| dc.description.abstract | Around 70-80% of the world’s coastline, and around 60% of the UK’s coastline, can be considered as ‘rocky’. Rocky coasts erode much slower than their softer sedimentary counterparts, but their rates of erosion and their evolutionary history are poorly known. In this dissertation I use a new combination of methods, cosmogenic nuclide exposure dating, structure-from-motion photogrammetry and sea-level modelling, to study a typical stretch of rocky coastline in north Torbay, Devon, southwest England. Torbay’s coast is characterised by the presence of shore platforms and raised beaches above modern sea level, situated on the north headland peninsula, named Hopes Nose. These elevated landforms must relate to a previous interglacial period, with warmer environments and higher sea-levels, and their preservation indicates very slow rates of coastal evolution within the area. I apply exposure dating using 36Cl to determine the degree of geomorphological inheritance from previous high sea-level stands, along north Torbay’s rocky cliffs and across the main body of the raised shore platform at Hopes Nose. I combine this analysis with the measurement of a new digital surface model, collected via drone imagery and structure-from-motion photogrammetry, across the headland to perform a morphometric analysis of the modern and elevated interglacial platform. Lastly, I determine a new estimate of relative sea-level change at the site, considering glacio-isostatic adjustment, using the SELEN sea-level model. Cosmogenic nuclide exposure dating reveals that the rocky coastline around north Torbay has been actively eroding throughout the late Holocene, through a series of stochastic mass movements and some incremental loss. Similarly, the exposure dating of the raised shore platform at Hopes Nose reveals it has been covered by distinctive sediments during the late Pleistocene and hence survived surface erosion. Morphometric analysis of the raised interglacial shore platform and the modern shore platform shows a similar evolutionary history, highlighting the changes in marine and aerial influence over the shore platforms formation. An analysis of the raised platform’s elevation, evaluated relative to modelled relative sea-level change, is most consistent with the platform being formed during the last interglacial period (Marine Isotope Stage 5e). As a result, this research also puts into question the overall height of the sea-level during MIS 5e, or the presence of a double peak within the record. Overall, this research demonstrates that the unique combination of methodologies can quantify coastal erosion and help decipher a rocky coastline’s history under both present and previous sea levels | en_GB |
