An ichnofacies is an assemblage of trace fossils 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 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, turbidity 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, in the shallower waters of the photic zone, 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 nutrients 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.
Recognized invertebrate ichnofacies
Marine Invertebrate IchnofaciesNameCommon IchnogeneraSubstrateInferred PaleoenvironmentScoyeniaSkolithos, Cruziana, Diplichnites, RusophycusVariable - typically sandstones; red beds may be nearbyDiagnostic of terrestrial/freshwater facies.PsilonichnusPsilonichnus, Coenobichnus, Cellicalichnus, MacanopsisHighly variable grain size, sand, soft substrateCoastal barrier islands, strand plains, delta plains, estuaries, lagoons, and bays.TrypanitesEntobia, Trypanites, Gastrochaenolites, Caulostrepsis, Maeandropolydora, ConchotremaHardground, endurated substratesCoastal cliffs, reefs, beachrockTeredolitesTeredolites, ThalassinoidesResistant woody and coaly substratesDriftwood, peatGlossifungitesDiplocraterion, Skolithos, Spongeliomorpha, Rhizocorallium, Arenicolites, Thalassinoides, FuersichnusFirmground, dewatered mudsShallow, marginal marine, deltaic or estuarine erosion surfaces. SkolithosSkolithos, Ophiomorpha, Arenicolites, DiplocraterionUnconsolidated littoral sandsBeaches and sandy tidal flats, shallow water, foreshore to upper-shoreface, above wavebaseCruzianaArthrophycus, Phycodes, Rhizocorallium, Teichichnus, Arenicolites, Rosselia, Bergaueria, Thalassinoides, Lockeia, Protovirgularia, Curvolithus, Dimorphichnus, Cruziana, RusophycusSand and silt heterolithic successions and organic detritusMid to distal continental shelves. Below normal wave base, but not necessarily below storm wave baseZoophycosZoophycos, Phycosiphon, ChondritesMarine softground, impure sands and siltsDeeper water, bottom of shelf; turbidite faciesNereitesNereites, Megagrapton, Protopaleodictyon, Spirophycus, Helminthoraphe, Glockerichnus, Spiroraphe, Cosmoraphe, Urohelminthoida, Desmograpton, Paleodictyon, ScoliciaFine-grained muds and clays interbedded with turbidite siltsDeep water, pelagic, base-of-slope turbidity systems
Recognized vertebrate ichnofacies
Vertebrate IchnofaciesLockley, M.G., Hunt, A.P., and Meyer, C.A., 1994. Vertebrate tracks and the ichnofacies concept: Implications for palaeoecology and palichnostratigraphy. In The Palaeobiology of Trace Fossils, ed. S.K. Donovan, Chichester, UK: John Wiley & Sons, p. 241-268.NameCommon IchnogeneraSubstrateInferred PaleoenvironmentChelichnus (Laoporus)Chelichnus, BrasilichniumUnconsolidated, larger-grained sandsAeolian sand dunesGrallatorGrallator, Jindongornipes, Koreanoformis, Avipeda, Brachychirotherium, Rhynchosauroides, EubrontesLacustrine shorelinesBrontopodusCharirichnium, Ceratopsipes, Amblydactylus, BrontopodusClastic or carbonateCoastal plain, marine shorelineBatrachichnusBatrachichnus, Limnopus, Amphisauropus, Dromopus, Dimetropus, Gilmoreichnus, ChirotheriumTidal flat-fluvial plainCharacichnosCharacichnos, Undichna, Lunichnium, Puertollanopus, Serpentichnus, Batrachichnus, HatcherichnusSemi-consolidated firmgroundsSubaqueous lacustrine, estuarine, and deltaic environments
See also Trace fossil classification Bioturbation
References
External links Types of Ichnofacies- University College London