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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
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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
364:
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.
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Paleosols below the Ames marine unit (Upper
Pennsylvanian, Conemaugh Group) in the Appalachian Basin, U.S.A.: variability on an ancient depositional landscape
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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.
42:, "seat rock", or "seat stone" in the geologic literature. Depending on its physical characteristics, a number of different names, such as
415:. 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
128:, will have occurred. In poorly developed paleosols, as seen in the soil profiles of modern poorly developed soils, called "
151:, in which a layer of peat accumulated that later became the overlying coal, modified the paleosol to create an underclay.
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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
441:
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
93:. As documented in various detailed studies, underclays and seatearths typically exhibit features characteristic of
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143:, 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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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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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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402:. 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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386:. Geological Society of America Abstracts with Programs v. 35, no. 6, p. 601
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351:, 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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312:, U.S.A., Journal of Sedimentary Research. v. 75, no. 6, pp. 997-1010.
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116:. In the better-developed paleosols, significant alteration of the
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325:, Geological Society of America Bulletin. vo. 72, pp. 1643-1660.
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Tonsteins in the Coalfields of Western Europe and North America
494:, Journal of Sedimentary Research. vol. A65, no. 1, pp. 77-90.
338:, Journal of Sedimentary Research. v. A65, no. 2, pp. 393-407.
172:-like refractory clay or mudstone composed predominantly of
108:, different types of pedogenic microfabrics, rhizocretions,
428:. Open-File Report 03-351. United States Geological Survey.
176:, called "flint clay". Flint clay breaks with a pronounced
252:. 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
50:, 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
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Another clay associated with coal beds is a smooth,
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30:is a British coal mining term that is used in the
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481:, Sedimentary Geology. v. 36, no. 1, pp. 41-49.
400:Dictionary of mining And mineral-related terms
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228:are found within carboniferous and other
321:Huddle, J.W., and S.H. Patterson, 1961,
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38:seam. Seatearths have also been called
490:McCarthy, T.S. and W.N. Ellery, 1995,
411:Burger, K., and H.H. Damberger, 1985,
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437:Gibling, M.R., and B.P. Rust, 1992,
380:Ober, E.G.., and S.G. Driese, 2003,
308:Driese, S.G., and E.G. Ober, 2005,
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204:, accumulating within swamps and
139:These studies demonstrate that a
74:. Underclays, which occur within
78:coal measures, commonly contain
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106:illuviated clay pore fillings
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112:nodules, root moulds, and
424:Outerbridge, W.F., 2003,
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187:Flint clay can be either
457:Perciveil, C.J., 1982,
124:and hydroxy-interlayer
477:Percival, C.J., 1983,
347:Joeckel, R.M., 1995b,
334:Joeckel, R.N., 1995a,
145:soil-forming processes
87:soil-forming processes
285:Jackson, J.A., 1997,
287:Glossary of geology
178:conchoidal fracture
511:Sedimentary rocks
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132:", of modern
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134:river deltas
102:slickensides
95:soil profile
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46:, fireclay,
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230:sedimentary
130:Inceptisols
126:vermiculite
264:References
245:diagenetic
238:sandstones
193:authegenic
184:in water.
164:Flint clay
118:mineralogy
80:Stigmarian
72:weathering
48:flint clay
40:seat earth
32:geological
250:silcretes
234:indurated
226:ganisters
155:Fire clay
122:smectites
99:pedogenic
91:paleosols
54:Underclay
44:underclay
28:Seatearth
18:Underclay
505:Category
258:Botswana
220:Ganister
189:detrital
141:paleosol
182:slaking
110:caliche
465:
445:
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198:strata
174:kaolin
206:mires
170:flint
149:swamp
463:ISBN
443:ISBN
366:ISBN
291:ISBN
202:peat
64:coal
60:clay
36:coal
256:of
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191:or
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391:^
301:^
272:^
260:.
20:)
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