Journal of the Geological Society, London, Vol. 158, 2001, pp. 831–841. Printed in Great Britain. Annual to sub-annual resolution of multiple trace-element trends in speleothems IAN J. FAIRCHILD 1 , ANDY BAKER 2 , ANDREA BORSATO 3 , SILVIA FRISIA 3 , RICHARD W. HINTON 4 , FRANK McDERMOTT 5 & ANNA F. TOOTH 1,6 1 School of Earth Sciences and Geography, Keele University, Staffs ST5 5BG, UK. (e-mail: i.j.fairchild@keele.ac.uk) 2 Department of Geography, University of Newcastle-on-Tyne NE1 7RU, UK. 3 Museo Tridentino di Scienze Naturali, via Calepina 14, Trento 38100, Italy. 4 Department of Geology and Geophysics, University of Edinburgh, West Mains Rd, Edinburgh EH9 3JW, UK. 5 Department of Geology, University College Dublin, Belfield, Dublin 4, Ireland. 6 Institut fu ¨r Geologie und Pala ¨ontologie, Universita ¨t Innsbruck, Innrain 5, 6020 Innsbruck, Austria. Abstract: This study aims to establish evidence for the widespread existence of preserved high-resolution trace element variations in speleothems that may have climatic significance. Ion microprobe analysis of speleothems reveals that annual to sub-annual variations in element chemistry exist at five, shallow western European cave sites (Crag Cave, County Kerry and Ballynamintra, County Waterford, Ireland; Uamh an Tartair, Sutherland, Scotland; Grotte Pere-Noe ¨l, Belgium; Grotta di Ernesto, NE Italy) with widely varying climatic, geomorphic and geological settings. The variations are not restricted to species (Mg, Sr and Ba) known to substitute directly for Ca in the calcite lattice, but include H, F, Na and P. Phosphorus (as phosphate) displays the greatest variability and may have the most significance as a proxy for the seasonal temperature cycle because of its role as a nutrient element. The technique allows estimation of growth rate of speleothems at any interval of interest, which is one of several possible uses in palaeoclimatology. Keywords: speleothem, carbonates, geochemistry, phosphates, palaeoclimate. There is a need for improved palaeoclimatic records at both high spatial and high temporal resolution in order to test our concepts of past climatic change in populated regions and aid projections of future change. This need has led to a rapidly increasing analysis of continental archives including speleothems. The most common type of speleothems studied for palaeoclimate are cylindrical stalagmites, which accrete predominantly vertically from CaCO 3 precipitated from drip water. Stalagmite drips are often supplied by tubular (soda straw) stalactites that grow mainly by linear extension at their tip. A third form of precipitates is crusts, formed by water flowing over a surface and which can develop into thick flowstones. Climate proxies studied in speleothems include growth rate (e.g. Genty & Quinif 1996; Qin et al. 1999; Proctor et al. 2000), stable isotopes (e.g. McDermott et al. 1999; Lauritzen & Lundberg 1999; Bar-Matthews et al. 1999), Sr isotopes (e.g. Banner et al. 1996; Goede et al. 1998; Verheyden et al. 2000) and trace elements (e.g. Ayalon et al. 1999; Hellstrom & McCulloch 2000). Whereas most proxies reflect averages on the decadal to centennial scale, microanalysis of trace elements (along with the study of visible or UV- fluorescent laminae) yields information at the annual to sub- annual level and hence has the potential to recover the changing nature of seasonality through time. Two micro- analytical studies on calcite speleothems (Roberts et al. 1998; Huang et al. 2001) and one on aragonitic speleothems (Finch et al. 2001) employing secondary ionization mass spectrometry (SIMS) on an ion microprobe have shown that such records exist, but their generality has yet to be established. Here we present outline descriptions of five examples to illustrate that such annual trace element variations are a normal, rather than an exceptional feature in shallow cave sites, and that several other trace elements, of contrasting geochemical character, show similar behaviour. The geochemical determination of an annual pulse allows the determination of growth rates, which is especially significant since many speleothems lack annual lamination (Baker et al. 1993). It may also prove possible in individual cases to quantitatively calibrate the trace elements for palaeoclimatic variables such as rainfall. Study sites and materials The study sites span a range of geographic, climatic, geological and pedological settings. Ballynamintra (County Waterford, SE Ireland) has a brown forest soil and underlies a wooded isolated hill made of Carboniferous limestone. The climate is mild (mean temperature 9.4 C), with 1200 mm annual rainfall and a summer soil moisture deficit. Uamh an (cave of) Tartair (8.6 C, Sutherland, NW Scotland, Roberts et al. 1998; Proctor et al. 2000) contrasts in that the soil is a thin moorland peat overlying Cambro-Ordovician dolomites and limestones; pre- cipitation is high (2000 mm annually) throughout the year, and there is winter snow cover. Grotta d’Ernesto (NE Italian Alps, McDermott et al. 1999; Fairchild et al. 2000; Huang et al. 2001) is developed in Jurassic dolomites and limestones over- lain by a brown forest soil in woodland, but is significantly cooler than the other sites with a mean temperature of 6.6 C. It has typically two months of winter snow cover and a summer soil moisture deficit despite an average 1300 mm annual rainfall. Grotte Pere-Noe ¨l (SE Belgium; Genty & Quinif 1996; Genty & Deflandre 1998; Verheyden et al. 2000) lies under woodland with a brown forest soil on Devonian limestones and dolomite. Whereas the other caves are all around 10–15 m below the surface, Pere-Noe ¨l lies at a depth of 70 m, butthis is compensated for by rapid percolation of water 831