17th October 2011, 12:54 PM
maurizio feo Wrote:OK, thank you both for the encouragement...
My question is about a paper I found in the Internet. It' by Robert Tykot and it's about carbon dating of a number of different sardinian locations: its title is: "Social Dynamics of the prehistoric central mediterranean" (Univ. London - 1999)
In the table reporting his (and other researchers') results there appear 7 columns, some of which I badly need help with (because I cannot find any agreement between this table and the Author's final conclusions)...
From left to right they read: (1) Site, (2) Context, (3) Lab N?, (4) 14C age, (5) Error, (6) 2sigma Calibrated age range (CALIB 3,0,3), (7)Reference. I do not think that column (3) and (7) are of any interest here and column (1) and (2) only serve the purpose of making the example complete.
In particular, what baffles me is the actual final dating of nuragic towers.
One example: (1) Nuraghe Duos Nuraghes, (2) Tower A floor , (3) I-14,774, (4) 4180, (5)+- 320, (6) cal. BC3333 (3075, 3067,3040) 2915, (7) MMA 3(1992): 278.
According to my (scarce and primitive) understanding, I should subtract 1995 from 4180 and then allow for a mistake of plus or minus 320 yrs.: this procedure should yeld two hypothetical dates (in my reckoning: 1905 - 2545) high and low limits to which the building of the tower may be attributed. In column (6) I dont find any of these numbers, though. Not that this bothers me, really, though if any of you can explain my mistake I would very much appreciate it...
My final question is, in fact:
How does this table (existing for many different Nuraghi, of course, with slightly different figures) accord with the Author's conclusions that attribute the prehistoric period Nuragic I to 1600-1300 a.C.?
Thank you in advance, for your patience
The crux is: Is column 4 the calibrated radiocarbon age or the uncalibrated age?
To calibrate a radiocarbon measurement of 'age at death' of the sample to a calendar date it has to be filtered through a calibration curve.
Also why are you subtracting 1995 from 4180? Is this a reference to BP (before present)? If so BP measurements are take from before 1950.
Column 6 is the calibrated date range which is an expression of a statistical function. Not just a simple high and low limits of the date. It would make more sense if you saw the density plots, which are graphs showing a visual representation of the date range.
Hope this helps.