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A paraconformity is a type of unconformity in which the sedimentary layers above and below the unconformity are parallel, but there is no obvious erosional break between them. A break in sedimentation is indicated, for example, by fossil evidence. It is also called nondepositional unconformity or
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during which no sediments were preserved in a region or were subsequently eroded before the next deposition. The local record for that time interval is missing and geologists must use other clues to discover that part of the geologic history of that area. The interval of geologic time not
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when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock. Namely, if the rock below the break is igneous or has lost its bedding due to metamorphism, then the plane of juncture is a nonconformity.
298:
675:
Septfontaine M. (1995): Large scale progressive unconformities in
Jurassic strata of the Prealps South of lake Geneva: interpretation as synsedimentary inversion structures. Paleotectonic implications. Eclogae geol. Helv., 88:3
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Septfontaine M. (1984): Le Dogger des Préalpes médianes suisses et françaises - stratigraphie, évolution paléogéographique et paléotectonique.- Mém. Soc. Helv. Sci. Nat., vol. 97, 121 p. (Birkhäuser éd.)
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of sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the overlying horizontal layers. The whole sequence may later be deformed and tilted by further
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deposition was not continuous. In general, the older layer was exposed to erosion for an interval of time before deposition of the younger layer, but the term is used to describe any break in the
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A buttress unconformity also known as onlap unconformity, occurs when younger bedding is deposited against older strata thus influencing its bedding structure.
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A blended unconformity is a type of disconformity or nonconformity with no distinct separation plane or contact, sometimes consisting of soils,
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Geological unconformity, Camelback mountain, Arizona, showing deposition of
Chattian sandstone (right) on Precambrian granite (left).
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227:. In these cases, the hiatus in deposition represented by the unconformity may be geologically very short – hours, days or weeks.
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activity. A typical case history is presented by the Briançonnais realm (Swiss and French
Prealps) during the Jurassic.
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U.S. Bureau of Mines
Dictionary of Mining, Mineral, and Related Terms published on CD-ROM in 1996.
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which represents a period of erosion or non-deposition. Disconformities are marked by features of
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the rocks beneath (unless the sequence has been overturned). An unconformity represents
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There is a billion-year gap in the geologic record where this 500-million-year-old
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Encyclopedia of
Science and Technology: An International Reference Work, Volume 14
601:(4th ed.). Upper Saddle River, N.J.: Pearson Prentice Hall. p. 405.
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3-D Structural
Geology: A Practical Guide to Surface and Subsurface Map
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An angular unconformity is an unconformity where horizontally parallel
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82:. The significance of angular unconformity (see below) was shown by
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at
Steamboat Butte in the valley of the Dry Cimmarron, New Mexico
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Rock surface indicating a gap in the geological record
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A nonconformity exists between sedimentary rocks and
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erosion. This type of erosion can leave channels and
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Monroe J.S., Wicander R. & Hazlett R.W. (2007).
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pseudoconformity. Short paraconformities are called
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547:"Siccar Point and Teaching the History of Geology"
8:
599:Principles of sedimentology and stratigraphy
63:or non-depositional surface separating two
747:. Springer Science & Business Media.
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626:Essentials of Earth History 4th Edition
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728:
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573:Physical geology: exploring the Earth
342:Taum Sauk Hydroelectric Power Station
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215:Angular unconformities can occur in
147:is an unconformity between parallel
689:Principles of Sequence Stratigraphy
307:(at the hammer) between underlying
71:of different ages, indicating that
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718:. McGraw-Hill. 1966. p. 192.
576:. Cengage Learning. p. 267.
51:in 1787 and photographed in 2003.
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105:The rocks above an unconformity
800:BGS Lexicon of Names Rock Units
417:rocks overlying steeply-tilted
796:"Redheugh Sandstone Formation"
630:. Prentice Hall, Inc. p.
336:overlies 1.5-billion-year-old
223:deposited by volcanoes during
1:
802:. British Geological Survey
102:in 1788, both in Scotland.
864:
395:age (444–433 Ma) Silurian
387:age (371–359 Ma) Devonian
768:Neuendorf K.K.E. (2005).
552:. University of Wisconsin
545:Keith Montgomery (2003).
774:. Springer. p. 73.
692:. Elsevier. p. 15.
476:Angular unconformity in
460:Angular unconformity in
114:represented is called a
86:, who found examples of
741:Groshong R. H. (2013).
622:Stokes, W. Lee (1982).
440:between the underlying
359:at Ratssteinbruch near
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686:Catuneanu O. (2006).
527:Hutton's Unconformity
252:Buttress unconformity
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88:Hutton's Unconformity
36:Hutton's Unconformity
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438:Angular unconformity
411:Angular unconformity
377:angular unconformity
260:Blended unconformity
200:Angular unconformity
192:Angular unconformity
163:in the rock record.
771:Glossary of Geology
657:, pp. 404–405.
597:Boggs, Sam (2006).
225:explosive eruptions
838:Historical geology
532:2015-09-24 at the
508:Great Unconformity
480:layers erupted by
444:and the overlying
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118:. It is a kind of
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423:Praia do Telheiro
389:Old Red Sandstone
153:sedimentary rocks
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478:pyroclastic rock
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312:Borden Formation
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107:are younger than
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120:relative dating
94:in 1787 and at
80:geologic record
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848:Unconformities
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239:Paraconformity
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175:Nonconformity
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843:Stratigraphy
804:. Retrieved
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554:. Retrieved
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442:Dockum Group
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381:Siccar Point
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100:Berwickshire
96:Siccar Point
84:James Hutton
59:is a buried
57:unconformity
56:
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344:, Missouri.
181:metamorphic
77:sedimentary
832:Categories
806:5 February
729:Boggs 2006
655:Boggs 2006
608:0131547283
556:2015-03-16
514:References
482:Chimborazo
425:, Portugal
393:Llandovery
219:layers of
67:masses or
49:John Clerk
421:rocks at
397:greywacke
391:overlies
385:Famennian
375:Hutton's
363:, Germany
266:paleosols
161:paleosols
157:subaerial
61:erosional
676:553–576.
530:Archived
502:See also
415:Triassic
338:rhyolite
331:dolomite
246:diastems
217:ash fall
210:orogenic
92:Jedburgh
73:sediment
45:Scotland
41:Jedburgh
464:, China
361:Dresden
340:, near
272:Gallery
778:
751:
696:
638:
605:
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383:where
206:strata
149:layers
116:hiatus
69:strata
550:(PDF)
126:Types
808:2023
776:ISBN
749:ISBN
694:ISBN
636:ISBN
603:ISBN
578:ISBN
111:time
65:rock
413:of
379:at
288:at
183:or
151:of
98:in
90:at
55:An
39:at
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632:65
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143:A
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Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
