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Lecture

exntinction.docx

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Department
Geology
Course
GEOL 2207
Professor
J.Finnis
Semester
Summer

Description
Extinctions 1. Concept of a biosphere • Understand the concept of a biosphere and Earth System Science and that the biosphere has evolved over time  Thin layer of life on the Earth‟s surface, composed of Ecosystems  Earth System Science: biosphere, hydrosphere, lithosphere, atmosphere 2. Principles of Stratigraphy (study of the manner in which strata are laid down) • Distinguish between the oldest and youngest portion of a geological section using principles of superposition, original horizontality and cross cutting relationships  Study of the layers of rock (stratigraphy) o Strata: layers of sedimentary rocks or lava flows)  Superposition: in layered strata (sedimentary rocks or lava flows)  What‟s on top is the youngest  Original horizontality: if it is tilted or folded, it was originally flat  Cross cutting relationships: unconformity = a period of non deposition or active erosion  What is oldest? Sediments or dike? Dikes are always younger than surrounding rock layers (always younger than the object that it is intruding) 3. Biostratigraphy (correlation of rocks using fossils) • Describe the concept of faunal succession and the use of fossils in correlation and in the subdivision of Earth history  Nicholas Steno  Strata of like age can be dated and correlated by the fossils they contain  Only works because species have changed through time; evolution  Amount of time a species exist: a fossil range • Recognize the qualities that make fossils useful in biostratigraphy  Short range = higher resolution  Common  Lived in environments where fossilization is likely to occur  Present in many different environments  Mesozoic = ammonites  Strata of like age can be dated and correlated by the fossils they contain, only works because species have changed through time o Fossils succeed each other vertically in a specific, reliable order that can be identified over wide horizontal distances o Faunal succession  Fossil range = the amount of time a species exists (from evolution to extinction)  Extinction events: end of cretaceous, late Triassic, Permo/Triassic, late Devonian, late Ordovician 4. Historical Figures • Identify important historical figures in the development of stratigraphy and biostratigraphy  Nicholas Steno (Late 1600s): principles of stratigraphy  James Hutton (Late 1700s): cross cutting relationships  William Smith (1799): principle of faunal succession  Geologists in the late 170ss started to get the impression that the earth was very old  James Usher (1581-1665): adds up all dates in bible, earth is 6000 years old  George Cuvier (1800s): mammoth remains in Europe, concludes mammoths were once living species that have become extinct  Geologists conclude: earth is ancient, earth has changed a lot through time 5. The concept of deep time • Appreciate the scale of changes that can occur over geological time scales  Geological time scale: dividing the 4.6 billion years of Earth‟s history into time periods  Many of these divisions based
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