Long-distance marker horizons from smallscale eruptions: British tephra deposits from the AD 1510 eruption of Hekla, Iceland

Icelandic tephras in northwest Europe that have been linked to specific eruptions include those from the major Holocene tephras Hekla 4, Hekla 3, Hekla AD 1104 and Öræfajökull AD 1362. Eight other tephras have been identified in the British Isles and Scandinavia, but they have not been correlated to specific eruptions. Icelandic tephras with volumes at least an order of magnitude smaller than the major Holocene deposits are also capable of forming extensive marker horizons, and although in distant parts these tephras may cover areas >1 x 10³km², their distributions are not continuous. In this paper, tephra deposits from the British Isles, correlated with deposits from the AD 1510 eruption of Hekla (Iceland), are assessed as an example of a distant marker horizon that has been formed by a tephra of a comparatively small volume. Important implications are that these types of tephras may have formed some, if not all, of the eight currently unattributed horizons known in the British Isles, and that extensive tephra horizons are not necessarily associated with environmentally significant eruptions.