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
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
Ordovician, Silurian, Devonian: named for places and tribes in
named for the important coal deposits it bears in
Subdivided into Mississippian and
Permian: named for
Triassic: named for
the three-fold division of rocks of this age in
Jurassic: named for
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.
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.)
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)
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
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
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
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)
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
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.
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,
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
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
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
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
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
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
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.
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 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
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
Paleozoic transgression/regression cycles in
1) Sauk (Cambrian/Ordovician)
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
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 base of the
There is also a very extensive black shale layer loaded with graptolites (graptolitic shale facies).
Tectonic Events of the Ordovician (Laurentia)
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)
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
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)
Mississippian Period in Laurussia
Most caves in the
Mississippian regression (of
Pennsylvanian Period in Laurussia
Collision of Gondwanaland with Laurussia formed Appalachian/Ozark/Ouachita Mountains
and basins in the western
Permian Period in Laurussia
Uplift of Appalachian/Ozark/Ouachita Mountains continued but finally ended in late Permian
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)
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
separated from Laurasia (
Laurasia broke up from east to west, and the
by subduction at its edges to produce the modern
Triassic rifting abundant in Newark Group of eastern
Normal faults, alluvial fan redbeds (with dinosaur footprints), and basalt flows are common
The resulting salt domes of the
An island arc
collided with western
"displaced" or "accreted" or "exotic" terranes
Mountains formed by these collisions shed large volumes of sediment to the continental interior
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
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
Sandstone of the
Sediments silted up
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
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
Foraminifera (unlike Paleozoic fusulinids) undergo adaptive radiation
Rudist bivalves shaped like horn corals dominate many reefs
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
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
of sea, inland seaway gone,
Active tectonics: continents continue spreading, several north‑south collisions occur
Nevadan (Jurassic of California): mostly emplacement of granitic plutons, metamorphism
of Utah to
of Arizona to
Basin and Range
rifting (Miocene to Recent of California to
Cause may have been
plate reconfiguration on
formed in intermontane basins (
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
The Closing of the
Rifting has opened
Glaciation began in
the Miocene on
Glaciation increased in the Pliocene but expanded dramatically in 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.
Cordilleran Ice Sheets covered
Sea level dropped
during glacials, making the
River systems were
Valley glaciers formed
as far south as
Plant zones were driven far south of their current ranges then returned north again.
Coastal Zones of
fjords and islands with hard bedrock (coast of
and islands made of glacial till (
river valleys cut by glacial runoff (
& lagoons‑‑stable coasts south of glacially‑effected
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.
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 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 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.
(platypus & echidna) are living egg‑laying mammals of the
Eupantotheres gave rise to marsupial (pouched) and placental mammals in the Cretaceous.
They thrived in
The opossum was the only marsupial
successful at invading
Australian marsupials are now threatened by competition with invading placentals.
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.
giants at end of Pleistocene in
Climatic change and human hunting are competing theoretical causes of the extinction.
Chapter 17 – Human Origins
Superfamily Tupaioidea (tree shrews)
Superfamily Lemuroidea (lemurs)
Superfamily Lorisoidea (bush babies)
Superfamily Tarsioidea (tarsiers)
Superfamily Ceboidea (South American monkeys, prehensile tail)
Superfamily Cercopithecoidea (African Monkeys)
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
temperatures reduced their range to southern
Apes arose in the Miocene of Africa as grasslands developed there, have 5‑cusp molars.
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:
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)
Fishes (ostracoderms, placoderms, acanthodians, cartilaginous fishes, bony fishes)
Ancestral (large) forms
Dinosaurs, pterosaurs, marine reptiles
Whales, bats, odd‑toed ungulates, even‑toed ungulates, proboscidians, rodents
Know prominent fossils (including reef formers, good index fossils, and top carnivores) of the following time periods:
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