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Trace Fossils
PaleontologyGeology 331
Characteristics of Trace Fossils that make them valuable in Paleoecology• Long Time Range – allows rocks of widely
different ages to be compared.• Narrow Facies Range – most trace fossils
are found in their preferred environment.• No Secondary Displacement – can not be
transported like body fossils.
The behavioral classification of trace fossils, showing the major categories, and some typical examples of each. Illustrated ichnogenera are: 1, Cruziana; 2, Anomoepus; 3, Cosmorhaphe; 4, Paleodicyton; 5, Phycosiphon; 6, Zoophycos; 7, Thalassinoides; 8, Ophiomorpha; 9, Diplocraterion; 10, Gastrochaenolites; 11, Asteriacites; 12, Rusophycus. (Based on Ekdale et al. 1984.)
Cubichnia = RestingRepichnia = CrawlingPascichnia = GrazingAgrichnia = FarmingFodinichnia = Deposit FeedingDwelling = DomichniaFugichnia = Escape
Terminology for trace fossil preservation, depending on the relationship of the trace to sediment horizons. (Based on Ekdale et al. 1984.)
One trace fossil may be produced by many different organisms. Here, all the traces are resting impressions, cubichnia, of the ichnogenus Rusophycus, produced by (a) the polychaete worm Aphrodite, (b) a nassid snail, (c) a notostracan branchiopod shrimp, and (d) a trilobite. (Based on Ekdale et al. 1984.)
Freshwater
Hardgrounds and
Firmgrounds and
Shoreface
Marine
Soft marine sediments
Ichnofacies
Skolithos burrows, Miss., WV. Skolithos Ichnfacies
Formation clues: Skolithosburrows in Aladdin Sandstone,
Black Hills, SD
Skolithos trace fossils in the Cambrian of Wyoming
Arenicola, sediment casings, and it’s burrow opening
Ophiomorphagallery of burrows.
Eocene of Mississippi.
SkolithosIchnofacies
Callianassaor Ghost Shrimp
Callianassa shrimp mounds: origin of Ophiomorpha. Tidal flat, Florida Keys.
Trilobite traces, Cruziana Ichnofacies
Rusophycus, resting Cruziana, crawling
Diplichnites, walking
Arthrophycus, Silurian. Cruziana Ichnofacies
Polychaete worm
Palaeophycus, Mississippian. Cruziana Ichnofacies
Olivellites, Pennsylvanian, WV. Cruziana Ichnofacies
Rhizocorallium, Penn. WV. Cruziana Ichnofacies
Bioturbation from abundant trace fossils, Cruziana Ichnofacies,
Ordovician dolomite, Wyoming
Zoophycos, Miss., KY. Zoophycos Ichnofacies. Underside of bed.
Zoophycos
Turbidite beds in Kentucky
Escape structure, Mississippian turbidite, KY
Helminthoidea, Tertiary. Nereites Ichnofacies
Paleodictyon, Nereites Ichnofacies
Psuedofossils: Load casts, Miss., WV.
Cambrian Substrate Revolution
Ichnofabric indices for different sedimentary/ichnofacies settings. These diagrams show the proportions of sediment reworked by bioturbation, as seen in vertical section and numbered from top to bottom: 1 (no bioturbation) to 5 (intensely bioturbated). (Courtesy of Mary Droser and Duncan McIlroy.)