Chapter 3 - Geologic Map and Cross-Section Interpretation

Question 1

Allochthon

Answer 1

A fault block or rock mass moved from its place of origin

Question 2

Autochthon

Answer 2

A rock mass underlying a thrust fault that has not moved from its location of origin

Question 3

Blind Thrust

Answer 3

A thrust fault that dies out in the subsurface as it loses slip and stratigraphic separation

Question 4

Detachment Fault

Answer 4

A low-angle normal fault associated with regional extension

Question 5

Dip-slip Fault

Answer 5

A fault in which the movement is parallel to the dip of the fault plane, such as a normal, reverse, or listric fault

Question 6

Fenster

Answer 6

A “window” into rocks underlying a thrust fault

Question 7

Footwall Block

Answer 7

The block that underlies a non-vertical fault

Question 8

Growth Fault

Answer 8

A fault that forms contemporaneously with deposition in sedimentary rock. The throw increases with depth and the sedimentary units on the downthrown side are thicker than the corresponding units on the upthrown side

Question 9

Hanging-wall Block

Answer 9

The block that overlies a non-vertical fault

Question 10

Heave

Answer 10

The amount of horizontal displacement on a fault

Question 11

Klippe

Answer 11

An outlier of a thrust sheet completely surrounded by the exposed footwall

Question 12

Key Beds

Answer 12

A well-defined, easily identified strata that is distinctive enough to be useful in correlation in mapping

Question 13

Listric Fault

Answer 13

A fault with a curved fault plane. Near the surface the fault plane is steeply dipping, but it becomes progressively flatter with depth. Listric faults may be normal or reversed

Question 14

Ma

Answer 14

Abbreviation for Mega annum, one million years

Question 15

Nappe

Answer 15

A sheetlike rock unit that has moved over other rocks (allochthonous) on a predominantly horizontal surface

Question 16

Net Slip

Answer 16

The distance between two formerly adjacent points on either side of the fault, measured on the fault surface

Question 17

Nonconformity

Answer 17

An unconformity formed by older igneous rocks in contact with younger sediments, indicating a missing time after the igneous intrusion

Question 18

Normal Fault

Answer 18

A dip-slip fault in which the hanging wall has moved down relative to the footwall. The dip of the fault is between 45° and 90°

Question 19

Oblique-slip Fault

Answer 19

A fault in which movement is not parallel to the strike or dip of the fault plane

Question 20

Offset

Answer 20

The horizontal component of displacement measured perpendicular to the strike of the disrupted unit

Question 21

Reverse Fault

Answer 21

A dip-slip fault in which the hanging wall has moved up relative to the footwall. The dip of the fault is between 45° and 90°

Question 22

Rule of V’s

Answer 22

The outcrop pattern of a formation as it crosses a valley forms a V shape (as viewed on a map). The V points in the direction that the formation underlies the valley.

Question 23

Strike Separation

Answer 23

The horizontal distance between a stratigraphic unit offset by a fault, measured along the strike of the fault. It is an apparent displacement.

Question 24

Strike-slip Fault

Answer 24

A fault in which movement is parallel to the strike of the fault plane

Question 25

Throw

Answer 25

The amount of vertical displacement on a fault, also, the vertical component of net slip

Question 26

Thrust Fault

Answer 26

A reverse fault in which the fault plane dips less than 45°

Question 27

Type Locality

Answer 27

The place where a geologic feature (such as a fossil species) was first recognized and described. It contains the type section

Question 28

Type Section

Answer 28

The originally described strata that constitutes a stratigraphic unit to which other parts of the unit may be compared. It is preferable to describe the location where the unit attains its maximum thickness and where the top and bottom unit are exposed.

Question 29

Unconformity

Answer 29

A gap in the geologic record; and interruption in the depositional sequence that implies uplift and erosion have removed part of the geologic record or non-deposition has occurred