Geologic Map and Cross-Section Interpretation

These flashcards summarize key terms and definitions related to geologic map interpretation and stratigraphy as covered in the lecture notes.

Angular Unconformity

An unconformity between two groups of rocks that are dipping at different angles.

Disconformity

An unconformity where the beds above and below are parallel, but the unconformity surface is not parallel to the bedding.

Eon

The largest subdivision of geological time; there are four eons: Hadean, Archean, Proterozoic, and Phanerozoic.

Epoch

Subdivisions of the Tertiary and Quaternary periods.

Era

Subdivisions of the eons; includes Paleozoic, Mesozoic, and Cenozoic.

GIS (Geographic Information System)

A computer-based tool used for mapping, analyzing, and visualizing geographic data.

GPS (Global Positioning System)

A radio navigation system that determines the exact location, time, and velocity using triangulation.

Ka (Kilo-annum)

A unit of time equal to one thousand years.

Key Beds

Well-defined strata that are distinctive enough for correlation in mapping.

Ma (Mega-annum)

A unit of time equal to one million years.

Magnetic Declination

The angle between true North and magnetic North.

Nonconformity

An unconformity where older igneous rocks are in contact with younger sediments.

Paraconformity

An unconformity where the beds are parallel above and below the break.

Law of Superposition

In an undeformed sequence of sedimentary rocks, the oldest rocks are at the bottom and the youngest are at the top.

Rule of V's

The rule stating that the V formed by a geologic unit crossing a stream valley will point in the direction the formation underlies the valley.

Township and Range System

A system dividing land into townships and ranges for land surveying primarily in the western United States.

Fossil Assemblages

Groups of several fossil species that are useful for correlating rock layers.

Cross-Cutting Relationships

A geologic principle stating that geological features that cut across others must be younger than the features they cut.

Fault

A fracture in rock along which there has been displacement.

Lithology

The study and description of the physical and chemical characteristics of rocks.

Unconformity

A gap in the geologic record indicating a period of erosion or non-deposition.

Facies

Distinctive lithological characteristics that can indicate a specific depositional environment.