Lab 7 – Structural GeologyLab 7 – Structural GeologyChapter 10Chapter 10

Turn In:Turn In:Lab 6Lab 6

Pre-Lab 7Pre-Lab 7

EC 2EC 2

Handouts:Handouts:Quiz 6Quiz 6

Lab 7Lab 7

Pre-Lab 8Pre-Lab 8

STRESSSTRESS - direct - direct pressure on the rock.pressure on the rock. Compressive = shortenCompressive = shorten Tensional = extensionTensional = extension

STRAINSTRAIN – when rock – when rock is stressed to the point is stressed to the point of failure = permanent of failure = permanent deformation.deformation.

http://www.tulane.edu/~sanelson/images/deformmeta.gif

DeformationDeformation

BedsBeds are said to be dipping if they are oriented more than 0are said to be dipping if they are oriented more than 0oo from from horizontal. (A cross-section sort of thing.)horizontal. (A cross-section sort of thing.)

Dip direction Dip direction is the compass direction a marble would roll down the is the compass direction a marble would roll down the top of the individual bed. (Not the topography…)top of the individual bed. (Not the topography…)

(A map view sort of thing.)(A map view sort of thing.)Which compass direction do these beds Which compass direction do these beds

appear to be dipping?appear to be dipping?(view looking approximately south)

W

Dip angleDip angle is the angle between horizontal and the flat face is the angle between horizontal and the flat face of the bed. (A cross-section sort of thing.)of the bed. (A cross-section sort of thing.)

How much do these beds appear to be dipping?How much do these beds appear to be dipping?

~35o

W

(view looking approximately south)

StrikeStrike is the compass direction 90is the compass direction 90oo from the dip direction, from the dip direction, and is one direction in which beds are laterally continuous.and is one direction in which beds are laterally continuous.

(A map view sort of thing.)(A map view sort of thing.)

Approximately which compass direction do these beds Approximately which compass direction do these beds appear to be striking?appear to be striking?

~35o

W

(view looking approximately south)

What does this look like What does this look like in map view?in map view?

(view looking southwest)

Topo map review – find the valley and the ridgesGeol map stuff – find the strike and dip symbols

What are the map units What are the map units relative to the picture?relative to the picture?

TS2 Tertiary seds TB1

TB2

Tertiary basalt 1

Tertiary basalt 2

20

N

2020

20

*

*

A

A’

What does this look likeWhat does this look like in cross-section? in cross-section?A A’

(view looking southwest)

20

N

2020

20

Sketch only – NOT TO SCALE.

TS2 Tertiary seds TB1

TB2

Tertiary basalt 1

Tertiary basalt 2*

*

A

A’

Quick Review:Quick Review: Identify the approximate dip Identify the approximate dip direction, dip angle, and strike in the close outcrop.direction, dip angle, and strike in the close outcrop.

~??o

The name of aThe name of a landform landform is determined by how the beds dip…is determined by how the beds dip…A side effect is the relations of older and younger beds…A side effect is the relations of older and younger beds…

Folds and Block DiagramsFolds and Block Diagrams

AnticlineAnticline = oldest = oldest rocks exposed in rocks exposed in the center.the center.

SynclineSyncline = = youngest rocks youngest rocks exposed in the exposed in the centercenter

Which directions are these beds dipping?Which directions are these beds dipping?What are the relations of older and younger beds?What are the relations of older and younger beds?

What are the names of the landforms?What are the names of the landforms?

www.geology.wisc.edu/courses/g112

Which way are the Which way are the beds dipping?beds dipping?

What are theWhat are thelandforms?landforms?

CFW ‘07

web.uct.ac.za/depts/geolsci/dlr/laingsburg

www.geology.wisc.edu/courses/g112

Which feature has on overturned limb?Which feature has on overturned limb?Which way is up on each limb?Which way is up on each limb?

Economic LookEconomic Look

Folds in alternating permeable and Folds in alternating permeable and impermeable layers = traps.impermeable layers = traps. Can trap water, oil, etc…Can trap water, oil, etc…

http://www.emporia.edu/earthsci/amber/students/shirley/anticlinetrap.gif

Mt. Withrow

As the Rocky Mountains formed, the strata (rock

layers) of the Earth's crust were subjected to stress which resulted in strain

(folding).

Ridges = resistant sandstoneValley = much less resistant

shale.

http://gsc.nrcan.gc.ca/natmap/cf/intro_e.php

Which way are the beds Which way are the beds dipping? dipping?

Where is the nose?Where is the nose?What is the name of the What is the name of the

structure? structure? Which way is it plunging?Which way is it plunging?

Stress Types and FaultsStress Types and Faults Compressive Stress:Compressive Stress: causes shortening of the causes shortening of the

body on which it actsbody on which it acts Reverse or Thrust Fault:Reverse or Thrust Fault: one rock gets one rock gets

pushed up over another.pushed up over another.

Tensional StressTensional Stress:: Causes lengthening of the Causes lengthening of the body on which it actsbody on which it acts Normal Fault:Normal Fault: One rock slides down and away One rock slides down and away

from anotherfrom another

Stress Types and FaultsStress Types and Faults

Shear Stress:Shear Stress: Causes shearing/tearing of the body Causes shearing/tearing of the body on which it acts.on which it acts. Strike-Slip Fault:Strike-Slip Fault: One rock slides past another One rock slides past another

horizontally. horizontally.

Stress Types and FaultsStress Types and Faults

Quick Review of Map Views –In each picture:

Which units are oldest/youngest?Which way are the beds dipping?What structures are present?

Quick Review of Map Views –In each picture:

Which units are oldest/youngest?Which way are the beds dipping?What structures are present?

Seismic InterpretationSeismic Interpretation Offshore Netherlands “F3” dataset courtesy of Paul deGroot of dGBOffshore Netherlands “F3” dataset courtesy of Paul deGroot of dGB Open-source seismic software from OpendTect.orgOpen-source seismic software from OpendTect.org

Seismic Interpretation LabSeismic Interpretation Lab 1) Strike and Dip

Put at least 10 strike-and-dip symbols on the horizontal section, consulting the vertical section as needed.

Identify and label a dome. Identify and label a basin. For the dome and basin you interpreted, explain the observations that

support your interpretations. Point out the observations noted on your sections:

Offshore Netherlands “F3” dataset courtesy of Paul deGroot of dGB Open-source seismic software from OpendTect.org

Seismic Interpretation Lab Ex. 1 horizontal sectionSeismic Interpretation Lab Ex. 1 horizontal section

Seismic Interpretation Lab Ex. 1 vertical sectionSeismic Interpretation Lab Ex. 1 vertical section

2) Plunging Fold On the east side of the horizontal section is a plunging fold.

Mark some strikes and dips around it, referring to the vertical sections.

Interpret whether the fold is an anticline or syncline:

Interpret which direction the fold is plunging:

Label the fold on the horizontal section with the proper symbol at its axis.

Describe how your observations support your interpretations:

Seismic Interpretation Lab Ex. 2, 3 horizontal sectionSeismic Interpretation Lab Ex. 2, 3 horizontal section

Seismic Interpretation Lab Ex. 2-5 vertical section Inline 102Seismic Interpretation Lab Ex. 2-5 vertical section Inline 102

Seismic Interpretation Lab Ex. 2-5 vertical section Inline 190Seismic Interpretation Lab Ex. 2-5 vertical section Inline 190

Seismic Interpretation Lab Ex. 2-5 vertical section Inline 290Seismic Interpretation Lab Ex. 2-5 vertical section Inline 290

Seismic Interpretation Lab Ex. 2-5 vertical section Inline 390Seismic Interpretation Lab Ex. 2-5 vertical section Inline 390

Seismic Interpretation Lab Ex. 2-5 vertical section Inline 490Seismic Interpretation Lab Ex. 2-5 vertical section Inline 490

3) Fault Tracing On the east side of the horizontal section is a prominent fault. Mark

the fault on the horizontal section.

Mark the same fault on each of the vertical sections, if it appears on that section.

What is the average strike direction of the fault? Average dip and direction?

What is the sense of offset on the fault: horizontal; or vertical?

What type of fault is it: reverse; thrust; normal; or strike-slip?

Complete the labeling of the fault on the horizontal section with the proper symbol.

Mark where the fault terminates on the horizontal section.

Discuss whether you can rule out that this fault has oblique slip. Could it be a mixture of types?

4) Unconformities On the east side near the middle of each vertical section there are

several unconformities (originating in a hiatus of sedimentation between deposition of delta lobes). These are evident as terminations of one bed (reflection) against another. Go through the 5 vertical sections and mark at least 5 terminations on each, with a short arrow pointing along a bed to its termination.

Mark one unconformity across all 5 vertical sections with the wiggly line symbol.

5) Reservoirs Reservoirs of fluid (oil, gas, water, steam) trapped in the rock pore

spaces tend to make seismic bright spots. Circle a few bright spots on the Inline vertical sections 102 and 190.

Discuss whether these potential oil reservoirs may be associated with any of the other features you have interpreted.