Example Application of Crossdating


After crossdating:
  • The true year of formation can be assigned for every ring of each sample
  • Past environmental and/or human events can be analyzed
  • Overlap in time can be found, as shown at right:
application of crossdating
old living tree
Photo provided by J.H. Speer
Living tree sample: Chronology from living trees:
  • Photo: Ponderosa pine in Oregon
  • Known bark date (e.g., the present year) is starting point
  • After crossdating samples from living trees, dendrochronology extends
    back in time, e.g., AD 1500.
old dead wood
Photo provided by H.D. Grissino-Mayer
Dead wood sample: Chronology from dead trees:
  • Standing snags or fallen logs, like this ponderosa pine remnant in New Mexico
  • Lived for a long time and died long ago
  • If dead trees lived concurrently with the living tree chronology:
    • Outer growth of dead trees crossdates with inner portions of living trees
    • Dendrochronology extended further back in time, e.g., AD 1200.
sampling at Tonto Ruin
Photo provided by H.D. Grissino-Mayer
Dendroarcheological sample: Chronology from archeological samples:
  • Wooden beams and uprights of ruins like the Tonto Ruin, Arizona
  • If archeological samples lived concurrently with the dead wood chronology:
    • Outer growth of structural samples crossdates with inner portions of dead trees
    • Dendrochronology extended further back in time, e.g., AD 800
    • Past human behavior reconstructed and analyzed

Good Idea: When you try skeleton plotting, think of how to apply the dates of ring formation



Paul R. Sheppard
Laboratory of Tree-Ring Research, The University of Arizona
Tucson, Arizona 85721 USA
office: (520) 621-6474, fax: (520) 621-8229
Comments to: sheppard@ltrr.arizona.edu