Surfaces characterized by onlap or toplap geometric relationships. Unconformity time-gaps may represent simply prolonged periods of sub-aerial exposures with minimal erosion, possibly with local valley or channel down-cutting. They may represent periods of uplift and major sub-aerial erosion of strata, or they may represent submarine erosion by turbidites, slump or submarine currents.
On this seismic line, several unconformities can be easily recognized by onlap and toplap (truncation) geometrical relationships. These unconformities limit stratigraphic cycles associated with 2sd order eustatic cycles.
Ellipsoid with an unique axis. An uniaxial ellipsoid corresponds to a sphere. The hydrostatic pressure can be represented by a uniaxial ellipsoid stress.
The hydrostatic or pore pressure acts in opposite sense than the geostatic pressure. One can speak in effective vertical pressure,i.e., the lithostatic pressure reduced by hydrostatic pressure.
When flow pattern varies with time. Streamlines cross layering and deflect it as flow-folds.
Postdepositional diapir growth (in the most extreme or ideal form) through prekinematic overburden. Thus, as the structure increases in relief by growing upward, its base remains at a constant depth, while its crest rises toward the sediment surface. More commonly, diapirs grow by combination of the ideal end members of active and passive piercement because sediments accumulate while the diapir works its way to the surface. This kind of active piercement involves forceful intrusion, which is probably possible only in relatively tall diapirs overlain by relatively thin overburden, unless the overburden is being extended or is fluid or usually weak.
This kind of active piercement involves forceful intrusion, which is possible only in relatively tall diapirs overlain by relatively thin overburden, unless the overburden: (i) is being extended, (ii) is fluid or (iii) usually weak.
A structurally high area in the crust produced by positive movements that raise or upthrust the rocks. Presently, the term uplift is used to express any kind of upward movement.
Upthrown Fault Compartment
Synonym of Hanging wall.
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Last update : January, 2006