Jordfallet at bohus : Reinterpreting the 14C dating of a medieval landslide event

Radiocarbon (14C) dating has, since its inception, become an integral part of disciplines such as geology and archaeology, underpinning many key findings made by researchers in the past seven decades. As 14C dating develops, the need arises to revisit older findings and legacy data which may well contain laboratory errors or post-analysis misinterpretations. In this paper we examine one such finding from Sweden, namely the 1958 14C dating of the great Jordfallet (“the Earthfall”) landslide, which was published in the very first volume of Radiocarbon in 1959. We further trace how the results of this 14C dating were misunderstood in a time prior to modern radiocarbon calibration, and the impact which this mistake has had throughout academic publications, state reports and local heritage literature through the course of over sixty years. Because of this flawed interpretation the credible date of 1249 AD given to the landslide by historical sources has been overlooked. Instead, a series of dates from the mid-12th and early 13th centuries have been attributed to the landslide event based on erroneous radiocarbon analysis, a mistake which has substantial implications for the understanding of both regional and international history in medieval Scandinavia.