HOLIVAR2006 Abstracts
High resolution multi proxy records from Atlantic peat deposits: NW Spain. A contribution to the ACCROTELM Project.
B.S. Stefanini, P.O. Oksanen and F.J.G. Mitchell
Botany Department, School of Natural Sciences, Trinity College, Dublin, Ireland
Contact: Bettina Stefanini (stefanb@tcd.ie)
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ACCROTELM is an EU funded project. Its aims are to collect, examine, and compare peat records from eight west European mire sites for evidence of abrupt climate changes over the last 4500 years.
This poster examines the most south-westerly of the ACCROTEM sites in the Xistral Mountains of north-west Spain. Pedrido is a small raised bog at about 800 m a.s.l. Results for macrofossils, humification, charcoal, loss on ignition, and pollen analyses are interpreted for relevance to rapid climate shifts and vegetation change. The chronology is mainly based on AMS 14C dates that have been wiggle matched.
Peat forming vegetation consisted mostly of grass and sedges that are generally well decomposed throughout the core. Shifts to moist conditions, as indicated by the macrofossil and humification records can be surmised at 3500, 3300, and 3100 cal. yr BP as well as at 1330 and 1230 cal. yr BP and are pronounced at the top of the core but do not reach the surface. While much of the core is well-humified, the macrofossil and humification records indicate dry shifts with especially decomposed material at 2750, 1760, and also at 1260 cal. yr BP. Charcoal is present in nearly all samples but two peaks at about 3170 and 1180 cal. yr BP stand out and have been interpreted as local occurrences of fire.
The pollen record shows a high, sometimes over 80%, incidence of tree pollen until about 3000 cal. yr BP when their gradual reduction gives way to phases of woodland recovery that end at about 1600 cal. yr BP. From that time onwards tree pollen accounts for about half of the pollen sum, the rest being made up mainly by grasses. A notable increase in cereal type pollen is encountered around 2350 cal. yr BP and a recent plantation of Pinus is recorded near the top of the core. Both Acari and pollen concentration show slowed accumulation rates towards the top of the core coinciding with the time of the LIA.
Proxies show some good agreement on climate change events over the last 4500 years in north-west Spain. These shifts are correlated with more widespread climate events.