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orion-list Radiocarbon

Concerning the four AMS dates of texts whose 2-sigma ranges 
start wholly later by 15-20 calendar years than a 63 BCE terminus 
according to the Seattle-Belfast calibration curve, consider the 
following data reported by Zurich and Tucson on contemporary 
papyrus texts.  (Numbers are the lab measurements [= "BP"]):

125 CE . . . Seattle/Belfast calibration curve 1898 +/- 11

  text's internal date:
  130 CE (Zurich) . . . . . 1917 +/- 42
  134 CE (Zurich) . . . . . 1892 +/- 32

  128 CE (Tucson) . . . . 1827 +/- 36
  130 CE (Tucson) . . . . 1799 +/- 57
  134 CE (Tucson) . . . . 1758 +/- 36

135 CE . . . Seattle/Belfast calibration curve 1839 +/- 13

Analysis: (a) the three Tucson dates (ave. 1793 +/- 25) disagree 
significantly with the two Zurich dates (ave. 1901 +/- 27).  Due to 
the significant disagreement, it is improper to combine or average 
the two labs' results, and the least likely explanation is that both 
labs equally share an error.  The most likely explanation is that 
one lab is wrong, leaving the other to be presumed approximately 
accurate.  (b) However all evidence argues against a significant 
offset between the two labs in their parchment datings (compare, 
e.g. both labs on 1QIsaA).  (c) therefore, presume a papyrus-
specific offset in one lab applicable to all of that lab's papyrus 
datings (two others for Zurich, one other for Tucson).  (d) Although 
not certain, the stronger argument may favor Tucson's papyrus 
datings being the correct ones.  This is based on a comparison 
between two presumed contemporary texts, one parchment 
(presumed dated accurately), and one papyrus, at Tucson.  Note 
the agreement:

   4Q249 papyrus: crypt A Midrash Sepher Moshe . . 2097 +/- 50
   4Q317 parchment: crypt A Phases of the Moon . .  2084 +/- 30

If an offset of c. 60 (Zurich discrepancy from the 135 BCE calibration 
curve data point) is assumed for all four of the Zurich papyrus (and 
date-bearing) texts, the recalibrated results are in excellent 
one-sigma agreement with the texts' true dates in all Zurich cases.

(e) The Tucson papyrus datings suggest a regional offset in one 
direction of some unknown magnitude (based on, e.g. the Tucson 
dating for 128 CE).  The direction of this offset is in agreement with 
that predicted by the 63 BCE terminus hypothesis.  (f) A regional 
offset in this direction of c. 15-20 in principle brings all AMS dates, 
except for 4QpPsA, in agreement with routine expected distribution 
of dates according to a 63 BCE terminus, given a further assumption 
(mine, from argument) that all "yachad" texts date from the c. 20-30 
years (single generation) leading up to 63 BCE.

The full argument and number-crunching cannot be presented here, 
but this is the essential reasoning.  The radiocarbon datings, it 
appears, are in good order except for 4QpPsA (and a possible 
question mark on 4Q266) in terms of a 63 BCE terminus, according 
to my analysis.  On 4Q266, although I attach no weight to the 
following statement, for those who do, Cross said of this text on the 
basis of palaeography: "can be no later than the first half of the 
first century BC" (1995, Anc. Lib., 96, 72n).  

Greg Doudna

For private reply, e-mail to Greg Doudna <gd@teol.ku.dk>
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