J. Boygle, Towards a Holocene tephrochronology for Sweden: geochemistry and correlation with the North Atlantic tephra stratigraphy, Journal of Quaternary Science, vol.19, issue.2, pp.103-109, 2004.
DOI : 10.1002/jqs.811

O. A. Braitseva, V. V. Ponomareva, L. D. Sulerzhitsky, I. V. Melekestsev, and J. Bailey, Holocene Key-Marker Tephra Layers in Kamchatka, Russia, Quaternary Research, vol.17, issue.02, pp.125-139, 1997.
DOI : 10.1017/S0033822200013904

U. Brehm, A. Gorbushima, and D. Mottershead, The role of microorganisms and biofilms in the breakdown and dissolution of quartz and glass, Palaeogeography, Palaeoclimatology, Palaeoecology, vol.219, issue.1-2, pp.117-129, 2004.
DOI : 10.1016/j.palaeo.2004.10.017

C. E. Buck, T. F. Higham, and D. J. Lowe, Bayesian tools for tephrochronology. The Holocene, pp.639-647, 2003.

C. Caseldine, A. Baker, and W. L. Barnes, A rapid, non-destructive scanning method for detecting distal tephra layers in peats. The Holocene, pp.635-638, 1999.

F. M. Chambers, J. R. Daniell, J. B. Hunt, K. Molloy, and M. Connell, Tephrostratigraphy of An Loch M??r, Inis O??rr, western Ireland: implications for Holocene tephrochronology in the northeastern Atlantic region, The Holocene, vol.14, issue.5, pp.703-720, 2004.
DOI : 10.1191/0959683604hl749rp

S. E. Coulter, J. R. Pilcher, V. A. Hall, G. Plunkett, and S. M. Davies, Testing the reliability of the JEOL FEGSEM 6500F electron microprobe for quantitative major element analysis of glass shards from rhyolitic tephra, Boreas, vol.130, issue.36, pp.163-169, 2010.
DOI : 10.1111/j.1502-3885.2009.00113.x

D. Vleeschouwer, F. Van-vliet-lanoe, B. Fagel, N. Richter, T. Boes et al., Development and application of high-resolution petrography on resin-impregnated Holocene peat columns to detect and analyse tephras, cryptotephras, and other materials, Quaternary International, vol.178, issue.1, pp.54-67, 2008.
DOI : 10.1016/j.quaint.2006.12.021
URL : https://hal.archives-ouvertes.fr/insu-00305247

A. J. Dugmore, Icelandic volcanic ash in Scotland, Scottish Geographical Magazine, vol.18, issue.3, pp.168-172, 1989.
DOI : 10.1007/BF02596870

A. J. Dugmore, G. Larsen, and A. J. Newton, Seven tephra isochrones in Scotland. The Holocene, pp.257-266, 1995.

A. J. Dugmore, A. J. Newton, K. E. Edwards, G. Larsen, J. J. Blackford et al., Long-distance marker horizons from small-scale eruptions: British tephra deposits from the AD 1510 eruption of Hekla, Iceland, Journal of Quaternary Science, vol.81, issue.6, pp.511-516, 1996.
DOI : 10.1002/(SICI)1099-1417(199611/12)11:6<511::AID-JQS284>3.0.CO;2-C

A. J. Dugmore, A. J. Newton, D. E. Sugden, and G. Larsen, Geochemical stability of fine-grained silicic Holocene tephra in Iceland and Scotland, Journal of Quaternary Science, vol.11, issue.2, pp.173-183, 1992.
DOI : 10.1002/jqs.3390070208

M. J. Gehrels, D. J. Lowe, Z. J. Hazell, and R. M. Newnham, A continuous 5300-yr Holocene cryptotephrostratigraphic record from northern New Zealand and implications for tephrochronology and volcanic hazard assessment, The Holocene, vol.16, issue.2, pp.173-187, 2006.
DOI : 10.1191/0959683606hl918rp

M. J. Gehrels, R. M. Newnham, D. J. Lowe, S. Wynne, Z. J. Hazell et al., Towards rapid assay of cryptotephra in peat cores: Review and evaluation of various methods, Quaternary International, vol.178, issue.1, pp.68-84, 2008.
DOI : 10.1016/j.quaint.2006.10.014

V. A. Hall, Assessing the impact of Icelandic volcanism on vegetation systems in the north of Ireland in the fifth and sixth millennia BC. The Holocene, pp.131-138, 2003.

V. A. Hall, S. J. Mcvicker, and J. R. Pilcher, Tephra-linked landscape history around 2310 BC of some sites in counties Antrim and Down, Biology and Environment -Proceedings of the Royal Irish Academy, pp.94-245, 1994.

V. A. Hall and J. R. Pilcher, Late-Quaternary Icelandic tephras in Ireland and Great Britain: detection, characterization and usefulness. The Holocene, pp.223-230, 2002.

T. Hang, S. Wastegard, S. Veski, and A. Heinsalu, First discovery of cryptotephra in Holocene peat deposits of Estonia, eastern Baltic, Boreas, vol.21, issue.4, pp.644-649, 2006.
DOI : 10.1111/j.1502-3885.2006.tb01170.x

G. Heiken, Morphology and Petrography of Volcanic Ashes, Geological Society of America Bulletin, vol.83, issue.7, pp.1961-1988, 1972.
DOI : 10.1130/0016-7606(1972)83[1961:MAPOVA]2.0.CO;2

G. Heiken, Atlas of Volcanic Ash, Smithsonian Contributions to the Earth Sciences, vol.12, issue.12, 1974.
DOI : 10.5479/si.00810274.12.1

A. P. Hodder, P. J. De-lange, and D. J. Lowe, Dissolution and depletion of ferromagnesian minerals from Holocene tephra layers in an acid bog, New Zealand, and implications for tephra correlation, Journal of Quaternary Science, vol.45, issue.3, pp.195-208, 1991.
DOI : 10.1002/jqs.3390060303

J. A. Holmes, A Tephra-dated study of Vegetation and Climate Change in the Mid- Holocene of North West Europe, 1998.

J. B. Hunt, P. D. Clift, C. Lacasse, T. L. Vallier, and R. Werner, Interlaboratory comparison of electron probe microanalysis of glass geochemistry, Proceedings of the Ocean Drilling Program, Scientific Results, pp.85-92, 1998.
DOI : 10.2973/odp.proc.sr.152.244.1998

J. B. Hunt and P. G. Hill, Tephra geochemistry: a discussion of some persistent analytical problems, The Holocene, vol.3, issue.3, pp.271-278, 1993.
DOI : 10.1177/095968369300300310

J. B. Hunt and P. G. Hill, An inter-laboratory comparison of the electron probe microanalysis of glass geochemistry, Quaternary International, vol.34, issue.36, pp.229-241, 1996.
DOI : 10.1016/1040-6182(95)00088-7

J. B. Hunt and P. G. Hill, Tephrological implications of beam size?sample-size effects in electron microprobe analysis of glass shards, Journal of Quaternary Science, vol.5, issue.36, pp.105-117, 2001.
DOI : 10.1002/jqs.571

E. Juvigné, Scheidetrichtermethode oder Zentrifugaltrennung zur quantitativen Gewinnung von Schwermineralen (Separating funnel or centrifugal method for the quantitative separation of heavy minerals) Senckenbergiana maritima, pp.171-174, 1979.

E. Juvigné, Distribution of widespread postglacial tephra sheets from the Eifel and the Central-Massif in NE France and neighbouring regions, Comptes Rendus de l'Académie des Sciences, pp.415-420, 1991.

C. Lacasse, Influence of climate variability on the atmospheric transport of Icelandic tephra in the subpolar North Atlantic, Global and Planetary Change, vol.29, issue.1-2, pp.31-55, 2001.
DOI : 10.1016/S0921-8181(01)00099-6

P. G. Langdon and K. E. Barber, Snapshots in time: precise correlations of peat-based proxy climate records in Scotland using mid-Holocene tephras, The Holocene, vol.8, issue.1, pp.21-33, 2004.
DOI : 10.1191/0959683604hl686rp

P. G. Langdon and K. E. Barber, The climate of Scotland over the last 5000 years inferred from multiproxy peatland records: inter-site correlations and regional variability, Journal of Quaternary Science, vol.8, issue.6, pp.549-566, 2005.
DOI : 10.1002/jqs.934

G. Larsen, A. Dugmore, and A. Newton, Geochemistry of historical-age silicic tephras in Iceland. The Holocene, pp.463-471, 1999.

G. Larsen and S. Thorarinsson, H4 and other acid Hekla tephra layers, Jökull, vol.27, pp.27-46, 1977.

D. J. Lowe and J. B. Hunt, A summary of terminology used in tephra-related studies Tephras, Chronology and Archaeology: Les Dossiers de l'Archaeo-logis 1, pp.17-22, 2001.

D. J. Lowe, R. M. Newnham, B. G. Mcfadgen, and T. F. Higham, Tephras and New Zealand Archaeology, Journal of Archaeological Science, vol.27, issue.10, pp.859-870, 2000.
DOI : 10.1006/jasc.1999.0614

W. S. Mackenzie and C. Guilford, Atlas of Rock-Forming Minerals in Thin Section, p.98, 1980.

C. Merlet, An accurate computer correction program for quantitative electron probe microanalysis, Mikrochimica Acta, vol.18, issue.1, pp.363-376, 1994.
DOI : 10.1007/BF01244563

E. Oelkers, General kinetic description of multioxide silicate mineral and glass dissolution, Geochimica et Cosmochimica Acta, vol.65, issue.21, pp.3703-3719, 2001.
DOI : 10.1016/S0016-7037(01)00710-4

R. Payne and J. Blackford, Microwave digestion and the geochemical stability of tephra, Quaternary Newsletter, vol.106, pp.24-33, 2005.

R. Payne, J. Blackford, and J. Van-der-plicht, Using cryptotephras to extend regional tephrochronologies: An example from southeast Alaska and implications for hazard assessment, Quaternary Research, vol.17, issue.01, pp.42-55, 2008.
DOI : 10.1002/jqs.636

R. Payne and M. J. Gehrels, The formation of tephra layers in peatlands: An experimental approach, CATENA, vol.81, issue.1, pp.12-23, 2010.
DOI : 10.1016/j.catena.2009.12.001

R. Payne, A. Kilfeather, J. Van-der-meer, and J. Blackford, Experiments on the taphonomy of tephra in peatlands, Suo, vol.56, pp.147-156, 2005.

N. J. Pearce, C. A. Bendall, and J. A. Westgate, Comment on ???Some numerical considerations in the geochemical analysis of distal microtephra??? by A.M. Pollard, S.P.E. Blockley and C.S. Lane, Applied Geochemistry, vol.23, issue.5, pp.1353-1364, 2008.
DOI : 10.1016/j.apgeochem.2008.01.002

N. J. Pearce, J. S. Denton, W. T. Perkins, J. A. Westgate, and B. V. Alloway, Correlation and characterisation of individual glass shards from tephra deposits using trace element laser ablation ICP-MS analyses: current status and future potential, Journal of Quaternary Science, vol.86, issue.36, pp.721-736, 2007.
DOI : 10.1002/jqs.1092

C. Persson, Tephrochronological investigations of peat deposits in Scandinavia and the Faroe Islands, Sveriges Geologiska Undersoekning, vol.65, pp.1-34, 1971.

J. Pilcher, R. S. Bradley, P. Francus, and L. Anderson, A Holocene tephra record from the Lofoten Islands, Arctic Norway, Boreas, vol.29, issue.2, pp.136-156, 2005.
DOI : 10.1111/j.1502-3885.2005.tb01011.x

J. R. Pilcher, V. A. Hall, and F. G. Mccormac, Dates of Holocene Icelandic volcanic eruptions from tephra layers in Irish peats, The Holocene, vol.5, issue.1, pp.103-110, 1995.
DOI : 10.1177/095968369500500111

G. M. Plunkett, J. R. Pilcher, F. G. Mccormac, and V. A. Hall, New dates for first millennium BC tephra isochrones in Ireland. The Holocene, pp.780-786, 2004.

A. M. Pollard, S. P. Blockley, and C. S. Lane, Some numerical considerations in the geochemical analysis of distal microtephra, Applied Geochemistry, vol.21, issue.10, pp.1692-1714, 2006.
DOI : 10.1016/j.apgeochem.2006.07.007

A. M. Pollard, S. P. Blockley, and K. R. Ward, Chemical alteration of tephra in the depositional environment: theoretical stability modelling, Journal of Quaternary Science, vol.67, issue.5, pp.385-394, 2003.
DOI : 10.1002/jqs.760

P. J. Potts, M. Thompson, and S. Wilson, G- Probe-1 -An international proficiency test for microprobe laboratories, 2002.

J. L. Pouchou and F. Pichoir, Quantitativeanalysis of homogeneous or stratified microvolumes applying the model PAP Electron Probe Quantitation, pp.31-75, 1991.

N. L. Rose, P. N. Golding, and R. W. Battarbee, Selective concentration and enumeration of tephra shards from lake sediment cores. The Holocene, pp.243-246, 1996.

R. Schmid, Descriptive nomenclature and classification of pyroclastic deposits and fragments, Geologische Rundschau, vol.70, issue.2, pp.41-43, 1981.
DOI : 10.1007/BF01822152

H. Staudigel, A. Yayanos, R. Chastain, G. Davies, E. A. Verdurmen et al., Biologically mediated dissolution of volcanic glass in seawater, Earth and Planetary Science Letters, vol.164, issue.1-2, pp.233-244, 1998.
DOI : 10.1016/S0012-821X(98)00207-6

J. Stockmarr, Tablets with spores used in absolute pollen analysis Pollen et Spores, pp.615-621, 1971.

T. R. Sweatman and J. V. Long, Quantitative Electron-probe Microanalysis of Rock-forming Minerals, Journal of Petrology, vol.10, issue.2, pp.332-379, 1969.
DOI : 10.1093/petrology/10.2.332

G. T. Swindles, A. Blundell, H. M. Roe, and V. A. Hall, A 4500-year proxy climate record from peatlands in the North of Ireland: the identification of widespread summer ???drought phases????, Quaternary Science Reviews, vol.29, issue.13-14, pp.1577-1589, 2010.
DOI : 10.1016/j.quascirev.2009.01.003

G. T. Swindles, G. Plunkett, and V. A. Hall, Late Quaternary tephrochronology of the North of Ireland, pp.41-45, 2008.

G. T. Swindles, G. Plunkett, and H. M. Roe, A delayed climatic response to solar forcing at 2800 cal. BP: multiproxy evidence from three Irish peatlands, The Holocene, vol.17, issue.2, pp.177-182, 2007.
DOI : 10.1177/0959683607075830

G. T. Swindles and H. M. Roe, Constraining the age of spheroidal carbonaceous particle (SCP) stratigraphies in peats using tephrochronology, Quaternary Newsletter, vol.110, pp.2-9, 2006.

I. Techer, T. Advocat, J. Lancelot, and J. M. Liotard, Dissolution kinetics of basaltic glasses: control by solution chemistry and protective effect of the alteration film, Chemical Geology, vol.176, issue.1-4, pp.235-263, 2001.
DOI : 10.1016/S0009-2541(00)00400-9

S. Thorarinsson, The eruptions of Hekla in historical times, I: The eruption of Hekla, 1947.

I. H. Thorseth, H. Furnes, and O. Tumyr, Textural and chemical effects of bacterial activity on basaltic glass: an experimental approach, Chemical Geology, vol.119, issue.1-4, pp.139-160, 1995.
DOI : 10.1016/0009-2541(94)00098-S

C. S. Turney, C. Van-den-bogaard, W. Dorfler, R. Glos, M. J. Nadeau et al., Extraction of rhyolitic component of Vedde microtephra from minerogenic lake sediments Two tephra layers bracketing late Holocene paleoecological changes in northern Germany Laacher See Tephra: A widespread isochronous late Quaternary tephra layer in Central and Northern Europe, Journal of Paleolimnology, vol.19, issue.2, pp.199-206, 1985.
DOI : 10.1023/A:1007926322026

D. Van-harten, On the estimation of relative grain frequencies in heavy mineral slides, Geologie en Mijnbouw, vol.44, pp.357-363, 1965.

S. Wastegård, Late Quaternary tephrochronology of Sweden: a review, Quaternary International, vol.130, issue.1, pp.49-62, 2005.
DOI : 10.1016/j.quaint.2004.04.030

S. Wastegård, M. Rundgren, K. Schoning, S. Andersson, S. Bjorck et al., Age, geochemistry and distribution of the mid-Holocene Hekla-S/Kebister tephra, The Holocene, vol.18, issue.4, pp.539-549, 2008.
DOI : 10.1177/0959683608089208

J. A. Westgate and M. P. Gorton, Correlation Techniques in Tephra Studies, Tephra Studies. Riedel, pp.73-94, 1981.
DOI : 10.1007/978-94-009-8537-7_5

D. Wolff-boenisch, S. R. Gislason, E. Oelkers, and C. V. Putnis, The dissolution rates of natural glasses as a function of their composition at pH 4 and 10.6, and temperatures from 25 to 74??C, Geochemica et Cosmochimica Acta, pp.4843-4858, 2004.
DOI : 10.1016/j.gca.2004.05.027

D. Wolff-boenisch, S. R. Gislason, E. Oelkers, and C. V. Putnis, The effect of fluoride on the dissolution rates of natural glasses at pH 4 and 25??C, Geochimica et Cosmochimica Acta, vol.68, issue.22, pp.4571-4582, 2004.
DOI : 10.1016/j.gca.2004.05.026

L. M. Zillén, S. Wastegard, and I. F. Snowfall, Calendar year ages of three mid-Holocene tephra layers identified in varved lake sediments in west central Sweden, Quaternary Science Reviews, vol.21, issue.14-15, pp.1583-1591, 2002.
DOI : 10.1016/S0277-3791(02)00036-7

G. Dr and . Swindles, School of Geography

. Tel, (0)113 34 39127; Fax: +44 (0)113 34 33308; E-mail: g, p.44