Paleoenvironmental fluctuations across the Jurassic–Cretaceous boundary from the Scotian margin, Canada

Lin, Noelle Jia-Rong (2023) Paleoenvironmental fluctuations across the Jurassic–Cretaceous boundary from the Scotian margin, Canada. Masters thesis, Memorial University of Newfoundland.

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Abstract

Two wells, Thebaud C-74 and South Desbarres O-76 were investigated to evaluate paleoenvironmental changes during the Jurassic/Cretaceous boundary on the Scotian margin, offshore Nova Scotia. A multi-technique approach using several proxies of paleoredox, productivity, terrigenous input, and paleosalinity was employed, resulting in identification of a geochemical anomalies in both wells associated with the boundary. A shift to more reducing conditions and elevated productivity correlate with low terrigenous input at the start of the anomaly, followed by a shift of redox and productivity proxies back to background levels and elevated terrigenous input and paleosalinity. These correlative relationships are consistent in both wells, reflecting a transition to anoxic/euxinic conditions at the start of the anomaly that was predominantly driven by the consumption of oxidative agents due to a higher abundance of decomposing organic matter. The lack of correlation between productivity and terrigenous input indicates that the increase in micronutrients driving elevated productivity is not related to an influx of terrigenous input, but rather upwelling. The positive correlation between terrigenous input and paleosalinity suggests limited fluvial input. These results agree with global paleoclimate and sealevel variations during the Late Jurassic/Early Cretaceous and reflect semi-arid/arid conditions related to relative sealevel fall and open ocean circulation as the North Atlantic Ocean expanded.

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