Late-Quaternary travertine at two sites near Stuttgart formed entirely during interglacial periods. The travertine contains structures from growth induced by bacteria, and such structures have been dated by 230Th/U mass spectrometry. The resulting ages from both sites imply growth episodes of short duration, with growth rates up to 5 mm yr−1, at 99,800 ± 1300 yr B.P. (2σ n = 8) and 105,900 ± 1300 yr B.P. (2σ n = 7). These episodes were likely part of marine isotope stage (MIS) 5.3. Deposition of silt interrupted travertine growth at one of the sites ∼105,000 yr B.P. Likely correlatives of this silt are the St. Germain I-B stade recorded in the Grand Pile peat bog and a cold episode ∼1000 yr long recorded by δ18O values in the GRIP ice core. Travertine also formed during stage 5.5 (∼115,000 yr) and during the early Holocene. We found no evidence for travertine accumulation in stages 2, 3, 4, and 5.1. At both sites, the Sr/U ratio and the initial 234U/238U activity ratio resemble those of modern spring water. However, the sites differ in the chemical composition of spring water and in stratigraphic sequence of travertine accumulation.

A stable isotope technique has been developed which uses 57Fe and 58Fe as labels and which enables the simultaneous measurement of Fe absorption from two test meals in infants. The method was evaluated by measuring Fe absorption from a commercial whey-adjusted infant formula in nine healthy infants aged 13–25 weeks. Each infant was fed 210 ml formula, labelled with either 57Fe or 58Fe, on four consecutive mornings, in random order. The total Fe content in each feed was 2.5 mg Fe; either as 2.5 mg 57Fe, or 0 6 mg 58Fe plus 1.9 mg Fe with normal isotopic composition. Isotopic enrichment of Fe in erythrocytes was measured by thermal ionization mass spectrometry 14 d after the last administration, and Fe absorption was calculated based on isotope ratio shifts, total circulating Fe and intake of each isotope. Geometric mean absorption for the 57Fe and 58Fe labels was 6.72 and 658% respectively, and the absorption of the two isotopes was not significantly different (Student's paired t test). By this technique, paired comparisons of Fe absorption can be obtained and systematic studies of the influence of dietary factors on Fe absorption during infancy can he conducted.