2.1.1 Body Fossils
18.104.22.168 Molds and Casts
2.2. Trace fossils
2.3. The meaning of fossils
2.4. The use of fossils
2.4.2. Plate tectonics
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
2.6. Unaltered soft parts
2.6.1. Protection from oxygen
2.7. Trace fossils
3. THE GEOLOGIC
TIME SCALE (Relative Time) Take tour:
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
six orders of Chronostratigraphic units, from larger to smaller:
|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
(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.
22.214.171.124. 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
126.96.36.199. 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.
188.8.131.52. 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.
184.108.40.206. Silurian System: 438 to 408 mya. First terrestrial plants and
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.
220.127.116.11. 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.
18.104.22.168. Carboniferous: Wide-spread coal swamps, foraminiferans, corals, bryozoans, brachiopods, blastoids, seed ferns, lycopsids, and other plants. Amphibians become more common. 360 to 280 mya
22.214.171.124.1. Mississippian Sub-System: 360 to 325 mya: Sharks and amphibians
abundant. Large and numerous scale trees and seed ferns.
First winged insects.
126.96.36.199.2. Pennsylvanian Sub-System: 325 to 280 mya. Great coal forests, conifers. First reptiles. First reptiles. Many ferns. The first mayflies and cockroaches appear.
188.8.131.52. 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.
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.
184.108.40.206. 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.
220.127.116.11. 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
18.104.22.168. Paleogene Subsystem: 65-24 mya
22.214.171.124.1. Paleocene Series: 65-54 mya. First large mammals and primitive primates, plesiadapiforms. First placental mammals.
126.96.36.199.2. Eocene Series: 54-38 mya. Mammals abound. Rodents appear. Primitive whales appear. Many modern types of mammals
188.8.131.52.3. 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.
184.108.40.206. Neogene Subsystem: 24-1.8 mya.
220.127.116.11.1. 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.
18.104.22.168.2. 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
22.214.171.124. 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.
126.96.36.199. Holocene Series: 11,000 ya to today. Modern man. Human civilization
5.2.Fundamental Principles in Geology
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.
(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
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.