Ichnological analysis of glacially-influenced sediments from the late Pleistocene to Holocene on the southeastern Canadian margin: Implications for palaeoclimate and palaeoceanography

Abstract

The study of trace fossils in glacially-influenced margins provides valuable insights into the changes in palaeoclimate and palaeoceanography during glacial-interglacial periods, by providing biological and ecological data of the benthic environment. Here we present a comprehensive ichnofabric characterisation of a sediment core located on an inter-canyon ridge on the SW Grand Banks Slope off Newfoundland, covering the Late Pleistocene–Holocene period (0–∼23 ka). The core analysis reveals 12 ichnogenera and an escape structure, with Phymatoderma, Tasselia, and Zoophycos being prominent and relatively abundant at specific levels. By examining the distribution of bioturbation content and degree along the core, we establish a strong association between moderate to high bioturbation and cold periods. The Last Glacial Maximum exhibits the highest abundance and diversity of trace fossils, particularly the deposit-feeding Phymatoderma and the deposit-feeding/equilibrium trace Tasselia, indicating benthic adaptation to seasonal food input and relatively high sedimentation rates. Conversely, the warmer deglaciation period shows limited bioturbation. Salinity stress may account for the abrupt decline in bioturbation degree during the early deglaciation. Additionally, the occurrence of large-sized Zoophycos coincides with the Younger Dryas cold event during the last deglaciation. These findings highlight the complexity of palaeoceanographic conditions and benthic environments in proximal glacially-influenced sites compared to distal hemipelagic and pelagic sites. The interplay between down-slope processes (such as turbidity currents and hyperpycnal flows) and along-slope processes (like contour currents) plays a crucial role in shaping the unique sedimentological regime of depositional sites and subsequently affecting the ichnofauna in glacially-influenced margins.