Flint Clay Research Articles

Bulk Densities of Selected Dried Natural and Fired Kaolin Clays

AbstractBulk (lump) densities of 31 kaolins were measured on the clay in the natural or raw state after drying at 100°C and after firing to 1510°C (2700°F). The kaolins were selected from such diverse origins as surface-weathered and sedimentary accumulations, hydrothermally altered bodies and flintclay deposits. The sedimentary group ranged in density from 0·82 to 1·85 in the dried raw clay, and 1·93 to 2·63 when fired. The hydrothermally altered clays ranged from 1·83 to 2·50 in the dried raw state, and 2·02 to 2·66 when fired. Flint clays ranged from 2·20 to 2·60 in the dried raw state (a “toasted clay” from Russia, 1.75), and 1·99 to 2·70 when fired. The effect of the genetic process on bulk density values is discussed and related.

Correlatives of the Greta Coal Measures in the Hunter Valley and Gunnedah Basin, New South Wales

Abstract Exposures of Early Permian strata in the Gunnedah Basin are described and it is shown that the Willow Tree, Werris Creek, Condadilly, and Wean Formations comprise similar successions consisting of prominent horizons of kaolinite clayrocks or flint clays at the base overlain by quartz‐lithic sandstone, siltstone, and conglomerate. It is concluded therefore that these formations pertain to the same stratigraphic unit and, since the flint clays do not differ appreciably from those characterizing the Greta Coal Measures at Wingen, that this stratigraphic unit represents extension of the measures in the Gunnedah Basin. The Willow Tree and Wean Formations are underlain by considerable thicknesses of kaolinitic soil that undoubtedly furnished the detritus for the alluvial and colluvial flint clay deposits. The presence of the soil indicates that during part of the Early Permian in northeastern New South Wales the climate was humid and at least subtropical.

Laterites and Flint Clays in the Early Permian of the Sydney Basin, Australia, and Their Palaeoclimatic Implications

ABSTRACT From a study of the association of flint clays and thick, lateritic palaeosols developed on Early Permian basalts at a depth of more than 1,200 m in the Quirindi Bore, it is concluded that during at least part of the Artinskian Stage in the Sydney Basin the climate was humid and tropical to subtropical. The concept however, is at variance with the popular belief that in accordance with other Gondwana countries, alternations of frigid and cold temperate conditions prevailed in Australia during the Early Permian and may have persisted through to the close of the period.

Stratigraphy and Sedimentation of Redbed Facies in Narrabeen Group of Sydney Basin, Australia

A study of a widespread within the Narrabeen Group of the Sydney basin indicates that the material is a transported laterite that was deposited in a piedmont deltaic environment and was derived from two major source areas. These conclusions are based on paleocurrent data, mineralogic and petrographic data, and geometry and stratigraphy of the redbeds. The Triassic Narrabeen Group has a maximum thickness of 520 m and is dominated by clastic sediments that were deposited in a fluvial environment. The widespread redbeds within the group have a variable thickness. Redbeds of the western Sydney basin, previously uncorrelated with major developments over the eastern part of the basin, are time-equivalent units and hence, sedimentation covered an area of more than 13,000 sq km. These redbeds, which are present near the top of the group, range in thickness from 90 to 180 m and are defined as the redbed facies. The most significant of this is the Bald Hill Claystone in the southern Sydney basin, which was found to correlate with the Wentworth Falls Claystone Member over the remainder of the basin; most of the data presented in this paper are centered around these units. Paleodrainage patterns within the redbed facies were determined on a basinwide scale and restricted to a vertical interval 30 m above and below the base of the Bald Hill Claystone and the Wentworth Falls Claystone Member. At a few widely spaced localities in the western Sydney basin, current data were compiled for complete Narrabeen Group sections. Paleodrainage direction in the section below the base of the Bald Hill Claystone and Wentworth Falls Claystone Member is dominantly southeastward, with an abrupt change in direction to northeast above the base of the units in the southern Sydney basin. A disconformity surface which separates the Bald Hill Claystone from the underlying units resulted when uplift in the south exposed large areas of volcanic rocks. Lateritization and ransportation of this material by the newly developed northerly drainage system yielded the Bald Hill Claystone. Drainage in the northern area of the basin remained unchanged and was southeastward throughout Narrabeen Group sedimentation. From the central area of the basin where the two systems merged, drainage was eastward. Flint clays associated with the redbeds are distributed over three areas of the Sydney basin (the southeastern part, the Blue Mountains, and the Putty area), and occur at the same stratigraphic level. The oolitic flint clays of the southern region (the Garie Formation), which are thought to represent transported bauxitic material, were deposited rapidly on the flanks of exposed bauxitized areas on the eastern and southern margins of the basin. The other deposits, which are more massive and relatively devoid of oolites, represent floodplain deposits formed in low swampy depressions in the western and northern Sydney basin, by an internal drainage system.

Origin of Cristobalite-Rich Tertiary Sediments in Atlantic and Gulf Coastal Plain: ABSTRACT

Chemically precipitated alpha-cristobalite is a common matrix constituent of many fine-grained siliceous Tertiary rocks of the Atlantic and Gulf coastal plains. It forms as a low-temperature authigenic mineral having a free growth morphology of fine blades arranged in spherulitic clusters 3-12 microns in diameter called lepispheres. Cristobalite lepispheres have been observed via scanning electron microscopy of fracture surfaces through a wide variety of lower to middle Tertiary flint clays, opal claystones, buhrstones, and pseudobuhrstones. Microspherulites of identical morphology also compose moderate to large percentages of offshore Caribbean-North Atlantic sediments of equivalent age including cherts, silicified limestones, and chalks. The source o silica for these deep-water sediments is thought to be fossil diatom and radiolarian tests. The immediate source of silica precipated as low-temperature cristobalite in coastal plain sediments generally has been ascribed to supposed volcanic sources in the Gulf Coast or Caribbean areas. Volcanic ash accumulations or direct precipitation from silica-rich bottom waters circulating above such ashes have been postulated. In major ocean basins explored by the Deep Sea Drilling Project, however, cristobalitic cherts are seldom associated directly with ash sequences although some diatom and radiolarian remains usually are preserved in these cherts. Scanning electron micrographs and petrographic studies of opaline claystones from South Carolina (Black Mingo Formation) have revealed many molds or tests of siliceous fossils preserved in a cristobalitic matrix of lepispheres similar, i not identical to, the matrix of deep-sea cristobalitic cherts thought to be derived from the in situ dissolution and reprecipitation of siliceous microfossils. These findings suggest a biogenous source of silica for most of the cristobalitic matrix of these Atlantic coastal plain sediments, an observation supported by the paucity of zeolites in the units. Siliceous tests also are observed in the Tallahatta Formation of Alabama, an indication that a biogenous source was important in the silicification of some Gulf coastal plain sediments as well. End_of_Article - Last_Page 1840------------

Geochemical Mechanics for the Dissolution, Transport, and Deposition of Aluminum in the Zone of Weathering

AbstractOrganic acids in the 0·01M concentration range representing amino-, aliphatic, and aromatic types present in humus dissolve 70–85 ppm Al from Arkansas bauxite at room temperature, whereas 0-03 ppm is dissolved in water. The species of Al in aqueous solution, calculated from stability data, range from Al3+ at pH 3 and lower, through Al2(OH)24+ at a maximum concentration at pH 4·5, Al(OH)2+ at a maximum at pH 4·7, Al(OH)2+ at a maximum at pH 60, to Al(OH)4- at pH 8·5 and higher. In salicylic acid an Al-Sal+ complex occurs between pH 1·5 and 8·5, and is at a maximum at pH 4·2. Solubility of Al obviously is pH dependent; also because of the vulnerability of organic acids to oxidation, the solubility and transport of Al is indirectly Eh dependent. Anions that combine with Al include OH- to form bauxite, PO43- to form lateritic phosphate such as the Bone Valley Formation, Fla., and SiO44- to form allophane or kaolin as noted in the kaolin synthesis by Linares and Huartes. Spongelike, pisolitic or oolitic structures, and mineral veins in bauxites, lateritic phosphates, and some flint clays attest to mobilization of Al in solution. Lignites and humus zones associated with latentes are a logical geologic source of these complexing organic solvents. Although Al is inherently mobile, such commonly available precipitating anions render Al relatively immobile.

Erratum to: Flint Clay by Hydrothermal Alteration of Sedimentary Rock in Mexico

The printer regrets that the first photograph appearing opposite p. 116 should have appeared opposite p. 104.

Kaolinite Claystones associated with the Wongawilli seam in the southern part of the Sydney basin

Abstract Kaolinite claystones that are similar in structure, texture and composition to the kaolin tonsteins of Western Europe, and to some of the flint clays of North America, are associated with the Wongawilli Seam in the southern part of the Sydney Basin, where they form thin persistent bands within the coal and somewhat thicker deposits immediately overlying the seam. The thin bands within the coal are fine grained and consist of brecciated to pelletal clasts composed of well‐ordered kaolinite set in a matrix of similar composition. The thicker deposits overlying the seam are much coarser grained and appear restricted in occurrence to the basin margins. They contain a predominance of oolites with kaolinite clasts bonded by a relatively sparse matrix and in places, remarkable ‘outgrowths’ of vermicular kaolinite. The origin of the deposits is discussed, and it is concluded that most of the unusual features of these claystones can be ascribed to a fluvial environment.

Pyrophyllite-bearing flint clay from the Cambewarra area, New South Wales

AbstractA thick deposit of flint clay in the Permian I llawarra Coal Measures of the southern part of the Sydney Basin, New South Wales, is described. The flint clays which have affinities with those of the Pennsylvanian of North America and with the kaolin coal tonsteins of the Westphalian, are associated with red-brown claystones that contain in addition to hematite, an abundance of a regular mixed layer clay mineral. Pyrophyllite generally forms a minor constituent only of the flint clays but in one part of the deposit it is more abundant than kaolinite. Although there are many puzzling aspects concerning the origin of the deposit, evidence suggests that the kaolinite and the pyrophyllite in the flint clays are detrital.

Flint Clay by Hydrothermal Alteration of Sedimentary Rock in Mexico

AbstractThis paper documents the first report of flint clay in Mexico, located at Estola, Guerrero, 199 km south of Mexico City, on Mexico Highway 95. It is the first report (known to the writers) of flint clay formed by hydrothermal alteration. It describes the in-situ alteration of a calcareous, silty shale to flint clay (well-ordered kaolinite).The changes during alteration are mineralogical, chemical, and structural. Calcite, comprising about one-third of the shale, quartz and probably some feldspar comprising a scant third, and a mixture of greenish-yellow (limonitic) clay minerals are dissolved or altered ultimately to white kaolinite (monomineralic). Calcium carbonate, free and combined silica, and iron compounds are dissolved, while simultaneously the alumina is relatively enriched. The fissility, inequigraularity, and cementitous fabric of shale are changed to the massively homogeneous, finegrained, interlocking fabric that is typical of flint clay.The sequence of changes, which overlap, are; (1) dissolution of carbonate minerals, (2) mobility of iron, replacement of quartz and feldspar by kaolinite; and (3) intensive “digestion” of rock substance to homogeneous, essentially monomineralic, kaolinite flint clay. Alunite, and secondary vein-calcite or gypsum may accompany the flint clay.This occurrence lends support to the concent that flint clay is formed from presumably only sedimentary parent rock.

Analogues of Flint Clays in Soviet Literature

AbstractThe term “flint clay” used in USA and several other countries, corresponds very closely to the term “toasted bread (sukhar) clay”. In both USA and U.S.S.R., the typical occurences of “toasted clays” are confined to deposits of the lower Carboniferous. In their properties and occurrence the well-studied toasted clays of the Borovichy deposit (Novgorod province) are highly similar to the flint clays of Missouri, differing significantly only in having lower bulk specific gravity and higher porosity than do Missouri flint clays. Varieties with excess free alumina (diaspore, boehmite) are observed both among “toasted” and flint clays. The author suggests the term “toasted complex” (sukharnii kompleks) which corresponds to W. D. Keller’s term “flint clay facies”. The clays of the “toasted complex” are sediments of ancient swamps and lakes which contained rich vegetation. Their source material was finaly dispersed silicate particles transported from dry land. The structure and properties of toasted clays are explained by the precipitation of kaolinite as colloidal clumps in which crystallization occurred with formation of intimate intergrowths and variously oriented segregations.

Flint Clay in the Coal-barren Triassic of the Sydney Basin, Australia

ABSTRACT Claystones that are similar in composition, texture and structure to some of the flint clays of the Olive Hill area, Kentucky, form a persistent marker bed in the coal-barren Triassic Narrabeen Group of the Sydney basin. The underlying sediments consist of a relatively thick succession of red-brown claystones, or chocolate shales, which, apart from the presence of abundant hematite, possess the same mineralogical and textural features as the flint clay. The chocolate 'shales are believed to represent a transported lateritic clay that was deposited in a nonreducing' environment. The flint clay probably resulted from a change to reducing conditions within the depositional basin.

Flint Clay and a Flint-Clay Facies

AbstractFlint clay is defined as a sedimentary, microcrystalline to crystalline clay (rock) composed dominantly of kaolin, which breaks with a pronounced conchoidal fracture and resists slaking in water. Additional ceramic (refractory) properties are implied, but not expressed, in the definition. Flint clay first given recognition in the U.S.A., has been observed on all continents; it will probably be found to be more abundant than its occurrences reported to date. It occurs in rocks mainly Carboniferous or Cretaceous in age, and is invariably associated with plant- or coal-bearing measures.The environment of deposition is commonly lowlying paludal, in basins in either clastic silicate rocks or in karstic carbonates. It is inferred that parent illitic and/or kaolinitic clay colloids were transported into the swamps and there under-went further dialysis, alteration, and eventual crystallization in situ, producing a notably homogeneous kaolinite clay possessing interlocking crystallinity. Some occurrences were further desilicated to high-alumina minerals, particularly to diaspore and boehmite.Flint clay is interpreted as being an intermediate member of a so-called flint-clay facies which is a claystone sequence ranging from high-alumina minerals (or potentially so) formed on the highest part, structurally and/or topographically, of the depositional area, and grading down-structure and/or lower in elevation through flint clay to iliite-kaolinite plastic clay and thence to marine illitic shale, all being equivalent stratigraphically. The geochemical reactions are depotassification of parent clay by substitution of K+ by H+, and desilication, especially where high-alumina minerals are formed.

Intersalation of potassium acetate in flint clay

Intersalation of potassium acetate in flint clay

Les minéraux argileux dans le tertiaire du bassin de Paris. Problèmes d'origine et de genèse

Montmorillonite, probably detrital, predominates in the formations which cover the chalk in the north and west of the Paris Basin (Thanetian and Sparnacian stages). Detrital kaolin, ori¬ ginating from the Massif Central, has been spread out in two layers in the Paris Basin (Sparnacian plastic clays and Miocene "granitic" sands). The Lutetian sequence of clays : kaolinite -illite montmorillonite -attapulgite is characteristic of the only complete geochemical cycle in the Tertiary layer of the Paris basin. The lagoon formations of the Ludian and Sannoisian stages consist chiefly of magnesium clays , attapulgite and sepiolite. Illite is predominant in the Oligocene, except in the continental formations (Millstone Grit clays) which contain mostly kaolinite. This latter is probably recently formed as is in part the kaolinite from flint clays.

Middle and Late Pennsylvanian Flint Clays

ABSTRACT Nearly all literature relating to flint clays of Pennsylvanian age in the eastern United States concerns deposits occurring in the lower part of the Pennsylvanian System. This report describes the geologic occurrence and the physical and mineralogical features of flint clay deposits of middle and late Pennsylvanian age in the eastern United States, many of which have not previously been described as flint clay. The brecciated texture, conchoidal fracture, and variegated color--including shades of yellow, brown, gray, green, and red--of these clays make them distinctive. They are composed primarily of well crystallized kaolinite. The flint clays are often closely associated with coals, and at several localities they occur in channels or lenses where the normal continuity of the coal bed has been interrupted by erosion or nondeposition. The flint clay is believed to have formed by alteration of ordinary fine-grained Pennsylvanian sediments in acid swamps in a manner similar to that recently proposed by Patterson and Hosterman (1960) to explain the formation of early Pennsylvanian flint clay in the Olive Hill district, Kentucky.

Sedimentary Facies in the Lower Allegheny Rocks of Western Pennsylvania

Lower Allegheny detrital rocks thicken to the north and west. The Vanport limestone thins to the west-southwest, northwest, and north by interfingering with marine shales and to the northeast by gradation into chert and flint clay. The area of thickest limestone was an area of tectonic stability. The wedge complex was an area of subsidence and differential filling. East-west changes across the northern wedge complex are more rapid. The tectonic pattern during lower Allegheny time is one of stability along a west-northwest trending belt and differential subsidence to the north and southwest.

Determination of Potassium in Silicate Minerals and Rocks by Neutron Activation Analysis

A procedure is described for the determination of sodium in natural silicate minerals by pile neutron activation and counting the induced gamma radiation in the irradiated specimen without chemical processing. An integral scintillation counter set to accept all gamma -rays with energies above 2.6 Mev is used for radioactivity measurement. Precision and absolute accuracy of the method are of the order of 1 to 2%, and interference by trace elements is virtually negligible. Results are presented for the analysis of the standard granite G-1, diabase W-1, argillaceous limestone NBS 1a, and flint clay NBS 97. (auth)

Origin of Pennsylvanian Underclay and Related Seat Rocks

Seat rocks, including underclay, underlie coal beds and show features such as roots, profiles similar to water-logged soils, lack of bedding, soil-like fracture, and gradation into normally bedded sedimentary rocks indicating that they were once soils. Coarse-grained seat rocks range from argillaceous to nearly pure quartz sandstone (ganister). Seat rocks composed of clay-sized particles (underclays) range from mixtures of illite, mixed-layer clay, and kaolinite to essentially pure kaolinite. Variations in the quartz or kaolinite content suggest that there are degrees of alteration in the formation of a seat rock and that all kinds of seat rock were formed by leaching of the substratum in a swamp. The increasing crystallinity of the clay minerals from plastic underclays to semiflint clay to flint clay and the corresponding increase in titanium support this conclusion. These two features suggest strongly that flint clays formed in place in an acidic swamp environment. The Olive Hill clay shows residual acidity. Seat rocks are affected by the chemical environments in the swamp before peat accumulation, during peat accumulation, and during coalification. Kaolinite is forming in present-day swamps and in wet acidic soils in Hawaii and probably formed in late Paleozoic swamps. The facts can be interpreted to show that all kinds of seat rocks could have formed in Pennsylvanian swamps and probably most did.

Relationship between the stratigraphy and petrography of Pottsville sandstones and the occurrence of high-alumina Mercer clay

Stratigraphic and petrographic study of 32 sections of the Mercer and Connoquenessing formations [Pennsylvanian] in western Pennsylvania has shown that certain consistent relationships exist between the presence or absence of high-alumina Mercer clay and the stratigraphy and petrography of underlying outcropping sandstones. In sections where flint or diaspore clays are present, the clay is underlain by 0-150 ft. of fine-to-medium-grained, very light-gray lower Connoquenessing sandstone. In sections where plastic clay or silty claystone occur below the Mercer coal, the clay is underlain by 20-150 ft. of fine-grained to conglomeratic, medium-light-gray upper Connoquenessing sandstone. The distribution of the high-alumina clay is believed to be related to ancient topographic highs where flint clay was deposited directly on the lower Connoquenessing sandstone. The upper Connoquenessing sandstone was deposited in adjacent topographic lows, while the flint clay still present on the topographic highs was leached to form diaspore. Areas where the upper Connoquenessing sandstone is thin or absent would be the most favorable regions for further prospecting for high-alumina Mercer clay in western Pennsylvania.