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  Encyclopedia of Keywords > Nature > Unconformity   Michael Charnine

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  1. An unconformity is a gap in the time record for that location.
  2. An unconformity is a surface of erosion or non-deposition. (Web site)
  3. An unconformity is a substantial break in the depositional record. (Web site)
  4. An unconformity is a buried erosion surface separating two rock masses or strata of different ages, indicating that sediment deposition was not continuous. (Web site)
  5. An unconformity is a gap, or break, in the geologic record.


  1. Nature of the basal Cambrian boundary - unconformity of regional (or even continental) scale.
  2. A first-order exploration criterion is irregularities of the basal unconformity in Paleo- to Mesoproterozoic red-bed basins.
  3. Below the basal unconformity, red hematitic and bleached clay-altered regolith grades down through chloritic altered to fresh basement gneiss.


  1. Technically, a fall line is an unconformity.
  2. Hutton Unconformity at Jedburgh, Scotland, illustrated by John Clerk in 1787 and photographed in 2003. (Web site)
  3. Each stoppage of the reef's growth leaves its mark in what is called an "unconformity" in the substance of the reef mass. (Web site)
  4. The Mississippian-Pennsylvanian unconformity and post-Mississippian topography and areal stratigraphy of Knox County, Indiana. (Web site)
  5. At Cigar Lake the unconformity assemblage hosts the ore.


  1. In the Alligator Rivers region, the known deposits are below the unconformity and like their Canadian counterparts, are generally much lower grade.
  2. Unconformity-related deposits - Unconformity-related deposits arise from geological changes occurring close to major unconformities.
  3. Active mining of unconformity-associated U deposits is restricted to the Athabasca Basin in Canada.
  4. Unconformity-related deposits of the Athabasca basin are the world's largest storehouse of high-grade U resources.
  5. However, very high-grade, large-tonnage U deposits are only found as the unconformity-associated type, of Mesoproterozoic age.


  1. There has been very little exploration to locate deeply concealed deposits lying above the unconformity similar to those in Canada.
  2. The Otish Mountains area of Quebec is another site of exploration for unconformity-associated U (Ruzicka, 1996a).

Angular Unconformity

  1. There are four types of unconformities: disconformity, nonconformity, angular unconformity and paraconformity. (Web site)
  2. Angular unconformity - Younger layers overlie an erosion surface on tilted or folded layered rock.
  3. This first evaporite deposits pass throughout a second angular unconformity to arenites, marls, halite, gypsarenites and olistostromes of variegated clays. (Web site)
  4. Angular unconformity: An unconformity in which the bedding planes of the rocks above and below are not parallel.

Great Unconformity

  1. It is clear from this that Dutton did not use the name Great Unconformity to imply a huge interval of time. (Web site)
  2. People also commonly assume that the Great Unconformity was so-named because of the enormous interval of time it represents. (Web site)
  3. People are sometimes surprised to learn that at Frenchman Mountain they can visit the Great Unconformity without taking a long hike. (Web site)
  4. But when Dutton coined the term Great Unconformity he didn't yet know the age of the rocks on either side of the unconformity. (Web site)

Grand Canyon

  1. The Great Unconformity is best known from dramatic exposures in the Inner Gorge of the Grand Canyon. (Web site)
  2. The Great Unconformity was coined by John Wesley Powell during his epic run of the Colorado River through the Grand Canyon, AZ in 1876. (Web site)


  1. Many deposits are associated with continental unconformities and have affinities with unconformity-associated U deposits ( I16).
  2. The evaporitic and post-evaporitic sequences are separated by an erosive unconformity; (c) the postevaporitic deposits are subdivided in three subunits. (Web site)
  3. This paper reviews the attributes and context of unconformity-associated uranium (U) deposits.
  4. Conventional models for unconformity-associated U deposits invoke late diagenetic to hydrothermal processes.
  5. A few of these are included as context, to help understand the phenomenal grades of unconformity-associated deposits.


  1. Polymetallic deposits are typically hosted by sandstone and conglomerate, situated within 25-50 m of the basement-sandstone unconformity.
  2. Rita conglomerates, Churuguarita reefal limestones) and rest with angular unconformity on older Eocene formations.

Siccar Point

  1. This puts this unconformity stratigraphically at a similar level to the unconformity at Siccar Point. (Web site)
  2. Immediately above the unconformity is a breccia of Dalradian material, analogous to that at Siccar Point. (Web site)


  1. The rocks above an unconformity are younger than the rocks beneath (unless the sequence has been overturned). (Web site)
  2. An unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition. (Web site)
  3. Below the unconformity, the metasedimentary rocks which host the mineralisation are usually faulted and brecciated.
  4. Often the underlying rocks were warped or tilted prior to the deposition of new materials over the unconformity.
  5. At the unconformity (the intersection of the vertical and horizontal rocks in the picture) there are pebbles of eroded Ordovician shale.


  1. An unconformity where beds above and below are parallel and no erosional surface is evident. (Web site)
  2. These marginal evaporites are capped by an erosional unconformity and continental clastic deposits. (Web site)
  3. Angular unconformity: Unconformity between sedimentary strata where the older underlying layers are tipped and the erosional surface is irregular.


  1. Our group observed a location in the Unconformity where the time gap between the two layers is estimated to be one billion years. (Web site)
  2. Such unconformity represents a gap in time of unknown duration, at least in a local geologic column. (Web site)


  1. When we find evidence of a hiatus in the stratigraphic record we call it an unconformity. (Web site)
  2. The surface marking in the break in deposition would be called an unconformity in geologic terms, and represents time missing from the depositional record. (Web site)


  1. Between the shales and overlying conglomerate careful scrutiny enables us to detect an unconformity by erosion without any unconformity of dip. (Web site)
  2. An angular unconformity with overlying Ordovician conglomeratic rocks has considerable local relief, with meter-scale scours and a valley fill 100 m thick. (Web site)
  3. The contact between the overlying red rocks and the greywackes is seen in many places, so visitors are able to investigate the unconformity in some detail. (Web site)

Noted Above

  1. As noted above, current economic Canadian U resources are contained entirely in unconformity-associated U deposits.
  2. None of the field evidences noted above requires there to be long periods of time to form the unconformity. (Web site)


  1. The unconformity recognized in the UNO trash pit is a disconformity. (Web site)
  2. The first diagram is the present-day structure with a Tertiary cover sequence over a significant regional unconformity.
  3. Between the Yeso Formation and the Bandelier Tuff is an unconformity, gap or break in the stratigraphic sequence due to either nondeposition or erosion.
  4. The unconformity represents an interval of geologic time, called the hiatus, during which no deposition occurred and erosion removed preexisting rock. (Web site)
  5. Unconformity ENDTERM BEGDEF" A surface that separates two strata. (Web site)


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  Originally created: November 02, 2007.
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