What problems are created for geologists by the presence of unconformities in the rock record?

Question

Is there any useful information that these features can give us?

Answer 1

Historically, Hutton's unconformity, at Siccar Point in Scotland was important in developing modern geological theory.

An unconformity  is a gap in the stratigraphic sequence due either to non-deposition, (sometimes called a non-sequence) or due to erosion. We therefore loose the information in the missing part of the sequence. An angular unconformity ( of which the Siccar point is a famous example) is relatively easy to see in the field, and indicates the rocks below the unconformity were subject to erosion, though the dates of the erosion may be difficult to determine. (of course the date of the unconformity contact may be dated if the overlying rocks are datable) If the unconformity is not angular, the only clues to it in the field will be a sudden jump in age indicated by the fossils (if present). If no fossils are present then more detailed  stratigraphic analysis may be needed tom prove any non-sequence/unconformity