Fossil speleothems

Figure 2. Co-variations of 6 Cct and 8 Oc, (given relative to the PDB standard) for some fossil speleothems (73951 - Igloo Cave, Nahanni Region, NWT, Canada 72040 - El Sotano de Soyate, SLP, Mexico 71003 — El Sotano de la Tinaja, SLP, Mexico 73039 — Crystal Cave, Bermuda 71042 - El Sotano del Arroyo, SLP, Mexico 74019 - Coldwater Cave, lA, USA) illustrating isotopic relationships that characterize deposition under equilibrium and non-equilibrium situations (from Harmon, 1975). Meaningful paleoclimate information can only be retrieved from speleothem calcite deposited under conditions of isotopic equilibrium.

By assuming that the 5 Oct value of the modern material is representative of the O-isotopic composition of speleothem calcite formed under interglacial conditions, both at present and in the past, then a record of 5 Oct variation for a fossil speleothem can be interpreted in terms of its climatic significance (e.g. Fig. 5). However, only a few recent speleothem paleoclimate studies have taken this approach to estimating the sense of 5 Oct variation for fossil speleothem calcite as a function of climate change. 

Table 3. Interpretation of the temperature dependence of changes in fossil speleothem O-isotopic composition. Data from the references cited in Figure 1.

High-altitude caves are not uncommon in the Eastern Alps, but the vast majority do not show active speleothem deposition. In addition, the origin of many of these alpinecave systems presently situated above timber line probably dates back well into the Tertiary (e.g., Frisch et al, 2000, 2001). Spannagel Cave is an exception inasmuch as it contains both active and fossil speleothems that can be reliably dated using U-series... 

Desmarchelier, J.M., Goede, A., Ayliffe, L.K., McCulloch, M.T., and Moriarty, K., 2000, Stable isotope record and its palaeoenvironmental interpretation for a late Middle Pleistocene speleothem from Victoria Fossil Cave, Naracoorte, South Australia, Quat. Set Rev. 19 763-774. 

Figure 4. Stable isotopic composition of active and fossil calcite speleothems and the Hochstegen Mm ble, Spminagel Cave. The diagrmn contain single sample data mid data from multiple subsmnples.

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