Opal in the Ogallala Formation in Kansas

Swineford, Ada; Franks, Paul C.

doi:10.2110/pec.59.01.0111

Cited by 12 publications

(7 citation statements)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…RESuLTs-In almost all cases the two opaline reflections as well as crystalline reflections were to be found. The broad opaline rings agree with those already described (Swineford and Franks, 1959;Jones and Milne, 1963) and need not be considered further here. The lowest proportion of crystalline material, as judged by relative intensity of the reflections, occurs in Equisetum (Fig.…”

supporting

confidence: 88%

“…characterized the silica of fresh diatoms as essentially amorphous and that of fossil specimens as only slightly crystalline, the latter showing a few, somewhat broad, diffraction rings on film when subjected to X-irradiation. Swineford and Franks (1959) examined diatomaceous opal and found some X-ray reflections ascribed to quartz and feldspar superimposed on two characteristic, very broad reflections of amorphous opal. In petrified wood there occurred opaline reflections together with X-ray reflections similar to those of low cristobalite and tridymite (Swineford and Franks, 1959).…”

mentioning

confidence: 99%

“…Swineford and Franks (1959) examined diatomaceous opal and found some X-ray reflections ascribed to quartz and feldspar superimposed on two characteristic, very broad reflections of amorphous opal. In petrified wood there occurred opaline reflections together with X-ray reflections similar to those of low cristobalite and tridymite (Swineford and Franks, 1959). Crystalline quartz was reported in the green alga 1 Received for publication 8 August 1966.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Crystalline Silica in Plants

Sterling

1967

American J of Botany

View full text Add to dashboard Cite

Crystalline silica has been found in Fragaria leaves, Equisetum shoots, diatomite, and tabaschir. Differing proportions of amorphous silica (opal) also occur in each of these. The crystalline X‐ray reflections of α‐quartz, low tridymite, or α‐cristobalite have been found in virtually all specimens. However, unidentified crystalline reflections are noted, particulary in the silica isolated from Fragaria leaves and diatomite.

show abstract

supporting

confidence: 88%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Crystalline Silica in Plants

Sterling

1967

American J of Botany

View full text Add to dashboard Cite

show abstract

“…At the boundary to the overlying Neuburg Kieselerde Member, common opaline nodules (see Swineford and Franks 1959;Niebuhr 2011a) with the Lower Cenomanian inoceramid bivalve index fossil Inoceramus crippsi occur ("Inoceramenlage" = inoceramid layer of Schneider 1933), which represent the crippsi Event associated with the first intra-Cenomanian sequence boundary SB Ce 1 (see Wilmsen 2003 andNiebuhr 2010 for details). Within the spiculitic silts of the Neuburg Siliceous Earth, nodules occur only loosely scattered and are often porous, and therefore not densely silicified.…”

Section: Litho-and Sequence Stratigraphymentioning

confidence: 99%

Silicified sea life – Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany)

Schneider¹,

Jäger²,

Kroh³

et al. 2013

Acta Geologica Polonica

View full text Add to dashboard Cite

Schneider, S., Jager, M., Kroh, A., Mitterer, A., Niebuhr, B., Vodražka, R., Wilmsen, M., Wood, C.J. and Zagoršek, K. 2013. Silicified sea life - Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany). Acta Geologica Polonica, 63(4), 555-610. Warszawa. With approximately 100 species, the invertebrate macrofauna of the Neuburg Kieselerde Member of the Wellheim Formation (Bavaria, southern Germany) is probably the most diverse fossil assemblage of the Danubian Cretaceous Group. Occurring as erosional relicts in post-depositional karst depressions, both the Cretaceous sediments and fossils have been silicified during diagenesis. The Neuburg Kieselerde Member, safely dated as Early Cenomanian to Early Turonian based on inoceramid bivalve biostratigraphy and sequence stratigraphy, preserves a predominantly soft-bottom community, which, however, is biased due to near-complete early diagenetic loss of aragonitic shells. The community is dominated by epifaunal and semi-infaunal bivalves as well as sponges that settled on various (bio-) clasts, and may widely be split into an early bivalve-echinoid assemblage and a succeeding sponge-brachiopod assemblage. In addition to these groups we document ichnofauna, polychaete tubes, nautilids and bryozoans. The fauna provides evidence of a shallow to moderately deep, calm, fully marine environment, which is interpreted as a largescale embayment herein. The fauna of the Neuburg Kieselerde Member is regarded as an important archive of lower Upper Cretaceous sea-life in the surroundings of the Mid-European Island.

show abstract

“…Clearly the problem of direct precipitate vs. recrystallization product is unsolved, yet the anomolous crystal structure (length-fast fibres), the 'trapped' water, the similarity in growth form between pore filling banded opal-CT and chalcedony (e.g. Swineford & Franks, 1959, Fig. 9, are features that seem more compatible with chalcedony being a recrystallization product of banded opal-CT.…”

Section: Chertification Processesmentioning

confidence: 99%

Chertification in the Mississippian Lake Valley Formation, Sacramento Mountains, New Mexico

Meyers

1977

Sedimentology

View full text Add to dashboard Cite

Chert distribution in the Lake Valley rocks is selective to mud‐supported facies; it is not related to proximity to unconformities. The facies selectivity of the chertification is believed to be a function of the depositional distribution of indigenous silica as sponge spicules, an interpretation that is supported by high positive qualitative correlation of chert with spiculitic rocks. Petrography indicates that the spicules were all originally siliceous, and that they all went through a moldic stage during which many molds were compactively destroyed and distorted. Remaining molds were subsequently cemented by calcite or chalcedony. Chert distribution and spicule petrography argue for an intraformational source for much of the silica. Chert micro‐fabrics are dominated by microquartz, a replacement of grains and lime mud; length‐fast chalcedony, a pore‐filling cement; and megaquartz, a post‐chalcedony pore‐filling cement. Petrography of compaction features within chert masses indicates that chertification occurred after some burial. Based on stratigraphic reconstruction this burial depth was a maximum of about 215 m. and was most likely a few metres to a few tens of metres. Petrography of chert‐calcite cement relationships indicates that chertification occurred before and during first generation, pre‐Pennsylvanian non‐ferroan calcite cementation, and was completed before late‐stage, post‐Mississippian ferroan calcite precipitation. Petrography of chert clasts in basal Rancheria (Meramecian) and basal Pennsylvanian conglomerates proves these clasts derived from the Lake Valley Formation and were chertified before redeposition. Thus, some cherts in the Lake Valley are pre‐Meramecian in age, but all are pre‐Pennsylvanian in age. Furthermore, association of the cherts with the non‐ferroan cements indicates the cherts were probably precipitated in meteoric phreatic lens established beneath the pre‐Meramecian and pre‐Pennsylvanian subaerial unconformities.

show abstract

Opal in the Ogallala Formation in Kansas

Cited by 12 publications

References 1 publication

Crystalline Silica in Plants

Crystalline Silica in Plants

Silicified sea life – Macrofauna and palaeoecology of the Neuburg Kieselerde Member (Cenomanian to Lower Turonian Wellheim Formation, Bavaria, southern Germany)

Chertification in the Mississippian Lake Valley Formation, Sacramento Mountains, New Mexico

Contact Info

Product

Resources

About