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Mechanisms of crustal subsidence

Mechanisms of crustal subsidence. Sedimentary basins Isostasy Basins due to stretching Basins due to cooling Basins due to convergence Basins due to tearing of crust. Principles of isostasy. Hawaiin seamount chain with flexed lithospheric lows. Basins due to stretching.

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Mechanisms of crustal subsidence

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  1. Mechanisms of crustal subsidence • Sedimentary basins • Isostasy • Basins due to stretching • Basins due to cooling • Basins due to convergence • Basins due to tearing of crust

  2. Principles of isostasy

  3. Hawaiin seamount chain with flexed lithospheric lows

  4. Basins due to stretching

  5. Mantle plumes associated with rifting – not required, but do occur e.g. North Atlantic rifting and emplacement of Tertiary igneous province

  6. Half-graben formation during rifting

  7. Faults, lakes and volcanoes dominate the landscape

  8. Lakes filling half-grabens with thinned lithosphere generating heating and volcanism

  9. Basins due to thermal subsidence

  10. Basins due to thermal subsidence after heating following rifting– passive margins

  11. Typical form of a passive margin

  12. Passive margin accumulates thick sediment that drapes the continent/ocean transition. Subsidence is slow and exponentially declines as cooling of rifted lithosphere slows.

  13. Basins due to convergence

  14. Crustal depressions due to loading during subduction – accretionary trench

  15. Basins due to loading of continental lithosphere – Foreland Basins

  16. Basins due to tearing – strike-slip basins(pull-apart)

  17. San Andreas Fault

  18. Basins due to tearing of crust – strike-slip basins

  19. Summary • Sedimentary Basin form by a number of means • Lithosphere can stretch (Rift basins) • Cool and subside (Passive margins) • Be loaded and bend (accretionary trench on oceans – Foreland basin on continents) • Tear apart to form pull-apart or strike-slip basins. • Isostasy is critical

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