Redox conditions across the Upper Cambrian in Western Newfoundland, Canada

Okafor, Miracle-Mary Chisom (2023) Redox conditions across the Upper Cambrian in Western Newfoundland, Canada. Masters thesis, Memorial University of Newfoundland.

[img] [English] PDF - Accepted Version
Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission.

Download (16MB)


The lower part of the Martin Point section (~ 110 m - rhythmites) spans the uppermost Shallow Bay and lowermost Green Point formations (uppermost Franconian‒ lowermost Trempealeauan) of the Cow Head Group (western Newfoundland, Canada). It records two post-SPICE events (SPICE – Steptoean Positive Carbon Isotope Excursion) marked by negative δ¹³Ccarb excursions (NL1 and NL2) that were also documented in South China. The petrographic and chemical screening of the investigated carbonate samples proves the preservation of at least near-primary geochemical signatures. The proxies of weathering (e.g., Mn, Fe, Al, and ΣREE), bioproductivity (e.g., δ¹³Corg, TOC, P, Ni, Zn, and Cu), and paleoredox (e.g., Cr, Th/U, Ce/Ce*) have been utilized to reconstruct the paleoenvironmental conditions during the post-SPICE events. The TOC, P, Ni, Cu, Cr, ΣREE, Mn, Fe, and U enrichment-factor profiles exhibit a positive pulse at the base of NL2 (upper negative δ¹³Ccarb excursion), followed by a drop. This might have resulted from shoaling organic-rich anoxic waters into an oxygenated shallow environment during transgression, which led to a negative shift in the δ¹³Ccarb and a decrease in TOC contents as well as an increase in the δ¹³Corg. The correlated enrichment in Zn and δ¹⁵Norg values and the Ce/Ce* around unity are consistent with the shoaling scenario. A similar scenario seems to be consistent with NL1 (lower negative δ¹³Ccarb excursion) although the lower resolution of correlated proxy variations makes the interpretations based on a few points and to be therefore taken with caution. The upper part of the Martin Point section spans the upper Martin Point Member (upper Furongian, ~90 m) of the Green Point Formation of the Cow Head Group. It records the HERB event (HERB - Hellnmaria-Red Tops Boundary) marked by a negative δ¹³Ccarb excursion at the base of the Econodontus notchpakensis conodont Zone. The HERB paleoenvironmental proxy enrichment profiles exhibit comparable patterns to those of the post-SPICE, which suggests that the HERB event started with a similar scenario of transgression and shoaling of organic-rich anoxic water into the water settings. However, the TOC profile shows a small gradual enrichment (~1 %), above the peak of the excursion, correlated with a broad negative δ¹³Corg shift (~2 ‰), and a positive Al/Ti shift. This may suggest possible minor interruptions by sealevel drop and/or an episode/pulse of enhanced wind-blown inputs of weathered terrigenous material.

Item Type: Thesis (Masters)
Item ID: 15986
Additional Information: Includes bibliographical references (pages 46-64)
Keywords: Upper Cambrian, post-SPICE paleoenvironment, eastern Laurentia, Martin Point (western Newfoundland, Canada)
Department(s): Science, Faculty of > Earth Sciences
Date: February 2023
Date Type: Submission
Digital Object Identifier (DOI):
Library of Congress Subject Heading: Geology--Newfoundland and Labrador--Cow Head Group

Actions (login required)

View Item View Item


Downloads per month over the past year

View more statistics