Understanding the late Holocene sea-level and abrupt coastal events history at Gress, Isle of Lewis, Northwest Scotland

• Main Author: Leoh, Khai Ken
• Other Authors: Adam D. Switzer
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Earth and Environmental Sciences; Sea level; Abrupt coastal event; Salt marsh; Lithology; Sedimentology; Diatom; Transfer function; Visual assessment
• Online Access: https://hdl.handle.net/10356/174797
• Institution: Nanyang Technological University

The late-Holocene relative sea-level (RSL) history of Scotland is intricate, as it lies close to the boundaries of the former British-Irish Ice Sheet (BIIS). which varies in thickness spatially and temporally. Due to ice unloading and forebulge collapse, glacial isostatic adjustments from BIIS and thus its long-lasting effect on recent RSL is not well studied in northwest Scotland. There are also little to no records on late-Holocene abrupt coastal events in this region. This study tackles mentioned research gaps, by employing a multi-proxy approach to study a salt marsh sediment core in Gress. We use a combination of lithology, sedimentology (grain size analysis and loss-on-ignition), diatom biostratigraphy, transfer function development and visual assessment method to achieve the objectives. The records show that RSL has fell during the late Holocene and regional RSL trend has been predominantly negative for the majority of the core’s record. A recent disappearance of Sphagnum moss, a typical high-marsh vegetation, alongside the exclusive appearance of Navicula salinarum and Tryblionella tryblionella diatom taxa, suggests a RSL switch to a regional positive tendency. No proxies indicate any potential abrupt disruptions to the gradual salt marsh accumulation at the field site, thus the possibility of tsunami or storm surge events are ruled out.