San Juan de Teotihuacan, Mexico - mexi041 Additional Site Information Stahle, Therrell, Villanueva, Sergio Gomez, Julie Report Notes: A Tree-Ring Analysis of 15 Montezuma Baldcypress (Taxodium Mucronatum) Trees at San Juan de Teotihuacán, Mexico Grant H. West and David W. Stahle Tree Ring Laboratory Department of Geosciences University of Arkansas Ozark Hall 113 479-575-3703 dstahle@uark.edu gwest@uark.edu August 14, 2008 Core specimens extracted from 15 Montezuma Baldcypress (Taxodium Mucronatum) trees in and around the town of San Juan de Teotihuacán, Mexico, were used estimate the age of these baldcypress and, if possible, develop a tree-ring chronology. The cores were mounted and polished, and crossdating was attempted for all specimens. Dated cores were then measured with a precision of 0.001 millimeter using a stage micrometer. Unfortunately, the growth rings on a majority of the trees could not be dated. This may be due to disturbance because the cores were removed from trees growing in yards and along paved streets. Tree-ring dating was attempted on all 15 trees, but only two trees could be crossdated with each other and with our existing baldcypress tree-ring chronologies from Rio Verde, San Luis Potosi. A numerical tree-ring chronology was made from the four dated cores from trees SJT06 and SJT07. The trees were growing on top of the most recent flood sedimentation layer in the valley. Though exact dates were not obtained for the oldest specimens from the site, a simple ring count from the bark year places the estimated inner date of core SJT04B at 1756. Ring counts on several other trees indicate that they germinated in the 18th century. These dates may help to constrain the date of this most recent sediment layer. COFECHA analysis: Chronology file name : MEXI041.CRN Measurement file name : MEXI041.RWL Date checked : 07JUL09 Checked by : B. Bauer Beginning year : 1842 Ending year : 2001 Principal investigators: Stahle Therrell Villanueva Sergio Gomez Julie Site name : San Juan de Teotihuacan UAFACC#=02-204 Site location : Mexico Species information : TAMU MONTEZUMA CYPRESS Latitude : 1940 Longitude : -09852 Elevation : 2292M Series intercorrelation: 0.478 Avg mean sensitivity : 0.317 Avg standard deviation : 1.798 Avg autocorrelation : 0.750 Number dated series : 4 Segment length tested : 50 Number problem segments: 4 Pct problem segments : 17.39 PART 5: CORRELATION OF SERIES BY SEGMENTS: San Juan de Teotihuacan 14:42 Tue 07 Jul 2009 Page 5 ----------------------------------------------------------------------------------------------------------------------------------- Correlations of 50-year dated segments, lagged 25 years Flags: A = correlation under .3281 but highest as dated; B = correlation higher at other than dated position Seq Series Time_span 1850 1875 1900 1925 1950 1975 1899 1924 1949 1974 1999 2024 --- -------- --------- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- ---- 1 SJT06A 1873 2001 .49 .50 .49 .18B .62 .64 2 SJT06B 1859 2001 .42 .61 .49 .48 .36 .31B 3 SJT07A 1842 2001 .29A .48 .49 .50 .80 .77 4 SJT07B 1879 2001 .39 .41 .16B .63 .62 Av segment correlation .40 .50 .47 .33 .60 .58 PART 7: DESCRIPTIVE STATISTICS: San Juan de Teotihuacan 14:42 Tue 07 Jul 2009 Page 8 ----------------------------------------------------------------------------------------------------------------------------------- Corr //-------- Unfiltered --------\\ //---- Filtered -----\\ No. No. No. with Mean Max Std Auto Mean Max Std Auto AR Seq Series Interval Years Segmt Flags Master msmt msmt dev corr sens value dev corr () --- -------- --------- ----- ----- ----- ------ ----- ----- ----- ----- ----- ----- ----- ----- -- 1 SJT06A 1873 2001 129 6 1 .530 4.09 9.73 2.239 .819 .310 2.66 .379 .011 2 2 SJT06B 1859 2001 143 6 1 .355 3.56 9.04 2.065 .675 .349 2.57 .396 -.101 1 3 SJT07A 1842 2001 160 6 1 .549 2.32 9.06 1.344 .702 .265 2.90 .290 .022 2 4 SJT07B 1879 2001 123 5 1 .485 2.54 6.97 1.616 .827 .353 2.51 .356 -.050 1 --- -------- --------- ----- ----- ----- ------ ----- ----- ----- ----- ----- ----- ----- ----- -- Total or mean: 555 23 4 .478 3.10 9.73 1.798 .750 .317 2.90 .353 -.028