R. Brant Laidler

Earth Sciences, Dalhousie University

The foraminifera in sediment cores from the central basin of St. Margaret's Bay, N. S. were studied in the hope that they would shed some light on the mode of origin of silty beds and laminae found in these cores. The two hypothesized modes of formation were: 1) in-situ concentration of the coarser components of the homogeneous muds from which finer sediment has been winnowed by storm waves and 2) the mobilization of coarser sediment nearshore by storm waves and subsequent transport into deeper water.

The foraminiferal data suggested that both processes were operating to some extent. Instances where species indigenous to the nearshore, more brackish parts of the bay (e.g. E. clavatum, E. incertum, E. advenum) were concentrated in the silty layers were countered by other situations wherein these same species were just as common in homogeneous as in silty samples, and by occurrences of the greatest faunal similarity between silty and homogeneous samples.

It was thought that some of the samples identified as being homogenous and normally sedimented may actually have been storm-sedimented zones, and hence closer in nature to the silty layers and laminae. This hypothesis is supported by the findings of Hayes (1967) who reported that no difference was found in the homogeneity of sediment cores before and after a severe storm, excepting the presence of a graded bed in the extreme top of some of the cores.

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Pages: 45
Supervisors: D. J. W. Piper