07_fossils_num_dating_09_post

07_fossils_num_dating_09_post - 07 Geologic Time 2 Fossils...

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cture 07: cture 07: 1 07: Geologic Time 2: Fossils, Absolute Dating, Age of Earth http://www.nrc.gov/
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cture 07: cture 07: 2 Why this is important •  •  The changing fossil record allows geologists to determine the  relative ages of rocks and to demonstrate the time-equivalence  of rock units from around the world. Fig. E.2b
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cture 07: cture 07: 3 Why this is important •  •  The fossil record, the length of geologic time, the  gradual nature of many geological processes, and  Charles Darwin’s own geological investigations  were instrumental in the development of his theory  of natural selection. Ordovician (~475 million  brachiopod. Photo: R.M.  Busch Devonian (~385 million  brachiopod. Photo: R.M.  Busch Cambrian (530 million  years ago) trilobites.  Photo: C. Clark
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cture 07: cture 07: 4 Why this is important •  •  The decay of radioactive isotopes provides the ticking clock for  dating geologic events, including the age of the Earth and the  solar system.
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cture 07: cture 07: 5 Basics: Fossils Fossil : the remnant or trace of an ancient living organism that has been  preserved in rock or sediment  Fig. E.4
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cture 07: cture 07: 6 Basics: Types of fossils 1. Frozen or dried body fossils Frozen wooly  Frozen wooly  mammoth mammoth news.bbc.co.uk
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cture 07: cture 07: 7 Basics: Types of fossils 2. Body fossils preserved in amber  (hardened tree sap) 3. Preserved hard parts bones teeth shells Fig. E.5b Fig. E.5c
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cture 07: cture 07: 8 Basics: Types of fossils 4. Replaced hard parts as a result of  permineralization  (process by which  minerals precipitate in porous material like wood (forming  petrified wood or bone from groundwater solutions that have seeped into the pores. Fig. E.5d
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cture 07: cture 07: 9 Basics: Types of fossils 5.  Molds and casts of body parts : if a shell, for example, dissolves out of the  enclosing rock, the cavity is a  mold ; if the mold later fills in with material,  it becomes a  cast . cast cast mold mold mold mold cast cast
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cture 07: cture 07: 10 10 Basics: Types of fossils 6.  Carbonized impressions of bodies:  feathers, insects, leaves, etc., leave an  imprint when pressed between layers of sediment; although most of the  original organic material is later removed, insoluble carbon remains as a  thin film.
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cture 07: cture 07: 11 11 Basics: Factors favoring fossilization 1. Death in an oxygen-poor environment prevents organic decay 2. Rapid burial: organism is enclosed in sediment before it can decay, be eaten, or disturbed by other processes. 3. Presence of hard parts (bones, shells, etc.).
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This note was uploaded on 09/25/2011 for the course GEOLOGY 100 taught by Professor Lepre during the Fall '11 term at Rutgers.

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07_fossils_num_dating_09_post - 07 Geologic Time 2 Fossils...

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