Ichnofabric index
File:Helminthopsis01.JPG{{Short description|Method to quantify bioturbation}}
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.{{Cite journal| first1 = C. G.| first2 = R. J. | title = Response of the marine infauna to Triassic–Jurassic environmental change: Ichnological data from southern England | journal = Palaeogeography, Palaeoclimatology, Palaeoecology | volume = 244| last1 = Barras | pages = 223–241 | year = 2007 | doi = 10.1016/j.palaeo.2006.06.040| last2 = Twitchett| issue = 1–4 | bibcode = 2007PPP...244..223B }}
Application
Ichnofabric 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.{{Cite journal| last2 = Smail| first1 = M. F.| first2 = S. E. | title = A Semiquantitative Field Method for Evaluating Bioturbation on Bedding Planes | journal = PALAIOS | volume = 12| last1 = Miller| issue = 4 | pages = 391–396 | date = 1 August 1997 | issn = 0883-1351| doi = 10.2307/3515338| jstor = 3515338| bibcode = 1997Palai..12..391M}} The vertical ichnofossil index is harder to measure; it involves quantifying the amount of disturbance to the original sedimentary fabric.{{Cite journal
| last1 = Droser | first1 = M.L.
| last2 = Bottjer | first2=D.J.
| year = 1986
| title = A semiquantitative field classification of ichnofabric
| journal = Journal of Sedimentary Research
| volume = 56
| issue = 4
| pages = 558–559
| url = http://jsedres.sepmonline.org/cgi/content/abstract/56/4/558
| doi=10.1306/212f89c2-2b24-11d7-8648000102c1865d
| bibcode = 1986JSedR..56..558D
| url-access = subscription
}}