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