Intergrowth and twinning in opal-CT lepispheres

Flörke, O. W.; Hollmann, R.; Rad, Ulrich von; Rösch, H.

doi:10.1007/bf00402354

Cited by 57 publications

(35 citation statements)

References 10 publications

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“…Besides well-bladed lepispheres, poorly bladed (stubby or spiny) lepispheres can also be ob¬ served (Plate 1, Figure 1). These stubby lepispheres are only evident in bedded porcellanites of the clayey environment (see also Flörke et al, 1976). Diage¬ netic quartz is missing in many of the clayey porcel¬ lanites investigated.…”

Section: Bedded Porcellanites (Clayey Environments)mentioning

confidence: 90%

“…On SEM photos of the skeletal surface (Plate 1, Fig¬ ures 3, 6) one can observe the typical groups of opal-CT blades, which are intergrown according to specific twinning laws of tridymite (Flörke et al, 1976). These opal-CT blades represent only an overgrowth, but because no appreciable opal-A contents could be determined by XRD, in situ replacement of the under¬ lying skeletons by opal-CT is highly probable.…”

Section: Preservation Of Radiolariansmentioning

confidence: 99%

“…A few isolated tiny opal-CT blades with ragged edges growing on earliestdiagenetic calcitic cement within a foraminifer chamber. This is a precursor stage of lepisphere formation (Flörke et al, 1976).…”

Section: Figurementioning

confidence: 99%

“…The incipient filling of open cavities is characterized by isolated opal-CT blades (about 1 µm long and 0.1 to 0.2 µm thick; Plate 2, Figure 4) developing into embryonic and finally into complete well-bladed lepispheres (Flörke et al, 1976, fig. 1).…”

Section: Nodular Porcellanites (Carbonate Environment)mentioning

confidence: 99%

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Eocene Porcellanites and Early Cretaceous Cherts from the Western North Atlantic Basin

Riech¹,

Rad²

1979

Initial Reports of the Deep Sea Drilling Project

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Major results from a petrographic study of porcellanites and cherts are as follows: 1) Acoustic Horizon A consists of isochronous but facies-independent lower to middle Eocene immature porcellanites. A biogenic silica source is inferred. The porous sediments are first cemented and later replaced by opal-CT, producing a dense or lepispheretype fabric. Porcellanites within the clayey environment include silicified (radiolarian) mudstones and turbidite sands rich in sponge spicules. Poorly consolidated Eocene chalks show gradual transi¬ tions to calcareous porcellanites, which contrast with the discrete nodules typical of more strongly lithified carbonates.2) Before chertification, early-diagenetic quartz occurs locally in porcellanites as replacement of foraminifer tests and latest-genera¬ tion cavity-filling cement.3) With increasing burial depth and age, radiolarians are trans¬ formed in situ from the original opal-A into opal-CT, and finally into quartz. The boundary between sediments containing siliceous fossils preserved as opal-A and as opal-CT coincides with the up¬ permost porcellanites of each site.4) The diagenetically mature Lower Cretaceous quartz cherts contain quartz-replaced lepispheres, suggesting a porcellanitic pre¬ cursor stage. This indicates an age-, temperature-, and facies-controlled maturation process from opal-A to quartz via opal-CT.

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Section: Bedded Porcellanites (Clayey Environments)mentioning

confidence: 90%

Section: Preservation Of Radiolariansmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Nodular Porcellanites (Carbonate Environment)mentioning

confidence: 99%

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Eocene Porcellanites and Early Cretaceous Cherts from the Western North Atlantic Basin

Riech¹,

Rad²

1979

Initial Reports of the Deep Sea Drilling Project

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show abstract

“…These are diagenetically immature, porcellaneous mudstone, with radiolarians that are completely filled by opal-CT (Plate 1, Figure 6). Some of these semiconsolidated rocks contain globulose masses of opal-CT lepispheres (Florke et al, 1976) in the finest size fraction after distintegration. Locally, they contain abundant montmorillonite which is probably responsible for the "aggregate polarization" of these rocks.…”

Section: Riechmentioning

confidence: 99%

Diagenesis of Siliceous Sediments, Porcellanites, and Cherts of the Moroccan Basin, Deep Sea Drilling Project Sites 370, 415, and 416

Riech¹

1980

Initial Reports of the Deep Sea Drilling Project

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Stratigraphic Distribution, Lithological Paragenesis, Depositional Environments and Diagenesis of Fossil Siliceous Sponges in Europe

Zimmerle¹

1991

Fossil and Recent Sponges

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Intergrowth and twinning in opal-CT lepispheres

Cited by 57 publications

References 10 publications

Eocene Porcellanites and Early Cretaceous Cherts from the Western North Atlantic Basin

Eocene Porcellanites and Early Cretaceous Cherts from the Western North Atlantic Basin

Diagenesis of Siliceous Sediments, Porcellanites, and Cherts of the Moroccan Basin, Deep Sea Drilling Project Sites 370, 415, and 416

Stratigraphic Distribution, Lithological Paragenesis, Depositional Environments and Diagenesis of Fossil Siliceous Sponges in Europe

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