Fig 3. Relationships of the ¹⁴C dated tree-ring sequenced samples from the Klock Feature 84 Ulmus sp. branch with IntCal20.

a. The laboratory stated data wiggle-matched against IntCal20. Two measurements for RY1001-1002 are combined as a satisfactory weighted average and there are then dates on RY1010-1018 and RY1021-1025. The likely non-modelled calibrated locations do not accommodate the known tree-ring spacing in detail. The two dates on RY1001-1002 identify 1527–1552 as the most likely placement (purple box). But this is not compatible with the other two dates given the tree-ring spacings (hence the expected, if the likely non-modelled dates on RY1001-1002 are correct, pink box is left floating in free space away from the IntCal20 curve). The wiggle-match, trying to accommodate all the dates therefore moves the modelled RY1001-1002 dates (solid green distribution) to a more recent placement (largely missing IntCal20 and hence achieving a poor OxCal Agreement value: 44.6<60) but allowing the other modelled dates (solid gray and solid cyan distributions) to be associated with IntCal20 (although the overall Amodel value is poor: 31<60). b. The raw IntCal20 dataset from which the modelled curve in a. is derived [111] highlighting the ETH dataset [108]–these raw data indicate greater possible variation which might allow the observed Klock data to fit better, including earlier, similar to the purple and pink boxes in a.