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7/30/2019 10A.ext Plates to Basin
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10A. BASEMENT-INVOLVED
EXTENSION: PLATE TO
BASIN SCALE
• Plate-Tectonic Habitat
• Full Grabens
• Transfer Zones
• Half Grabens
• Accommodation Zones
• Normal and Oblique Extension
TopicsDivergent & Passive Margins
Plate-Tectonic Habitat
Rifted Margin Evolution
passive margin
salt
overpressured shale
Basin styles
simple
shear
pure
shear
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Upper plate vs. lower plate margin
simple-shear model
Closed Atlantic with related rift structuresRifted Margin Evolution
original idea later idea
Thermal uplift and subsidence
rift sequence
drift sequence
Regional unconformities
North Sea
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Basin Styles
undeformed full graben deformed full graben
domino blocks
internal deformation required
rotated block with keystone grabenramp-flat half graben
internally deformed half graben
Internally undeformed full graben
Internally deformed full graben
Sequential rigid-block restoration
Rhine Graben
North Sea
deep crustal
seismic
profiledeep seismic line
Deep seismic profile across Viking Graben
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Rift framework below passive marginArea-balanced forward model of growth full graben
Area-depth relationship and requisite strain Transfer Zones
Structural asymmetry switches along strike Rio Grande rift
Strike-slip boundary fault
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strike-slip
boundary fault
Embudo
fault
zone
Valles
caldera
Rio Grande rift
location map
accommodation-zone volcanism
Embudo
fault
zone
view SE, across Valles caldera
Rio Grande riftRhine Graben
Rhine Graben
Rhine Graben
Bresse Graben
Accommodation-zone transform fault
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Accommodation-zone transform fault Accommodation-zone transform fault
Half graben as the fundamental unit of rifting
Half Grabens
Half graben: Grand Tetons, western U. S.
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Half-graben with extension in HW
Profile across Lake Malawi, East African rift valley
Profile across central Gulf of Suez
Area balance of half graben
use the
net area
constant
BLT half
graben
Oblique simple-shear modelStrain in rollover
e = [sin α / sin (α - ψ)] -1 (3)
e90 = (1 / cos ψ) - 1 (α = 90°) (4)
α = arctan [(e + 1) sin ψ] / [(e + 1) cosψ - 1] (1)
Connection between strain and shear angle
Bulk strain in rollover
Domino extension
Structural style depends on relative dips of dominoes and
master fault
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Experimental Model
e = 28%
Fault predicted with calculated shear angle
Gulf of Suez cross section GGulf of Suez cross section G
measurements
10 km
Lake Malawi
α = arctan [(e + 1) sin ψ / [(e + 1) cos ψ - 1]]
General relationships
between half grabensAccommodation Zones Accommodation zone stratigraphy
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Structural asymmetry switches along strike Accommodation zones
Effects of
Extension
Direction
Extension
perpendicular
to rift
Extension
oblique to rift
Oblique
extension with
offsets
Normal and
oblique
extension
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Gulf of
Suez:
oblique
opening
Gulf of
Suez
Gulf of SuezGulf of Suez
deformed half graben
direction of
asymmetry
changes
along strike
ST 10A-2
Identify extensional style elements
Determine extension direction
Find locations of maximum uplift
Define probable traps
Identify extensional style elements
Determine extension direction
Find locations of maximum uplift
Define probable traps
