Breakup unconformity

break up unconformity Archives

The grabens form discrete basins that typically fill with coarse-grained clastic sediments derived from the hanging walls of their bounding faults.

Normal faulting is predominantly listric and fault block rotation during sedimentation results in local stratigraphic discordances.

Flank uplifts provide a huge gradient advantage for sediment delivery to the adjacent alluvial and lacustrine settings.

Local volcanism ranges from quietly effusive to catastrophic plinian eruptions; they contribute lava flows and volcaniclastics to the local stratigraphy as well as shape rift valley topography.

This transition is accompanied by lithospheric cooling and a change in the subsidence mechanism from predominantly brittle failure to flexural. Stratigraphically the transition is represented by an unconformity, often called a break-up unconformity.

The addition over time (100-200 million years) of water and sediment is part of the isostasy equation.

Passive margins contain some of the thickest, most extensive sedimentary accumulations on Earth; continent-parallel lengths are measured in 1000s of kilometres, their thickness more than 10 km.