464 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1955 



The 1929 "Crossing of the Gap" initiated a period of intense activity 

 in dendroarcheology. Earlier and still earlier ruins were dated in the 

 Central Pueblo area ; independent master chronologies were developed 

 for the Rio Grande by W. S. Stallings and for northeastern Utah by 

 Schulman ; and now the dates of several hundred ruins and a chronol- 

 ogy for the Southwest reaching back 2,000 years have been estab- 

 lished. By similar methods dates have been obtained by various in- 

 vestigators for less ancient works of man in Norway, Sweden, 

 Germany, and, particularly, by J. L. Giddings in Alaska. 



As an example, we may note a recent application (1952) of this 

 method, namely, the extension of the Puebloan chronology into B. C. 

 times. The ring sequence in a very sensitive and consistent ancient 

 beam of Douglas fir from Mummy Cave, northeastern Arizona, was 

 definitively dated by comparison with master chronologies and with 

 individual specimens long dated and available for several localities 

 in that area. The inner part of a portion of the Mummy Cave beam 

 is illustrated in plate 2. 



This extension of the known chronology then made possible the 

 dating of a number of short charcoal fragments from an early archeo- 

 logical site near Durango, Colo. Among these fragments was one 

 with attached bark, the outer ring of A. D. 46 providing the earliest 

 precise culture date presently available for the Southwest. Some 

 of the evidence on which this extension of the Southwestern chronology 

 is based is shown in figure 2. 



It will be evident from the foregoing that, in general, the successful 

 application of tree-ring analysis to archeological datmg requires two 

 principal favoring factors which are, unfortunately, by no means 

 widely found: 



1. One or more living species must exist in which, on at least some 

 type of site, the amiual rings are sharply defined, show fairly high 

 year-to-year changes in ring width, vary in essentially parallel fashion 

 along different radii and from tree to tree, and provide centuries- 

 long sequences. 



2. Available archeological beams must be of the datable species 

 and from the datable types of sites, in general must overlap the time 

 range of the master clironology for at least 50 years, and must have 

 sufficiently high ring sensitivity to provide unqualified dating, ( Since 

 the ring chronologies in any region tend to be much alike over broad 

 areas, the preceding restriction is not so severe as it might otherwise 

 be.) 



For specially favored localities of the Pueblo area, ring chronologies 

 in some species are so simple and consistent that reliable archeological 

 beam dating, given a sufficiently long master chronology, is an ab- 

 surdly simple matter. But this is far from true in general. Definitive 

 beam dating requires, first, a professionally secure solution of all 



