EESA06 - Lec 8.doc

7 views7 pages
22 Apr 2012
School
Course
Professor
EESA06 Lecture 8
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
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in
-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
-establish time of first and last appearance of each species geologic range
Note: certain species only live in certain time periods
What kinds of fossils are most useful for stratigraphic work?
-short-lived, widespread
-assemblages (groups) of species
-e.g. ammonites
Unlock document

This preview shows pages 1-2 of the document.
Unlock all 7 pages and 3 million more documents.

Already have an account? Log in

Get OneClass Notes+

Unlimited access to class notes and textbook notes.

YearlyBest Value
75% OFF
$8 USD/m
Monthly
$30 USD/m
You will be charged $96 USD upfront and auto renewed at the end of each cycle. You may cancel anytime under Payment Settings. For more information, see our Terms and Privacy.
Payments are encrypted using 256-bit SSL. Powered by Stripe.