What is convolute lamination?
What is convolute lamination?
Convolute lamination is a common fold structure within turbidite beds, attributed to the deformation of sediment during or soon after deposition of the host bed. Folds show a down-flow asymmetry and doubly-vergent diapiric geometries (‘mushroom’-shaped structures).
How convolute lamination form?
Convolute bedding forms when complex folding and crumpling of beds or laminations occur. This type of deformation is found in fine or silty sands, and is usually confined to one rock layer. Convolute laminations are found in flood plain, delta, point-bar, and intertidal-flat deposits.
What are convolute folds?
convolute folds is primarily a shear stress due to the increasing pore pressure in liquefied cohesionless coarse-grained sandy layers and ductile or brittle deformation (folded or dislocated layers) in more cohesive muddy layers.
What causes soft-sediment deformation?
Soft-sediment deformation structures are the result of liquefaction or fluidization in water-saturated unconsolidated sediments. Liquefaction or fluidization may be caused by various natural processes [1–4].
What is ripple cross lamination?
The form of cross-lamination (see crossstratification) produced by the migration of wave-generated ripples, or combined flow ripples (i.e. ripples formed by a combination of wave action and unidirectional flow).
What is a parallel fold?
A fold in which the orthogonal thickness of layers remains constant throughout, so that adjacent, bounding, fold surfaces are parallel. Because of their geometry, parallel folds cannot maintain their profiles over long distances; their form changes along the axial plane.
Where does soft sediment deformation occur?
Soft-sediment deformation structures are common on passive continental margins, in trenches at. subduction zones, and in strike-slip environments. Rocks from all these tectonic environments are. incorporated into orogens, where soft-sediment deformation structures should be common.
How will you distinguish one bed to another?
Bedding refers to sedimentary layers that can be distinguished from one another on the basis of characteristics such as texture, composition, colour, or weathering characteristics (Figure 9.22). They may also be similar layers separated by partings, narrow regions marking weaker surfaces where erosion is enhanced.
What is the difference between cross bedding and ripple marks?
RIPPLE MARKS are produced by flowing water or wave action, analogous to cross-bedding (see above), only on a smaller scale (individual layers are at most a few cm thick). The cross-beds or (more accurately) cross-laminae are inclined to the right, thus the water was flowing from left to right.
What do ripple marks signify?
In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water (current or waves) or wind.
Where does convolute lamination occur in the ocean?
Convolute bedding occurs in both marine and nonmarine sediments of many environmental types. Although essentially syndepositional, its development generally lags behind deposition to a greater or lesser degree. Convolute laminations found in turbidite deposits are ascribed to the forces known to exist in turbidity currents.
How are convolute laminations and load structures related?
The significance of convolute laminations and load structures in turbidites has been discussed. Convolute laminae are related to flow reflections against bounding slopes. Basal load casts are related to decelerations of high-density flows against bounding slopes.
Where are pseudonodules and convolute lamination found?
Soft-sediment deformation structures, like convolute lamination and pseudonodules, are common in deep-marine turbidites, but details of their origin and timing of formation remain a source of debate.
Why are convolute laminations found in turbidite deposits?
Convolute laminations found in turbidite deposits are ascribed to the forces known to exist in turbidity currents. Convolutions are a fossil record of the forces (current action, loading, sudden regular releases of pressure) acting on a laminated bed during sedimentation.