Lecture 14+15 (Fossils) Flashcards
(27 cards)
How old are fossils?
Over 11 000 years
How old are subfossils?
Less than 11 000 years
What is the most important condition for something to become a fossil?
It must be buried quickly
Which areas have the highest rate of fossilization?
Areas with a high rate of accumulation (prevents organic matter decay)
What is analytical connection?
The body of the organism is completely in tact
What are oxic conditions?
Conditions of the environment have oxygen dissolved into them. Benthic organisms exist and destroy dead organisms
What are anoxic conditions?
No oxygen. Benthic organisms do not exist to destroy a dead organism, therefor better chance to fossilize!
What are usually the first things to vanish during fossilization?
Pigments
What are the 3 different kinds of fossils?
1) Body Fossils
2) Trace Fossils (ichnofossils)
3) Chemical Fossils (Biomarkers)
What are body fossils?
Direct, or altered remains of ancient organisms (teeth, shells etc)
What are trace fossils?
Evidence of the activity of ancient organisms
What are chemical fossils?
Organic compounds produced by various organisms that exist in the strata
What are the 6 types of fossil preservation?
1) Recrystallization
2) Moldic Preservation
3) Perminerallization
4) Carbonization
5) Congealment
6) Fossilization in Amber
What is recrystallization?
Conversion of the original minerals into different minerals.
What is the most common transformation during the process of recrystallization?
Aragonite (grey, translucent)—> Calcite (white, opaque)
What is moldic preservation?
When the original test or shell is dissolved. Shape of the former organism is given by lithified sediment infill.
What is the mold and what is the cast in moldic preservation?
Mold: Preserves exterior
Cast: Preserves interior
What is moldic preservation replacement?
The empty space created by moldic preservation has fluids which continue to circulate and precipitate mineral. Can get a well preserved fossil with weird physical properties (Mass of minerals without order)
What is the most frequent case of replacement?
Pyritization-gold!!
What is permineralization?
Occurs in certain organisms with hard, porous body parts (ex: vertebrate bone). Soft tissue decays, then fluid fills the bone pores with inorganic material like opal or chalcedony
What is carbonization?
Kind of fossilization wherein the fossil is buried deep within the Earth’s crust and all the organic material is expelled, except carbon.
What is the most frequent organism fossilization?
Carbonization
What are 2 of the more rare forms of fossilization and what makes them unique?
Congealment and Fossilization in Amber- able to preserve the bodies 3D structure
What is congealment?
Occurs at high latitudes where low temp is kept constant over long periods. Soil at the surface is frozen and forms permafrost. Frozen swamps form. Organisms are trapped and killed by swamp.
