Reports: UR855332-UR8: Defining and Differentiating Marine Coastal Facies and Subenvironments: A Foraminiferal Approach

Stephen J. Culver, East Carolina University

Two new undergraduates commenced work on the third year of this project in September 2016. As in the previous year eight vibracores (four for each student) were selected from a suite of vibracores collected in Onslow Bay, North Carolina. One student worked on cores from the shoreface and inner shelf off Bogue Banks and the other on cores from the Bogue Inlet complex (inlet channel and ebb tide delta). Cores were logged under the tutelage of Dr. Kathleen Farrell, NC Geological Survey, and Holocene sediment was sampled for grain-size and foraminifera.

The two undergraduate students successfully completed Honors theses in May 2017. As in the previous year, shoreface, inner shelf, inlet channel and ebb tide delta subenvironments, although similar in sediment characteristics, could be distinguished based on foraminiferal assemblages. As in the previous year interpretations were complicated due to the presence of Miocene foraminifera derived from seabed exposures of Miocene sediments in Onslow Bay. The students presented the results of their work in posters at the South East Geological Society of America Conference, Richmond, VA in March 2017. The posters were well received in particular because the eight logged sediment cores were part of the poster presentations.

A particularly interesting laminated mud and sand unit in two cores proved to be barren of foraminifera. It closely resembles intertidal deposits from the northern Outer Banks that accumulated during Marine Isotope Stage 3 based on OSL dating. This has implications for late Pleistocene sea levels. This unit is being targeted in the third year of this project.

The Master’s student who joined the project in January 2016, and whose task is to characterize modern siliciclastic coastal subenvironments with foraminiferal assemblages, completed sampling for foraminifera in October 2016. The goal is to provide a modern model whereby Holocene samples from cores worked on by undergraduate students can be classified via multiple discriminant analysis into known subenvironments of deposition based on foraminiferal assemblages. In summer 2016, the graduate student, under the guidance of Dr. David Mallinson, East Carolina University, conducted a seismic survey over the sites of several shoreface and inner shelf cores to understand the stratigraphic architecture of the study area. In August 2017 the Master’s student and Culver visited the Smithsonian Institution, Washington, D.C. to confirm identification of foraminifera via comparison with primary and secondary type material lodged in the Cushman Room. The modern model is the subject of an abstract, accepted in August 2017, for a poster that will be presented at the annual GSA meeting in Seattle in October 2017.

In addition to conducting research, an equally important role of the graduate student is to act as mentor to undergraduates involved in this project. Much time has been spent on this activity and, as a result, the production of competent Honors project reports was a much more efficient process in year 2 of this project.

The final two undergraduate students who will contribute to this project commenced work in August 2017. They have conducting readings and have selected locations in cores utilized in previous years where additional microfossil samples will be taken to provide a more detailed understanding of Holocene environmental change. Their research will be modeled on that of their predecessors. One of the undergraduate students from the second year of this project is now a graduate student in Geological Sciences at East Carolina University and will conduct coastal research for her MS thesis.