The early Neoproterozoic sedimentary Succession B of northwestern Laurentia: Correlations and paleogeographic significance

Rainbird, R H; Jefferson, C W; Young, Grant M.

doi:10.1130/0016-7606(1996)108<0454:tenssb>2.3.co;2

Cited by 163 publications

(127 citation statements)

References 65 publications

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“…The Neoproterozoic ocean was most likely sulfate poor (30), with probably no more than about 10% of the present-day concentration of 28 mM. Recent arguments suggest higher sulfate concentrations can be maintained during ferruginous conditions (21), and are supported by sulfate evaporite deposition (31). A level of approximately 3 mM before the beginning of the event, supplemented by riverine continental flux about twice that the of present day, could provide sufficient sulfate.…”

Section: Results Of a Time-dependent Scenariomentioning

confidence: 99%

Biologically induced initiation of Neoproterozoic snowball-Earth events

Tziperman

Halevy

Johnston

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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The glaciations of the Neoproterozoic Era (1,000 to 542 MyBP) were preceded by dramatically light C isotopic excursions preserved in preglacial deposits. Standard explanations of these excursions involve remineralization of isotopically light organic matter and imply strong enhancement of atmospheric CO 2 greenhouse gas concentration, apparently inconsistent with the glaciations that followed. We examine a scenario in which the isotopic signal, as well as the global glaciation, result from enhanced export of organic matter from the upper ocean into anoxic subsurface waters and sediments. The organic matter undergoes anoxic remineralization at depth via either sulfate-or iron-reducing bacteria. In both cases, this can lead to changes in carbonate alkalinity and dissolved inorganic pool that efficiently lower the atmospheric CO 2 concentration, possibly plunging Earth into an ice age. This scenario predicts enhanced deposition of calcium carbonate, the formation of siderite, and an increase in ocean pH, all of which are consistent with recent observations. Late Neoproterozoic diversification of marine eukaryotes may have facilitated the episodic enhancement of export of organic matter from the upper ocean, by causing a greater proportion of organic matter to be partitioned as particulate aggregates that can sink more efficiently, via increased cell size, biomineralization or increased C∶N of eukaryotic phytoplankton. The scenario explains isotopic excursions that are correlated or uncorrelated with snowball initiation, and suggests that increasing atmospheric oxygen concentrations and a progressive oxygenation of the subsurface ocean helped to prevent snowball glaciation on the Phanerozoic Earth.carbon isotopes | CO2

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Section: Results Of a Time-dependent Scenariomentioning

confidence: 99%

Biologically induced initiation of Neoproterozoic snowball-Earth events

Tziperman

Halevy

Johnston

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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“…The homocline succession is composed of the predominantly sedimentary Hornby Bay and Dismal Lakes groups (Kerans et al 1981) and regionally extensive, extrusive volcanics of the Coppermine River Group (Barager and Donaldson 1973), which are unconformably overlain by carbonate and siliciclastic strata of the Neoproterozoic Rae Group, Shaler Supergroup (Rainbird et al 1996).…”

Section: Regional Geologic Setting and Agementioning

confidence: 99%

Reconstructing sea-level change from the internal architecture of stromatolite reefs: an example from the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada

Kah¹,

Bartley²,

Frank³

et al. 2006

Can. J. Earth Sci.

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The Mesoproterozoic Dismal Lakes Group, arctic Canada, contains a relatively thin, yet regionally extensive stromatolitic reef complex that developed subtidally during a major transgression, shoaled to sea level, and was overlain by intertidal to supratidal carbonate and evaporite strata. The September Lake reef complex exhibits a complex internal architecture that records the interaction between stromatolite growth and changes in accommodation space derived from both higher order (4th- or 5th-order, parasequence-scale) changes in sea level and the variable bathymetry of the sea floor. Reef growth, which was initiated during three sea-level cycles, records progressive marine transgression over depositional lows that were formed during pre-reef subaerial exposure and erosion of the underlying strata. A fourth sea-level cycle, represented by spectacular coniform stromatolites with >10 m of synoptic relief, marks a more dramatic rise in sea level and establishment of the main reef complex. Aggradation and eventual shoaling of the reef complex occurred over an additional six sea-level cycles. Only basinward regions of the September Lake reef complex preserve vertical stacking of reefal packages in response to sea-level fluctuations. In contrast, in the main reef core, sea-level fluctuations resulted in subaerial exposure of the reef top, variable karst development, and the progressive infilling of reef topography by progradational reef elements. Assessment of stromatolite growth patterns reveals the complex nature of the reef architecture and permits the determination of higher order changes in relative sea level that were responsible for reef development.

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“…Callana carbonates, constrained in age to be older than the Rook tuff (802 ± 10 Ma, U-Pb zircon; Fanning et al 1986), reveal carbon isotopic values of -3‰ (Lambert 1984), suggesting a continuation of moderately elevated isotopic values well into the Neoproterozoic. If Callana carbonates can be shown to be correlative with the Mikkelson Island Formation, lower Shaler Supergroup, as proposed by Rainbird et al (1996), this age may also mark the time after which carbon isotopes rise dramatically to typically high Neoproterozoic values .…”

Section: Extending the Global Carbon Isotopic Recordmentioning

confidence: 89%

“…The similarity of Strathcona Sound paleomagnetic poles both to those of the Nauyat Formation and to the well-constrained Logan Sill pole (1109 2 4 − + Ma, U-Pb baddeleyite; Krogh et al 1987), however, suggests that the Bylot Supergroup may have been deposited wholly within the Mesoproterozoic (Fahrig et al 1981;Knight and Jackson 1994). If these estimates are correct, it is unlikely that Bylot Supergroup deposition was coeval with that of the Shaler Supergroup and correlatives of Sequence B, which have maximum ages between 1077 ± 3 and 1003 ± 3 Ma (U-Pb detrital zircon; Rainbird et al 1996). Biostratigraphic evidence cannot further constrain depositional ages; acritarch taxa from the Bylot Supergroup consist largely of unornamented leiosphaerids (Hofmann and Jackson 1994).…”

Section: Agementioning

confidence: 98%

δ<SUP>13</SUP>C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations

Kah¹,

Sherman²,

Narbonne³

et al. 1999

Can. J. Earth Sci.

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Abstract:The Bylot Supergroup, northern Baffin Island, contains >1500 m of platform, shelf, and slope carbonates deposited between -1270 and -723 Ma. Limited chronostratigraphic data have led to the broad correlation of the Bylot Supergroup with predominantly Neoproterozoic successions in northern and western Laurentia; yet, detailed correlation has been impossible given biostratigraphic and lithostratigraphic limitations. Carbon-isotope chemostratigraphy represents a potential dataset to constrain such interregional correlations. Carbon isotopic data from the Bylot Supergroup and broadly coeval successions from Somerset Island and northwest Greenland reveal distinct stratigraphic trends in δ 13 C, with intervals of moderate 13 C enrichment (+3.5 ± 1‰) punctuated by excursions to slightly negative values (-1.0 ± 1‰). Although the scale of the observed variation is muted relative to Neoproterozoic standards, the dissimilarity of values to those recorded in northwestern Laurentia suggests that these strata delineate a discrete depositional interval. Comparison of isotopic values with published data indicates that δ 13 C values between approximately -1.0 and +4.0‰ are characteristic of the interval between -1300 and -800 Ma. This pattern is distinct from that of younger Neoproterozoic successions, which typically record values >+5‰, and older Mesoproterozoic successions, which record values near 0‰, and suggests that these moderately positive values may be useful for broad time correlation. Compilation of new and published data permits the tentative reconstruction of a global Mesoproterozoic carbon isotopic curve.Résumé : Le Supergroupe de Bylot, dans le nord de l'île de Baffin, est formé de >1500 m de carbonates qui furent déposés sur une plate-forme continentale et un talus, entre -1270 et -723 Ma. Les données chronostratigraphiques limitées n'autorisent qu'une corrélation d'ordre général entre le Supergroupe de Bylot et les successions principalement néoprotérozoïques des régions septentrionales et occidentales de Laurentia; jusqu'à présent, il a été impossible d'établir une corrélation détaillée en raison du petit nombre de données biostratigraphiques et lithostratigraphiques. La chimiostratigraphie des isotopes du C a fourni un ensemble de données pouvant aider à mieux définir les corrélations inter-régionales. Les résultats des analyses d'isotopes du C pour le Supergroupe de Bylot et les successions grossièrement contemporaines de l'île Somerset et du nord-ouest du Groenland révèlent des tendances stratigraphiques distinctes dans les valeurs de δ 13 C, avec des intervalles d'enrichissement modéré de 13 C (+3,5 ± 1‰), ponctués d'incursions de valeurs légèrement négatives (-1,0 ± 1‰). Même si l'échelle de la variation observée est atténuée par rapport aux standards du Néoprotérozoïque, les valeurs différentes de celles enregistrées dans le nord-ouest de Laurentia suggèrent que ces strates représentent un intervalle de sédimentation discontinue. La comparaison des données isotopiques avec celles déjà publiées in...

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The early Neoproterozoic sedimentary Succession B of northwestern Laurentia: Correlations and paleogeographic significance

Cited by 163 publications

References 65 publications

Biologically induced initiation of Neoproterozoic snowball-Earth events

Biologically induced initiation of Neoproterozoic snowball-Earth events

Reconstructing sea-level change from the internal architecture of stromatolite reefs: an example from the Mesoproterozoic Sulky Formation, Dismal Lakes Group, arctic Canada

δ<SUP>13</SUP>C stratigraphy of the Proterozoic Bylot Supergroup, Baffin Island, Canada: implications for regional lithostratigraphic correlations

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