The taphonomy of Last Glacial–Interglacial Transition (LGIT) distal volcanic ash in small Scottish lakes

Abstract

Pyne-O’Donnell, S. 2010: The taphonomy of Last Glacial–Interglacial Transition (LGIT) distal volcanic ash insmall Scottish lakes. Boreas, 10.1111/j.1502-3885.2010.00154.x. ISSN 0300-9483.An extensive micro-tephrostratigraphic survey of three small lakes in the Scottish Inner Hebrides was conductedencompassing the Last Glacial–Interglacial Transition (LGIT). The lakes are highly contrasting in terms of lakearea to catchment ratio, the presence or absence of stream inlets draining the catchment, and in the complexity ofthe catchment drainage network. A suite of distal Icelandic volcanic ashes was consistently detected in all threelakes, with three, namely Penifiler Tephra, Vedde Ash and Ashik Tephra, being common to all the lakes. Theseashes were chosen to examine the taphonomic intercomparability of ash location and concentration among thelakes. Findings reveal that the part played by catchment inlets in determining ash concentration and within-basinlocationappliestomicrotephra layersasmuchasitdoesinstudiesofmacrotephra layerthickness. ThepositionofashconcentrationmaximaisalsoshowntovarysignificantlyfordifferentLGITperiodsandmaybeaconsequenceof lake-level changes, especially during the early Holocene. High-resolution stratigraphic analysis through theVedde Ash visible macrotephra at Loch Ashik reveals a high degree of complexity in taphonomic behaviour be-tween the different geochemical components, with possible implications for the correct interpretation of the iso-chron position. The detection of multiple intact ash isochrons and the taphonomic processes responsible for theirdeposition should prove useful in future tephrostratigraphic surveys, as well as having applications within otherpalaeolimnological disciplines.Sean Pyne-O’Donnell (e-mail: Sean.Pyne-Odonnell@geo.uib.no), Centre for Quaternary Research, Department ofGeography, Royal Holloway, University of London, Egham TW20 0EX, UK; present address: Department of EarthScience, University of Bergen, Alle´gaten 41, N-5007 Bergen, Norway; received 5th November 2009, accepted 19thFebruary 2010.