| index fossil n. The fossil remains of an organism that lived in a particular geologic age, used to identify or date the rock or rock layer in which it is found. Also called guide fossil. |
index fossil
n
(Earth Sciences / Geological Science) a fossil species that characterizes and is used to delimit a geological zone Also called zone fossil
index fossil ( n d ks ) The fossil remains of an organism that lived in a particular geologic age, used to identify or date the rock or rock layer in which it is found. The best type of index fossils are usually those of swimming or floating organisms that evolved quickly (and therefore did not cover a long span of geologic history) and were able to spread over large areas. Ammonites and graptolites are good index fossils. |
ThesaurusLegend: Synonyms Related Words Antonyms
| Noun | 1. |  index fossil - a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is foundfossil - the remains (or an impression) of a plant or animal that existed in a past geological age and that has been excavated from the soil |
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