Lithostratigraphy Flashcards
1
Q
Basic unit in lithostratigraphy:
A
Formation
2
Q
Formations must:
A
- have a distinct lower and upper boundary
- have a type section
- have been laterally continuous during formation
- be stratigraphically continuous from top to bottom
- Be mappable on a standard quadrangle-scale map
3
Q
Formations need to be
A
geologically located, not gastrologically
4
Q
Members:
A
Laterally continuous distinct strata within a formation can be formally named. A member might be too thin to be mappable
- Distinct units of bed/s within formation. May not be continuous, occur in all locations or be mappable but will be distinctive
5
Q
Group
A
Several stratigraphically continuous formations can be combined into a formal group
6
Q
Supergroup
A
Groups are occasionally combined into a supergroup
7
Q
Lithostratigraphic boundaries:
A
- Angular unconformity
- Disconformity - not flat (has been eroded)
- Paraconformity - beds appear to be conformal but there is a major unconformity
- Nonconformity - relationship between igneous and metamorphic and sedimentary
8
Q
Unit boundaries can be
A
Isochronous boundaries (rare) or Diachronous boundaries (usual)
9
Q
Fence Diagrams:
A
- Lithological correlation, but other sorts of correlation can be used here
- Presenting how different columns might link together and get an idea what is happening in 3D space
10
Q
Block Diagrams:
A
- Either 3D image of current geology/geography, or interpretations of facies relationships, geological evolution
11
Q
Lithostratigraphic units:
A
- A stratum or body of strata, usually layered, often tabular
- Conforms to the law of superposition and
- defined on the basis of lithic characteristics and stratigraphic position
- Concerned with composition - not time or fossils
- Can’t reappear (unless fault) - gets replaced by something with different name
