Hovind: Lies in the Textbook

Edge and I have discussed the "Geologic Column" concept in more specific topics elsewhere. We agreed that it is a timeline - A graphic representation of the relative positions and durations of the various geologic time units. Strictly speaking, the types of rocks that exist in the world are irrelivent to the geologic column.As such, it could be rightfully claimed that it exists only in graphic representations.I didn't bother checking your link content, but I presume it's the Glenn Morton collection of various locations where there are indeed sections of rock that include all the time periods over a cosiderable range. But these are stratagraphic sections, not "geologic columns".Actually, if the Earth were found to have uniform stratigraphic sections everywhere, this might be excellent evidence for creationism. It would be damn hard to explain with geologic process concepts as we know them.Moose

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Professor, geology, Whatsamatta U
Evolution - Changes in the environment, caused by the interactions of the components of the environment.
"Do not meddle in the affairs of cats, for they are subtle and will piss on your computer." - Bruce Graham

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Can you explain what indicator fossils are and how they were identified?

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Can you explain why indicator fossils are used?

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The more proper term is "index fossil". These are fossils that were discovered to be restricted to specific times in geologic history. These time frames might be fairly broad, say such as the Cambrian and Ordovician periods, but I believe the truly useful index fossils are those confined to much smaller time units.Time to trot out my favorite web page: Radiometric Dating and the Geological Time Scale
Circular Reasoning or Reliable Tools?
by Andrew MacRaeIn short, it was discovered that when various rock stratigraphic sections are studied, certain specific fossils were always found to be in the same place in the section. As you went from the bottoms to the tops of the sections, you would always find the various fossils in the same order of appearance.The rocks were dated by relative stratigraphic position - Deeper means older. The fossils were thus also dated.Now, all this showed that the specific fossils (index fossils) were characteristics of rocks of certain specific ages. Thus, if you found a certain index fossils, you could be confident that the rock unit was of a certain age.Now this does tend to sound like circular reasoning - "The rocks dated the fossils, the fossils date the rocks". But first of all, it was the rocks that dated the fossils. It was discovered that specific fossils were of specific ages. Therefore, if you found a specific fossil, you knew you were at a specific age.Well, a rather muddled explanation. Maybe someone else can do better.Moose