National Physical Laboratory Radiocarbon Measurements II

Abstract

The following list comprises measurements made since those reported in NPL I and is complete to the end of November 1963.Ages are relative to a.d. 1950 and are calculated using a half-life of 5568 yr. The measurements have been corrected for fractionation and referred to 0.950 times the activity of the NBS oxalic acid as a contemporary reference standard. The quoted uncertainty is one standard deviation derived from a proper combination of the parameter variances, viz. those of the standard and background measurements over a rolling twenty-week period, of the sample measurements from at least three independent fillings, of the δC13 measurements and of the de Vries effect (assumed to add an additional uncertainty equivalent to a standard deviation of 80 yr). Any uncertainty in the half-life has been excluded so that relative C14 ages may be correctly compared. Absolute age assessments, however, should be made using the accepted best value for the half-life and the appropriate uncertainty included. If the net sample activity is less than 4 times the standard error of the difference between the sample and background activities, a lower limit to the age is reported equivalent to a sample activity of 4 times the standard error of this difference.The description of each sample is based on information provided by the person submitting the sample to the Laboratory.The work reported forms part of the research programme of the Laboratory and is published by permission of the Director.

Middle and Later Stone Age chronology of Kisese II rockshelter (UNESCO World Heritage Kondoa Rock-Art Sites), Tanzania

“…Although the stratigraphic position of the samples initially dated by the National Public Laboratory (UK) was not reported [ 44 ], Inskeep did provide the excavation level of the samples as a personal communication to Michael Mehlman, appearing in his 1989 Ph.D. thesis [ 17 ], which we report in Table 1 . In order to better control the age and depositional history of the shelter, we generated 25 additional AMS 14 C dates of the carbonate fraction of unburnt ostrich eggshell fragments of known stratigraphic position.…”

“… UBA are University of Belfast AMS dates on unburnt OES. NPL are National Public Laboratory conventional 14 C dates on burnt OES [ 44 ]. δ 13 C values were measured for UBA samples by AMS to correct for instrument fractionation and have not been normalized to international standards (and therefore should not be used as stable isotopes values for inter-study comparisons).…”

“…The full site report was delayed at least in part by Inskeep’s shift in academic focus to southern Africa beginning in 1957–1959 [ 43 ]. A note published in 1964 [ 44 ] on the age of Kisese II (on which Inskeep was not an author) failed to include the stratigraphic position of four conventional 14 C measurements on burnt OES fragments. The stratigraphic uncertainty of the dated specimens effectively removed Kisese II from seminal discussions about the timing and tempo of African prehistory [ 45 – 48 ].…”

Institute of Geological Sciences Radiocarbon Dates III

“…In situ tree boles and recumbent trunks rest on 0.6 m peat bed which overlies soft gray silty clay seen to be > 1 m thick, (50° (Callow et al, 1964) and IGS-C14/13 (Welin, 1971), with which the forest bed may be laterally continuous. Formation of the peat-forest bed possibly commenced to seaward in the lee of an early shingle spit of the Dungeness complex and migrated landwards with rising sea level of the mid-to late-Holocene (Flandrian transgression), forming a diachronous layer.…”