Stylolite

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Macrostylolites in a limestone.

Stylolites (Greek: stylos, pillar; lithos, stone) are serrated surfaces within a

tectonic activity.[5][6]

Classification of stylolites

In structural geology and diagenesis, pressure solution or pressure dissolution is a deformation mechanism that involves the dissolution of minerals at grain-to-grain contacts into an aqueous pore fluid in areas of relatively high stress and either deposition in regions of relatively low stress within the same rock or their complete removal from the rock within the fluid. It is an example of diffusive mass transfer. Stylolites are formed by this process.

Stylolites can be classified according to their geometry or their orientation and relationship to bedding.[4]

Geometric classification

Park and Schot (1968) recognized six different geometries in stylolites:[4]

  1. Simple or primitive wave-like
  2. Sutured type
  3. Up-peak type (rectangular type)
  4. Down-peak type (rectangular type)
  5. Sharp-peak type (tapered and pointed)
  6. Seismogram type

Relationship to bedding

Horizontal stylolites
This is the most commonly observed stylolite type. They occur parallel or nearly parallel to the bedding of rocks. This type is most frequently found in layered sedimentary rocks, mostly in carbonate rocks, which have not been affected by intensive tectonic structural activity or metamorphism.
Inclined stylolites or slickolites
This type occurs oblique to bedding. It appears in rocks which are both affected or unaffected by tectonic activity, and can also be found in metamorphic and layered igneous rocks.
Horizontal-inclined (vertical) or crosscutting stylolites
This type is a combination of horizontal and inclined types of stylolites. Horizontal stylolites usually have a higher amplitude than inclined stylolites. Horizontal-inclined can be found in rocks affected by pressure parallel to the bedding plane followed by pressure perpendicular to bedding.
Vertical stylolites
This type of stylolite is related to the bedding at right angles. It may or may not be associated with tectonic activity. It is caused by pressure acting perpendicularly to the bedding.
Interconnecting network stylolites
This type is a network of stylolites, which are related to each other with relatively small angles. This type can be divided into two subtypes. Stylolites of subtype A are characterized by higher amplitudes. They are related to the bedding either horizontally, or at a small angle. Stylolites of subtype B usually appear in rocks which have been affected by tectonic and/or metamorphic activity. These stylolites have a low amplitude with undulations. Their relation to the bedding can vary from horizontal to vertical.
Vertical-inclined (horizontal) or crosscutting stylolites
This type is a combination of horizontal or inclined and vertical stylolite types. In this case the inclined or horizontal stylolites were formed first and the vertical later. This type can be divided into two subtypes by directions of displacement of the inclined stylolites. In subtype A, the displacements could have happened during vertical stylolization, while in subtype B, the displacements could have happened before vertical stylolization.

Development

A stylolite is not a

stable isotope
systematics in limestone on either side of a stylolite plane and found differences confirming different degrees of fluid-rock interaction.

In order for a stylolite to develop, a

dissolve needs to be present, along with a pore network through which dissolved solids can migrate by advection or diffusion from the developing stylolite. Stylolite development can be improved with porosity, as it localizes stress on grains, increasing the stress there. Therefore, it is suggested that bedding-parallel stylolites form in areas of high porosity,[9] and most of the transverse stylolites form along preexisting fractures.[2]

Significance

Stylolites are significant in several fields. In

cement. In stratigraphy, weathering of stylolites generates apparent bedding in many stratigraphic sections and loss of material along stylolites can have a result similar to erosion, with significant stratigraphic thinning. In hydrology, stylolites prevent fluid flow and, in other settings, serve for fluid flow. Also, stylolites are indicators of compressive stress in tectonic studies, and development of transverse stylolites contributes to crustal shortening parallel to the direction of their column.[2]

Gallery

  • A stylolite viewed in thin section in plane polarized light in a packstone, Oehrlikalk formation of the Axen nappe, Wellenberg, Switzerland
    A stylolite viewed in thin section in plane polarized light in a packstone, Oehrlikalk formation of the Axen nappe, Wellenberg, Switzerland
  • Stylolite in a Slovakian limestone
    Stylolite in a Slovakian limestone

See also

References

  1. ^ Dunham J.B.; Larter S. (1981). "Association of Stylolitic Carbonates and Organic Matter: Implications for Temperature Control on Stylolite Formation". AAPG Bulletin. 65.
  2. ^ a b c Middleton, Gerard V., Encyclopedia of sediments and sedimentary rocks, 2003, p. 90-92
  3. doi:10.1306/74D70D12-2B21-11D7-8648000102C1865D
    .
  4. ^
    doi:10.1306/74D71910-2B21-11D7-8648000102C1865D
    .
  5. S2CID 128917505
    .
  6. ^ Petrology of the sedimentary rocks, F.H. Hatch, R.H. Rastall p. 382
  7. ^ Fletcher, C.C. and Pollard, D.D. 1981 Anticrack model for pressure solution surfaces. Geology, 9, 419-24.
  8. ^ Rye, DM, and Bradbury, HJ (1988): Fluid flow in the crust: an example from a Pyrenean thrust ramp. American Journal of Science (288): 197-235.
  9. ^ Merino, E., Ortoleva, P., and Strickholm, P., 1983. Generation of evenly-spaced pressure-solution seams during (late) diagenesis: a kinetic theory. Contributions to Mineralogy and Petrology, 82: 360-370.
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