Exam 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 Thrust belt typically propagates into foreland basin,

moving depocenter in the direction of thrust motion Piggyback BasinPiggyback 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

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Foreland basins can accumulate exceptionally thick (~10 km) stratigraphic successions

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Homewood et al. (1986)

CONVERGENT SETTINGS

Intracratonic BasinIntracratonic 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 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’

Basin formation in strike-slip

TRANSFORM SETTINGS Pull-apart basinsPull-apart basins - caused by releasing step or

dilational jog in fault system Strike-slip basinsStrike-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)

Ridge- convergence system transform: Dead Sea rift

Garfunkel (1981)

BASINS AS TECTONIC MARKERS

AccretionTerranes are ‘fault-bounded 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 strike-slip

Present-day distribution of Tethyan fusilinids (red dots - ‘home territory’)

M.W. McElhinneyM.W. McElhinney