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Topic: Unconformity

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	Unconformity - Wikipedia, the free encyclopedia
		An unconformity represents time during which no sediments were deposited and 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.
		An unconformity exists between sedimentary rocks and metamorphic or igneous rocks when the sedimentary rock lies above and was deposited on the pre-existing and eroded metamorphic or igneous rock.
		An unconformity where horizontally parallel strata of sedimentary rock is deposited on tilted and eroded layers that may be either vertical or at an angle to the overlying horizontal layers.
	en.wikipedia.org /wiki/Unconformity (280 words)

	Unconformities Summary - Unconformities Information
		Unconformities of large scale (i.e., cartographic unconformities) have been used by some geologists to delineate large groups of sedimentary formations that are bounded by unconformities.
		In study of unconformities, it is preferred that evidence from at least two of the three categories be used to recognize an unconformity and criteria from all three categories, if possible, be used to assess the scope of an unconformity.
		In other words, an unconformity may be thought of as a stratigraphic break that is significant in terms of lost record and a diastem as an insignificant break by the same measure.
	www.bookrags.com /sciences/earthscience/unconformities-woes-02.html (807 words)

	Hunting - Glossary - Discover The Outdoors (Site not responding. Last check: 2007-11-07)
		An unconformity develops during a period of time in which no sediment is deposited.
		Structurally, unconformity may be regarded as planar structures separating older rocks below from younger rocks above, representing the ‘break’ as defined in (1) and (2) above.
		A plane of unconformity may be a surface of weathering, EROSION or denudation, or a surface of non-deposition, or possibly some combination of these factors.
	www.dto.com /hunting/glossary/index.jsp?startwith=u (632 words)

	Unconformities and the Flood
		Unconformities are the geologic features which convinced Hutton and Lyell that the earth was old.
		At the unconformity (the intersection of the vertical and horizontal rocks in the picture) there are pebbles of eroded Ordovician shale.
		That means that the unconformity on top of the Precambrian is of late Paleozoic age and that means that this is in the middle of post flood recolonization or in the middle of the flood according to other YEC models.
	home.entouch.net /dmd/unconformity.htm (707 words)

	Unconformity, LLC. - Graphic Design Studio - Washington, DC - Unconformity.com - Home (Site not responding. Last check: 2007-11-07)
		Unconformity is an integrated design and marketing firm with a staff of 10 based in Old Town Alexandria, Virginia.
		Unconformity offers the broad range of services and senior-level sophistication you expect from larger firms, with the personal service, fast response and flexibility of a small shop.
		Unconformity is designed to be different from others.
	unconformity.com (285 words)

	Frenchman Mountain and the Great Unconformity (Site not responding. Last check: 2007-11-07)
		Unconformities are important because they represent missing intervals of the geologic record, like pages missing from a history book.
		The Great Unconformity represents about 1.2 billion years, which is more than one fourth of the age of the Earth.
		But when Dutton coined the term Great Unconformity he didn't yet know the age of the rocks on either side of the unconformity.
	www.unlv.edu /Colleges/Sciences/Geoscience/pub/rowland/Virtual/geology.html (276 words)

	Unconf.html (Site not responding. Last check: 2007-11-07)
		The Great Unconformity is arguably the most significant outcrop of rock on the planet.
		The Great Unconformity is the contact between the Precambrian and the Cambrian - a gap of 1.2 billion years - one fourth of the age of the Earth.
		No, the Great Unconformity, as named by one of my heroes - Major John Wesley Powell - in 1869, is the contact between the Primeval World (when life was mostly single-celled creatures), and the world in which the continents and the life upon them really began to evolve.
	members.aol.com /saines1/Unconf.html (582 words)

	Appalachians
		Below the unconformity is the Paleozoic sediments which consist not only of sands and shales but also very thick piles of carbonate and dolomite.
		If you look at the sediments just under the unconformity on the right and move to the left you will see layer after layer erosionally truncated by the unconformity until you get to hill where bed A is at the surface of the unconformity.
		The relationship between this reflector and the unconformity shows that the valley to the right of the hill was infilled in a rather gentle way otherwise the sediments would be chaotic.
	home.entouch.net /dmd/appalach.htm (1162 words)

	SOFIA - OFR 94-276 - Fate and Pathways of Injection-Well Effluent in the Florida Keys - Geologic Setting
		This study was partially initiated on the premise that a region-wide subaerial unconformity, known as the Q3 unconformity (Perkins, 1977), can prevent or retard vertical movement of fluids.
		This unconformity had been identified as an effective aquitard beneath the Dade County Landfill, where it retards downward migration of landfill leachates (Shinn and Corcoran, 1988).
		The unconformity and underlying limestone have been called the Ft. Thompson Formation, after the type locality on the Caloosahatchee River (Parker and Cooke, 1944; Parker et al., 1955).
	sofia.usgs.gov /publications/ofr/94-276/geosetting.html (1133 words)

	UEX Corporation - Black Lake - Tue Mar 7, 2006 (Site not responding. Last check: 2007-11-07)
		BL-23 was intended to pierce the unconformity on Line 118N approximately 160 metres east of the point where uranium mineralization was intersected in BL-18.
		A major fault zone was intersected just above the unconformity at 309.0 metres and, as is characteristic of the Eastern Fault Zone, the minerals dravite, pyrite and siderite were found to be present along fractures on the margin of the fault.
		The combination of a major fault zone, hydrothermal alteration in the sandstone, a strongly graphitic and brecciated basement immediately below the unconformity, and uranium mineralization indicate that the required processes for the emplacement of an unconformity-type uranium deposit typical of the Athabasca Basin were active in the vicinity of hole BL-23.
	www.uex-corporation.com /s/BlackLake.asp (3213 words)

	Department of Geological & Atmospheric Sciences - Angular Unconformity (Site not responding. Last check: 2007-11-07)
		Put most simply: "Sediments are usually deposited in horizontal layers." While there are some clear exceptions to the rule (cross-bedding in sand dunes or the foreset beds in deltas, for example), Steno's observation holds true in almost all cases.
		The plane of contact between the upper and lower sediment is the angular unconformity.
		James Hutton's interpretation of an angular unconformity was thus a watershed in the history of geology as a science, often cited as the event that opened the door to our modern view of the Earth.
	www.ge-at.iastate.edu /courses/Geol_100/old_files/angular.html (424 words)

	Jurassic Ergs, Colorado Plateau
		Seven regional Jurassic unconformities are recognized from the base of the Wingate Sandstone to the base of the Morrison Formation across the Colorado Plateau.
		Therefore the unconformities are recognized and defined based on regional lateral relations, especially regional low-angle discordances and on lapping relations of overlying strata.
		The unconformity is restricted by Jurassic and recent erosion to the SW corner of Utah and consequently yields little regional evidence to its original extent and origin.
	jan.ucc.nau.edu /~rcb7/Jurassic_erg.html (920 words)

	HIATUSES IN THE TACONIC STRATIGRAPHIC SUCCESSION: GEOLOGY OF WHAT'S NOT THERE (Site not responding. Last check: 2007-11-07)
		Submarine unconformities are present between mixed carbonate-siliciclastic strata (Trenton Group) and overlying fl shale (Collingwood Shale of Ontario, "Utica" Shale of NY, Antes and Martinsburg Shale of PA).
		Thus, the locations of these unconformities in conjunction with the timing and duration of the associated hiatuses help delineate the dynamic history of the Appalachian basin during the Taconic orogeny.
		Although the unconformity is fairly localized, lithologic patterns across the unconformity are consistent with a sequence-bounding unconformity, in part the response to eustatic fall.
	gsa.confex.com /gsa/2002AM/finalprogram/abstract_44924.htm (429 words)

	Lever--Eocene-Oligocene sequence
		The upper unconformity is usually erosional, and at Woodpecker Bay dissolution of a layer of rhodolithic limestone indicates subaerial exposure of the unconformity surface.
		The restriction of the upper unconformity to the area north of Punakaiki suggests that a local tectonic event, or tectonic basin controls, may be the cause of the erosion.
		Whaingaroan unconformities that are observed in the South Pacific are younger than the age of the upper unconformity.
	www.rsnz.org /publish/nzjgg/2001/28.php (373 words)

	Geology111-Lecture 6 (Site not responding. Last check: 2007-11-07)
		The record of Earth processes, however, is recorded primarily in the sedimentary rock record, which can only be dated as older or younger than igneous units which formed after it (ones that cross cut it or overlie it), or before it (ones that are truncated by it or underlie it).
		Unconformities represent missing sequences of sedimentary rock (a time hiatus).
		The relative length of time represented by the hiatus can be estimated by the nature of the unconformity.
	www.geol.binghamton.edu /faculty/naslund/Geol.111.lec6.html (278 words)

	Unconformity (Site not responding. Last check: 2007-11-07)
		Unconformity between sedimentary strata where the older underlying layers are tipped and the erosional surface is irregular.
		Unconformity between parallel layers of sedimentary rock which is recognizable due to an irregular erosional surface.
		An irregular erosional surface between strata and igneous or metamorphic rock.
	oliver.geology.adelaide.edu.au /staff/asmumm/excursions/halletcove/unconformity.html (70 words)

	Carlin Canyon, Nevada
		The Carlin Canyon unconformity is a classic geologic locality where two orogenic events are preserved.
		The unconformity is easy to see north of I-80 just west of the tunnels near Carlin.
		The hill left of the river is a dip slope in the limestone.
	www.uwsp.edu /geo/projects/geoweb/participants/dutch/VTrips/CarlinCanyon.HTM (442 words)

	Revisiting Hutton's Unconformities
		Much the same lesson was drawn from other striking unconformities those of Newton Point, Arran, and in the bank of the River Jed, near Jedburgh.
		The dip of the Devonian strata is gentle, almost horizontal, and the dip of the Silurian strata is almost vertical.
		This degree of irregularity is lacking at the unconformity, although the "confused" junction may be attributed to a limited degree of differential weathering.
	www.biblicalcreation.org.uk /scientific_issues/bcs100.html (2079 words)

	International Stratigraphic Guide (Site not responding. Last check: 2007-11-07)
		They are composed of diverse types of any kind or kinds of rocks, but the lithologic properties of these rocks, their fossil content, or the chronostratigraphic span of the rocks on either side of the bounding unconformities are significant only to the extent that they serve to recognize the bounding unconformities.
		Unconformity-bounded units are objective stratigraphic units established and identified without regard for the genetic or causal interpretation of their bounding unconformities.
		An unconformity in which the bedding planes above and below the stratigraphic break are essentially parallel.
	www.stratigraphy.org /uncon.htm (310 words)

	Glossary
		Disconformity: contact between younger and older beds is marked by a visible, irregular or uneven erosional surface.
		Paraconformity: beds above and below the unconformity are parallel and no erosional surface is evident; but can be recognized based on the gap in the rock record.
		Nonconformity: develops between sedimentary rock and older igneous or metamorphic rock that has been exposed to erosion.
	strata.geol.sc.edu /terminology/unconformity.html (216 words)

	The Globe and Mail : globeinvestor : UEX Receives Shea Creek Uranium Project Exploration Update from COGEMA
		Only 12 of the planned 20 unconformity impacts were completed during the fall drilling program as a result of a late start up.
		In addition to the mineralization intersected at the unconformity, which confirms the continuity of the deposit, the mineralized interval deeper in the basement is associated with a cross-cutting structure of the kind that typically yields higher grades where it subcrops at the unconformity in the vicinity of a graphitic conductor.
		SHE-113, the third pilot hole in the Colette area, served primarily as a pilot-hole positioned for a number of directional cuts planned for 2005 to test for the presence of mineralization 100 metres to the north of the main mineralized zone of the Colette Deposit.
	www.globeinvestor.com /servlet/WireFeedRedirect?cf=GlobeInvestor/config&vg=BigAdVariableGenerator&date=20050210&archive=cnw&slug=1302102790 (2307 words)

	Grand Canyon Laboratory
		Unconformities may be recognized on a geologic map in several ways.
		The ages of the formations are given in the legend of the geologic map.
		The fossils indicate the presence of an unconformity.
	www.gpc.edu /~pgore/geology/historical_lab/grandcanyonlab.htm (1598 words)

	Volume 31 No. 2
		This pre-Lancian unconformity (U1) extends eastward from the Sevier overthrust belt in northwestern Wyoming to the southwest margin of the Williston cratonic basin in the tri-state area of Montana and the two Dakotas.
		Chronostratigraphic data from five areas scattered from west to east across 600 km of the Western Interior Basin bracket the ages of this unconformity with precision that is based on isotopic ages, magnetozone boundaries, and ammonite range zones.
		Deposition on top of this unconformable surface occurred 3.5 Myrs earlier in NW Wyoming than in SE Montana.The erosion represented by the unconformity migrated eastward with time, generally removing 2 Myrs of strata as it went.
	pubs.gg.uwyo.edu /CTGs/CTG_31-2.htm (1103 words)

	An Unconformity (Site not responding. Last check: 2007-11-07)
		Sometimes, an area where layers of sediments have been deposited is uplifted, and the surface experiences erosion.
		If more layers of sediments are subsequently added on top of this erosion surface, the resulting feature is called an unconformity.
		Identify and label the unconformity on your diagram.
	www.classzone.com /books/earth_science/terc/content/investigations/es2903/es2903page08.cfm?chapter_no=investigation (89 words)

	GFF-online presents: Transgressive oolites onlapping a Silurian rocky shoreline unconformity, Gotland, Sweden (Site not responding. Last check: 2007-11-07)
		The major facies-elements forming the rocky shoreline are 1) several subaerially exposed reefs, which were eroded during falling base-level and which form the topography, and 2), onlap of oolite grainstones which were deposited during the subsequent rise of the base-level.
		Five localities along the rocky shoreline are discussed in detail here, viz., Svalings 1 where the unconformable boundary is accessible, and Bara 1-4 where the petrography of the onlapping oolite has been studied.
		The Slite Rocky Shoreline Unconformity (SRSU) is herein considered as the platform-proximal equivalent to the sequence boundary separating the regressive Fröjel Formation and the transgressive Bara Oolite Member (lowermost Halla Formation) in the Klintehamn area on western Gotland.
	www.gff-online.se /site/article.asp?articleID=493 (379 words)

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