 M.Y. 380‑450 cc 1.5 m
Australopithecus boisei 2.2‑1.2 M.Y. 380‑450 cc 1.5 m
Homo habilis 2.0‑1.6 M.Y. 650‑800 cc 1.2 m
Homo erectus 1.6‑0.3 M.Y. 800‑1300 cc 1.7 m
Homo sapiens 0.1‑0.0 M.Y. 1000‑2000 cc 1.8 m
Neanderthal Man (replaced
Homo erectus, large brow ridges, elaborate burials)
Cro‑Magnon Man (replaced
Neanderthal 40,000 B.P., made cave art in
Modern Man (developed from earlier
forms, domesticated plants & animals)
All human species
appear to have evolved in
Human evolution is
a case of neoteny (retention of juvenile characters: large head, sparse hair).
Human evolution was
an Ice Age phenomenon and has been linked with the simultaneous appearance of
many "grotesque giants" among the northern mammals (Irish elk, polar
bear, etc.)
ESCI 103 ‑‑
Review sheet for final exam
Know important
contributions of the following scientists:
Louis Alvarez Lord Kelvin Adolph Seilacher Charles Walcott
Charles Darwin Charles Lyell William Smith Alfred Wegener
Know the age, plate
boundary type, and continents involved in the formation of the following
mountain ranges:
Urals
Know era of origin
and peak diversity for the following:
Prokaryotes
(bacteria and cyanobacteria [including stromatolites])
Eukaryotes (single
celled and multicellular)
Ediacara Fauna (know
significance and reason for preservation)
Burgess Shale Fauna
(know significance and reason for preservation)
Gymnosperms
Angiosperms
Fishes
(ostracoderms, placoderms, acanthodians, cartilaginous fishes, bony fishes)
Amphibians
Ancestral (large) forms
Frogs
Reptiles
Dinosaurs, pterosaurs, marine reptiles
Snakes
Birds
Archaeopteryx
Penguins
Carnivorous giants
Song birds
Mammals
Whales, bats, odd‑toed ungulates,
even‑toed ungulates, proboscidians, rodents
Humans
Know prominent fossils
(including reef formers, good index fossils, and top carnivores) of the
following time periods:
Archean
Proterozoic
Cambrian
Paleozoic
Mesozoic
Cenozoic
Have a full grasp of
the important aspects of the following topics:
Uniformitarianism,
composition of atmosphere, history of solar system and earth, relative and
absolute dating, geologic time scale, organic evolution, plate tectonics,
glaciation events