Geochemistry

Banding Together

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Science  27 Sep 2013:
Vol. 341, Issue 6153, pp. 1431
DOI: 10.1126/science.341.6153.1431-b
CREDIT: C. C. SHEN ET AL., SCIENTIFIC REPORTS 3 (16 SEPTEMBER 2013) © 2013 NATURE PUBLISHING GROUP

Speleothems (stalagmites, stalagtites, and related secondary mineral deposits formed in caves) are commonly dated by counting the growth bands they contain and assuming that those bands are annual markers. How good is this assumption? Shen et al. present results of a study of a 300-year-old laminated stalagmite from Xianren Cave, China, using high-precision radiometric 230Th dating with a 2σ precision of half a year. They find that the layers of the speleothem do not always deposit annually, as is commonly assumed, and that band counting can under- or overcount elapsed time by several years or more per decade in some cases. Thus, caution needs to be applied when using band counting as a dating tool for speleothems, particularly because even small errors in dating can affect the interpretation of some rapid climate change events; high-precision absolute-dated radiometric chronologies should be used when possible.

Sci. Rep. 3, 2633 (2013).

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