Types of Ichnofacies

The trace fossils have remained in appearance rather constant since Cambrian, even if their producers might have been different. The trace fossil assemblages can be divided according the palaeoenvironmental scheme into a number of ichnofacies named after a characteristic trace fossil. The ichnofacies indicate a particular sedimentary facies and can be identified on the basis of its trace fossil assemblage

Distribution of Ichnofacies
The typical position of the major ichnofacies in marine and continental environments: Cr - Cruziana; G - Glossifungites;
N - Nereites; Ps - Psilonichnus; Sc - Scoyenia; Sk - Skolithos; Te - Teredolites; Tr - Tripanites; Z - Zoophycos
(after Benton & Harper, 1997)
 
Woodground Rockground Firmground Loose- and softground Sedimentology / environment
Marine Freshwater Freshwater Marine Energy Bathymetry Grainsize
Teredolites
Trypanites
Glossifungites
Scoyenia
-
Psilonichnus
-
Backshore
Sand
Rusophycos?
Skolithos
High
Beach
Sand
-
Arenicolites?
Arenicolites
Event
Shelf
Sand silt
Fuersichnus?
Cruziana
Medium
Lagoon /
shelf
Sand, silt
Mermia
Nereites
Event
Slope to
abyssal
Sand, mud
Zoophycos
Low
Mud
Scheme indicating relationships of ichnofacies with environment (after Bromley, 1996).


Nereites Ichnofacies

The Nereites Ichnofacies is recognized by the presence of meandering pascichnia (Nereites, Neonereites and Helminthoide), spiral pascichnia (Spirorhaphe), and agrichnia (Paleodictyon and Spirodesmos). Vertical burrows are almost entirely absent.
Nereites Ichnofacies
Nereites Ichnofacies viewed in pelagic carbonate ooze. 
(after Benton & Harper, 1997)
This ichnofacies indicates deep-water environments, including ocean floors and deep marine basins. The trace fossils occur in muds deposited from suspension, and in the mudstones and siltstones of distal turbidites.



Zoophycos Ichnofacies

The Zoophycos Ichnofacies is characterized by complex fodinichnia (Zoophycos, and sometimes other deep traces such as Thalassinoides) in tiered arrangements.
Zoophycos Ichnofacies
(after Benton & Harper, 1997)
The ichnofacies occurs in a range of water depths between the abyssal zone and the shallow continental shelf, in normal background conditions of sedimentation. The Nereites Ichnofacies may be a matching association found at similar water depths during times of turbidite (event) deposition.



Cruziana Ichnofacies

The Cruziana Ichnofacies shows rich trace fossil diversity, with horizontal repichnia (Cruziana and Aulichnites), cubichnia (Rusophycus, Asteriacites and Lockeia), and vertical burrows.
Cruziana Ichnofacies
(after Benton & Harper, 1997)
This ichnofacies represents mid and distal continental shelf situations, below normal wave base, but may be affected by storm activity.



Skolithos Ichnofacies

The Skolithos Ichnofacies can be recognized by a low diversity of abundant vertical domichnia burrows (Skolithos, Diplocraterion and Arenicolites), fodinichnia (Ophiomorpha), and fugichnia.
Skolithos Ichnofacies
(after Benton & Harper, 1997)
All these traces typically indicate intertidal situations where the organisms have to be able to respond rapidly in stressful conditions. The Skolithos Ichnofacies was at first seen as occurring only in the intertidal zone, but it is also typical of other shifting sand environments, such as the tops of storm sand sheets and the tops of turbidity flows.



Psilonichnus Ichnofacies

The Psilonichnus Ichnofacies shows a low diversity assemblage of small vertical burrows with basal living chambers (Macanopsis), narrow sloping T-shaped and Y- shaped burrows (Psilonichnus), root traces, and vertebrate footprints.
Psilonichnus Ichnofacies
(after Benton & Harper, 1997)
This ichnofacies is typical of backshore, dune areas, and supratidal flats on the coast



Scoyenia Ichnofacies

The Scoyenia Ichnofacies is characterized by a low diversity trace fossil assemblage, mainly simple horizontal fodinichnia (Scoyenia and Taenidium), with occasional vertical domichnia (Skolithos) and repichnia produced by insects or freshwater shrimps (Cruziana, Isopodichnus).
Scoyenia Ichnofacies
(after Benton & Harper, 1997)
The traces are preserved in fluvial and lacustrine sediments, often in the silts and sands of redbed sequences. Associated subaerial palaeosoils and aeolian sands may contain domichnia and repichnia of insects, and dinosaur and other tetrapod foot-prints.



Glossifungites Ichnofacies

The Glossifungites Ichnofacies is characterized by domichnia (Glossifungites and Thalassinoides) and sometimes plant root penetration structures. Other behavioural trace fossil types are rare.
Glossifungites Ichnofacies
(after Benton & Harper, 1997)
The traces occur in firm, but not lithified sediments, such as muds and silts in marine intertidal and shallow subtidal zones. The firm grounds may develop in low energy situations such as salt marshes, mud bars, of high intertidal flats, or in shallow marine environments where erosion has stripped off superficial unconsolidated layers of sediment.



Trypanites Ichnofacies

The Trypanites Ichnofacies is characterized by domichnial borings of worms (Trypanites), bivalves (Gostrochaenolites), barnacles (Rogerella) and sponges (Entobia).
Trypanites Ichnofacies
(after Benton & Harper, 1997)
These are formed in shoreline rocks or in lithified limestone hard grounds on the seabed. Bioerosion traces made by gastropods and echinoids are rarely preserved in ancient cases.



Teredolites Ichnofacies

The Teredolites Ichnofacies is identified by the presence of borings in wood (especially Teredolites), especially those produced by marine bivalves such as the modern ship worm, Teredo.
Teredolites Ichnofacies
(after Benton & Harper, 1997)