Pollen chronology of the Glen Roy-Loch Laggan proglacial lake drainage

Abstract

Synopsis Palynological evidence confirms that the Glen Roy-Loch Laggan proglacial lakes were impounded by ice of the Loch Lomond (Late Devensian) readvance. The highest stage of the lakes persisted until the time of the juniper pollen zone; the lowest stage had disappeared by the time of the beginning of the birch pollen zone. Drainage from the Pattack basin continued to discharge eastward through the Feagour, the lowest of the lake overflow channels, until the time of the birch-hazel pollen zone.

The recognition of glacial retreat from palynological data: A review of recent work in the British Isles

“…Pennington, 1964), and sediment samples in her investigation may be affected by this (Sissons, 1980). Hand-operated samplers, such as the Russian corer or the Hiller corer used by Macpherson (1978) have a metal tip extending below the sampling chamber which prohibits the sampling of the basal sediments. At sites showing very compressed pollen stratigraphies with limited temporal resolution, such as at Macpherson's (1978) Feagour Channel site, there must remain the possibility that the unsampled sediment contains earlier pollen zones critical to the analysis.…”

“…Hand-operated samplers, such as the Russian corer or the Hiller corer used by Macpherson (1978) have a metal tip extending below the sampling chamber which prohibits the sampling of the basal sediments. At sites showing very compressed pollen stratigraphies with limited temporal resolution, such as at Macpherson's (1978) Feagour Channel site, there must remain the possibility that the unsampled sediment contains earlier pollen zones critical to the analysis. An alternative approach utilises the piston corer which can sample the basal sediments at a site providing the sediment is sufficiently cohesive to be retained.…”

“…The pollen str<jtigraphy of the Devensian Lateglacial and early Flandrian periods in the British Isles is well known (Pennington, 1977). Donner (1957) employed this stratigraphy in establishing the extent of glaciation of Godwin Pollen Zone Ill age (later known as the Loch Lomond Stadial): in this work the absenre of sediments of pre-Zone IV age at a site was regarded <is evidence for ice-occupation during Zone Ill. Palynological investigations by several workers , 1981Walker and Lowe, 1977Pennington, 1978;Macpherson, 1978;Ince, 1981 ; Tipping, 1984Tipping, , 1986 of the period between the Loch Lornond Stadial and the appearance of tree taxa in the Flandrian, together with the adoption o i local pollen assemblage zonation (1.p.a.z.) (West, 1970), has led to a more refined biostratigraphic scheme than that ot Cjodwin ( 1 940, 1975).…”

“…These p.a. zones can <iIso be recogniscd more widely in wcstern Scotland (Tipping, 19861. Some workers (Pennington, 1978;Macpherson, 1978;Lowe and Walker, 1981 ; Walker and Lowe, 1985) have utilised this detailed biostratigraphy to infer from pollen analyses the sequential retreat of Loch Lomond Readvance glaciers in the English Lake District and parts of highland Scotland. In these studies, delayed sedimentation due to prolonged ice-occupation has been proposed as the reason for the apparent absence of early postglacial pollen assemblages at the base of some pollen sites.…”

Alluvial fans and an outwash fan in upper Glen Roy, Lochaber

“…The gravel interbeds could be either debris flow deposits derived from a nearby ice front or valley side, or fluviatile gravels laid down in shallow water bodies. Thixotropic laminated clayey silt was seen by MacPherson (1978) section F and was proved to a depth of 2-7 m. It yielded unidentifiable organic fragments, but no pollen. This bed of silt may be a continuation of that in section F. Overlying the laminated beds at the base of the succession there are upwards of 20 m of poorly-sorted gravel and sand in an overall coarsening upwards sequence (Figs.…”