ASSESSING THE UTILITY OF FORAMINIFERAL ASSEMBLAGES IN DEVELOPING LATE HOLOCENE SEA-LEVEL RECORDS IN NEWFOUNDLAND, CANADA

At the furthest extent of the Laurentide Ice Sheet 18,000 years ago, Newfoundland was completely covered by the Newfoundland Ice Dome. By 11,000 yrs BP, only the central dome and alpine glaciers in the Long Range Mountains remained, as the southern and eastern portions of the island deglaciated much faster than the north and west. By 10,000 yrs BP about 70% of the island was ice free with the exception of patchy alpine regions. Ice had fully retreated from Newfoundland 8,000 years ago. Newfoundland’s deglaciation has caused a complex and variable post-glacial sea level history around the island. A paleogeographic reconstruction of an ice-contact deltaic highstand from 12,000 BP siting 75 m above present sea level in the Springdale-Halls Bay area of northern Newfoundland suggests that marine incursion due to extreme glacial isostatic depression occurred up to 10 km inland. Relative sea-level (RSL) reconstructions on the southeastern coast of Newfoundland show continuous submergence, relative sea-level rise, due to the isostatic response since deglaciation. To deduce the current rate of potentially accelerated sea-level rise, the glacial isostatic response needs to be quantified from longer-term RSL records. Previous studies have constrained sea-level changes through glacial and glaciomarine sediment distribution and salt marsh stratigraphic reconstructions using peat and basal ¹⁴C dates. A composite RSL record extending back ~3000 BP from these studies has an average temporal uncertainty of ~250 years poorly constraining RSL change in the Late Holocene. Here, we investigate if current sea-level reconstruction techniques using elevation-dependent zones of salt marsh foraminifera are feasible and if so, a more precise method of attaining Newfoundland RSL records. A short modern transect and core were sampled from a small salt marsh in southern Newfoundland with a mean tidal range of ~1.4 m. Preliminary results show Balticammina pseudomacrescens and Jadammina macrescens are the dominant agglutinated foraminifera throughout the core and track a recent accelerated sea-level transgression.