ICHNOFOSSILS
What are ichnofossils?
- Are trace fossils or biogenic sedimentary structures which represents the
fossilized behavior or activities of organisms. (They are not fossilized bodies, but
fossilized activities.)
o Trace Fossil – preserved in rocks where body fossils are rare. (e.g.
shallow marine sandstones and deep marine shales). Diaganesis has little
effect on trace fossils. Not subjected to post-mortem transport and are
automatically in situ (on site).
o Body Fossil – less abundant in some places; tends to bioturbate the
sediment. Diagenesis may destroy or distort body fossils. Can be
transported to form unnatural death assemblages.
- Has long time range – allows rocks of widely different ages to be compared.
- Has narrow facies range – most trace fossils are found in their preferred
environment. (Facies – body of rock with specified characteristics, may include
physical, chemical, and biological features.)
- Has no secondary displacement – cannot be transported like body fossils.
Classification Systems
• Linnaean Classification – involves using of a binomial system. Ichnotaxa
include the ichnogenera and ichnospecies, simply used to define morphological
differences.
• Preservational – (Involves the surface of the sedimentary layer)
o Exogenic are formed on top of the sediment.
o Endogenic traces are formed within the sediment.
▪ Full relief is when all sides of the trace are exposed and the
boundaries are clearly defined within the enclosing sediment.
▪ Semirelief is when just one side is seen projecting from a bedding
plane. (Hyporelief and Epirelief, Positive and Negative)
• Morphological
o 1. Traces on the bedding planes. (Tracks vs Traces)
o 2. Structures within the sediment. (Burrows – formed within soft sediment;
Borings – formed through hard subtrate)
o 3. Excrement (Faecal pellets or strings – less than 10mm, and coprolite)
o 4. Others – root penetration structures and non-faecal pellets.
• Behavioral –
o Cubichnia – resting traces; structures conventionally interpreted as
resting traces, with the shape of the trace commonly reflecting the shape
of the trace maker.
o Domichnia – dwelling traces; dwelling burrows; more or less the
permanent home of the organism.
What are ichnofossils?
- Are trace fossils or biogenic sedimentary structures which represents the
fossilized behavior or activities of organisms. (They are not fossilized bodies, but
fossilized activities.)
o Trace Fossil – preserved in rocks where body fossils are rare. (e.g.
shallow marine sandstones and deep marine shales). Diaganesis has little
effect on trace fossils. Not subjected to post-mortem transport and are
automatically in situ (on site).
o Body Fossil – less abundant in some places; tends to bioturbate the
sediment. Diagenesis may destroy or distort body fossils. Can be
transported to form unnatural death assemblages.
- Has long time range – allows rocks of widely different ages to be compared.
- Has narrow facies range – most trace fossils are found in their preferred
environment. (Facies – body of rock with specified characteristics, may include
physical, chemical, and biological features.)
- Has no secondary displacement – cannot be transported like body fossils.
Classification Systems
• Linnaean Classification – involves using of a binomial system. Ichnotaxa
include the ichnogenera and ichnospecies, simply used to define morphological
differences.
• Preservational – (Involves the surface of the sedimentary layer)
o Exogenic are formed on top of the sediment.
o Endogenic traces are formed within the sediment.
▪ Full relief is when all sides of the trace are exposed and the
boundaries are clearly defined within the enclosing sediment.
▪ Semirelief is when just one side is seen projecting from a bedding
plane. (Hyporelief and Epirelief, Positive and Negative)
• Morphological
o 1. Traces on the bedding planes. (Tracks vs Traces)
o 2. Structures within the sediment. (Burrows – formed within soft sediment;
Borings – formed through hard subtrate)
o 3. Excrement (Faecal pellets or strings – less than 10mm, and coprolite)
o 4. Others – root penetration structures and non-faecal pellets.
• Behavioral –
o Cubichnia – resting traces; structures conventionally interpreted as
resting traces, with the shape of the trace commonly reflecting the shape
of the trace maker.
o Domichnia – dwelling traces; dwelling burrows; more or less the
permanent home of the organism.
