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An Introduction to

Structural Styles and Tectonicsin Petroleum Geology

COMPRESSION

Dr Kevin C. HillUniversity of Melbourne

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Thrust Faultsusually at a low angle to bedding, they

repeat stratigraphic section.

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Detachments,often parallel to bedding, they

separate different structural styles

D e t a c h m e n t

Contorted Beds

P a r a l l e l B e d s

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Thrust repeat in duplex

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Section repeated in Break-Thrust

Fold first, then thrust forelimb

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Section repeated inBreak-Thrust

Fold first, thenthrust forelimb

Forelimb

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Fault-bendFolding

3 types of fold-thrust interactions

ramp

ramp Fault-propagationFolding

DetachmentFolding

Detachment

Detachment

Detachment

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Fault-bend fold or

ramp anticline

PalaeozoicLimestone Cretaceous clastics

Over 40 kmdisplacement

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INCOMPETENT

Typical hanging wall shape

Step spacing dependson thickness changes

major step is locus of younger extensional faults

Major thrust faults don'toverlap significantly

Double the faulted section , net shortening always ~50%

Where thickened section encountersfootwall step motion is transferred

to new fault

Major faults are younger in direction of tectonic transport

FIXEDPOINT

Faults cut up-section indirection of tectonic transport

Faults tend to be parallel to beddingin incompetent rocks and oblique in

competent rocks

COMPETENT "BEAMS"

Idealized Thrust Fault Development

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Position of hinges locate ramp

Gentle dip on top of anticlinegives regional tilt

Ramp height = elevation of horizon on top of

anticline minus regional elevationRegional elevation

Elevation of top must be known

Dip of limb = dip of rampE

E

D

DD

C

CC

B

BB

A AA

RAMPHEIGHT

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Fault Propagation Fold

Tip

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A fault propagation fold inCarboniferous slates, South Wales

TRef I

d

0 1 2 m

after Chapman & Williams (1984)

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Loss of displacementby folding

Tip

Loss of displacementby imbrication

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Detachment fold

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Typical detachments in theAlberta Disturbed Belt

Concentric Fold Detachments

"Sole Fault" Detachment

"Front Fold" Detachment

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Detachment fold then break-

thrust through forelimb

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FLAT

RA M P COMPETENTROCK

INCOMPETENT

Ramp anticline

Ramp / flat geometry

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Possible hangingwall / footwallrelationships

FWF

HWF - Hangingwall Flat

HWR - Hangingwall RampFWF - Footwall FlatFWR - Footwall Ramp

FWFFWF

FWR

FWRHWF

HWF

1.2.

3.4. 5.

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Cape Liptrap – near Melbourne

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Competent beds deform

independently

Internally deformedcompetent beds

D e t a

c h m e n

t

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Competent beds deform

independentlyRamp anticline

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Hook structure top

Ramp anticline

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1.00

1.375

After Liu & Dixon 1995

Competent (strong) beds

deform independently

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DD

R R

1

2

2

Thrust over young beds

Section thickenedby duplication

Thrust cuts up sectionin direction of transport

Thickness normalThickness normal

Normal stratigraphicsequence

Normal stratigraphicsequence

Normalstratigraphic

interval

Thickening

Flat R a m p

3

4

What happens to bed 1 to the right and to beds 3 & 4 to the left?

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Wage

Shelf Kubor-Mendi Trough

Basin Toro

B a s i n T o r o Shelf Toro

Shelf Toro

Kutubu Mubi

NE

Regional Kutubu - Wage - Nembi SectionSW

A

NembiValleyWage

KutubuIagifu

Omati Trough HediniaIorogabaiu Mubi

0

0

5

5

10

10

km

km

Darai Limestone

Miocene (distal)

Eocene

Ieru Formation

(Miocene)

(Cretaceous)

Toro Sandstone

Jurassic

Basement

(Neocomian)

(Paleozoic)0 20 km

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Gulf of Papua

BintuniBasin

SalawatiBasin

KutubuOilfield

HidesGasfield

SFS

Neogene Basin

Late Mio-PlioceneForeland Basin

ArafuraPlatform

T a s m a n L i n e

F ly

Platform

Tangguh Gas Province

New GuineaOil & Gas

CenderawasihBay

250 km Pandora-Pasca

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Fold Belt

HighlandsHighway

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After Dahlstrom 1970

Simple Transfer

Zone

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After Dahlstrom 1970

Footwallboundary

Bedding surfacein upper part of

thrust sheet

Opposed plungesaligned above

buried tear

Tear fault

Bedding surfacein lower half of the thrust sheet

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Mananda

Hides

Juha

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Model for the offset of fold axesabove a footwall lateral ramp

Hides?

Juha?

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FOOTWALL

RAMP ANTICLINE

FLAT

RAMP

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Iagifu-Wage Regional Section

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SAR

Mananda

Moran

Agogo

Paua

IagifuHedinia

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Looking ESE

Previous Modelextent to the west

Iagifu Hedinai

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