Redox‐State and Bioproductivity of the Glaciogenic Early Cryogenian Rapitan Iron Formation (Cranswick River, Canada): Constraints From Combined Cadmium—Chromium Isotopes

Geochemistry Geophysics Geosystems, Journal Year: 2025, Volume and Issue: 26(4)

Published: April 1, 2025

Abstract The Rapitan Group (Northwest Territories, Canada) includes banded iron formation (BIF), an unusual sediment type that is associated with late Neoproterozoic glaciations, in this case, the early Cryogenian Sturtian glaciation. New non‐traditional stable isotope data from jasper and hematite (IF) Cranswick River area contribute new insights regarding water chemistry changes respective depositional basin during glacier advance retreat. Cr signatures are characterized by strongly positively fractionated δ 53 values (+0.68–1.47‰), attesting to oxidized surface waters entire episode. Relatively weakly 114 Cd (−0.02 +0.28‰), absence of organic matter samples, indicate a low bioproductivity BIF deposition. Detailed fluctuations over intermittent retreat cycle recorded studied section, however, reveal ephemeral increase primary production (excursion slightly elevated values) just after deposition diamictite layer, which agrees corresponding values. This evidence attests sensitivity Cd‐Cr double tracer applied BIFs reconstruct basins track climate accompanied glacial episodes. When compared younger (Marinoan/Ediacaran) Urucum Brazil, section differs lack negative Ce anomalies its rare earth element patterns, implying column oxidation was not as strong Marinoan/Ediacaran

Language: Английский

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Surface water oxygenation and low bioproductivity during deposition of iron formation of the Jacadigo Group (Brazil): Insights from combined cadmium – Chromium isotopes

Chemical Geology, Journal Year: 2024, Volume and Issue: 657, P. 122101 - 122101

Published: April 25, 2024

The Banda Alta Formation (Urucum district, Mato Grosso do Sul, Brazil) comprises ~600 Ma Fe and Mn deposits, which are among the world's youngest largest Neoproterozoic sedimentary formations (IF; MnF). These have been deposited in a redox-stratified, marine sub-basin (Jacadigo Basin), was strongly influenced by glacial advance/retraction cycles with temporary influx of continental freshwater upwelling metal-enriched deep anoxic seawater. Cr Cd isotopes measured on meticulously separated hematite mesobands from drill core samples relatively homogenous throughout ca. 325 m thick sequence sampled Fm., average authigenic δ53Cr values +0.93 ± 0.24 ‰ (2σ; n = 23) δ114Cd −0.14 0.14 15). significant enrichment Cr, parallel strong enrichments other redox sensitive elements (U, Mo), attests for effective efficient reduction removal processes surface waters during where Fe2+-rich reached oxygenated layer exposed to atmosphere episodic glacier retreat stages. Assuming similar quantitative pathway dissolved iron oxyhydroxides, so-inferred signature Jacadigo Basin water is significantly lower than signatures modern ocean range ~0.4 ~1 even ~0.3 ‰. It possibly reduced primary production levels nutrient utilization rates deposition Late Group, compared today. This despite inferred oxidized that must prevailed this time, as implied positively fractionated isotope pronouncedly negative Ce-anomalies recorded seawater-like, shale-normalized Rare Earth Element Yttrium (REY) patterns exhibited mesobands. Data presented herein speak for: (1) stable, isotopically heavy input at time deposition, implying high atmospheric O2 (2) likely quantitative, reductive incorporation / adsorption Cd, respectively, into/onto precipitating (3) prevalence low concentrations cycles. Banded considered suitable archives reconstructing bioproductivity past depositional basin, including those prevalent conditions, via employing CrCd double tracer iron-rich

Language: Английский

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A proposed chronostratigraphic Archean–Proterozoic boundary: Insights from the Australian stratigraphic record

Precambrian Research, Journal Year: 2024, Volume and Issue: 406, P. 107377 - 107377

Published: April 6, 2024

The Mount Bruce Supergroup (MBS) in Western Australia has been central to debates surrounding Precambrian stratigraphic subdivision and is one of the few relatively conformable successions that records both chronometric Archean-Proterozoic boundary (APB) Great Oxidation Event/Episode (GOE) which previously proposed as most practical basis for a chronostratigraphic boundary. Current understanding lithostratigraphy, chemostratigraphy, geochronology MBS supports placement APB vicinity contact between Hamersley Turee Creek Groups, although precise awaits generation integration more detailed chemostratigraphic GOE with physical record. presently defined at 2500 Ma will suffice until consensus reached regarding revised definition based on GOE, reconciliation proxy this event. However, Australian record suggests either base first glacial diamictite, or top last banded iron formation (BIF) below GOE. option would exclude some BIF from Siderian, cases be terminal period Archean, whereas second places all diamictite new start Paleoproterozoic. It further named primarily reflect influence, rather than influence relies less obvious laboratory-based proxies its identification.

Language: Английский

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Highly siderophile element and Re-Os isotope systematics of a Neoproterozoic Iron Formation and its temporal relation to glaciation events

Geochimica et Cosmochimica Acta, Journal Year: 2024, Volume and Issue: unknown

Published: Sept. 1, 2024

Language: Английский

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New advances on the carbon isotope and rare earth elements chemostratigraphy of the late Ediacaran Tamengo Formation (Corumbá Group, Brazil)

Journal of South American Earth Sciences, Journal Year: 2023, Volume and Issue: 133, P. 104696 - 104696

Published: Nov. 21, 2023

Language: Английский

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Rapid bioproductivity recovery following the Marinoan glaciation: Evidence from Sr-Cr-Cd isotopes and trace elements in the Morraria do Sul cap dolostone, Brazil

Chemical Geology, Journal Year: 2024, Volume and Issue: unknown, P. 122548 - 122548

Published: Dec. 1, 2024

Language: Английский

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