2006-07-26 06:47:24 · 3 answers · asked by dat dude 1 in Science & Mathematics ➔ Earth Sciences & Geology
It depends on the relative placement of the igneous rock in relation to the fossils. If the igneous rocks are in a dike or sill cutting through the fossil beds, then the fossils must be older than the igneous rock. If the fossils incorporated some of the igneous materials into their formation, then that gives the relative age of the fossils as being fairly close to that of the igneous body.
2006-07-26 06:53:29 · answer #1 · answered by idiot detector 6 · 1⤊ 1⤋
As Not a perfect fool said, it depends mostly on relative position. If you have a fossil bearing sedimentary layer in a sequence between two igneous layers, then the dates of those igneous layers can give you a range of dates that the fossil bearing layer would be within.
I.e. if you had an ash layer somewhere below your fossil dated at 120 million years old, and a basalt layer above your fossils dated at 70 million years old, you would know that your fossils are between 70 and 120 million years old. Comparisons with other sequences, and the similarities between formations and fossils between the sequences may help to narrow down that date.
2006-07-26 06:59:16 · answer #2 · answered by Anonymous · 0⤊ 0⤋
They provide a reference.
2006-07-26 06:53:43 · answer #3 · answered by ag_iitkgp 7 · 0⤊ 0⤋