Ichnofabric index

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Trace fossils occupy a large proportion of this bedding plane.

The Droser-Bottjer ichnofabric index is a method used to quantify the degree of bioturbation in a sedimentary rock. It involves grading the amount of trace fossil activity on a scale of 1–6; a value of 1 indicates that bioturbation is entirely absent, whereas the highest grade would involve a bedding plane containing over 60% trace fossil cover.[1] This index can be applied in either a vertical or horizontal aspect. The vertical component provides an indication of the interplay between physical and chemical aspects of the environment and the degree of biological activity.[2] The vertical ichnofossil index is harder to measure; it involves quantifying the amount of disturbance to the original sedimentary fabric.[3]


  1. ^ Barras, C. G.; Twitchett, R. J. (2007). "Response of the marine infauna to Triassic–Jurassic environmental change: Ichnological data from southern England". Palaeogeography Palaeoclimatology Palaeoecology. 244: 223–241. doi:10.1016/j.palaeo.2006.06.040. 
  2. ^ Miller, M. F.; Smail, S. E. (1 August 1997). "A Semiquantitative Field Method for Evaluating Bioturbation on Bedding Planes". PALAIOS. 12 (4): 391–396. doi:10.2307/3515338. ISSN 0883-1351. 
  3. ^ Droser, M.L.; Bottjer, D.J. (1986). "A semiquantitative field classification of ichnofabric". Journal of Sedimentary Research. 56 (4): 558–559. doi:10.1306/212f89c2-2b24-11d7-8648000102c1865d.