Paleoenvironmental changes across the Late Cambrian–Early Ordovician in western Newfoundland

Wang, Luyi (2019) Paleoenvironmental changes across the Late Cambrian–Early Ordovician in western Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

The Martin Point section (western Newfoundland, Canada) spans the uppermost Cambrian Broom Point and Martin Point members of the Green Point Formation (upper Furongian). The investigated interval (~ 90 m) consists of rhythmites of thinly-bedded marine carbonates (lime mudstones) alternating with green and black shale and thin conglomerate beds. Samples were extracted from the micritic carbonates and their preservation was petrographically and geochemically examined. The δ¹³Corg profile exhibits a positive shift (~ 2 ‰) associated with the globally well documented negative δ¹³Ccarb excursion at the HERB (Hellnmaria – Red Tops Boundary) and correlates with similar distinct shifts in the Al, Si, and ΣREE components, thus suggesting contributions from detrital organic matter relatively depleted in ¹²C likely induced by an eustatic sea-level drop and enhanced terrigenous inputs. Similarly, the δ¹⁵Norg variations are consistent with the proposed sea-level drop. This is also correlated with positive shifts on the Fe and Mn profiles reflecting overprinting of terrigenous inputs rather than reflecting the fluctuations in redox conditions.

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