Mechanisms of crustal subsidence Sedimentary basins Isostasy Basins due to stretching Basins due...
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Transcript of Mechanisms of crustal subsidence Sedimentary basins Isostasy Basins due to stretching Basins due...
Mechanisms of crustal subsidenceMechanisms of crustal subsidence
Sedimentary basinsSedimentary basins IsostasyIsostasy Basins due to stretching Basins due to stretching Basins due to coolingBasins due to cooling Basins due to convergenceBasins due to convergence Basins due to tearing of crustBasins due to tearing of crust
Principles of isostasy
Hawaiin seamount chain with flexed lithospheric lows
Basins due to stretchingBasins due to stretching
Mantle plumes associated with rifting – not required, but do occur e.g. North Atlantic rifting and emplacement of Tertiary igneous province
Half-graben formation during rifting
Faults, lakes and volcanoes dominate the landscape
Lakes filling half-grabens with thinned lithosphere generating heating and volcanism
Basins due to thermal Basins due to thermal subsidencesubsidence
Basins due to thermal subsidence after heating following rifting– passive margins
Typical form of a passive margin
Passive margin accumulates thick sediment that drapes the continent/ocean transition.
Subsidence is slow and exponentially declines as cooling of rifted lithosphere slows.
Basins due to Basins due to convergenceconvergence
Crustal depressions due to loading during subduction – accretionary trench
Basins due to loading of continental lithosphere – Foreland Basins
Basins due to tearing – Basins due to tearing – strike-slip basinsstrike-slip basins
(pull-apart)(pull-apart)
San Andreas Fault
Basins due to tearing of crust – strike-slip basins
SummarySummary
Sedimentary Basin form by a number of Sedimentary Basin form by a number of meansmeans
Lithosphere can stretch (Lithosphere can stretch (Rift basinsRift basins)) Cool and subside (Cool and subside (Passive marginsPassive margins)) Be loaded and bend (Be loaded and bend (accretionary trenchaccretionary trench
on oceans – on oceans – Foreland basinForeland basin on continents) on continents) Tear apart to form Tear apart to form pull-apart or strike-slip pull-apart or strike-slip
basinsbasins.. Isostasy is criticalIsostasy is critical