Marsh foraminifera from Nanaimo, British Columbia (Canada): Implications of infaunal habitat and taphonomic biasing

Marsh foraminiferal faunas from nine cores in two transects in and around Nanaimo inlet were examined to assess the implications of infaunal habitat and taphonomic processes for biofacies formation, High marsh faunas live slightly deeper infaunally compared to those in the low marsh, reflecting harsher conditions in the high marsh, Most living Jadammina macrescens occur from 0-20 cm in the high marsh and from 0-11 cm in the low marsh; the main depth preference is from 2-8 cm, Most living Trochammina inflata occur between 0-25 cm in the high marsh and from 0-20 cm in the low marsh, Haplophragmoides wilberti is most abundant overall between 3-7 cm, being almost absent at the surface in all cores, H, wilberti is found primarily between 0-15 cm in the high marsh, and from 0-12 cm in the low marsh. Most living Miliammina fusca occur from 0-10 cm, with maximum abundance in the top 3 cm, Five cluster analyses of the foraminiferal data using a sample base of 0-1, 0-3, 0-5, 0-7 and 0-10 cm, respectively, discriminated five biofacies in each case, which were then used to determine which near-surface aliquot is most analogous to deeper subsurface biofacies, Results show near-surface sediment sampling should be done through the 0-10 cm interval, This aliquot allows the main infaunal species characteristics to be observed, yet is thin enough that epifaunal species are also accurately represented, These results indicate that at least in coastal British Columbia traditional sampling strategies that assess modern marsh foraminiferal occurrence based only on examination of the uppermost 0-1 cm will not give an accurate representation of actual marsh species distribution, Modern marsh foraminiferal distribution assessment based on the thicker surface interval that we propose will permit researchers to delineate both subtle and dramatic sea level changes more precisely. This precision is critical not only in studies designed to differentiate the magnitude of seismic events but also to recognize subtle relative sea level change events as well.