How the geo strata are identified as time periods

In terms of dating geologic age, basalt is an excellent marker. Using Potasium 40 or Argon dating will get you a fairly accurate date of a volcanic event.Now for arguements sake we have a layer or basalt, the sedementry rock, then more basalt - We can be fairly certain of the time period of the sedimentry rock.For the sake of the discussion, lets assume that the layer of sediment has a fossil percular to it. By looking for this particular fossil in other sedimentry rock will give us the date of that rock as well.Edited by MG1962, : No reason given.

Ahh okay thank you for that - I was under the impression there was enough potassium in basalt.And yeah the comment about fossil dating may have been a little too general. I dont have a reference, but I recall reading some time ago that plankton was being used to improve the dating of deposits. If I can find the article again I will post a link.