Clay-Ironstone Concretion Preserving Fabrics Due to Progressive Compaction

Oertel, Gerhard; Curtis, C. D.

doi:10.1130/0016-7606(1972)83[2597:ccpfdt]2.0.co;2

Cited by 137 publications

(69 citation statements)

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“…Furthermore, there appears to be a progressive radial decrease in authigenic constituents, particularly if the central zone samples are excluded. This result accords with the observations of Lippmann (1955), Raiswell (1971 ), and Oertel and Curtis (1972), who interpreted similar data in terms of concretion growth by cementation of pore space during progressive compaction of the host shale. The relatively low cement contents of the calcite centers might indicate late-stage dissolution of calcite.…”

Section: Isotopic and Chemical Relations Chemical Compositionsupporting

confidence: 82%

“…Lippmann (1955) proposed that the ratio of acid-soluble to acid-insoluble components in concretions may be used to estimate the sediment porosity at the time of concretion growth and argued that his results demonstrated extremely high porosities (t=:;;75 percent) in some instances. Oertel and Curtis (1972) provided novel structural data that generally substantiate Lippmann's (1955) deductions, but they also presented evidence that a stage of slow, protracted growth followed the initial stage of rapid growth of their concretions. Girin (1967) and Galimov and others (1968) suggested that concretions preserve a sequential record of the diagenetic processes to which the host rock was subjected.…”

Section: Introductionmentioning

confidence: 96%

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An organic origin for the carbonate concretions of the Ohio Shale

Criss¹,

Cooke²,

Day³

1988

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Section: Isotopic and Chemical Relations Chemical Compositionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 96%

An organic origin for the carbonate concretions of the Ohio Shale

Criss¹,

Cooke²,

Day³

1988

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“…Obviously, all calculated strain values distinctly exceed aspect ratios (R f ) of 1.0; therefore, we conclude that concretions were not formed at or near the sediment-water interface. According to studies of Oertel and Curtis (1972) or Behrmann and Kopf (1993) on Table 6. Carbon and oxygen stable isotope mass spectrometry data from 29 samples from Sites 889, 891, and 892.…”

Section: Deformational Fabrics and Strainmentioning

confidence: 99%

Diagenetic Carbonates from Cascadia Margin: Textures, Chemical Compositions, and Oxygen and Carbon Stable Isotope Signatures

Kopf¹,

Sample²,

Bauer³

et al. 1995

Proceedings of the Ocean Drilling Program

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Active fluid venting and carbonate formation occur in the accretionary prism in the Cascadia subduction zone off Vancouver Island and Oregon. Methane-derived authigenic carbonates are precipitated in the uppermost terrigenous sediments by subduction-induced dewatering. They can be divided into cemented silts and sands containing less than 10% carbonate cements and concretions composed partially or wholly of carbonate. Textures, chemical compositions, and carbon and oxygen isotope signatures of 64 specimens of mainly carbonate concretions from Ocean Drilling Program Sites 889/890, 891, and 892 were studied using different methods. Mineralogically, the carbonate cement consists of high-magnesian calcite, dolomite, and calcite with varying amounts of detrital constituents. Results from x-ray fluorescence, x-ray diffraction, and electron microprobe analyses suggest dominance of high magnesian calcite in most of the carbonate concretions. Complex carbonates and protodolomite to pure dolomite are found in minor amounts. Cemented sediments and concretions taken in the vicinity of a prominent fault zone at Site 892 show an almost pure calcitic composition and the most intense deformation of all material drilled in the Cascadia Margin. Concretion fragmentation is believed to be caused by both brecciation and hydrofracture from mechanical stress and lowered lithostatic load during upward migration of rocks and fluids along the fault plane. Strain evaluation based on distortions of initially homogeneous marker particle distributions (the Fry technique) obtained aspect ratios (R f ) between 1.2 and 1.71 reflecting uniaxial shortening in the sediment as a response to compaction prior to carbonate formation. Compactional strains (e z , elongation parallel to core axis) are found to range from -0.17 to -0.42 and give evidence for significant settling of the sediment prior to concretion formation. Evidence for post-formational compaction, displacement of carbonate, or recrystallization incipient diagenesis could not be observed. Stable carbon and oxygen isotope signatures identify distinct groups of methane-derived carbonate concretions. Almost half of the examined concretions show variable carbon isotope signatures, ranging from -12%c to -52%c PDB (Peedee belemnite) with no systematic trend downhole. These carbonate concretions evidently reflect precipitation from thermogenic methane, probably with contributions of biogenic methane in minor amounts. A second set of samples is characterized by δ 13 C values between -6% 0 to +24%o PDB. Values between -4%o and 0%o reflect marine carbonate precipitated from seawater. The substantial enrichment in 13 C is most likely caused by supply of CO 2 evolved from fermentation in the sediment pile. Oxygen isotope ratios largely scatter around δ 18 θ values for modern ocean water (-l%c to +6%c PDB). Exceptional "light" δ 18 θ signatures with values ranging from -ll%o to -17%e PDB were only found in the vicinity of a prominent fault zone at Site 892. That depletion in 18 O may be expla...

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“…As discussed by Macquaker & Adams (2003), although this may sometimes be the case (cf. Oertel & Curtis 1972), many fissile shales are not laminated and their fissility is a secondary property largely related to weathering (Ingram 1953). Fissility is not a good rock classification criterion, because some mudstones are then merely freshly exposed shales.…”

Section: Origin Of Stratification In Shalesmentioning

confidence: 99%

More gaps than shale: erosion of mud and its effect on preserved geochemical and palaeobiological signals

Trabucho‐Alexandre¹

2014

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Clay-Ironstone Concretion Preserving Fabrics Due to Progressive Compaction

Cited by 137 publications

References 0 publications

An organic origin for the carbonate concretions of the Ohio Shale

An organic origin for the carbonate concretions of the Ohio Shale

Diagenetic Carbonates from Cascadia Margin: Textures, Chemical Compositions, and Oxygen and Carbon Stable Isotope Signatures

More gaps than shale: erosion of mud and its effect on preserved geochemical and palaeobiological signals

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