Correlation and FossilsCorrelation and Fossils

WOOHOO!WOOHOO!

Applying Principles of Relative Dating to Applying Principles of Relative Dating to Determine Geologic History of an AreaDetermine Geologic History of an Area

The process of matching rocks or geologic The process of matching rocks or geologic events occurring at different locations of the events occurring at different locations of the same age is calledsame age is called

CORRELATIONCORRELATION

Correlation of rock layers often Correlation of rock layers often relies upon fossilsrelies upon fossils

William Smith (late l700’s) noted that rock layers in William Smith (late l700’s) noted that rock layers in widely separated areas could be identified and widely separated areas could be identified and correlated by their distinctive fossil content correlated by their distinctive fossil content

This led to the "principle of fossil This led to the "principle of fossil successionsuccession““

Fossils succeed one another in a definite and Fossils succeed one another in a definite and determinable order, and therefore any time period can determinable order, and therefore any time period can be recognized by its fossil contentbe recognized by its fossil content

Index FossilsIndex Fossils

Index fossilsIndex fossils - any animal or plant that is characteristic - any animal or plant that is characteristic of a particular span of geologic time or environment.of a particular span of geologic time or environment.

2 criteria must be met2 criteria must be met

Life form lived over a wide geographic area – Life form lived over a wide geographic area – horizontal distributionhorizontal distribution

Life form existed for a short period of time – short Life form existed for a short period of time – short vertical distributionvertical distribution

NYS Index FossilNYS Index Fossil

Again….Corellation…Again….Corellation… Correlation- or CO-RELATION (two or more Correlation- or CO-RELATION (two or more

things related) is a critical tool in the things related) is a critical tool in the reconstruction of Earth’s history. reconstruction of Earth’s history.

Geologists look for a sequence of rocks (an Geologists look for a sequence of rocks (an “order”) that is the same in two or more areas, “order”) that is the same in two or more areas, and can therefore say they are the same age!and can therefore say they are the same age!

Let’s check it out!!Let’s check it out!!