Introduction to Stratigraphy

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From which languages is the term 'stratigraphy' derived?

Latin and Greek

What is stratigraphy?

Branch of geology concerned with the study of rock layers (strata) and layering (stratification)

What is a stratum?

A layer of rock characterized by particular lithologic properties and attributes that distinguish it from adjacent layers

What is historical geology also known as?

Stratigraphy Signup and view all the answers

What questions can be answered by studying stratigraphy?

<ol> <li>When the rocks were formed. 2) Where else are such rocks found.</li> </ol> Signup and view all the answers

What is the Law of Original Horizontality?

Sedimentary strata are horizontal, or nearly so, when deposited. Signup and view all the answers

Why is the evidence available for studying stratigraphy limited?

Due to weathering, erosion, burial, and metamorphism, a lot of evidence is destroyed or hidden. Signup and view all the answers

What is the Principle of Superposition?

In any section of undisturbed sedimentary strata, the oldest stratum is at the base and the youngest is at the top. Signup and view all the answers

What is the Principle of Cross-Cutting Relationship?

A rock body (or feature) that cuts across another rock body (or feature) is the younger of the two. Signup and view all the answers

What is the Principle of Inclusion?

A rock body that contains inclusions of pre-existing rocks is younger than the rocks from which the inclusions were derived. Signup and view all the answers

What is the Law of Floral and Faunal Succession?

Each formation in a sequence contains a distinct group of fossils which is not repeated in rocks above and below it, and the diversity and complexity of living organisms increases in younger rocks. Signup and view all the answers

How can we recognize rock sequences that have been overturned?

They are generally easy to recognize by their sedimentary structures, such as cross-bedding, ripple marks, graded bedding, and mud cracks. Signup and view all the answers

What are the assumptions made when applying the Principle of Superposition?

Rocks (layers) were essentially horizontal when they were deposited, and the rocks have not been so severely deformed that the beds are overturned. Signup and view all the answers

What happens to rock bodies or features in the Principle of Cross-Cutting Relationship?

The rock body or feature that cuts across another is the younger of the two. Signup and view all the answers

What does the Principle of Inclusion tell us about the age of rock bodies?

A rock body containing inclusions of pre-existing rocks is younger than the rocks from which the inclusions were derived. Signup and view all the answers

How do fossils contribute to the Law of Floral and Faunal Succession?

Each formation in a sequence contains a distinct group of fossils which is not repeated in rocks above and below it, and the diversity and complexity of living organisms increases in younger rocks. Signup and view all the answers