TYPES OF UNCONFIRMITY

Here are the main types of unconformities: Angular Unconformity, Disconformity, Nonconformity, Paraconformity, Blended Unconformity.

Jan 18, 2021 - 06:00
Jul 9, 2024 - 23:56
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TYPES OF UNCONFIRMITY

Unconformity

  • A buried erosional or non-depositional surface that divides two different-age rock masses or strata indicates that sediment deposition was not continuous.
  • Although the older layer was often exposed to erosion before the younger layer was evicted, the phrase is used to characterize any discontinuity in the sedimentary geological record.

 

Unconformity formation

 

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  • Unconformities are gaps in the geologic record that can be used to identify events of crustal deformation, erosion, and sea-level changes.
  • They are a feature of stratified rocks and are consequently most commonly found in sediments (but they may also be found in stratified volcanics).
  • They are surfaces that produce a significant gap (hiatus) in the geological record between two rock masses (incorrectly, "time" is absent).
  • Unconformities describe instances when deposition ceased, some previously deposited rock was removed by an erosion interval, and then deposition restarted.

 

Unconformity Types

Disconformity

  • A disconformity is a gap between parallel strata of sedimentary rocks caused by erosion or non-deposition. Subaerial erosion characteristics distinguish disconformities.
  • Soils and waterways from this type of weathering may be found in rocks.
  • A paraconformity is a kind of disconformity in which the separation is only a bedding plane with no discernible buried erosional surface.

 

Nonconformity

  • When the sedimentary rock rests above and was deposited on the pre-existing and eroded metamorphic or igneous rock, a nonconformity exists.
  • The plane of junction is a nonconformity if the rock underneath the break is igneous or has lost its bedding owing to metamorphism.

 

Angular deviation

  • An angular unconformity occurs when horizontally parallel sedimentary rock strata are deposited over tilted and eroded layers, causing angular discordance with the horizontal layers above.
  • Later on, more orogenic activity may distort and skew the whole sequence.

 

Paraconformity

  • A paraconformity is a kind of unconformity in which strata are parallel, there is no visible erosion, and the unconformity's surface resembles a simple bedding plane.
  • Sometimes it's known as nondepositional unconformity or pseudoconformity. Diaastems are short paraconformities.
  • A diastem is a short paraconformity.

 

Buttress unconformity

  • When younger bedding is placed against older strata, a buttress unconformity arises, altering the bedding structure.

 

Blended unconformity

  • A blended unconformity is a type of disconformity or nonconformity that lacks a defined plane or contact separation and may consist of rock-derived soils, paleosols, or pebble beds.

 

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arulprasanth Arul Prasanth - MSc Geology graduate offering comprehensive study materials in Geology, Physics, and English. With a focus on clarity and effectiveness, I aim to provide students with the tools necessary for academic success.