This date list contains a selection of C14dates of geological samples obtained from March 1963until July 1966. The preceding date lists (HannoverI, III, IV) give a description of preparation andmeasuring methods.

The dates reported here represent a portion of thosedetermined in 1966, The Radiocarbon DatingLaboratory of the Instituto Venezolano deInvestigaciones Científicas carries out a synthesisof benzene for each sample and detects the activitywith a liquid scintillation spectrometer. Forroutine measurements, 3 cc synthesized benzene and 1cc commercial toluene, with PPO and dimethyl-POPOPscintillators, are used in a special small countingvial. The modern standard is 95% of the NBS oxalicacid, which gives a net modern count rate of 23.9cpm. The background is now 8.5 cpm.

The following list covers measurements of bomb-producedC14 in series of cereals and grassescollected on the northern hemisphere from 1956through 1966. Samples were measured in order todetermine the yearly addition of bomb producedC14 at a single locality, and to detectpossible geographic variations in the distributionand uptake of bomb-generated C14 interrestrial plant material during years with greatlyvarying additions of bomb C14.Measurements are given in the ∆ scale (Lamont VIII),i.e. per mil deviations from 0.95 times the activityof the NBS oxalic-acid standard (the naturalC14 level).

Most of the measurements reported here have beenobtained with the 4.5-L CO2 counterpreviously described (Kiel I; Erlenkeuser, 1965). Afew samples have been dated with a 3-L proportionalcounter. The copper counter is surrounded by 28 GMcounters in the form of a double ring. The totalassembly is shielded by 10 cm of old lead. Neitheran inner lead shield between counter andanticoincidence ring nor screening of sensitivevolume by a quartz tube-as in the 4.5-L counter-hasbeen used. Background of the small counter is 17.20cpm or The 0.95x NBS value is 9.5 cpm at 400 torr. Withinstatistical error background does not depend onatmospheric pressure. The 3-L counter is placedunder a concrete wall, 2.5 m in length and 9.4 m inheight.

In all measurements reported in La Jolla I through IVand for the first of those herein reported (LJ-994to LJ-1025 and LJ-GAP-1 to LJGAP-15), we followedthe procedure designed by Suess (1954) in producingacetylene (C2H2) forradiocarbon counting. For the subsequent samples,however, the following reaction forC2H2 synthesis was used:

The measurements reported in this list were made in theLouvain C14 dating laboratory in 1966.Sample preparation, counting procedure andcalculation method are described in the previouslists. Ages are calculated on the basis of aC14 half life of 5570 yr (Godwin,1962). Errors, including the experimental standarddeviation of the counting rate of the background, ofthe modern standard and of the unknown sample, areexpressed by 1σ (Crèvecoeur and others, 1959).

The C14 dates given below are a continuationof the work presented in our previous list (RIKENII), and have been obtained by countingCO2 at ca. 2 atm pressure in a 2.7 Lstainless steel counter. Results obtained during1966 are described.

The Radiocarbon Dating Laboratory of the Oak RidgeInstitute of Nuclear Studies (ORINS) was developedas a teaching and research facility in the SpecialTraining Division. This facility is available toparticipants enrolled in variouscourses held at ORINS, research groups associatedwith the 41 universities that make up the Oak RidgeAssociated Universities (ORAU), and other colleges,unversities or institutions interested in this labfor teaching or research.

The following list of dates is compiled from samplesprepared since publication of our last date list(OWU II) and includes determinations throughNovember, 1966. Equipment and operating proceduresare the same, except that the sample conversionsystem has been altered to include a second vacuumpumping system and a separate oxygen/nitrogencombustion train.

This date list includes those series of samplescompleted in this laboratory as of November, 1966.The B.P. ages are based upon A.D. 1950, and arecalculated with a half-life value of 5568 yr. Allsamples were counted at least twice for periods ofnot less than 1000 min each. Errors quoted arederived from measurements of sample, background, andmodern-age calibration, but do not include anyhalf-life error. All samples were pretreated with 3NHCl, and some, where noted, received additionalpretreatment with 2% NaOH for the removal ofpossible humic contaminants.