Maps

Question 1

Blind Thrust

Answer 1

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

If the fault plane terminates before it reaches the Earth’s surface, it is referred to as a blind thrust fault. Because of the lack of surface evidence, blind thrust faults are difficult to detect until they rupture. The destructive 1994 quake in Northridge, California, was caused by a previously undiscovered blind thrust fault.

Because of their low dip, thrusts are also difficult to appreciate in mapping, where lithological offsets are generally subtle and stratigraphic repetition is difficult to detect, especially in peneplain areas.

Question 2

Detachment Fault

Answer 2

A low-angle normal fault. Also known as a sole fault.

Question 3

Dip-slip fault

Answer 3

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

Question 4

Footwall block

Answer 4

The block that underlies a non-vertical fault

Question 5

Fossil Assemblages

Answer 5

A group of fossils that occur at the same stratigraphic level

Question 6

Growth fault

Answer 6

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 7

Hanging wall block

Answer 7

The block that over lies a non-vertical fault

Question 8

Heave

Answer 8

The amount of horizontal displacement on a block

Question 9

Index fossil

Answer 9

A fossil that identifies and dates the strata in which found. It combines a wide geographic range with a narrow stratigraphic occurrence.

Question 10

Key beds

Answer 10

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

Question 11

Listric Fault

Answer 11

A spoon-shaped fault. near the surface the fault plane is steeply dipping, but it becomes progressively flatter with depth. Listric faults may be normal or reverse.

Question 12

Net Slip

Answer 12

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

Question 13

Normal Fault

Answer 13

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 degrees.

Question 14

Oblique-slip fault

Answer 14

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

Question 15

Offset

Answer 15

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

Question 16

Reverse fault

Answer 16

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 degrees.

Question 17

Rule of V’s

Answer 17

The outcrop pattern of a formation as it crosses a valley forms a v shape. The v direction indicates the dip of the underlying formation

Question 18

Strike separation

Answer 18

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

Question 19

Strike-slip fault

Answer 19

a fault in which movement is parallel to the strike of the fault plane.

Question 20

Throw

Answer 20

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

Question 21

Thrust fault

Answer 21

A reverse fault in which the fault plane dips less than 45 degrees.

Question 22

Type Locality

Answer 22

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

Question 23

Type Section

Answer 23

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 are both exposed.

Question 24

Unconformity

Answer 24

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