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Underclay, which consists of siliceous refractory clay rich in hydrous aluminium silicates, is also called fireclay. Just as not all underclays are fireclays, not all fireclays are underclays. Within carboniferous and other coal-bearing strata, fireclay quite commonly comprises many underclays. The
236:
cementation within the subsurface. Detailed studies of ganisters, which occur either as seatearths or elsewhere within coal-bearing strata, have found them to be ancient paleosols, which are equivalent in both physical characteristics and origin to modern silica-cemented soils, called
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Flint clays associated with coal typically occur as thin, laterally continuous layers (bands), called "tonsteins", found within coal beds. In the case of tonsteins found within coal, the formation of flint clays resulted from the alternation of glass comprising
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in origin. Detrital flint clays consist of kaolinite-rich sediments eroded and transported from uplands deeply weathered under tropical climates and redeposited within the coastal plains, in which coal-bearing
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on the underclay while it formed the ground surface prior to being buried by organic sediments. Plant growth, waterlogging, and other processes that occurred during the development of a mire or
353:
in J. Reinhardt and W.R. Sigleo, eds., Paleosols and
Weathering Through Geologic Time: principles and Applications. Geological Society of America Special Paper. no. 216, pp. 81-102.
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alteration of sediments by weathering, plants, and other soil processes comprising underclay resulted in the formation of the vast majority of fireclay that comprises underclay.
325:
Paleosols below the Ames marine unit (Upper
Pennsylvanian, Conemaugh Group) in the Appalachian Basin, U.S.A.: variability on an ancient depositional landscape
338:
Tectonic and paleoclimatic significance of a prominent upper
Pennsylvanian (Virgilian/Stephanian) weathering profile, Iowa and Nebraska, USA
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that can be used in the manufacture of silica brick. They are cemented with secondary silica and have a characteristic splintery fracture.
31:, "seat rock", or "seat stone" in the geologic literature. Depending on its physical characteristics, a number of different names, such as
404:. in Compte Rendu 4:433-448, IXICC International Congress on Carboniferous Stratigraphy and Geology, Southern Illinois University Press.
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As defined, ganisters can be created by either the cementation of quartzose by surficial soil-forming processes to form silcrete, or by
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Sedimentation on the distal reaches of the
Okavango Fan, Botswana, and its bearing on calcrete and silcrete (ganister) formation
117:, will have occurred. In poorly developed paleosols, as seen in the soil profiles of modern poorly developed soils, called "
140:, in which a layer of peat accumulated that later became the overlying coal, modified the paleosol to create an underclay.
450:
in V.P. Wright, ed., pp. 87-111, Paleosols: Their
Recognition and Interpretation. Princeton, Princeton University Press
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accumulated. Authegenic flint clays consist of sediments altered in place after deposition as beds within acid, such as
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Paleopedologic and paleohydrologic records of precipitation seasonality from Early
Pennsylvanian "underclay" paleosols
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435:
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in K.H. Wolf and G.V. Chilingarian, George, eds., Diagenesis, III. Developments in
Sedimentology. v. 47, pp. 621-655
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strata independent of coal beds. Thus, as in the case of fireclays, not all ganisters are seatearths. Ganisters are
82:. As documented in various detailed studies, underclays and seatearths typically exhibit features characteristic of
132:, which is either developed in or comprises an underclay, largely reflects the effects of plants and other
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roots. Synonyms for underclay included seat clay, root clay, thill, warrant, coal clay, and warrant clay
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The
Firestone Sill Ganister, Namurian, northern England—the A2 horizon of a podzol or podzolic palaeosol
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428:
Silica-cemented paleosols (ganisters) in the
Pennsylvanian Waddens Cove Formation, Nova Scotia, Canada
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development. Depending on the specific underclay, these soil features can include some combination of
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The palehydrologic history of coal underclays based upon
Pennsylvanian paleosols in eastern Tennessee
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109:, i.e. leaching and translocation of alkali and alkaline earth elements and the kaolinitization of
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Paleosols containing an albic horizon: examples from the upper Carboniferous of northern Britain
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Pedogenesis of some Pennsylvanian underclays; ground-water, topography, and tectonic controls
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Underclays typically show considerable evidence of having been altered by plant activity and
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literature. As noted by Jackson, a seatearth is the layer of sedimentary rock underlying a
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Isopach map and regional correlations of the Fire Clay tonstein, central Appalachian Basin
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or other fine-grained sediment, either immediately underlying or forming the floor of a
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and floodplains, there might not exist any noticeable alteration of the underclay.
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391:. Mines Bureau Special Publication SP 96-1, 2nd ed, United States Bureau of Mines.
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seam. Underclay typically contains fossil roots and exhibits noticeably developed
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by acidic waters after it accumulated as thin beds within peat swamps or mires.
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375:. Geological Society of America Abstracts with Programs v. 35, no. 6, p. 601
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340:, Palaeogeography, Palaeoeclimatology, Palaeoecology. v. 118, pp. 159-179.
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United States Bureau of Mines and American Geological Institute, 1996,
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301:, U.S.A., Journal of Sedimentary Research. v. 75, no. 6, pp. 997-1010.
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105:. In the better-developed paleosols, significant alteration of the
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314:, Geological Society of America Bulletin. vo. 72, pp. 1643-1660.
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Tonsteins in the Coalfields of Western Europe and North America
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483:, Journal of Sedimentary Research. vol. A65, no. 1, pp. 77-90.
327:, Journal of Sedimentary Research. v. A65, no. 2, pp. 393-407.
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161:-like refractory clay or mudstone composed predominantly of
97:, different types of pedogenic microfabrics, rhizocretions,
417:. Open-File Report 03-351. United States Geological Survey.
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165:, called "flint clay". Flint clay breaks with a pronounced
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241:. Modern formation of ganisters has been observed in the
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Origin of Pennsylvanian underclay and related seat rocks
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and are either in whole or in part buried soils, called
39:, and ganister, can be applied to a specific seatearth.
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Gardner, T.W., E.G. Williams, and P.W. Holbrook, 1988,
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Underclay is a seatearth composed of soft, dispersible
278:, 4th ed. American Geological Institute, Alexandria.
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Another clay associated with coal beds is a smooth,
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19:is a British coal mining term that is used in the
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470:, Sedimentary Geology. v. 36, no. 1, pp. 41-49.
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389:Dictionary of mining And mineral-related terms
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217:are found within carboniferous and other
310:Huddle, J.W., and S.H. Patterson, 1961,
27:seam. Seatearths have also been called
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479:McCarthy, T.S. and W.N. Ellery, 1995,
400:Burger, K., and H.H. Damberger, 1985,
426:Gibling, M.R., and B.P. Rust, 1992,
369:Ober, E.G.., and S.G. Driese, 2003,
297:Driese, S.G., and E.G. Ober, 2005,
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193:, accumulating within swamps and
128:These studies demonstrate that a
63:. Underclays, which occur within
67:coal measures, commonly contain
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95:illuviated clay pore fillings
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93:, pedogenic ped structures,
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101:nodules, root moulds, and
413:Outerbridge, W.F., 2003,
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176:Flint clay can be either
446:Perciveil, C.J., 1982,
113:and hydroxy-interlayer
466:Percival, C.J., 1983,
336:Joeckel, R.M., 1995b,
323:Joeckel, R.N., 1995a,
134:soil-forming processes
76:soil-forming processes
274:Jackson, J.A., 1997,
276:Glossary of geology
167:conchoidal fracture
500:Sedimentary rocks
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121:", of modern
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103:soil horizons
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169:and resists
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123:river deltas
91:slickensides
84:soil profile
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35:, fireclay,
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219:sedimentary
119:Inceptisols
115:vermiculite
253:References
234:diagenetic
227:sandstones
182:authegenic
173:in water.
153:Flint clay
107:mineralogy
69:Stigmarian
61:weathering
37:flint clay
29:seat earth
21:geological
239:silcretes
223:indurated
215:ganisters
144:Fire clay
111:smectites
88:pedogenic
80:paleosols
43:Underclay
33:underclay
17:Seatearth
494:Category
247:Botswana
209:Ganister
178:detrital
130:paleosol
171:slaking
99:caliche
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434:
357:
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187:strata
163:kaolin
195:mires
159:flint
138:swamp
452:ISBN
432:ISBN
355:ISBN
280:ISBN
191:peat
53:coal
49:clay
25:coal
245:of
197:.
180:or
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380:^
290:^
261:^
249:.
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