| 单词 | index fossil |
| 例句 | To do this, scientists use index fossils to compare different rock layers. Miller & Levine Biology 2018-01-01T00:00:00Z There is no specific limit on how short the time span has to be to qualify as an index fossil. Physical Geology 2015-01-01T00:00:00Z The most useful index fossils come from lifeforms that were geographically widespread and had a species lifespan that was limited to a narrow time interval. An Introduction to Geology 2017-01-01T00:00:00Z The grounds were often more interesting than the matches, the All England Lawn Tennis and Croquet Club being such an index fossil from the nineteenth century. Frames of Reference 2015-03-02T05:00:00Z In other words, index fossils can be found in many places around the world, but only during a narrow time frame. An Introduction to Geology 2017-01-01T00:00:00Z A good index fossil should be specific to a time period but widespread enough to be found in many places. Miller & Levine Biology 2018-01-01T00:00:00Z |
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