Composition of biotite phenocrysts in Ordovician tephras casts doubt on the proposed trans-Atlantic correlation of the Millbrig K-bentonite (United States) and the Kinnekulle K-bentonite (Sweden)

Haynes, John T.; Melson, William G.; Kunk, Michael J.

doi:10.1130/0091-7613(1995)023<0847:cobpio>2.3.co;2

Cited by 42 publications

(24 citation statements)

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“…Based on the geochemical data, the Millbrig K-bentonite is correlated with the Kinnekulle K-bentonite (Huff, Bergström & Kolata, 1992;Bergström et al 1995), a prominent marker horizon at the base of the Keila Stage in Baltoscandia. This suggestion is in accordance with transcontinental biozonal correlation (Huff, Bergström & Kolata, 1992), although the investigation of biotite phenocrysts has thrown some doubt upon its value (Haynes, Melson & Kunk, 1995).…”

Section: D Isotopic Excursion In North Americamentioning

confidence: 69%

Evidence for a widespread carbon isotopic event associated with late Middle Ordovician sedimentological and faunal changes in Estonia

Ainsaar

Meidla

Martma³

1999

Geol. Mag.

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An episode of remarkable biotic, climatic, sea-level and facies changes took place during the late Viruan (Caradoc) epoch in the Baltoscandian area. We studied the carbon isotopic composition of carbonate sediments from this period. Data on the stable carbon isotopic composition of whole-rock carbonates from three south Estonian core sections, together with those on ostracode, distribution are presented. In two core sections, a positive δ13C shift of 2 ‰ was revealed in the upper part of the Keila Stage (mid-Caradoc). The comparison of isotope and ostracode data in the sections suggested the occurrence of a gap of late Keilan age in the marginal area of the basin equivalent to the North Estonian Confacies Belt. The beginning of the excursion approximately coincided with climatic and sea-level changes in the shallow shelf area. The peak of the late Keilan excursion preceded the biotic crises and maximum black shale accumulation in the Baltoscandian palaeobasin. An approximately synchronous carbon isotopic event has been reported from North America, referring to a possible global oceanographic event in the Caradoc epoch. Although the positive carbon isotopic excursion and related environmental events of the late Keilan age have some unique features, they show more similarities to the end-Ordovician and Silurian events, characterized by oceanic change from stratified state to thermohaline circulation state, than to warm anoxic events related to eustatic sea-level rise.

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Section: D Isotopic Excursion In North Americamentioning

confidence: 69%

Evidence for a widespread carbon isotopic event associated with late Middle Ordovician sedimentological and faunal changes in Estonia

Ainsaar

Meidla

Martma³

1999

Geol. Mag.

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“…reported (Haynes, Melson & Kunk, 1995). Laser 40 Ar/ 39 Ar analysis (see Appendix 1) of selected biotite phenocrysts was carried out at the Geological Survey of Canada, Ottawa.…”

Section: Methodsmentioning

confidence: 99%

“…For example, the MgO-FeO pair and cationic ratio Mg/(Mg + Fe 2+ ) of the phlogopite phenocrysts further help to identify the extent of magmatic fractionation (Fig. The Deicke, Millbrig and Kinnekulle Kbentonites of eastern North America and Europe show Mg/(Mg + Fe 2+ ) ratio ranges of 0.59-0.64, 0.44-0.54 and 0.43-0.44, respectively (Haynes, Melson & Kunk, 1995;Min, Renne & Huff, 2001). MgO is concentrated in less fractionated melts whereas FeO accumulates in more fractionated magmas (Batchelor, 2003).…”

Section: B Composition Of the Russell Magmatic Sourcementioning

confidence: 99%

Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians

2005

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A 6 cm thick K-bentonite, herein defined as the Russell Bed, occurs in an Upper Ordovician deep-basin shale succession in eastern Ontario, Canada, forming part of the distal Taconic foreland in eastern North America. The bed lies within the pygmaeus graptolite Biozone, which is about 451 to 452 Ma in age. Although some bentonites are reported from this interval in eastern North America, we are reporting the first set of compositional data for a bentonite of this age. Gamma-log correlation identifies a potential minimum distribution area of < 2 × 10 5 km 2 for the K-bentonite, covering part of southern Quebec, New York State and eastern Ontario. The deposit coincides with the first influx of distal turbdites into this shale basin, associated with Taconic flysch, and simultaneous abrupt ventilation of the once anoxic deep-water basin, which had formed initially after foundering of the Upper Ordovician carbonate platform. Concurrent intrabasinal extinction of several graptolite species suggests that change in sedimentation, palaeoceanography and volcanism were linked to a regional external process. Compositionally, the bentonite is distinct from the older Ordovician platform deposits in eastern North America. The deposit contains abundant titaniferous phlogopite with 1.6 % BaO, fluoroapatite with 2.5 % F, and dynamically shaped glass spherules now altered to clay. The spherules and clay matrix constitute 45 % of the bed and, compositionally, define an illite (> 90 %)smectite (I/S) structure with about 7.5 % K 2 O %. Age-dating by Ar-Ar analysis of the phlogopite crystals yielded a younger than expected (440-445 Ma) age. This difference, along with evidence of localized chloritization of phlogopite, likely reflects known post-Ordovician hydrothermal activity within the basin. On the basis of several geochemical proxies, the magmatic source of the Russell K-bentonite falls within the trachyandesite field and was Ba-enriched. Comparison of geochemistry and mineralogy with older, Middle to Late Ordovician and younger Early Silurian K-bentonites within the Taconic orogen along eastern Laurentia and Baltica reveals that the potential source magma for the Russell Bed was more mafic, more alkaline, and less fractionated than sources typical of older (platform) bentonites. Instead, it is more similar to the younger Llandovery bentonites of Scandinavia and Scotland. It remains uncertain if it signals local or regional compositional change in volcanic source in the northern Appalachians.

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“…For example, the abundance and stratigraphical similarity of Caradoc beds in North America and Baltoscandic prompted Huff et al (1992) to propose that these two regions were in close proximity at that time. Haynes et al (1995) challanged the proposed correlation of the Millbrig and Kinnekuile beds on the basis of an apparent dissimilarity in biotite compositions. However, current studies (Huff et al 1997a) suggest that the Millbrig beds consist of multiple units, at least one of which is chemically indistinguishable from the Kinnekulle bed.…”

Section: Palaeotectonic Setting and Volcanic Sourcementioning

confidence: 98%

Ordovician K-bentonites in the Argentine Precordillera: relations to Gondwana margin evolution

Huff

Bergström

Kolata

et al. 1998

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Ordovician K-bentonites have now been recorded from >20 localities in the vicinity of the Argentine Precordillera. Most occur in the eastern thrust belts, in the San Juan Limestone and the overlying the Gualcamayo Formation, but a few ash beds are known also from the central thrust belts. The oldest occur in the middle Arenig I. victoriae lunatus graptolite (Oe. evae conodont) Zone, and the youngest in the middle Llanvirn P. elegans (P. suecicus)

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Composition of biotite phenocrysts in Ordovician tephras casts doubt on the proposed trans-Atlantic correlation of the Millbrig K-bentonite (United States) and the Kinnekulle K-bentonite (Sweden)

Cited by 42 publications

References 0 publications

Evidence for a widespread carbon isotopic event associated with late Middle Ordovician sedimentological and faunal changes in Estonia

Evidence for a widespread carbon isotopic event associated with late Middle Ordovician sedimentological and faunal changes in Estonia

Petrology and potential tectonic significance of a K-bentonite in a Taconian shale basin (eastern Ontario, Canada), northern Appalachians

Ordovician K-bentonites in the Argentine Precordillera: relations to Gondwana margin evolution

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