Date of Award

Winter 1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Ocean & Earth Sciences

Program/Concentration

Oceanography

Committee Director

George F. Oertel

Committee Member

Martin A. Buzas

Committee Member

Stephen J. Culver

Committee Member

Michael S. Kearney

Committee Member

Donald J. P. Swift

Abstract

The coastal zone of the southern Delmarva Peninsula exhibits a wide variety of barrier island system subenvironments. This study investigates whether 20 a priori subenvironments can be distinguished from each other on the basis of abiotic environmental variables, pollen assemblages, living foraminiferal populations, and total (living plus dead) foraminiferal assemblages.

The physical data collected from the coastal zone were subjected to canonical variate analysis which discriminated 83% of the stations in 19 groups. These groups were clustered into two internally overlapping sets which represented the inside and outside of the inlet.

Twenty-two pollen types were found in low-energy marsh and mud-flat environments. Canonical variate analysis of pollen data showed that the inner, middle, and outer parts of the lagoon were clearly discriminated suggesting that variations in modern pollen assemblages from the barrier lagoon can be used in paleogeographic interpretations under warm climatic conditions.

Sixty-eight foraminiferal species were recorded from 57 surface sediment samples. The values of species diversity (H(S)) and equitability (E) exhibit a striking contrast between the marshes and other areas. The marshes had higher values of species diversity and equitability than the tidal flats and the channels-inlets-shoreface. Stepwise regression analyses indicate correlation of the five most frequently occurring species in living populations (>30% of the total stations) and the seven most frequently occurring species in total assemblages (>30% of the total stations) with combinations of one to three environmental variables at the 95% level.

Neither living nor total foraminiferal distribution data allow for recognition of the 20 a priori subenvironments. Ten biofacies are defined by the distribution patterns of the dominant living species (>25% of the population); eight biofacies are defined by the distribution patterns of the dominant species (>25% of the assemblage) in total assemblages. Canonical variate analysis were performed to test whether the 20 a priori subenvironments are statistically distinct. Results indicated that 11 discrete biofacies were defined by living foraminiferal populations, and different set of 11 biofacies (brackish marsh and channel, restricted tidal bay, inner muddy sand flat, middle sandy bays-washover fan, middle to outer bays-ebb deltas-shoreface, mud flats, inner protected fringe marsh, inner exposed fringe marsh, outer fringe marsh, intermediate tidal channel, and deep tidal channel) were defined by total foraminiferal assemblages.

On the basis of this study, modern physical, pollen and foraminiferal data are useful for discriminating sedimentary environments of a barrier island system, and provide a model for paleoenvironmental interpretations in late Quaternary coastal deposits. However, the total foraminiferal assemblage model must be applied with caution because the character of fossil assemblages in short cores from the outer fringe marsh and tidal flats indicates that taphonomic loss of foraminiferal tests is both considerable and variable.

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DOI

10.25777/1c1m-n215

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