The seabed geomorphology and geological structure of the Firth of Lorn, western Scotland, UK, as revealed by multibeam echo-sounder survey

Abstract

This paper presents recently collected swath bathymetry from the Firth of Lorn. 553 km 2 of data were collected during 2012-2013 as part of the INIS Hydro (Ireland, Northern Ireland and Scotland Hydrographic Survey) programme.The area proves to consist of bedrock-dominated seabed, divided into narrow, stratigraphicallyconstrained and glacially-over-deepened basins. The bedrock is composed of late Proterozoic Dalradian metasediments overlain unconformably by Old Red Sandstone (ORS) sediments and lavas of ?Silurian-age. The central region of the Firth of Lorn is dominated by a vertical cliff, up to 150 m high and extending for approximately 24 km. This feature, here termed the Insh Fault, may have originated as a Dalradian extensional fault, been reactivated as an ORS feature and now forms a fault-line scarp with resistant ORS rocks on the downthrown side, flanking the more deeply eroded metasediments exposed in the basin. Tertiary intrusives are common, in particular, swarms of Paleocene dolerite dykes exposed on the sediment-free bedrock surfaces, and can be traced for many kilometres.Evidence for past glaciation is widespread, manifest in the extensive erosion of the bedrock platforms and the abundance of well-preserved moraines and over-deepened basins. The survey region includes the Corryvreckan Whirlpool and Great Race, beneath the tidal flows of which occur submarine dunes.

BRITICE Glacial Map, version 2: a map and GIS database of glacial landforms of the last British–Irish Ice Sheet

“…(, ), Hill (), Holden (), Hollingworth (), Howarth (, b, c, d), Howe et al . (), Huddart (, ), Huddart & Bennett (), Hughes (, ), Hughes et al . (, ), Jansson & Glasser (), Johnson (, b) Johnson et al .…”

Submarine deglacial sediment and geomorphological record of southwestern Scotland after the Last Glacial Maximum

“…Bailey et al, 1924;Sissons, 1983;Peacock et al, 1989;Benn & Evans, 1993;Ballantyne, 1999;Golledge, 2010), until recently relatively little work has been conducted on the adjacent marine areas of the continental shelf (Baltzer et al, 2010;Peacock et al, 2012). New bathymetry data acquired from the Inner Hebrides have permitted Howe et al (2012Howe et al ( , 2015 and Dove et al (2015) to carry out broad-scale mapping of the seabed geology and geomorphology. However, there has been no detailed study relating the Late Quaternary offshore stratigraphy to the observed landform assemblages, or that explores the role of relative sea-level (RSL) change on ice sheet retreat.…”

“…existing multibeam bathymetry data, newly gridded to best-possible horizontal resolution. These enabled novel interpretations of previously undetected features, or modified interpretations (from Dove et al, 2015;Howe et al, 2015) on the basis of the new observations; 3. new sediment core data from the study area;…”

Progress in marine geoconservation in Scotland’s seas: assessment of key interests and their contribution to Marine Protected Area network planning

“…At a more local scale, the geomorphological and sedimentary archives of the west coast fjords of Scotland augment the terrestrial evidence for the later stages of deglaciation of the last British-Irish Ice Sheet and the subsequent re-expansion of glaciers in the north and west Highlands during the Loch Lomond (Younger Dryas) Stade McIntyre and Howe, 2010;McIntyre et al, 2011;Howe et al, 2015b;Audsley et al, 2016;Small et al, 2016). The fjord sediments also record palaeoenvironmental changes during the Holocene (Howe et al, 2002;Nørgaard-Pedersen et al, 2006;Baltzer et al, 2010;Cage and Austin, 2010;Cundill and Austin, 2010;Mokeddem et al, 2010) and form sinks for organic carbon from terrestrial sources (Burrows et al, 2014).…”