1. PALEONTOLOGY
1.1 The beginnings of paleontology
2. FOSSILIZATION
2.1. Fossils
2.1.1 Body Fossils
2.1.1.1 Molds and Casts
2.2. Trace fossils
2.3. The meaning of fossils
2.4. The use of fossils
2.4.1 Evolution
2.4.2. Plate tectonics
2.4.3. Paleogeography-paleoenvironments
2.4.4. Dating rocks
2.5. Types of fossil preservation
2.5.1. Original preservation of hard parts
2.5.2. Altered hard parts
2.5.3. Permineralization
2.5.4. Carbonization
2.5.4. Recrystallization
2.5.6. Replacement
2.6. Unaltered soft parts
2.6.1. Protection from oxygen
2.6.2. Freezing
2.6.2 Dehydration
2.7. Trace fossils
2.7.1. Tracks
2.7.2. Trails
2.7.3. Burrows
2.7.4. Borings
3. THE GEOLOGIC
TIME SCALE (Relative Time) Take tour:
Visit
the Web Geological Time Machine at UCMP-Berkeley University
3.1. Subdivision of the geologic time.
It is the subdivision of the geologic time (time based on the evolutionary
trends of fossils) into units of different duration. The purpose of
subdividing the time from the origin of Earth to present, that is, from
4.6 b.y.. (billion years) to present, is to recognize smaller time intervals
which define episode of the history of evolution of life on Earth. These
divisions are known as Chronostratigraphic units or Relative Time
We recognize
six orders of Chronostratigraphic units, from larger to smaller:
Units based
on Evolution
(Relative
time) |
Units based
on numerical assignation (Absolute time) |
| 1st Order:
Eonothem |
Eon |
| 2nd Order:
Erathem |
Era |
| 3rd Order:
System |
Period |
| 4th Order:
Series |
Epoch |
| 5th Order:
Stage |
Age |
| 6th Order:
Chronozone |
Chron |
These units
were recognized throughout the work of paleontologist working in Europe
for the last three centuries.
In recent years,
after the recognition of radioactivity, and radioactive decay, geologist
recognized that isotopes could be used to numerically dates, the so-called
"absolute time units" the subdivision based on the history of evolution
of life on Earth, resulting in the establishment of twin or parallel set
of units known as Geochronologic units, these geochronologic units are
also referred to as ‘absolute ages’ because they are expressed in numbers,
that is, they are the numerical values assigned to the former Chronstratigraphic
units.
3.2. Definition of the units based on the evolution of life on Earth:
3.2.1. Eonothem: "Eon" also means any span of one billion years. The largest
division of geologic time, including several eras and lasting for
hundreds of millions or billions of years. Originally there were only two
eons, the Precambrian and the Phanerozoic, because of the long span included
in Precambrian, now we recognize two separate eonothems, the Archean
(previously Archeozoic) and the Proterozoic.
3.2.2. Erathem: A geologic division that includes several periods, but
smaller than an eon. Generally lasts for many tens or hundreds of millions
of years, and often characterized by distinct life forms - e.g. the Cenozoic
is the "age of mammals". Commonly recognized Erathems are the Paleozoic
(ancient life), Mesozoic (middle life), and Cenozoic (new life). Precambrian
divisions such as the Proterozoic and the Archean were conventionally eras
but are now referred to as eons. New Precambrian eras include the Sinian,
the Riphean, the Huronian, etc.
3.2.3. System: Is the most commonly used unit of geologic time, representing
one subdivision of an era. Eras may have from two to six or seven systems
each. Each system generally lasts for some thirty to eighty million years
(the only exception, the mere 1.6 million year long Quaternary, is actually
a hold-over from the 19th century formulation, as its numeric name indicates).
3.2.4. Series: A subdivision of a geologic system, a Series usually corresponds
to subdivision of the system into a lower, middle and upper part, although
the Jurassic System contains Series of special designation such as the
Liasic.
3.2.5. Stage: A subdivision of a geologic Series, usually lasting between
five and ten million years, although there are also shorter and longer
stages. The Stage is the fundamental concept of time in geology, which
includes the interval of time represented by the vertical distribution
of a particular fossil assemblage at a given geographic locality.
3.2.6. Chron: The smallest subdivision of geologic time lasting only a
million years or even less. Usually is defined by the fossil content of
a short interval of one species or an assemblage of species.
NOTE: You are
responsible for:
(1) Retaining
in the right order (from higher to lower) all the units of the geologic
time scale (see your text).
(2) Identifying
the origin of each term o name given to the major units of the geologic
time scale (System/Perioid and up).
(3) Identifying
the original geographic location from where the major geologic units were
defined.
4. MAJOR INTERVALS
OF TIME: CHRONOSTRATIGRAPHIC UNITS
4.1. Precambrian: Fossils extremely rare, consisting of primitive aquatic
plants. Evidence of glaciations. Oldest dated algae, over 2,600 my. Oldest
dated meteorites: 4,500 my.
4.1.1. Hadean Eonothem: 4.6 to 3.9 billion years ago. "Rockless Eon" -
The solidifying of the Earth's continental and oceanic crusts.
4.1.2. Archeozoic Eonothem (Archean): 3.9 to 2.5 billion years
ago. "Ancient Life" - The first life forms evolve - one celled organisms.
Blue-green algae, archaeans, and bacteria appear in the sea. This begins
to free oxygen into the atmosphere.
4.1.3. Proterozoic Eonothem: 2.5 billion years ago to 540 mya. First multicellular
life: colonial algae and soft-bodied invertebrates appear. Oxygen build-up
in the Mid-Proterozoic. A mass extinction occurred. The continents had
merged into a single supercontinent called Rodinia.
4.1.3.1. Vendian/Ediacaran System: Vendian biota (Ediacaran fauna) multi-celled
animals appear, including sponges. A mass extinction occurred.
4.2. Phanerozoic Eonothem: "Visible Life" Organisms with skeletons or hard
shells. 540 mya through today. 600 to 540 Million Years Ago
4.2.1 Paleozoic Erathem: "Ancient Life", 540 to 248 mya
4.2.1.1. Cambrian System: First abundant record of marine life "The Age
of Trilobites" 540 to 500 mya
"Age of Trilobites"
-The Cambrian Explosion of life occurs; all existent phyla develop. Many
marine invertebrates (marine animals with mineralized shells: shell-fish,
echinoderms, trilobites, brachiopods, mollusks, primitive graptolites).
First vertebrates. Earliest primitive fish. Mild climate. The supercontinent
Rodinia began to break into smaller continents (no correspondence to modern-day
land masses). Mass extinction of trilobites and nautiloids at end of Cambrian
(50% of all animal families went extinct), probably due to glaciation.
4.2.1.2. Ordovician System: 505 to 438 mya. First fishes, invertebrates
dominate. Primitive plants appear on land. First corals. Primitive fishes,
seaweed and fungi. Graptolites, bryozoans, gastropods, bivalves, and echinoids.
High sea levels at first, global cooling and glaciation, and much volcanism.
North America under shallow seas. Ends in huge extinction, due to glaciation.
4.2.1.3. Silurian System: 438 to 408 mya. First terrestrial plants and
animals.
The first
jawed fishes and uniramians (like insects, centipedes and millipedes) appeared
during the Silurian (over 400 million years ago). First vascular plants
(plants with water-conducting tissue as compared with non-vascular plants
like mosses) appear on land (Cooksonia is the first known). High seas worldwide.
Brachiopods, crinoids, corals.
4.2.1.4. Devonian System: "The Age of Fishes" 408 to 360 mya. First amphibians,
ammonites, fishes abundant.
Fish and land
plants become abundant and diverse. First tetrapods appear toward the end
of the period. First amphibians appear. First sharks, bony fish, and ammonoids.
Many coral reefs, brachiopods, crinoids. New insects, like springtails,
appeared. Mass extinction (345 mya) wiped out 30% of all animal families)
probably due to glaciation or meteorite impact.
4.2.1.5. Carboniferous: Wide-spread coal swamps, foraminiferans, corals,
bryozoans, brachiopods, blastoids, seed ferns, lycopsids, and other plants.
Amphibians become more common. 360 to 280 mya
4.2.1.5.1. Mississippian Sub-System: 360 to 325 mya: Sharks and amphibians
abundant. Large and numerous scale trees and seed ferns.
First
winged insects.
4.2.1.5.2. Pennsylvanian Sub-System: 325 to 280 mya. Great coal forests,
conifers. First reptiles. First reptiles. Many ferns. The first mayflies
and cockroaches appear.
4.2.1.6. Permian System: "The Age of Amphibians" 280 to 248 mya. Mass extinction,
most kinds of marine animals, including trilobites. Southern glaciation.
"The Age of Amphibians" - Amphibians and reptiles dominant. Gymnosperms
dominant plant life. The continents merge into a single super-continent,
Pangaea. Phytoplankton and plants oxygenate the Earth's atmosphere to close
to modern levels. The first stoneflies, true bugs, beetles, and caddisflies,
The Permian ended with largest mass extinction. Trilobites go extinct,
as do 50% of all animal families, 95% of all marine species, and many trees,
perhaps caused by glaciation or volcanism.
4.3. Mesozoic -Era Middle Life- "The Age of Reptiles": 248 to 65 mya
4.3.1. Triassic System: First dinosaurs, abundant cycads and conifers.
Triassic Period
248 to 208
mya. The first dinosaurs, mammals, and crocodyloformes appear. Mollusks
are the dominant invertebrate. Many reptiles, for example, turtles, i chthyosaurs.
True flies appear. Triassic period ends with a minor extinction 213 mya
(35% of all animal families die out, including labyrinthodont amphibians,
conodonts, and all marine reptiles except ichthyosaurs). This allowed the
dinosaurs to expand into many niches.
4.3.2. Jurassic System: First birds, first mammals, dinosaurs and ammonites
abundant. Jurassic Period: 208 to 146 mya. Many dinosaurs, including the
giant Sauropods. The first birds appear (Archaeopteryx). The first flowering
plants evolve. Many ferns, cycads, gingkos, rushes, conifers, ammonites,
and pterosaurs. Minor extinctions at 190 and 160 mya.
4.3.3. Cretaceous System: 146 to 65 mya: First flowering plants, climax
of dinosaurs and ammonites, K/T extinction.
4.3.3.1. Lower Cretaceous Series: 146-98 mya. The heyday of the dinosaurs.
The first crocodilians, and feathered dinosaurs appear. The earliest-known
butterflies appear (about 130 million years ago) as well as the earliest-known
snakes, ants, and bees. Minor extinctions at 144 and 120 mya.
4.3.3.2. Upper Cretaceous Series: 98-65 mya. High tectonic and volcanic
activity. Primitive marsupials develop. Continents have a modern-day look.
Minor extinction 82 mya. Ended with large extinction (the K-T extinction)
of dinosaurs, pterosaurs, ammonites, about 50 percent of marine invertebrate
species, etc., probably caused by asteroid impact or volcanism.
4.4. Cenozoic Era -New Life- "The Age of Mammals": 65 mya through today
4.4.1.Tertiary System: 65 to 1.8 mya
4.4.1.1. Paleogene Subsystem: 65-24 mya
4.4.1.1.1. Paleocene Series: 65-54 mya. First large mammals and primitive
primates, plesiadapiforms. First placental mammals.
4.4.1.1.2. Eocene Series: 54-38 mya. Mammals abound. Rodents appear. Primitive
whales appear. Many modern types of mammals
4.4.1.1.3. Oligocene Series: 38-24 mya. Starts with a minor extinction
(36 mya). Many new mammals (pigs, deer, cats, rhinos, tapirs appear). Grasses
common. Large running mammals.
4.4.1.2. Neogene Subsystem: 24-1.8 mya.
4.4.1.2.1. Miocene Series: 24-5 mya. More mammals, including the horses,
dogs and bears. Modern birds. South American monkeys, apes in southern
Europe, Ramapithecus. First abundant grazing mammals.
4.4.1.2.2. Pliocene Series: 5-1.8 mya. First hominids (australopithecines).
Modern forms of whales. Megalodon swam the seas. Large carnivores.
4.4.2. Quaternary System: "The Age of Man": 1.8 mya to today
4.4.2.1. Pleistocene Series: 1.8-.011 mya. The Last Ice Age. Early
man, northern glaciation. The first humans (Homo sapiens) evolve. Mammoths,
mastodons, saber-toothed cats, giant ground sloths, and other Pleistocene
megafauna. A mass extinction of large mammals and many birds happened about
10,000 years ago, probably caused by the end of the last ice age.
4.4.2.2. Holocene Series: 11,000 ya to today. Modern man. Human civilization
5. HOW DO
WE TELL TIME?
5.1. Relative time (ages). We are now able to tell geologic time thanks
to the scientific contribution of great investigators, among them, Georges
Cuvier, Nicholas Steno, William Smith, and James Hutton. They provided
a set of principles that are the basis for telling time in fossil-bearing
rock and laid down the concepts of Stratigraphy.
5.2.Fundamental Principles in Geology
5.2.1. Catastrophism-Creationism
Georges
Cuvier (1769-1832). Georges Cuvier's important study Recherches sur les
ossemens fossiles des quadrupèdes [Research on the Fossil Bones
of Quadrupeds] was first published in France in 1812. The Discours sur
les révolutions du globe [Discourse on the Revolutionary Upheavals
on the Surface of the Earth] was the introduction to the larger work.
5.2.2.
Nicholas Steno (1638-1686). Steno’s contributions to geology was
a set of principles still in use, these are: (1) the Principle of Original
horizontality; (2) the Principle of Superposition; and (3) the Principle
of Lateral continuity.
(1)
the
Principle
of
Original
horizontality.
The
Principle
of
Original
Horizontality
was
proposed
by
the
Danish
geological
pioneer
Nicholas
Steno
(1638-1686).
This
principle
states
that
layers
of
sediment
are
originally
deposited
horizontally
under
the
action
of
gravity.
The
principle
is
important
to
the
analysis
of
folded
and
tilted
strata.
(2) the Principle of Superposition.The
law of superposition (or the
principle of superposition) is a key
axiom based on observations of natural
history that is a foundational principle
of sedimentary
stratigraphy and so of other geology
dependent natural sciences:
Sedimentary
layers are deposited in a time sequence,
with the oldest on the bottom and the
youngest on the top.
(3) the Principle of Lateral continuity.
all sedimentary rocks are originally
deposited horizontally. Sedimentary
rocks that are no longer horizontal
have been tilted from their original
position.
"Strata either perpendicular to the
horizon or inclined to the horizon
were at one time parallel to the
horizon." Steno, 1669
5.2.3.
William Smith (1769 –1839). Smith’s contribution was the Principle
of Faunal and floral succession
5.2.4.
James Hutton (1726-1797).
His major contribution
was the book “the history of the Earth”. He added the Principle of Uniformitarianism:
The present is the key to the past.
Uniformitarianism is
one of the most important unifying concepts in the geosciences.
This concept developed in the late 1700s, suggests that catastrophic processes
were not responsible for the landforms that existed on
the Earth's surface. This idea was diametrically opposed
to the ideas of that time period which were based on
a biblical interpretation of the history of the Earth.
Instead, the theory of uniformitarianism suggested
that the landscape developed over long periods of time
through a variety of slow geologic and geomorphic processes.
The term uniformitarianism was
first used in 1832 by William
Whewell, a University of Cambridge scholar,
to present an alternative explanation for the origin
of the Earth. The prevailing view at that time was that
the Earth was created through supernatural means and
had been affected by a series of catastrophic events
such as the biblical Flood. This theory is called catastrophism.
The ideas behind uniformitarianism originated
with the work of Scottish geologist James
Hutton. In 1785, Hutton presented at the meetings
of the Royal Society of Edinburgh that the Earth had
a long history and that this history could be interpreted
in terms of processes currently observed. For example,
he suggested that deep soil profiles were formed by the
weathering of bedrock over thousands of years. He also
suggested that supernatural theories were not needed
to explain the geologic history of the Earth. The theory of uniformitarianism was
also important in shaping the development of ideas in
other disciplines. The work of Charles
Darwin and Alfred
Wallace on the origin of the Earth's species
extended the ideas of uniformitarianism into
the biological sciences. The theory of evolution is
based on the principle that the diversity seen in the
Earth's species can be explained by the uniform modification
of genetic traits over long periods of time.
Uniformitarianism suggests that the
continuing uniformity of existing processes should be
used as the framework for understanding the geomorphic
and geologic history of the Earth. Today, most theories
of landscape evolution use the concept of uniformitarianism
to describe how the various landforms of the Earth came
to be.
Sir
Charles Lyell, 1797-1875.
Hutton's ideas did not gain major support
of the scientific community until the work of Sir
Charles Lyell. In the three volume publication
Principles of Geology (1830-1833), Lyell presented
a variety of geologic evidence from England, France,
Italy, and Spain to prove Hutton's ideas correct and
to reject the theory of catastrophism.
5.3. Absolute
time (ages)
5.3.1.Radioactivity