| Summary: | <p>We describe a new method for the measurement of <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M2" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><mi mathvariant="normal">U</mi><mo>/</mo><mi mathvariant="normal">Pb</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="30pt" height="14pt" class="svg-formula" dspmath="mathimg" md5hash="e043b0a717ed7605fa31d32304cccc94"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-33-2022-ie00001.svg" width="30pt" height="14pt" src="gchron-4-33-2022-ie00001.png"/></svg:svg></span></span>
ratios by isotope dilution multi-collector inductively coupled plasma mass
spectrometry (MC-ICP-MS) for the dating of geologically young clean
carbonates, particularly speleothems. The method is intended for materials
containing little or no initial <span class="inline-formula"><sup>232</sup></span>Th. We illustrate and validate the
method with four examples ranging from 0.57 to 20 Ma. The new method
is capable of applying the <span class="inline-formula"><sup>235</sup></span>U–<span class="inline-formula"><sup>207</sup></span>Pb and
<span class="inline-formula"><sup>238</sup></span>U–<span class="inline-formula"><sup>234</sup></span>U–<span class="inline-formula"><sup>206</sup></span>Pb chronometers, common Pb and quantifiable
residual <span class="inline-formula"><math xmlns="http://www.w3.org/1998/Math/MathML" id="M9" display="inline" overflow="scroll" dspmath="mathml"><mrow class="chem"><msup><mi/><mn mathvariant="normal">234</mn></msup><mi mathvariant="normal">U</mi><msup><mo>/</mo><mn mathvariant="normal">238</mn></msup><mi mathvariant="normal">U</mi></mrow></math><span><svg:svg xmlns:svg="http://www.w3.org/2000/svg" width="52pt" height="15pt" class="svg-formula" dspmath="mathimg" md5hash="a9cbbcfe4acccbf09a9fda48c3a2a269"><svg:image xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="gchron-4-33-2022-ie00002.svg" width="52pt" height="15pt" src="gchron-4-33-2022-ie00002.png"/></svg:svg></span></span> disequilibrium permitting. These provide an
alternative to the more widely used <span class="inline-formula"><sup>238</sup></span>U–<span class="inline-formula"><sup>206</sup></span>Pb chronometer, which
can be highly inaccurate for samples that are <span class="inline-formula"><</span> ca. 20 million years old,
owing to uncertainties in the excess initial <span class="inline-formula"><sup>234</sup></span>U (hence, excess
radiogenic <span class="inline-formula"><sup>206</sup></span>Pb) commonly observed in speleothems.</p>
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