|Palamakumbura, R. 2018. A new palaeogeographic model for the post-glacial marine and estuarine sediments of the Firth of the Forth, Scotland. Nottingham, UK, British geological Survey. (OR/18/016).|
This report provides an overview of the post-glacial sedimentary evolution of the Firth of the Forth during the late Quaternary. The superficial sediments of the Firth of the Forth vary in thickness from 10 m to nearly 150 m. An understanding the superficial sediments has uses for understanding geotechnical properties, for groundwater modelling and any potential geothermal energy sites. Therefore, this report aims to provide a preliminary understanding of the nature of the superficial sediments across the Firth of the Forth and wider controls of their deposition. The overall aim of this work is to understand the three-dimensional spatial distribution of superficial sediments across the Firth of Forth.
The report is in two parts, firstly looking at the literature to develop a model for the post-glacial evolution of the Firth of the Forth and types of sediments that are expected. Secondly, using borehole records to look at the composition of the superficial sediments and assess the developed model.
From the literature a palaeogeographic model for the Firth of the Forth was developed for the post-late glacial maximum (LGM) time. This model (testable hypothesis) describes eight major events and their topographic feature or sedimentary deposit. This model includes: 1) a post- glacial sea-level incursion; 2) collapse of the LGM ice sheet; 3) sea-level fall resulting in a local beach deposit; 4) fluvial/estuarine deposition; 5) Younger Dryas glaciation; 6) fluvial/estuarine deposition; 7) marine transgression; and 8) a marine regression. This model is based on data and interpretations from a combination of journal publications and BGS memoirs.
The BGS held borehole records from across the entire Firth of the Forth are used to describe the composition and variability of the superficial sediments and test the literature-based model for the post-glacial evolution of the region. Although the borehole records are a relatively low resolution dataset they still provide the first information of the compositional make-up of the thickest sedimentary sequences across the Firth of the Forth.
The data provided in geotechnical borehole records is an important stepping-stone toward further work, such as more detailed sedimentary interpretations from field work and new drilled core. Furthermore a useful outcome of further work would be a geotechnical classification of the highly variable superficial sediments across the Firth of Forth.