Insights into the Sea-Level History of the South Shetland Islands from Ground Penetrating Radar on Livingston Island, Antarctica

Abstract

The sea-level curve for the South Shetland Islands (SSI) is atypical from what would be expected in a near-field setting in that it shows a nearly constant slow rate of relative sea-level (RSL) fall through most of the Holocene with a large increase in the rate of RSL fall within the last 600 years. However, most RSL reconstructions from the islands are based solely on the crest elevation of raised beaches. Is more to the RSL history of the SSI hidden within the architecture of the beach ridges? In order to answer this question approximately 12 km of ground-penetrating radar (GPR) profiles and optically stimulated luminescent samples were collected on the South Beaches of Livingston Island within the SSI. In GPR profiles, two broad types of reflections were identified: seaward-dipping reflections and landward-dipping reflections. In addition, scarps of bedrock were identified beneath areas of landward-dipping reflections. The seaward-dipping reflections are interpreted as prograding beach deposits created during normal RSL fall while the landward-dipping reflections are interpreted as overwash deposits preserved from periods of RSL rise. The scarps beneath the beach ridges likely formed as wave cut scarps during sea-level rise. The stratigraphy of the beach ridges suggests higher-order sea-level fluctuations marked by a general sea-level fall interrupted by minor rises in sea level. These higher-order RSL fluctuations support earlier assertions of a weak rheology beneath the SSI; not surprising given their active arc setting. Our results highlight the use of beach stratigraphy in preserving records of past RSL fluctuations.

AAPG Datapages/Search and Discovery Article #90372 © 2020 AAPG Pacific Section Convention, 2020 Vision: Producing the Future, Mandalay Beach, Oxnard, CA, April 4-8, 2020 (Cancelled)