Warm Period Growth of Travertine during the Last Interglaciation in Southern Germany

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.