A Varve Chronology for Ireland?

Extensive, rhythmically laminated glaciolacustrine deposits, which formed during the recession of the B.I.I.S., underlie much of the Irish Midlands and occur in other lake basins throughout Ireland. Similar deposits in Scandinavia have been recognised as varves (annually laminated sediments) and have been used to construct a high resolution chronology of deglaciation dynamics on land, including the rate of ice sheet retreat, and the nature of meltwater discharges, and to correlate these events with ice and marine core records, allowing the connections between ice dynamics, ocean and atmospheric circulation to be established at a high resolution. This project will investigate the possibility of establishing a similar chronology for the B.I.I.S..

Preliminary analyses of cores from Knocknanool bog near Athlone including detailed sedimentological descriptions, particle size analyses of laminations, SEM analyses of clay fabrics and of surface texture of coarse silt and sand-sized material indicate that these are varved sediments.

Further cores to a maximum depth of 13m were collected at Carrigynachtan Bog in 2005, using ground penetrating radar from the NERC Geophysical Equipment Facility in order to locate the edges of the basin. These are currently being analysed.

Rhythmically laminated glaciolacustrine sediments, Knocknanool Bog, central Ireland. Dark layers are clay (winter) layers

Link to presentation given at IQUA Annual General Meeting, Spring 2004: Glaciolacustrine Sediments in Paleo-Lough Ree: A possibility for a varve chronology?