Geol topic 4

What is the study of rock layers and their relationships in time and space known as?

Stratigraphy

Which principle states that in an undisturbed sequence of sedimentary rocks, the oldest layer is at the bottom?

Principle of Superposition

What principle allows you to conclude that sedimentary layers were tilted after they were deposited?

Principle of Original Horizontality

What does the Principle of Lateral Continuity suggest?

Rock layers will extend outwards in all directions until they pinch out or hit a barrier.

According to the Principle of Cross-Cutting Relationships, what can be said about a geologic feature that cuts through another rock body?

It is younger than the rock it cuts.

If you observe a layer of Sandstone that contains chunks of Granite, which rock is older?

The Granite

What does an 'Unconformity' represent?

A gap in the geologic record caused by erosion or non-deposition.

Which type of unconformity separates younger sedimentary strata from older, tilted or folded strata?

Angular Unconformity

What is a 'Nonconformity'?

Sedimentary rock sitting on top of eroded Igneous or Metamorphic rock.

Which type of unconformity is often the hardest to detect?

Disconformity

What is the basic fundamental unit of Lithostratigraphy?

Formation

What does Lithostratigraphy correlate rocks based on?

Physical and chemical characteristics (Rock type)

Which of the following is NOT a characteristic of a good Index Fossil?

It lived for a very long period of geologic time.

What does Biostratigraphy use to correlate rock units?

The fossil content (faunal succession)

If Rock Unit A is correlated to Rock Unit B based solely on Lithology, does that mean they formed at the exact same time?

No, lithostratigraphy is independent of time.

What does the Principle of Inclusions state?

The inclusions found inside a rock must be older than the rock containing them.

What does a 'Hiatus' in stratigraphy refer to?

The interval of time not represented by strata.

Which stratigraphic unit is larger than a Formation?

Group

Who is credited with formulating the principles of Superposition, Original Horizontality, and Lateral Continuity?

Nicolas Steno

What principle predicts the pattern of fossils from Trilobites to Dinosaurs to Humans?

Principle of Faunal Succession

When a river cuts a canyon through rock layers, what does this demonstrate?

Lateral Continuity

If an igneous dike cuts through three layers of sedimentary rock but is cut off by an unconformity at the top, what can be said about the dike?

It is older than the three sedimentary layers but younger than the unconformity.

What does 'Correlation' in geology refer to?

Demonstrating correspondence between rock units in different areas.

Which would be most useful for correlating rock units between two different continents?

A global index fossil (like a specific ammonite).

In a 'Disconformity', how is the erosion surface oriented to the bedding planes?

Parallel