Establishing chronologies for woodland small hollow and mor humus deposits using tephrochronology and radiocarbon dating

Abstract

Chronological precision is a pre-requisite for all palaeoecological analyses, especially in more recent Holocene deposits such as small hollow peat and mor humus in woodlands. Here, tephrochronology was employed to improve the chronological control of such deposits to aid subsequent sub-fossil insect analyses from three sites in western and southwestern Ireland. Six tephra layers were detected from the three small hollows but only one from the mor humus sites. Four of the layers were matched to known tephra horizons regularly recorded in Ireland while two new tephras of possible Azores and Grímsvötn origin were recorded. The latter tephra may be the first definitive record of Laki 1783-4 from Ireland and is potentially an important new chronological marker for Irish palaeoecological investigations of late Holocene deposits. Results suggest that tephrochronology is a successful additional chronological tool for small hollow palaeoecological studies but is less helpful in mor humus deposits.