Evidence for the occurrence of Vedde Ash in Sweden: radiocarbon and calendar age estimates

A tephra layer of rhyolitic composition has been recorded in sediments from Lake Madtjärn, southwestern Sweden. Geochemical analyses have shown that the tephra is identical to the rhyolitic component of the middle Younger Dryas Vedde Ash. A series of AMS radiocarbon measurements places the radiocarbon age of the tephra within a 14C plateau at 10 400–10 300 14C y BP. Based on a linear Younger Dryas sedimentation rate and assumptions about the apparent synchroneity of changes in lake sediments, tree rings and ice-core records, the calendar year age of the tephra concentrations is estimated at 12 045–11 975 yr BP, which accords well with the age of the equivalent tephra in the GRIP core.