Histo

• Nonconformity is when beds above and below are parallel and the unconformity is identified by some evidence such as lack of diagnostic fossils in some horizons
• Historical Geology deals with the origin of the Earth and it's development through time.
• Historical Geology strives to establish an orderly chronological arrangement of the physical and biological changes and events that have occured in the geologic past
• Relative dating is placing geologic events in a sequential order as determined from their positions in the geologic record.
• Relative dating is putting rocks and events in their proper sequence of formation
• Relative dating is dating of rocks and rock units with the use of - fossils and correlation of different strata
• Relative dating is does not require numerical ages of rocks or fossils or events.
• Law of Superposition can be applied in an undisturbed succession of sedimentary rock layers, the oldest layer is at the bottom and the youngest layer is at the top
• Law Original Horizontality states that sedimentary particles settle from water under the influence of gravity. Therefore, sediment is deposited in essentially horizontal layers
• Law of Lateral Continuity states that sediment extends laterally in all directions until it thins and pinches out or terminates against the edge of the depositional basin.
• Cross-cutting Relationships states that an igneous intrusion or a fault must be younger than the rocks it intrudes or displaces
• Inclusions any rock fragments that are included in rock must be older than the rock in which they are included
• Unconformity is any significant break in time within a stratigraphic column.
• Types of Unconformities:

  • Angular Unconformity
  • Disconformity
  • Paraconformity
  • Nonconformity
• Disconformity is an unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition
• Paraconformity - is a type of disconformity - is a type of unconformity in which strata are parallel; there is little apparent erosion and the unconformity surface resembles a simple bedding plane. It is also called non – depositional unconformity or pseudoconformity.
• Nonconformity - older metamorphic or igneous rocks are overlain by younger sedimentary strata
• Angular Unconformity - tilted or folded sedimentary rocks that are overlain by younger, more flat-lying strata.
• Absolute dating provides specific dates for rock units or events expressed in years through radiometric dating.
• Radioactive decay is the process whereby an unstable atomic nucleus is spontaneously transformed into an atomic nucleus of a different element
• Three Types of Radioactive Decay:

  • Alpha decay
  • Beta decay
  • Electron capture
• Half-life is the time it takes for one-half of the atoms of the original unstable parent element to decay to atoms of a new, stable daughter element.
• Carbon-14 dating is based on the ratio of carbon 14 to carbon 12 and is generally used to date once-living material.
• Tree-ring dating - The age of a tree can be determined by counting the growth rings in the lower part of the trunk. Each ring represents one year’s growth, and the pattern of wide and narrow rings can be compared among trees to establish the exact year in which the rings were formed.
• Cross-dating- the procedure of matching ring patterns from numerous trees and wood fragments in a given area.
• Precambrian – constitute about 88% of all geologic time.
• Earth’s early atmosphere evolved from a carbon dioxide-rich one to one with free oxygen and an ozone layer, organisms appeared as much as 3.5 billion years ago, and surface waters began to accumulate
• Acasta Gneiss in Canada- Earth’s oldest known body of rocks; is about 4.0 billion years old.
• Detrital sedimentary rocks in Australia with zircons (ZrSiO4) 4.4 billion years old.
• FIVE MAJOR EXTINCTION:

  • Ordovician Mass Extinction
  • Late Devonian Mass Extinction
  • Permian – Triassic Mass Extinction
  • Triassic-Jurassic Mass Extinction
  • Cretaceous - Tertiary Mass Extinction
• Chicxulub crater 2nd largest impact crater found in Yucatan Peninsula in Mexico
• Hadean Eon

  • (4,600 – 4,000Ma)
  • Formation of the Earth and its Moon
  • Oldest known mineral ZIRCON (4.4 Ga)
  • Oldest known rock Acasta Gneiss (4.03 Ga)
  • Late Heavy Bombardment
• Archean Eon

  • (4,000 – 2,500Ma)
  • First known oxygen-producing bacteria and first stromatolites
  • Oldest cratons on earth such as the Canadian Shield and Pilbara Craton
  • First supercontinent Vaalbara
• Proterozoic Eon

  • (2,500 – 541 Ma)
  • Oxygen Catastrophe/Great Oxygenation Event
  • Bushveld Igneous Complex
  • Formation of supercontinent Rodinia
  • Formation of Snowball Earth during Huronian Glaciation and Cryogenian Glaciation
  • Banded Iron Formations
• Cambrian Period

  • (541 – 485 Ma)
  • Cambrian Explosion/Diversification of Life
  • Age of Trilobites
  • Cambria-Latin name of Wales
  • Formation of Supercontinent Pannotia
• Ordovician Mass Extinction

  • (450 Ma to 440 Ma)
  • 2nd largest mass extinction
  • 85% casualty on all marine and land species
  • 60% marine invertebrates died
• Late Devonian Mass Extinction

  • (408 Ma to 360 Ma)
  • 5th largest mass extinction
  • 80% of all living species; primarily the marine community have been wiped out
  • Extinction of cooksonia, tribulate corals, stromatoporoids, ostracoderms, and placoderms.
• Permian – Triassic Mass Extinction

  • “The Great Dying”
  • (about 252 Ma)
  • Largest mass extinction
  • Elimination of over 95% of marine and terrestrial species
  • Extinction of trilobites, eurypterids, acanthodians, blastoids
• Triassic-Jurassic Mass Extinction

  • (201 Ma)
  • 53% marine genera observed went extinct
  • 80% calculated marine species went extinct
  • Extinction of conodonts
• Cretaceous - Tertiary Mass Extinction

  • 76% of all species lost
  • Extinction of dinosaurs and ammonites
  • Meteorite impact is the possible cause