The Environmental Discrimination of Barrier Island Sediments, by the S.E.M
Environmental discrimination was undertaken on five Barrier Island samples, representing overwash, inlet, flood tidal delta, aeolian and beach environments. S.E.M. textural analysis, utilizing a checklist of thirty-six common surface features, coupled with photographic evidence was used to analyse the nearshore samples. Checklist results in the form of binary data, were subjected to discriminant analysis. Checklist results were unable to discriminate between samples, which revealed a glacio-marine type texture pattern. Longshore drift eroded glacially derived quartz grains, marine processes then superimposed a new textural suite to create a glacio-marine textural assemblage. Three phases of superimposition are tentatively proposed: (a) Mechanical abrasion. (b) Chemical solution/precipitation. (c) Secondary mechanical phase. Discriminant analysis was unable to distinguish between the Five nearshore samples but was able to discriminate between the nearshore samples anc. two control samples (Kalahari Desert and Brazilian crushed quartz). Two-group analysis was also performed and indicated generic linkage between nearshore samples, particularly overwash and dune sediments. Environmental discrimination was not possible by one method alone, a combination of qualitative and quantitative methods was needed. Two grain types were indicated in both onshore and offshore samples and a bi-modal provenance is proposed for these samples (see Inlet plate 1, 2, 3, 4). In conclusion it was possible to identify large scale textural development but more subtle discrimination between nearshore samples was not possible.
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