ENVIRONMENTAL CONTROL ON TAPHONOMIC SIGNATURE IN THE CANADIAN HIGH ARCTIC

MUÑOZ, DIEGO F.; BAYER, MARÍA SOL; AITKEN, ALEC

Saskatoon

Congreso; CPC Canadian Paleontology Conference 2018; 2018

Department Geological Sciences - University of Saskatchewan

Late Quaternary fossil molluscan assemblages are abundant in raised glaciomarinesediments in the Canadian High Arctic (Dyke et al., 1996). It is possible torecognize different kinds of sedimentary environments according to shellpreservation patterns that define taphofacies(Kidwell and Flessa, 1996;Behrensmeyer et al., 2000; Zuschin et al., 2000). Therefore, our aim is to determine if the variety ofsedimentary environments exhibited in late Quaternary glaciomarine sedimentsfrom Axel Heiberg Island (AHI) are reflected by molluscan shell assemblagetaphonomic pattern. To accomplish this, we studied 23 samples from differentlocations around AHI that consisted of more than 30 individuals per bivalvespecies. The sedimentary environments presented in the samples includefjord-head deltas (proximal glaciomarine), estuarine (distal glaciomarine) andsubglacial tills. Specimen taphonomic attributes,such as right/left valve ratio, rounding, fragmentation, presence of periostracum, abrasion andbioerosion were described by way of ordinal taphonomic grades, as arbitraryranks, or as binary character states. A taphonomicanalysis was performed on the three most abundant species: Mya truncata (n=1020), Hiatella arctica(n=945) and Astarte borealis (n=670). We used a Principal Coordinate Analysis (PCO) based onManhattan distances to explore relationships among samples in terms of theirpreservation patterns. The preservation patterns of assemblages permitteddifferentiation between environments. Estuarine environments segregated fromfjord-head delta and subglacial environments along the first ordination axis(PCO1=67.89%). Estuarine environments are characterized by low fragmentationand good periostracum preservation in with respect to fjord-head delta and subglacialenvironments. On the other hand, subglacial environments exhibited high scoresof abrasion and rounding and were segregated along the second axis(PCO2=16.36%) with respect to estuarine environments. The preservation patternsrecorded in fjord-head delta environments overlapped others environments. A pairwise PERMANOVA with Bonferroni correctionconfirmed that assemblages from estuarine and fjord-head delta environments(p=0.012) were actually segregated in the multivariate space. [The same happened with assemblages from estuarine and subglacialenvironments (p=0.014) as well as assemblages from glacial and estuarineenvironments (p=0.032)]. These partial results suggest that the sedimentary environmentsrecorded in Late Quaternary glaciomarine sediments from AHI are reflected by differentand characteristic preservation patterns in the molluscan assemblages.Therefore, the taphonomical signal of bivalve assemblages provides additionalinformation that could help us to predict and reconstruct the late Quaternarydepositional environments from AHI.