Correlation of Rock Strata
Matching Rock Strata Formed from
Different Locations that were Formed at the
1. Index Fossils-Used to correlate rock sequences from
different locations. Using index fossils it is possible to
determine that two different rock types were formed at the
same time. Index fossils have the following parameters:
a. Must have lived for a short geologic time span (geologically this could be
millions of years).
b. Must have had a wide geographic distribution.
c. Must be easily identified.
2. Volcanic Ash Falls-many volcanoes can erupt explosively leaving a layer of
ash over large areas. This rapid geological event can leave a single layer of
ash over a large area making time correlation from different areas very accurate.