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Molluscan predators are rarely preserved in Late Pleistocene and Holocene marine sediments from the Canadian High Arctic. Predator-prey interactions in molluscan assemblages recorded as round holes in shells, recognized as the trace fossil Oichnus, are even less well known for Quaternary molluscan assemblages from the High Arctic. Because these biological interactions recorded in molluscan shells are an essential source of information for palaeoecological and environmental reconstructions, this study aims to identify Oichnus ichnospecies in bivalve shells to unveil the possible gastropod predators that were not recorded in Quaternary sediments from the Canadian High Arctic, particularly on Axel Heiberg Island (AHI). The whole assemblage consisted of a total of 3586 shells, where drilling frequency was 0.013 and prey effectiveness was 0.58. Boreholes were observed mainly in Astarte borealis, Hiatella arctica and Mya truncata (96% of the total assemblage) with a low drilling frequency. Those borings showed two different designs identified as Oichnus simplex and O. paraboloides, which could be produced by predatory gastropods belonging to the Naticidae and Muricidae families. The higher number of O. paraboloides observed in different prey species indicates that naticid gastropods produced a greater number of boreholes than muricid gastropods. These boreholes are preferentially located on the central area of A. borealis valves in the Late Quaternary bivalve shell assemblages from AHI. These findings provide evidence of predator-prey interactions, and therefore palaeoecological evidence that help us to understand the trophic structure of Late Quaternary benthic communities of the Canadian High Arctic. [ABSTRACT FROM AUTHOR]

Throughout northern Canada, live-collected, pre-bomb, deposit-feeding marine molluscs from calcareous sediments yield greater apparent radiocarbon ages than do suspension feeders. We explore the size of this effect in a set of 57 paired datings of deposit feeders, mainly Portlandia arctica, and suspension feeders, mainly Hiatella arctica and Mya truncata, collected from both calcareous and non-calcareous Holocene sediments. Deposit feeders from calcareous sediments are older than their suspension-feeding counterparts by as much as 2240±130 14 C years. This is attributed to the uptake of 'old' bicarbonate derived from calcareous bedrock. The age discrepancy between suspension and deposit feeders in calcareous terrain is non-systematic in space and time, thereby invalidating the application of a correction. In contrast, the age comparisons are concordant at sites located on the Precambrian Shield. In terrestrial environments underlain by carbonate, previous acceptance of dates on deposit feeders led to erroneous interpretations of deglaciation and relative sea-level history, in both the North American and the Eurasian Arctic. This has prompted several researchers to exclude deposit feeders from their late Quaternary reconstructions. The same chronological problem of deposit-feeding molluscs now needs to be more widely acknowledged by the marine community. [ABSTRACT FROM AUTHOR]