2.2 Stratigraphy and Cross Sections

Question 1

Stratigraphy

Answer 1

A branch of geology dealing with the order and succession of rock strata, their occurrence, sequence, lithology, composition, fossils, and correlation

Question 2

Stratification

Answer 2

A structure produced by deposition of sediments in beds or layers (strata), laminae, lenses, wedges, and other essentially tabular units

Question 3

Stratified

Answer 3

Arranged in or composed of strata or layers

Question 4

Stratigraphic sequence/succession

Answer 4

Refers to the original succession of stratified rocks

Question 5

Steno’s Principles

Answer 5

1. Principle of original continuity
2. Principal of original horazontality
3. Principle of superposition
4. Principle of cross-cutting relationships

Question 6

Principle of original continuity

Answer 6

Layers are continuous and end only by thinning, lithological transition, or a abutment against a barrier

Question 7

Principle of original horizontality

Answer 7

When sediments are deposited the beds are horizontal

Question 8

Principle of superposition

Answer 8

any new sedimentary layer must be added on top pf existing layers

Question 9

principle of cross-cutting relationships

Answer 9

If a body or discontinuity cuts across a stratum, it must have formed after that stratum

Question 10

Interpretation

Answer 10

Interpretation must rely on available data
- Site data is complete
- Interpretation is always required

Question 11

Unconformities

Answer 11

A stratigraphic break

Question 12

Angular conformity

Answer 12

an erosional surface that truncates older, tilted sedimentary layers

Question 13

Disconformity

Answer 13

A break in a sedimentary sequence which does not involve a difference of inclination between strata on each side of the break

Question 14

Nonconformity

Answer 14

Sediments are deposited on top of an eroded surface of igneous or metamorphic rocks

Question 15

Marker Beds

Answer 15

Bed of rock strata that are easily distinguished and are traceable over a long horizontal distance

Question 16

Fossils

Answer 16

• Limestone’s are rich in fossils
• Shale’s often have preserved fossils
• Sandstone’s sometimes have fossils
• They represent life in former times

Question 17

Evolution

Answer 17

• Life evolve from simple to more complex forms
• Faunal successions and stratigraphic sequences are in the same order

Question 18

Mapping Unit

Answer 18

Used to group deposits of similar age, materials, and appearance into formations

Question 19

Mapping Units

Answer 19

Bed: A lithologically distinct layer (not normally named unless it is a marker bed) - the smallest recognizable stratigraphic unit
Member: Also a lithologically distinct layer and part of a formation
Formation: Primary units used to map in geology. Range in scale from cm to km - must have a sufficient extent to be useful in mapping.
Group: Two or more formations that share certain lithological characteristics.