Trace Fossils Paleontology Geology 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. Cubichnia = Resting Repichnia = Crawling Pascichnia = Grazing Agrichnia = Farming Fodinichnia = Deposit Feeding Dwelling = Domichnia Fugichnia = Escape 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.) 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.) Ichnofacies Freshwater Marine Hardgrounds and Soft marine sediments Firmgrounds and Shoreface Skolithos burrows, Miss., WV. Skolithos Ichnfacies Formation clues: Skolithos burrows in Aladdin Sandstone, Black Hills, SD Skolithos trace fossils in the Cambrian of Wyoming Arenicola, sediment casings, and it’s burrow opening Ophiomorpha gallery of burrows. Eocene of Mississippi. Skolithos Ichnofacies Callianassa or 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.).