Environmental and relative sea-level reconstruction from isolation basins in NW Scotland using geochemical techniques

Abstract

Isolation basins from Northwest Scotland provide the longest near-field records of relative sea-level (RSL) change in the world (0 to > 16kyr BP). These archives contributed to quantitative models of glacial isostatic adjustment since the last glacial maximum. Isolation basin RSL reconstructions have been primarily based on salinity reconstructions from biological data such as foraminifera and diatoms. However, preservation problems and non-analogue situations can limit their usefulness. Therefore, it is necessary to identify other proxies from isolation basin to improve RSL reconstructions. Also isolation basin sediments are potentially high-resolution records of climate change from both the land and the oceans simultaneously, but little research has been undertaken. This thesis presents the results of a range of isotopic and geochemical measurements that were thought to be suitable proxies for palaeosalinity and palaeoclimate reconstructions. Tephrochronology was also applied to improve the existing geochronological controls of isolation basin sequences by attempting to identify Icelandic tephra layers. A combination of isotopic measurements; δ(^13)Corg, C/N ratios δ(^13)Ctoram, δ(^18)Otoram, (^87)Sr/(^86)Sr from foraminifera and δ(^13)Odiatoms, were preformed on contemporary and fossil archives. Results show δ(^13)Corg, C/N ratios measurements are as sensitive indicators of palaeosalinity, as biological reconstructions on Holocene aged sediment. Overall this thesis highlights the benefits of multi proxy palaeosalinity studies in order to gain a fuller understanding of the complex changes isolation basins experience during an isolation or connection events. A climate signal from an isolation basin that experienced a gradual isolated over the Holocene has been detected for the first time using geochemical techniques biogenic silica (BSi02) and total organic carbon (TOC).