Transcript PowerPoint Presentation - ISOSTASY - UW

Exam
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Short answer questions
Diagram interpretation
Some multiple choice
Material from discussion sections will be
included
Lab material will not be covered (although
diagrams may be used)
Powerpoint presentations at
http://www.geology.wisc.edu/~laurel/204/
TECTONIC BASINS
The sedimentary
record of tectonic
processes
CONVERGENT SETTINGS
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Thrust belt typically propagates into foreland basin,
moving depocenter in the direction of thrust motion
Piggyback Basin: basins that are on the hanging wall of
a thrust fault and move with the hanging wall.
Sediments evolve from fine-grained turbidites to shallow
water continental seds over time
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Foreland basins can accumulate exceptionally thick (~10 km)
stratigraphic successions
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Homewood et al. (1986)
CONVERGENT SETTINGS
Intracratonic Basin: large-scale basins far
from mountain belts that form very wide,
gentle synclines. Commonly large but not
very deep
Locations of intracratonic
basins worldwide
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Characterized by basins
separated by arches or
domes. Generally middle
Cambrian or younger seds
deposited on Precambrian
basement. Most seds
marine, deposited by
epeiric seas (i.e., where
ocean transgressed on
continent). Deepest parts of
basins continued to receive
sediments during marine
regressions.
TRANSFORM SETTINGS
Strike-slip fault = a fault on which the
movement is parallel to fault’s strike
 Basins form where irregularities in fault
system cause depocenters to form locally
 Distinctive in that they are not regional in
extent
 Fill with material sourced locally and from
plate that is ‘passing by’
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Basin formation in strike-slip
TRANSFORM SETTINGS
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Pull-apart basins - caused by releasing step or
dilational jog in fault system
Strike-slip basins form in transtensional regimes
and are usually relatively small but also deep;
they are commonly filled with coarse facies
(e.g., alluvial fans) adjacent to lacustrine or
marine deposits
 Examples: Salton Sea, California; Ridge
basin, California; Dead Sea, Israel
3 simple types of
transform margin
San Andreas fault
system
Extends from Mendocino
transform-transform-trench
triple junction to Rivera
ridge-trench-transform
triple junction
McDonald et al. (1979)
Alpine fault
continental
trench-trench
transform
Grindley (1974)
Ridgeconvergence
system
transform:
Dead Sea rift
Garfunkel (1981)
BASINS AS TECTONIC MARKERS
Accretion
Terranes are ‘faultbounded blocks of
crust that accrete to
the ancient cores of
the continents. The
process makes the
continents increase in
extent and rewords
them into what
amounts to geologic
collages’
- David G. Howell
(1985)
X-section through Cordilleran
Terranes
Sutures bound accreted terranes
 Note that movement by which terranes
were emplaced may be reverse or strikeslip
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Present-day distribution of Tethyan
fusilinids (red dots - ‘home territory’)
M.W. McElhinney