Eustatic sea-level patterns from the Lower Silurian (Llandovery Series) of southern Norway and Estonia

Johnson, Markes E.; Baarli, B. Gudveig; Nestor, Heldur; Rubel, Madis; Worsley, David

doi:10.1130/0016-7606(1991)103<0315:eslpft>2.3.co;2

Cited by 55 publications

(27 citation statements)

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“…6), that is, the unit containing the thick ash bed here identified as the Osmundsberg K-bentonite. The biostratigraphic interpretation of the Rumba Formation by Johnson et al (1991) is likely to be correct, and we suggest that the 'O' bed is the Osmundsberg K-bentonite. Figure 13 illustrates the stratigraphic position and thickness of the volcanic ash beds identified as the Osmundsberg K-bentonite in eight sections in Baltoscandia, from southeastern Norway to western Estonia.…”

Section: Sections In Estoniamentioning

confidence: 63%

“…69). Interestingly, this brachiopod also occurs in the Rytterås Formation in the Oslo region, Norway (Johnson et al 1991, fig. 6), that is, the unit containing the thick ash bed here identified as the Osmundsberg K-bentonite.…”

Section: Sections In Estoniamentioning

confidence: 88%

“…The latter unit has not yielded zonal graptolites and its correlation has been somewhat controversial. That is, whereas Kaljo (1990, table 2) assigned it to the uppermost Aeronian, Johnson et al (1991) placed the unit in the lower Telychian, presumably based on the occurrence of Stricklandia laevis, which is not known from pre-Telychian strata (Cocks et al 1984, fig. 69).…”

Section: Sections In Estoniamentioning

confidence: 99%

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The Lower Silurian Osmundsberg K-bentonite. Part I: stratigraphic position, distribution, and palaeogeographic significance

1998

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A large number of Lower Silurian (Llandovery) K-bentonite beds have been recorded from northwestern Europe, particularly in Baltoscandia and the British Isles, but previous attempts to trace single beds regionally have yielded inconclusive results. The present study suggests that based on its unusual thickness, stratigraphic position and trace element geochemistry, one Telychian ash bed, the Osmundsberg K-bentonite, can be recognized at many localities in Estonia, Sweden and Norway and probably also in Scotland and Northern Ireland. This bed, which is up to 115 cm thick, is in the lower–middle turriculatus Zone. The stratigraphic position, thickness variation and geographic distribution of the Osmundsberg K-bentonite are illustrated by means of 12 selected Llandovery successions in Sweden, Estonia, Norway, Denmark, Scotland and Northern Ireland. In Baltoscandia, the Osmundsberg K-bentonite shows a trend of general thickness increase in a western direction suggesting that its source area was located in the northern Iapetus region between Baltica and Laurentia. Because large-magnitude ash falls like the one that produced the Osmundsberg K-bentonite last at most a few weeks, such an ash bed may be used as a unique time-plane for a variety of regional geological and palaeontological studies.

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Section: Sections In Estoniamentioning

confidence: 63%

Section: Sections In Estoniamentioning

confidence: 88%

Section: Sections In Estoniamentioning

confidence: 99%

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The Lower Silurian Osmundsberg K-bentonite. Part I: stratigraphic position, distribution, and palaeogeographic significance

1998

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“…6). Johnson et al 1991). Note that the break in δ 13 C data on Anticosti Island in the S. sedgwickii Zone is the result of a very shallow-water unit that yielded no brachiopods for sampling.…”

Section: Discussionmentioning

confidence: 99%

Carbon isotope chemostratigraphy of the Llandovery in Arctic Canada: Implications for global correlation and sea-level change

Melchin¹,

Holmden²

2006

GFF

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Stratigraphic and δ 13 C data from the Rhuddanian to lower Telychian succession on Cornwallis Island, Arctic Canada show evidence of a significant positive δ 13 C excursion in the upper Aeronian and weak positive shifts in the mid-Rhuddanian and uppermost Rhuddanian-lower Aeronian. The lower and upper Aeronian levels coincide with times of continental glaciation in Gondwana and these can be correlated with events recorded in the δ 13 C records from Dob's Linn (Scotland), Anticosti Island (Quebec), and Estonia. In most instances in the C-isotope records appear to coincide closely with local sea-level changes. The available data suggest that the global environmental impact of the late Aeronian glaciation was greater than that of the early Aeronian event. The data support the hypothesis that changes in degree of carbonate platform exposure and weathering resulting from of a combination of local and global (glacioeustatic) sea-level changes (particularly sea-level fall) were an important controlling factor in the generation of positive δ 13 C excursions in this time interval. These changes shifted the isotope value of the C-weathering flux entering shelf seas, which in turn resulted in positive δ 13 C excursions of varying magnitudes in shelf and deep basinal settings. These varied regionally in magnitude in close correspondence with differences in local sea-level histories.

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“…The sea-level curve (Fig. 3), reproduced from Johnson et al (1991b), was derived by correlating depth-related benthonic communities in carbonate-dominated cratonic shelf sequences on six early Palaeozoic continents: Laurentia, Baltica, Avalonia, Siberia, South China and Gondwana. Johnson et al (1991b) …”

Section: Chronology and Eustasymentioning

confidence: 99%

Sequence stratigraphical analysis of late ordovician and early Silurian depositional systems in the Welsh Basin: a critical assessment

Woodcock¹,

Butler²,

Davies³

et al. 1996

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Sequence stratigraphical concepts are applied to a 55 km long transect through the uppermost Ordovician and lower Silurian rocks of the Welsh Basin and the adjoining Midland Platform. The study focuses on sedimentary rocks deposited during the Llandovery epoch (about 439-430 Ma).An early Llandovery slope apron of hemipelagite and laterally supplied mudstone turbidites shows the influence of eustatic sea-level changes. Two complete depositional sequences are recognized. Transgressions and highstands on the platform were accompanied by laminated hemipelagite deposition in the basin, recording anoxic bottom waters in a stratified watermass. The intervening regressions generated unconformities on the platform and producedbioturbated basinal sediments in a more oxic environment.By contrast, the extent and timing of sandstone-turbidite and debrite systems in the basin are strongly affected by tectonic activity. Easterly derived late Llandovery facies relate directly to faulting and submarine mass wasting along the basin margin. Southerly derived late Llandovery to mid-Wenlock sandstone-lobe systems were the products of tectonic uplift in extrabasinal source areas and were partially confined within intrabasinal tilted fault blocks. Subsidence analysis confirms a basinal stretching event in late Llandovery (Telychian) time and shows that it also affected the adjacent Midland Platform. The depositional systems of this period constitute elements of a dual-sourced depositional sequence, within which eustatic effects are masked by the strong influence of relative base-level changes attendant to tectonism.The architecture of the early Silurian Welsh Basin illustrates the complexities of applying sequence stratigraphical models where there is an interleaving of several depositional systems, each modulated by a different mix of eustatic, tectonic and input controls.

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Eustatic sea-level patterns from the Lower Silurian (Llandovery Series) of southern Norway and Estonia

Cited by 55 publications

References 0 publications

The Lower Silurian Osmundsberg K-bentonite. Part I: stratigraphic position, distribution, and palaeogeographic significance

The Lower Silurian Osmundsberg K-bentonite. Part I: stratigraphic position, distribution, and palaeogeographic significance

Carbon isotope chemostratigraphy of the Llandovery in Arctic Canada: Implications for global correlation and sea-level change

Sequence stratigraphical analysis of late ordovician and early Silurian depositional systems in the Welsh Basin: a critical assessment

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