Cone-in-cone: how it occurs in the Devonian; Series in Pennsylvania (U.S.A.); with Further Details of its Structure, Varieties, etc.

Gresley, W. S.

doi:10.1144/gsl.jgs.1894.050.01-04.46

Cited by 10 publications

(4 citation statements)

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“…In cone-in-cone samples that are symmetrical about a medial plane (i.e. nodules or layer-parallel veins) the apices generally point inward, and the bases lie at the sediment:nodule interface (Cole, 1893; Gresley, 1894; Woodland, 1964; Marshall, 1982). In those studies it was therefore interpreted that the cones grew from the apices toward the bases.…”

Section: Discussionmentioning

confidence: 99%

“…That the lower cone halts the growth of the upper cone is evident from the full conic shapes of cones that reach the bottom surface versus the incomplete cones of those up-section. These incomplete cones can be considered to correspond to the conic scales of Gresley (1894).…”

Section: Discussionmentioning

confidence: 99%

“…Throughout the sample, strands dip near 55° from horizontal, either to the left or right in thin section. Corrugations mark the intersections of clay rings (Gresley, 1894; Franks, 1969) with the thin section, based on the annular geometry of host-rock strands in map view (Fig. 6d).…”

Section: Sample Descriptionmentioning

confidence: 99%

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Dolomite overgrowths suggest a primary origin of cone-in-cone

Hooker

Cartwright

2016

Geol. Mag.

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A long-debated aspect of cone-in-cone structures is whether the mineral aggregates composing the structure precipitated with their conical form (primary cone-in-cone), or whether the cones formed after precipitation (secondary cone-in-cone). A calcite deposit from the Cretaceous of Jordan bears all the defining characteristics of the structure. Trace dolomite within the sample supports the primary cone-in-cone hypothesis. The host sediment is a biosiliceous mudstone containing abundant rhombohedral dolomite grains. Dolomite rhombohedra are also distributed throughout the calcite of the cone-in-cone. The rhombohedra within the calcite locally have dolomite overgrowths that are aligned with calcite fibres. Evidence that dolomite co-precipitated with calcite, and did not replace calcite, includes (i) preferential downward extension of dolomite overgrowths, in the presumed growth-direction of the cone-in-cone, from the dolomite grains on which they nucleate, and (ii) planar, vertical borders between dolomite crystals and calcite fibres. Because dolomite overgrows host-sediment rhombohedra and forms part of the cones, it follows that the host-sediment was incorporated into the growing cone-in-cone as the calcite precipitated, and not afterward. The host-sediment was not injected into the cone-in-cone along fractures, as the secondary-origin theory suggests. This finding implies that cone-in-cone in general does not form over multiple stages, and thus has greater potential to preserve the chemical signature of its original precipitation.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Dolomite overgrowths suggest a primary origin of cone-in-cone

Hooker

Cartwright

2016

Geol. Mag.

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“…Concretions with cone-in-cone structure and their origin have been an intriguing subject of study for over a century (Sorby, 1859;Gresley, 1894;Tarr, 1921Tarr, , 1922Tarr, , 1932Shaub, 1937;Usdowski, 1963;Durrance, 1965;MacKenzie, 1972). Cone-in-cone structures without a spherulitic association have been described by Brown (1954), Woodland (1964), Gilman & Metzger (1967), Franks (1969) and MacKenzie (1972), among others.…”

Section: Introductionmentioning

confidence: 99%

Origin of spherulitic and cone-in-cone concretions in Cambro-Ordovician black shales, St Lawrence Estuary, Quebec, Canada

Hesse

Fong²,

Schümann

2019

Geol. Mag.

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Spherulitic concretions are very rare among carbonate concretions that generally consist of micritic carbonate. The occurrence of spherulitic concretions in Cambro-Ordovician black shales of unknown stratigraphic age on a mid-channel island in the St Lawrence Estuary in Quebec is a new example in addition to only three hitherto reported occurrences of spherulitic carbonate concretions. Their origin is still poorly understood. These concretions occur in close association with, and show various transitions to, cone-in-cone structure. The spherules, measuring 0.5 to 12 mm in diameter, consist of intergrown fine fibres of ferroan calcite and quartzine, pointing to the formation of the concretions below the sulfate-reduction zone. A phenomenological theory of spherulitic crystallization relates the thickness δ of an impurity-rich layer in front of impurity-rejecting growing crystals to the impurity-diffusion coefficient D and the growth velocity G of the crystal by δ = D/G. In spherulite-forming environments, extremely small values of δ (in the order of <10−4 cm) in conjunction with cellulation lead to spherulitic fibre growth. The theory of spherulitic crystallization is here applied to sedimentary deposits for the first time. The intimate association of calcite and quartzine in the concretions requires a chemical change from alkaline to acidic conditions, which occurs below the carbonate-reduction zone owing to the dissolution of sponge spicules or radiolarians. The transition from spherulite to the silica-free cone-in-cone structure occurs when the silica reservoir that acted as an impurity is exhausted in the crystallization process.

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Silicified Cone-in-Cone Structures from Erfoud (Morocco): A Comparison with Impact-Generated Shatter Cones

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Cone-in-cone: how it occurs in the Devonian; Series in Pennsylvania (U.S.A.); with Further Details of its Structure, Varieties, etc.

Cited by 10 publications

References 0 publications

Dolomite overgrowths suggest a primary origin of cone-in-cone

Dolomite overgrowths suggest a primary origin of cone-in-cone

Origin of spherulitic and cone-in-cone concretions in Cambro-Ordovician black shales, St Lawrence Estuary, Quebec, Canada

Silicified Cone-in-Cone Structures from Erfoud (Morocco): A Comparison with Impact-Generated Shatter Cones

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