An ichnofacies is an assemblage of

trace fossil A trace fossil, also known as an ichnofossil (; from el, ἴχνος ''ikhnos'' "trace, track"), is a fossil record of biological activity but not the preserved remains of the plant or animal itself. Trace fossils contrast with body fossils, ...

s that provides an indication of the conditions that their formative organisms inhabited.

Concept

Trace fossil assemblages are far from random; the range of fossils recorded in association is constrained by the environment in which the trace-making organisms dwelt. Palaeontologist

Adolf Seilacher Adolf "Dolf" Seilacher (February 24, 1925 – April 26, 2014) was a German palaeontologist who worked in evolutionary and ecological palaeobiology for over 60 years. He is best known for his contributions to the study of trace fossils; constructi ...

pioneered the concept of ichnofacies, whereby the state of a sedimentary system at its time of deposition could be deduced by noting the trace fossils in association with one another.

Significance

Ichnofacies can provide information about water depth,

salinity Salinity () is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). It is usually measured in g/L or g/kg (grams of salt per liter/kilogram of water; the latter is dimensionless and equal ...

turbidity Turbidity is the cloudiness or haziness of a fluid caused by large numbers of individual particles that are generally invisible to the naked eye, similar to smoke in air. The measurement of turbidity is a key test of water quality. Fluids can ...

and energy. In general, traces found in shallower water are vertical, those in deeper water are more horizontal and patterned. This is partly because of the relative abundance of suspended food particles, such as

plankton Plankton are the diverse collection of organisms found in Hydrosphere, water (or atmosphere, air) that are unable to propel themselves against a Ocean current, current (or wind). The individual organisms constituting plankton are called plankt ...

, in the shallower waters of the

photic zone The photic zone, euphotic zone, epipelagic zone, or sunlight zone is the uppermost layer of a body of water that receives sunlight, allowing phytoplankton to perform photosynthesis. It undergoes a series of physical, chemical, and biological proc ...

, and partly because vertical burrows are more secure in the turbulent conditions of shallow water. In deeper waters, there is a necessary transition to sediment feeding (extracting

nutrient A nutrient is a substance used by an organism to survive, grow, and reproduce. The requirement for dietary nutrient intake applies to animals, plants, fungi, and protists. Nutrients can be incorporated into cells for metabolic purposes or excret ...

s from the mud). Food availability, hence trace type, is also controlled by energy: high energy environments keep food particles suspended, whereas in lower energy areas, food settles out evenly, and burrows will tend to spread out to cover as much area as economically as possible. Ichnofacies have a major advantage over using body fossils to gauge the same factors: body fossils can be transported, but trace fossils are always ''in situ''.

Concept

Significance

Recognized Invertebrate Ichnofacies

Recognized Vertebrate Ichnofacies

See also

References

External links