EESA06H3 Lecture Notes - Proterozoic, Stromatolite, Magnetite

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Published on 17 Jun 2012
School
UTSC
Department
Environmental Science
Course
EESA06H3
Professor
EESA06 Lecture March 14, 2009
How are fossils formed?
-shells buried and preserved unaltered (<100 million years)
-cavities filled with silica, calcium carbonate, iron a process called mineralization
Methods: Fossilization
-freezing
-drying
-asphalt
-amber
-carbonization
-permineralization (most common)
-peat bogs
-paraffin
-volcanic ash
Permineralization
-die in or near water
-soft parts consumed by bacteria
-sedimentation (fine grained = more detail; chemical makeup of rock = colour)
-more sed’s pile on = pressure = rock
-mineral rich water = changes to the shell
-uplift
-erosion
Ammolite an organic gemstone
-ammonite fossils
-iridescent aragonite with trace elements (Fe, Mn, Al, Ba)
Trace fossils
-preserved tracks, trails, burrows, borings
-ichnology study of trace fossils
-bioturbation process of disturbing sediment
Fossils as clues to ancient environments
-palaeoecology study of ancient organisms and their environments
-clues from: fossil types, assemblages, fossil morphology, trace fossils
Crinoid aka. “sea lily”, loose like a mop head on a tall stem made up of rings & plates, found in the
shallow seas.
Fossils and stratigraphy
-how do we use fossils in stratigraphy?
-to establish relative age of rock units, correlate units (rocks that represent the same time period in
different locations)
-what information do we need to do this?
-relative age of rock units
-fossil species present in each unit
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Document Summary

Shells buried and preserved unaltered (<100 million years) Cavities filled with silica, calcium carbonate, iron a process called mineralization. Sedimentation (fine grained = more detail; chemical makeup of rock = colour) More sed"s pile on = pressure = rock. Mineral rich water = changes to the shell. Iridescent aragonite with trace elements (fe, mn, al, ba) Palaeoecology study of ancient organisms and their environments. Clues from: fossil types, assemblages, fossil morphology, trace fossils. Sea lily , loose like a mop head on a tall stem made up of rings & plates, found in the shallow seas. To establish relative age of rock units, correlate units (rocks that represent the same time period in different locations) Establish time of first and last appearance of each species geologic range. Note: certain species only live in certain time periods. The fossils of short-lived species are more useful than fossils that lived over long periods of time.

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