Tools & tillage: a journal on the history of the implements of cultivation and other agricultural processes (5.1984/1987)

C-14 DATES

25

the Past Ten Years’ Excavations in Aamosen
Bog, West Zealand), in: Aarboger for nordisk
Oldkyndighed og Historie, 1953.
Troels-Smith, J.: Pollenanalytische Untersuch-
ungen zu einigen schweizerischen Pfahlbau-
problemen, Das Pfahlbauproblem, in: Mono-
graphien zur Ur- und Friihgeschichte der
Schweiz, Bd. 11, 11-58. Basel 1955.
Troels-Smith: Ivy Mistletoe and Elm. Climate In-
dicators-Fodder Plants. A Contribution to the
Interpretation of the Pollen Zone Border VII-
VIII, in: Geological Survey of Denmark IV

series, vol. 4, No, 4, p.4-32, Copenhagen
1960.
Troels-Smith, J.: Naturwissenschaftliche Beitrage
zur Pfahlbauforschung, in: Archaologie der
Schweiz, 4, 1981, 3.
Troels-Smith, J.: Vegetationshistoriske vidnes-
byrd om skovrydninger, planteavl og husdyr-
hold i Europa, specielt Skandinavien (1), in:
Introduksjonen av jordbruk i Norden. Sympo-
sium i Oslo 14. og 15. april 1980. (ed.) Thorleif
Sjovold. Det Norske Videnskaps-Akademi,
Oslo 1982, 39-62.

CALIBRATION OF C-14 DATES

It has long been realized that ages in C-14
years deviate from true calendar years. To
stress this difference dates in C-14 years are
often denoted as b.c./a.d. instead of the
common B.C./A.D. applied to calendar
years. C-14 dates are calibrated by C-14
measurements of dendrochronologically
dated samples. Especially the long American
series of bristlecone pine have furnished den-
dro samples suitable for a calibration of C-14
dates into calendar years (e.g. R. M. Clark,
Antiquity, XLIX, 251, 1975). Recently long
series of year rings of oak from Central
Europe and from Ireland have supplied simi-
lar samples. These series together with
shorter series of Douglas fir from North
America, have formed the basis for a second
generation of high precision calibration
curves (e.g. Pearson et al., Radiocarbon, 25,
179, 1983).
In the Table below, C-14 dates mentioned
in the paper have been converted into calen-
dar years both according to Clark, 1975, and
to the more precise curves by Pearson et al.,
1983:

C-14 years
Calendar years
(Clark, 1975)
Calendar years
(Pearson, 1983)
4160 b.c
5040 B.C.
3800-3400 b.c
4590-4250 B.C.
3600 b.c
4450 B.C.
3100 b.c
3885 B.C.
3930-3795 B.C.
3100-2700 b.c
3885-3485 B.C.
3930-3365 B.C.
3000 b.c
3785 B.C.
3700-3680 B.C.
3000-2600 b.c
3785-3370 B.C.
3700-3355 B.C.
2000 b.c
2520 B.C.
• 2460 B.C.
1300 b.c
1595 B.C.
1520 B.C.

According to the new high precision calibra-
tion curves, a single C-14 year often corres-
ponds to a time interval in calendar years
where all ages within the interval are almost
equally probable. Thus 3100 b.c. in C-14
years corresponds to the time interval 3930-
3795 B.C. in calendar years, and 2700 b.c.
corresponds to 3485-3365 B.C. The time in-
terval 3100-2700 b.c. in C-14 years, there-
fore, has been converted to 3930-3365 B.C.
in calendar years as the most likely equiva-
lent.
So far the high precision curves only ex-
tend back to 3200 b.c. in C-14 years.
Henrik Tanker