Date of Award

5-2019

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

College/School

College of Science and Mathematics

Department/Program

Earth and Environmental Studies

Thesis Sponsor/Dissertation Chair/Project Chair

Jorge Lorenzo-Trueba

Committee Member

Sandra Passchier

Committee Member

Mark Chopping

Committee Member

Charles Dill

Abstract

Barrier Islands comprise 10% of the Earth’s shorelines, fringing every continent except Antarctica. Despite their ubiquity, much about the medium to long-term evolution of these coastal systems remain poorly understood, mostly due to the destruction of the geologic record as barriers migrate landward under the influence of rising sea level. Even where modern barriers and related strandplain systems have prograded and regressed, leaving evidence of their former geometries in the form of relict shorelines, field investigations often require intensive labor and time commitments to interpret past evolution. In this work, several investigations are undertaken to use novel numerical modeling techniques coupled with field interpretation and comparison to gain insights into the evolution of barrier islands from relict geomorphic features preserved on the continental shelf seabed and the surfaces of modern barriers. Much of these efforts focus on ‘drowned’ barrier features, or the remnants of barrier islands left stranded on the shelf during landward migration that occurred in the late Pleistocene and early Holocene, as well as patterns of abandoned foredune ridges generated during late Holocene shoreline progradation. Among the most intriguing results herein is the possibility that the internal dynamics of barrier islands can lead to periodic backstepping and partial deposition of the barrier structure without the need to invoke changing environmental forcing. Moreover, it can be shown that combinations of internal dynamic state and environmental forcing from relatively sudden changes in rate of sea-level rise could lead to a rich suite of barrier retreat behaviors. This might explain the morphologies of drowned barrier features produced during glacial meltwater and outburst flood ‘pulses’ prior to 8 kya. More importantly, these insights may prove practical in modern systems, where anthropogenic climate change threatens barrier islands with historically unprecedented rates of sea-level rise.

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