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The origin of lamination in stalagmites from Katerloch Cave, Austria: Towards a seasonality proxy

2008; Volume: 13; Issue: 3 Linguagem: Inglês

10.22498/pages.16.3.21

1563-0803

Ronny Boch, Christoph Spötl,

Geological formations and processes

Macroto microscopic layering, comparable to that in polar ice, corals and some lake and marine sediments, is common in many speleothems. Laminated stalagmites and flowstones occur from the highand mid-latitudes down to low-latitude cave sites. In many cases, the observed lamination is demonstrably of annual origin and is an expression of seasonality (Broecker et al., 1960; Frisia et al., 2003). Locally, however, event laminae on sub-annual to multi-annual timescales are present, being stochastic or periodical in nature (e.g., Baker et al., 2002). Various material properties give rise to macroand microscopic lamination patterns in speleothems, most notably changes in mineralogy (Railsback et al., 1994) and crystal fabric (Kendall and Broughton, 1978; Frisia et al., 2000), as well as the abundance and distribution of pores, fluid and particle inclusions or organic components. The latter, when exposed to a source of blue or ultraviolet light, cause fluorescence, which is a useful tool to study lamination patterns (e.g., Meyer et al., 2006). Laminated speleothems have received increasing attention in recent years, as they provide very highly resolved paleoenvironmental proxy records for the terrestrial realm when combined with high-precision U-Th dating. Exploitation of their full potential for paleoscientific reconstructions requires a thorough calibration and validation of speleothem lamina proxy data, which ideally should be performed for each cave site using a combination of multi-annual cave monitoring and comparison with nearby meteorological data (e.g., Mattey et al., 2008). Constantdiameter (or candle-stick; see Fig. 1A) stalagmites are best suited for lamina-based paleoclimate studies because their morphology indicates rather constant growth, and the lamina thickness directly reflects the amount of annually precipitated carbonate, which is controlled by the prevailing environmental conditions. In order to better understand the mechanism of lamina development and to assess the paleoenvironmental potential of annually layered stalagmites, Katerloch Cave in Austria was monitored over a period of three years. A holistic approach was used, which comprised analyses of soil air, cave air, drip water, modern calcite precipitates on artificial substrates and stalagmite samples.