Date of Award

Fall 1987

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Ocean & Earth Sciences

Program/Concentration

Geology

Committee Director

Dennis A. Darby

Committee Member

Joseph H. Rule

Call Number for Print

Special Collections LD4331.G4E92

Abstract

Elemental composition (Fe, Ti, Mn, Mg, V, Cu, Ni, Zn, and Cr) and Fourier shape analysis of magnetically separated detrital ilmenite from seven Pleistocene and modern beach sand deposits of the Southeastern Virginia Coastal Plain were used to distinguish each deposit. Geomorphic expression, crosscutting relationships and proximity to the present shoreline differentiates the relative age of the seven sampled beach deposits. Analysis of ilmenite elemental composition, independent of geomorphic expression, distinguished beach sands of

different age and was successful in determining that each beach contained ilmenite similar in composition. Of the seven beach ridges tested, subtle yet significant differences in ilmenite elemental composition were used to discriminate between all but the three most recent deposits (Diamond Springs Scarp, Dawleys Corner Ridge, and Cape Henry). Trace-element data from these three beach sands were significantly different from all older deposits, yet failed to be statistically different from each other. Statistically similar elemental composition in detrital ilmenite grains along the up to 90 km length of these seven beach ridges can be attributed to thorough sediment mixing and/or a common primary or proximal source for each individual sand ridge.

Because this new correlation technique was proven to be successful in these beach deposits where geomorphic expression and proximity to the present shoreline helps determine relative age, ilmenite trace-element content studies should be useful in distinguishing sands of different age where no surface expression exists or where the sands are of a discontinous nature.

Fourier shape analysis of detrital ilmenite delineated the oldest and youngest sands from all deposits of intermediate age; however, shape analysis was unsuccessful in determining any shape differences between the intermediate age deposits. Ilmenite grain shape of the intermediate age beaches were more well-rounded with less surface irregularities. Typically more abraded sands tend to represent mature sands that are a result of multicycle transportation. The oldest beach (Suffolk Scarp) and the youngest (Cape Henry) had more surface sculptures, representing grains which probably have experienced only single cycle transportation. Thus ilmenite shape analysis of Virginia's beach ridge sands reflect the relative maturity of the sand. The similarity between Suffolk Scarp and Cape Henry ilmenite grain shape and composition is surprising considering the apparent different origin and proximal source for these two deposits.

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DOI

10.25777/ht7j-qq58

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