Department or Program

Environmental Studies

Second Department or Program

Geology

Abstract

In Scarborough Marsh, there is a 4,000 to 10,000 year record of deposition and sea level rise. The purpose of this project is to use stratigraphic principles, organic geochemistry, and radiocarbon dating to investigate the history of Scarborough Marsh, with a focus on understanding the nature of a 3,000 year old stump and associated sand horizon located approximately 1 meter below the surface of the marsh. A total of seven sediment cores have been collected and described; additionally, the cores have been analyzed for carbon-13 isotopic signatures, percent carbon, and carbon to nitrogen ratio values. In the central and northern end of the marsh, silty intertidal and/or dune sands with the buried stumps are overlain by salt marsh peats. Multiple 1-5 centimeter thick sand layers are preserved in the marsh sediments, the thickest of which is associated with the 3,000 year old buried stump horizon. The grain size and spatial extent of these sand layers have been analyzed to determine if they are overwash deposits. Additionally, three working hypotheses were developed at the outset of the project—the first proposes a massive storm depositing salt water and sand, followed by the gradual rise of sea level; the second suggests a paleo-seismic event and resultant tsunami depositing salt water and sand, followed by a lowering of the land surface, enough to facilitate the immediate colonization by salt marsh plants; the third and final hypothesis relates to changing hydrodynamics within the study area, with a shift in inlet positioning and/or a paleo-stream channel altering spatial depositional patterns. Overall, each hypothesis was designed to explain the death of the trees living just above sea level. Ultimately, the death of the trees and the coincident sand lens are explained by a paleo-seismic event, a lowering of the land elevation, and a resultant tsunami depositing salt water and sand. Through time, transgressional sea level rise and the increasing tidal range have reworked the sand deposit, especially in the southern regions of the present-day marsh. Additional radiocarbon dating and foraminifera analyses will provide researchers with additional information relating to the nature and timing of the proposed event. Furthermore, exploring similar deposits found throughout Maine and the northeastern Atlantic coast will help researchers unpack the regional scale of the proposed event.

Level of Access

Restricted: Embargoed [Bates Community After Expiration]

First Advisor

Bev Johnson

Date of Graduation

5-2018

Degree Name

Bachelor of Science

Number of Pages

110

Components of Thesis

1 pdf file

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