Early Holocene Dendrochronology and Calibration of 14C Dating

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Dendrochronologists at the Laboratory of Tree-Ring Research, University of Arizona, have established a continuous bristlecone pine tree-ring chronology from one locality in eastern California that reaches from the present back to 6700 B.C. Wood from the trees has been used to calibrate the radiocarbon time scale in calendrical years back to 6450 B.C. An attempt will be made to connect discontinuous segments of the tree-ring chronology that now reach back to about 9500 B.C., or, through the entire Holocene into Late Glacial times. Samples dating earlier than 6450 B.C. will be used for further radiocarbon calibration at the NSF-University of Arizona Accelerator Mass Spectrometer facility. This is of considerable scientific interest because this data set is the only one that might now, and for some time, provide truly annual resolution for independent verification of a similar radiocarbon calibration based on European oak and pine. The temporal overlap between the oak and pine is not however based on tree-ring cross- dating, but on matching patterns of radiocarbon activity near 8750 B.P. Several bristlecone pine series now in hand are 14C dated to the early Holocene. One appears to have high potential for verifying the pattern of radiocarbon activity relied upon in the European work. This interdisciplinary work is important because it permits new levels of accuracy in measurement of the rates of change in many global environmental processes. The wood itself, through other kinds of analyses, can provide new information on the nature and range of variation in climatic and other environmental parameters.