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A trace fossil, also ichnofossil, is a geological record of biological activity. Ichnology is the study of such traces, and is the work of ichnologists. Trace fossils may consist of impressions made on or in the substrate by an organism: for example, burrows, borings (bioerosion), urolites, footprints and feeding marks, and root cavities. The term in its broadest sense also includes the remains of other organic material produced by an organism — for example coprolites or chemical markers — or sedimentological structures produced by biological means - for example, stromatolites. Trace fossils contrast with body fossils, which are the fossilized remains of parts of organisms' bodies, usually altered by later chemical activity or mineralization.
The wave base, in physical oceanography, is the maximum depth at which a water wave's passage causes significant water motion. For water depths deeper than the wave base, bottom sediments and the seafloor are no longer stirred by the wave motion above.
Bioerosion describes the breakdown of hard ocean substrates – and less often terrestrial substrates – by living organisms. Marine bioerosion can be caused by mollusks, polychaete worms, phoronids, sponges, crustaceans, echinoids, and fish; it can occur on coastlines, on coral reefs, and on ships; its mechanisms include biotic boring, drilling, rasping, and scraping. On dry land, bioerosion is typically performed by pioneer plants or plant-like organisms such as lichen, and mostly chemical or mechanical in nature.
Thorson's rule is an ecogeographical rule which states that benthic marine invertebrates at low latitudes tend to produce large numbers of eggs developing to pelagic and widely dispersing larvae, whereas at high latitudes such organisms tend to produce fewer and larger lecithotrophic (yolk-feeding) eggs and larger offspring, often by viviparity or ovoviviparity, which are often brooded.
The history of paleontology traces the history of the effort to understand the history of life on Earth by studying the fossil record left behind by living organisms. Since it is concerned with understanding living organisms of the past, paleontology can be considered to be a field of biology, but its historical development has been closely tied to geology and the effort to understand the history of Earth itself.
In geology, depositional environment or sedimentary environment describes the combination of physical, chemical and biological processes associated with the deposition of a particular type of sediment and, therefore, the rock types that will be formed after lithification, if the sediment is preserved in the rock record. In most cases the environments associated with particular rock types or associations of rock types can be matched to existing analogues. However, the further back in geological time sediments were deposited, the more likely that direct modern analogues are not available.
Paleodictyon is a pattern, usually interpreted to be a burrow, which appears in the geologic marine record beginning in the Precambrian/Early Cambrian and in modern ocean environments. Paleodictyon were first described by Giuseppe Meneghini in 1850.
Diplichnites are arthropod trackways with two parallel rows of blunt to elongate, closely spaced tracks oriented approximately perpendicularly to the mid-line of the trackway. The term is more often used for the ichnofossils of this description; however, similar trackways from recent arthropods are sometimes given this name as well.
Skolithos is a common trace fossil ichnogenus that is, or was originally, an approximately vertical cylindrical burrow. They can reach lengths of up to about 35 cm (14") and diameters of up to about 5 cm (1.6").
An ichnofacies is an assemblage of trace fossils that provides an indication of the conditions that their formative organisms inhabited.
The Beacon Supergroup is a geological formation exposed in Antarctica and deposited from the Devonian to the Triassic. The unit was originally described as either a formation or sandstone, and upgraded to group and supergroup as time passed. It contains a sandy member known as the Beacon heights orthoquartzite.
Diplocraterion is an ichnogenus describing vertical U-shaped burrows having a spreite between the two limbs of the U. The spreite of an individual Diplocraterion trace can be either protrusive or retrusive. Some ichnospecies have both types. The presence/absence of funnel-shaped openings should not be used as an ichnotaxobase due the high probability that the upper portions of the trace may have been eroded away.
Ophiomorpha is an ichnotaxon, usually interpreted as a burrow of an organism living in the near-shore environment. The burrow lining is more or less smooth on the inside, and densely to strongly mammalated or nodose on the outside, due to the packing of fecal pellets for support of the burrow. Branching is irregular but Y-shaped where present. It is often considered part of the Skolithos ichnofacies, where it has occurred since the early Permian, though it has also occurred in deep water settings since the Late Jurassic, such as well-oxygenated turbidites.
The Straight Cliffs Formation is a stratigraphic unit in the Kaiparowits Plateau of south central Utah. It is Late Cretaceous in age and contains fluvial, paralic, and marginal marine (shoreline) siliciclastic strata. It is well exposed around the margin of the Kaiparowits Plateau in the Grand Staircase – Escalante National Monument in south central Utah. The formation is named after the Straight Cliffs, a long band of cliffs creating the topographic feature Fiftymile Mountain.
Helminthopsis is the ichnogenus of a type of trace fossil that is found preserved on the bedding planes of fine-grained sedimentary rocks. It is characterized by short, curvilinear, non-branching, parallel-sided, unlined traces on bedding surfaces. It is thought to represent the submarine feeding trails of an invertebrate organism that worked the surface of muddy substrates in search of food. Because Helminthopsis traces never cross over themselves, the ichnogenus is distinguished from similar traces assigned to the Gordia ichnogenus. The similar sounding, but now obsolete, ichnogenus Helminthoida refers to a somewhat similar trace characterized by regular, back-and-forth meanders, whereas Helminthopsis traces are irregular.
The Spearfish Formation is a geologic formation, originally described from the Black Hills region of South Dakota, United States, but also recognised in North Dakota, Wyoming, Montana and Nebraska. It is a heterogeneous red bed formation, commonly with siltstone and gypsum low in the formation and sandstone and shale higher up. Other rock types include claystone, conglomerate, dolomite, and oil shale. It is typically regarded as Permian–Triassic in age, although its original description included Jurassic rocks.
Anthony J. Martin is a paleontologist who has taught at Emory University since the early 1990s. He is best known for his books, An Introduction to the Study of Dinosaurs, Life Traces of the Georgia Coast and Dinosaurs without Bones He is married to artist Ruth Schowalter.
Spreite, meaning leaf-blade in German are stacked, curved, layered structures that are characteristic of certain trace fossils. They are formed by invertebrate organisms tunneling back and forth through sediment in search of food. The organism moves perpendicularly just enough at the start of each back-and-forth pass so that it avoids reworking a previously tunneled area, thereby ensuring that it only makes feeding passes through fresh, unworked sediment.
Karen Chin is an American paleontologist and taphonomist who is considered one of the world's leading experts in coprolites.
The Algoa Group is one of five geological groups which comprise the coastal Cenozoic geological deposits in South Africa. The Algoa Group contains six formations which range from Middle Eocene to Late Holocene in age.
References
- ↑ Clifton, H.E., Thompson, J.K., 1978. Macaronichnus segregatis: a feeding structure of shallow marine polychaetes. Journal of Sedimentary Petrology 48, 1293–1302.
- ↑ Pemberton, S.G., Spila, M., Pulham, A.J., Saunders, T., MacEachern, J.A., Robbins, D., Sinclair, I.K., 2001. Ichnology and Sedimentology of Shallow to Marginal Marine Systems. Geological Association of Canada, Short Course Notes, Vol. 15. AGMV Marquis, St. John’s
- ↑ Seike, K., Yanagishima, S.I., Nara, M., Sasaki, T., 2011. Large Macaronichnus in modern shoreface sediments: identification of the producer, the mode of formation, and paleoenvironmental implications. Palaeogeography, Palaeoclimatology, Palaeoecology 311, 224––229.
- ↑ Quiroz, L.I., Buatois, L.A., Mangano, M.G., Jaramillo, C.A., Santiago, N., 2010. Is the trace fossil Macaronichnus an indicator of temperate to cold waters? Exploring the paradox of its occurrence in tropical coasts. Geology 38, 651–654.
- ↑ Crippa, G., Baucon, A., Felletti, F., Raineri, G., Scarponi, D. 2018. A multidisciplinary study of ecosystem evolution through early Pleistocene climate change from the marine Arda River section, Italy. Quaternary Research 89(2). Abstract available at http://www.tracemaker.com
