CONTINENTAL BREAKUP
Geometric aspects of continental breakup: How do continents break ? Pure shear vs simple shear ...
The animation below shows an example of asymmetric extension (the simple shear strin regime is dominant, from Stampfli & Marchant, 1997). Note that 1/ the normal faults on both margins have the same dip direction, and 2/ that volcanic activity tends to localize in the upper plate (ie, the plate above the detachment surface). These features are certainly symptomatic of asymmetric extension.
• to: Transtensive phase
• to+10Myr: Lithospheric breakup via simple shear
• to+15Myr: Asthenospheric diapir and thermal uplift dominated by pure shear
• to+20Myr: Denudation of sub-continental mantle
• to+25Myr: Sea floor spreading extension can carry on within the upper plate;
• to+40Myr: Young passive margin and newly formed oceanic floor.