Paleontology Geology 331 Characteristics of Trace Fossils that make them valuable in • 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, ; 2, ; 3, Cosmorhaphe; 4, Paleodicyton; 5, Phycosiphon; 6, Zoophycos; 7, Thalassinoides; 8, ; 9, Diplocraterion; 10, Gastrochaenolites; 11, ; 12, . (Based on Ekdale et al. 1984.) Terminology for trace preservation, depending on the relationship of the trace to horizons. (Based on Ekdale et al. 1984.) One may be produced by many different organisms. Here, all the traces are resting impressions, cubichnia, of the ichnogenus Rusophycus, produced by (a) the polychaete Aphrodite, (b) a nassid snail, (c) a notostracan branchiopod shrimp, and (d) a . (Based on Ekdale et al. 1984.) Ichnofacies

Freshwater Marine

Hardgrounds and Soft marine Firmgrounds and Shoreface

Skolithos , Miss., WV. Ichnfacies Formation clues: Skolithos burrows in Aladdin , Black Hills, SD Skolithos trace fossils in the of Wyoming Arenicola, sediment casings, and it’s 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, . Cruziana Ichnofacies

Polychaete worm Palaeophycus, Mississippian. Cruziana Ichnofacies Olivellites, , WV. Cruziana Ichnofacies Rhizocorallium, Penn. WV. Cruziana Ichnofacies from abundant trace fossils, Cruziana Ichnofacies, , Wyoming Zoophycos, Miss., KY. Zoophycos Ichnofacies. Underside of bed. Zoophycos Turbidite beds in Kentucky Escape structure, Mississippian turbidite, KY Helminthoidea, Tertiary. Ichnofacies , 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.)