Foraminiferal evidence for recent paleoenvironmental change in Core Sound, North Carolina / by Rebecca J. Pruitt.
| Author/creator | Pruitt, Rebecca J. author. |
| Other author | Culver, Stephen J., degree supervisor. |
| Other author | East Carolina University. Department of Geological Sciences. |
| Format | Theses and dissertations |
| Production | 2008. |
| Description | xiii, 174 leaves : illustrations (some color), maps (some color) ; 29 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Subject | Core Sound, a shallow, narrow estuary located in the southern Outer Banks, was studied to document foraminiferal and geochemical changes occurring over the past approximately 120 years. Modem distribution and abundance of foraminifera was established using 76 surface samples collected in 2004. Changes through time were determined by comparison with data from 1959; five biofacies were present at that time. Estuarine, Open-Sound, Salt-Water-Lagoon, Tidal-Delta, and Salt-Marsh. Five mainland bay cores were also analyzed using foraminiferal and stable isotopic techniques. Radionuclides (Pb-210 and Cs-137) were used to determine sediment accumulation rates and to establish a chronostratigraphic framework for the cores. Four biofacies were defined in the 2004 data including Marsh, Estuarine High Salinity A, Estuarine High Salinity B, and Estuarine Low Salinity. Comparison with the 1959 data showed a correlation between the 1959 Open Sound biofacies and the modem Estuarine Low Salinity biofacies due to the presence of calcareous and coarsely agglutinated species. Both studies found a Salt Marsh biofacies characterized by finely agglutinated species. The 1959 Salt-Water Lagoon biofacies correlates with the modem Estuarine High Salinity B biofacies due to the abundance of calcareous species. The occurrence of Quinqueloculina species allows correlation between the 2004 Estuarine High Salinity A biofacies and the 1959 Tidal-Delta biofacies. Based upon results of discriminant analysis of modem distributional data, mainland bay cores show no significant foraminiferal change through time. [delta]¹⁵N and C:N ratios fluctuate slightly in these cores but show no significant changes throughout the core. [delta]¹³C values become slightly more depleted up-core. All intervals, however, remain in the "marine" range (<- 23). Comparison with the 1959 data demonstrates that two significant changes have occurred in foraminiferal assemblages over 45 years. First, the Salt-Water Lagoon biofacies of 1959 contained primarily Elphidium species. The modem equivalent (Estuarine High Salinity B), however, is dominated by Ammonia parkinsoniana, indicating a decline in proportions of Elphidium species over the past 45 years. Comparison with a similar study in Long Island Sound suggests that this may be a result of increased eutrophication, although there is no independent evidence for this in Core Sound. Second, the distribution of Quinqueloculina species has become more widespread immediately adjacent to the Core Banks barrier islands over the past 45 years although the reasons for this are unclear. No significant changes of foraminiferal or geochemical signatures occurred in the mainland bay cores. However, [delta]C signatures become slightly more negative up-core and may be due to a reduction in the number of open inlets. |
| General note | Presented to the faculty of the Department of Geological Sciences. |
| General note | Advisor: Stephen J. Culver |
| Dissertation note | M.S. East Carolina University 2008 |
| Bibliography note | Includes bibliographical references (leaves 113-126). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
Availability
| Library | Location | Call Number | Status | Item Actions |
|---|---|---|---|---|
| Joyner | University Archives | ASK AT SPECIAL COLLECTIONS DESK | ✔ Available | Request Material |
| Electronic Resources | Access Content Online | ✔ Available |