Preservation of Fossil Remains (L11) Flashcards
What is the field of taphonomy?
can be defined most simply as the study of post-mortem processes
What processes are included in Taphonomy?
the causes of death itself,
and
processes of decay and disintegration
What does it mean that Fossilization tends to be the exception rather than the rule?
it means that for remains of living things to become a fossil, it requires exceptional conditions in order to happen
Two ways that detruction of remains in death?
large scavengers take the soft tissues and scatter the hard parts
insects come and lay their eggs on hte dead remain (larvae makes tissue decompose)
What do microbes do in the cellular and molecular level?
they break down organic matter further
What is dissolution?
The chemical breakdown of hardparts by dissolving of their minerals (a form of chemical weathering)
What is Abrasion?
meaning erosion of hard tissues due to “sandblasting” effects of suspended sediment particles
What is the general rule of survival of fossil records?
Hardparts have a greater chance of survival in the fossil record than do soft tissues
Why is that hardparts have a greater chance of survival?
because they are more robust and stable and are more resistant to destruction overall
But why are hardparts rarely preserved fully intact?
because soft tissue decay removes connective tissues, like ligaments, and etc that held the hard parts together
Disarticulation?
Dissociation and scattering of hard parts
Fragmentation?
meaning the actual breakage of these dissociated elements
Why are action of waves and currents on dead remains viewed in a negative way? What are some special cases where its not?
because they usually lead to their transportation from where the animal actually lived, and also tend to be destructive to the remains.
but sometimes, the orientations of fossil remains disturbed after death can indicate aspects of the environment in which they were deposited
What are 3 factors that favour the preservation of remains and why?
an absence of oxygen (keeps scavengers away)
and rapid burial (discourages savenging)
Chemical reactions in porewaters of the sediment promote percipitation of more minerals in/on remiains fater burial
What are the 2 mienral forms that calcium carbonate occur in?
aragonite - chemically unstable at and near Earth’s surface
calcite - tends to be more chemically stable
what is another common skeletal material?
silica - in the form of opal
What is the form of calcium phosphate in skeletal materian and in which parts is it found?
Apatite occurs in vertebrate bones and teeth
What kind of preservation happens of skeletal remains composed of stable minerals?
it gets preserved without significant change in chemical makeup or internal structure
What are 2 examples of stable minerals
Calcite and Silicia
Why are hardparts more prone to be preserved close to their original state?
b/c they are lessp prone to breakdown
What is aragonite?
the other mineral form of calcium carbonate compoosed of sheets of aragonite crystals and less chemically stable than calcite
In what type of rocks are most if not all fossils preserved in?
sediment
What is permafrost?
how frozen remains of extinct organisms are found in (extremely rare)
How do permafrosts happen?
mammoths or animals could be walking on the surface of a glacier, fall into the water which freezes
What is another medium where you can find fossils and what is it specifically?
Amber
is a fossil tree resin, with antibacterial properties that stop remains from bacterial decay
What are the 4 main types of alteration processes
Recrystalization
Petrifaction
Replacement
Carbonization
Recrystalization
under conditions of higher temp and pressures than at the surface, the crystal of a given mineral tend to increase in size, which leads to the LOSS OF FINE DETAILS IN A FOSSIL
Petrifaction (Permineralization)
occurs when mineral matter fills pores of the remains of an organism
occurs in bones b/c they are very porous.
What is hte mineral that fills the pores (Petrifaction) of dino bones
Chalcedony (form of silica)
Replacement
When organic matter or minerals of an organism can be replaced by diff mineral substances
occurs at microscopic level
In “replacement” what are calcite shells commonly replaced with?
silica, pyrite, or apatite
Carbonization
when carbon rich remains have their elements released with carbon left behind through low-grade cooking whcih results from light heat of burial
As a result, the remains are enriched in carbon
Carbonization
when carbon-rich remains such as plant tissue have their elements released through low-grade cooking that results from light heat of burial
only carbon is left beheind making the remains enriched in carbon
What is an example of Carbonization?
Coal
External Mould
when a hollow object like clam is buried, with its valves held together, sediment surrounds the object and produces this
Internal Mould
is when sediment gets inside the clam and fills the empty space and when the shell dissolves, we are left with an internal mould
How are Casts formed?
when an external mould is infilled by sediment or precipiated minerals
appears as a REPLICA of the original buried object
How are casts produced?
like chocolate easter bunnies
