Stratigraphy

Stratigraphy is a branch of geology that studies rock layers (strata) and layering (stratification). It is primarily used in the study of sedimentary rock and volcanic layers. The process of stratigraphy involves two main principles: the Principle of Original Horizontality and the Principle of Superposition.

Principles of Stratigraphy

The Principle of Original Horizontality suggests that due to the influence of gravity, layers of sediment are originally deposited horizontally. This principle is important in determining the relative ages of rock layers and the fossils they contain.

The Principle of Superposition states that in an undisturbed sequence of sedimentary rocks, the oldest rocks are at the bottom and the youngest are at the top. This principle is fundamental to the interpretation of Earth's history from stratigraphic records.

Types of Stratigraphy

There are several sub-disciplines within stratigraphy, each with its own specific focus:

• Lithostratigraphy is the study of physical and lithological characteristics of rock layers.
• Biostratigraphy is based on correlating and assigning relative ages of rock strata by using the fossil assemblages contained within them.
• Chronostratigraphy is the study of time equivalency of rock strata.
• Magnetostratigraphy is a chronostratigraphic technique used to date sedimentary and volcanic sequences.

Importance of Stratigraphy

Stratigraphy is crucial in understanding Earth's history. It provides evidence of the existence and evolution of life, and it helps in the search for resources like oil and gas. Stratigraphy also plays a key role in the study of climate change, as it provides a record of past climates.

See Also

• Geology
• Sedimentary rock
• Volcanic layers
• Climate change