Spatial variability of foraminifera and pollen in two nearshore sediment sites, St. Georges Bay, Nova Scotia

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Abstract
Spatial variability of sediment texture, foraminiferal, and pollen assemblages were studied at two core sites in St. Georges Bay, using data from replicate cores spaced about 1 m apart. Despite the similarity of water depth (22 m) and location (3.6 km offshore) of the two sites, correlatable sediment textural units could not be clearly distinguished except for the ubiquitous presence of a surface layer of fine-grained sediment. Textural parameters strongly indicate distinctive Holocene depositional histories at each site, which appear to be related to local submarine morphological features.Despite the between-site textural heterogeneity, the depositional histories of all the cores can be correlated spatially and temporally by means of selected paleontologic parameters. In all cores the top 20–30 cm of sediment was found to coincide with the historical weed pollen assemblage zone; hence, the uppermost fine sediment layer most probably reflects an increased influx of fine-grained sediment associated with deforestation and other local land use practices. At both sites, the ratio of common modern calcareous to arenaceous foraminifera species can be used to reveal comparable relative sea level records in each of the cores. However, critical evaluation of combined lithological and faunal data is necessary to distinguish an apparent decrease in water depth that can arise from an increased influx of nearshore sediment and species rather than a real change in relative sea level.Detailed statistical analysis of the variation in foraminiferal abundance parameters shows that absolute abundance data cannot be used for determining relative sedimentation rates in nearshore environments and suggests that biofacies correlations in these environments should be based on assemblages of comparatively abundant species. Within-site similarity in both foraminiferal and palynological assemblages is generally lower for the texturally more heterogeneous site at Linwood than at the more uniformly muddy site near Pomquet. However, relatively high within and between-site correlations of pollen taxa are evident throughout all sediment intervals that comprise more than 50% mud, regardless of differences in sediment sorting parameters and changes in paleodepths at the depositional sites.It appears that studies of the depositional histories of nearshore Holocene sediments in the Atlantic coastal region are most likely to yield results when analysis of combined textural, microfaunal, and palynological parameters is carried out on cores obtained from relatively low-energy depositional sites. It is predicted that for upper Holocene marine sediments, the coarser the texture of a core the less representative it will be of the overall paleoecological history of a region.