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Marine Invertebrate Paleo

Marine Invertebrate Paleo. Trace Fossils. Trace Fossils. Ichnology = The study of trace fossils What is a trace fossil? Tracks, trails, resting impression, feeding traces, etc. Significance: Why study trace fossil? Best clues to fossil behavior

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Marine Invertebrate Paleo

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  1. Marine Invertebrate Paleo Trace Fossils

  2. Trace Fossils • Ichnology = The study of trace fossils • What is a trace fossil? • Tracks, trails, resting impression, feeding traces, etc. • Significance: Why study trace fossil? • Best clues to fossil behavior • Almost always preserved in place, unlike shells and bones that can be transported considerable distances. • Recognizable in cores/ deep-sea photos • Enhanced by diagenesis of the sediments. • Occur in all types of environments (terrestrial, freshwater, and marine) • Only in last few decades have paleoecologist recognized a truly organic origin for many of these features.

  3. Paradox of Trace Fossils • Different organisms responsible for similar traces in different environments! • The same organisms can make different traces in different contexts!

  4. Trace Fossil Classification • Based on morphology only (i.e., descriptive) • Use a Linnaean-type classification system in Ichnology • Ichnogenera • Ichnospecies • Binomial system • Types of Classification Systems in Literature • Biological System (based on different groups; e.g., Trilobites) • Problem many times you do not know which group made the trace. • Behavioral System (based on type of behavior exhibited) • Sedimentary System (based on type of sediment the traces are found in) • Behavioral classification system found to be most useful so we will use it

  5. Behavioral Classification • Resting Traces = Cubichnia • Organisms at rest, either on the surface or within substrate • Can get impression or imprint of ventral morphology • Dwelling Traces = Domichnia • Either burrows into soft substrate or borings into wood or rock. • Dwelling burrows are usually lined with organic matter. • Feeding Traces • Mining = Fodinichnia • Burrow have an ephemeral outline, unlined walls and may show systematic feeding behavior • Usually infaunal, non-selective deposit feeders • Grazing = Pascichnia • May form highly systematic traces from usually grazers • “lawn mower strategy” • Locomotion = Repichnia • Walking or crawling along substrate in non-systematic fashion

  6. Borings as Trace Fossils • Traces in hard substrates, rock, shells, bones, wood, etc. • Most borings are constructed for shelter and protection and fall within the Domichnia • Some borings may be classified as Fodinichnia, e.g. fungi, termites, predatory snails, etc. • Some may be a combination of both types

  7. Survey of Boring Organisms • Penetrative Thallophytes (algae, fungi, lichens) • Most Domichnia, fungi may be Fodinichnia • Boring Bryozoans • They bore by chemical means (phosphoric acid) • Domichnia • Boring Brachiopods • Pedicle bores calcareous substrates • Anchoring • Drilling Tubellaria (flat worms) • Bore a keyhole shaped hole in oyster and other bivalve shells • Food • Boring Polychaetes • Shells, reefs, and other limestone structure • Mechanical means jaws and setae • My use chelating agent or dilute acids

  8. Drilling Cephalopods • Rasp with their radula a hole in clams and snails • Rasp holes of varying size and shape and position • Drilling Gastropods • Drill holes are characteristic and recognizable in fossil • Chemical and physical means • Muricids and Naticids gastropods mainly • Boring Porifera (sponges) • Cliona • Complex galleries branching and interconnecting within the substrate (dwelling) • Rock Boring Bivalves • Merely a habitation • Conical shape • Mechanical and chemical • Will not cross-cut another boring, stop drilling instead. • Wood Boring Bivalves (Teredo or ship worm) • Boring follow the grain of wood for dwelling • Avoid other borings in the wood

  9. Controls of Trace Fossils in Marine Environment • Depth zonation (Seilacher, 1967) • Possible to use traces as bathymetric indicators? • Change from vertical burrow in shallow water to more horizontal burrows with depth. • Also increasing complexity found with depth • The model is empirical and has not been tested completely. • Paleooxygenation via trace fossils (Tony Ekdale and Chuck Savrda) • Different identified traces are found under different oxygen concentrations requirements of their makers.

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