PALEOCLIMATE IMPLICATIONS OF MASS-SPECTROMETRIC DATING OF A BRITISH FLOWSTONE

The timing of growth phases in a cave flowstone from Yorkshire, Englan d, has been precisely dated by thermal ionization mass spectrometric U -238-U-234-Th-230 dating, Six growth periods of both short duration an d fast growth rate are separated by nondepositional hiatuses, The ages of these phases were determined to be 128.8 +/- 2.7, 103.1 +/- 1.8, 8 4.7 +/- 1.2, 57.9 +/- 1.5, 49.6 +/- 1.3, and 36.9 +/- 0.8 ka, There is a remarkably good correlation between the periods of active speleothe m growth and the timing of solar insolation maxima, derived from orbit al parameters, which has not previously been reported. Speleothem grow th theory and evidence from other terrestrial paleoclimate records sug gest that episodic, rapid growth phases at the insolation maxima are m ost likely to be caused by changes in either precipitation intensity o r volume, which caused switching in the routing of water flow in the u nsaturated zone above the cave, Such a result provides new evidence of the importance of variations in solar insolation for terrestrial pale oclimate and offers the potential for derivation of a paleowetness ind ex from speleothem growth.